<TITLE: Lactic Acid Based Hot Melt Adhesives: Preparation and Properties
ACADEMIC DOMAIN: technology
DISCIPLINE: materials engineering
EVENT TYPE: doctoral defence discussion
FILE ID: UDEFD010
NOTES: continuation of UDEFP010

RECORDING DURATION: 124 min 34 sec

RECORDING DATE: 25.4.2003

NUMBER OF PARTICIPANTS: unknown

NUMBER OF SPEAKERS: 3

S1: NATIVE-SPEAKER STATUS: Finnish; ACADEMIC ROLE: research student; GENDER: male; AGE: 31-50

S2: NATIVE-SPEAKER STATUS: Finnish; ACADEMIC ROLE: senior staff; GENDER: male; AGE: 31-50

S3: NATIVE-SPEAKER STATUS: Portuguese; ACADEMIC ROLE: senior staff; GENDER: male; AGE: 31-50

SS: several simultaneous speakers>



<PRESENTATION UDEFP010 by S1>

<S2> mr <FOREIGN> kustos </FOREIGN> er mr candidate ladies and gentleman the dissertation of er <NAME S1> lactic acid based hot melt adhesives preparation and properties er deals with one of the hot topics in modern polymer science and technology namely synthesis and applications of biopolymers , er biopolymers may be defined in several ways er they they may be , er based on renewable crude materials they usually are environmentally or in vivo degradable or er to harmless substances er and they may be biocompatible in many applications , here we can see some , of the general classes of of biopolymers of course , there there there is a huge number of biopolymers according to the mentioned er definitions , er many of them are natural polymers or or modified natural polymers er in this case er the main focus was on aliphatic polyesters and their copolymers based mainly mainly on lactic acid and teflon caprolactone . er lactic acid is a a biomaterials based hydro- er hydroxy acid er produced through fermentation eps- epsilon caprolactone is a synthetic er monomer er these <COUGH> monomers in copolymer form enable a large spectrum of er properties to be tailored from crystalline high melting poly L lactic er er lactide to partly crystalline rather low melting polycaprolactone the intermediate grades being amorphous of the nature , er degradation rate and physical properties can be adjusted er rather nicely er within this polymer family . er biopolymers have already found er substantial applications in in biomedical field however in bulk applications and in everyday life the biopolymers are just in their emerging phase er last er summer science published er this kind of table of the production capacities of er biopolymers and er er er cargill dow of course is is the major producer today , er in the dissertation of <NAME S1> a copolymer of er er lactic acid and caprolactone with a composition of er 81 to 19 molar ratio was investigated with the aim er to use er them as a hot melt adhesive in industrial applications , this dissertation er consists of five publications in four of which <NAME S1> is the first author all the papers have er already passed er critical referee procedures , er in general as already mentioned we can consider the topic to be very important and interesting both from the scientific and industrial perspective let us er start the detailed examination of the dissertation <P:12> <WHISPERING> (xx) </WHISPERING> </S2>
<S3> i will also start with some general comments on on the thesis , it's erm quite original work in fact it's the first paper that there is on the using of polylactide based er materials on on hot melt melt adhesives er it has er a good planning of experiment and it was well carried out i think it's er quite relevant it's tried to propose is new applications for PLA that but i believe they can only come to industry with a large scale production and a low cost for polylactides and we are going to discuss that later on and it is er generally well written and presented it has just enough results not too many but enough for for for a PhD thesis tries to uses to use different techniques and it's very applied let's say there is a very clear industrial aim in the thesis and it's that's very well carried out er but because of that sometimes the the scientific level is not er so good as the as the applied level let's say , and in fact in some cases more techniques could could be used to to characterise the materials , er it is also my feeling that er paper number four is a bit out of the thesis let's say it's not very well in in in (incorporated) with the all- the other the other four papers , this is now some criticism er the bibliographic review could be better it could be much more extensive and detailed it's only 67 references and er er some some topics could be better treated in there and there are also some several graphs that are quite strange in the scales that we are also going to see and there is a little bit lack of statistical analysis in in in some of the this is my my general comments , i don't want to i don't if you want to comment on any of those please </S3>
<S1> er in in paper four er i also described that er mhm as you mentioned that it was little bit er different than than the other other four papers so so er i only considered the adhesive part of of of of this this polymer and and these subchapters are done done by me </S1>
<S2> er in this work er structural property correlation is one of the key issues and er and er interests at least myself a a lot er in the introductory part er one expects er to find er clearly defined the the the the definition of an ideal hot melt er polymer . ho- how would er candidate er define an ideal hot melt polymer er and the mech- mechanism in in from the polymer polymer's perspective er of the of the performance of the of the polymer in hot melt er processing , is it more er based on er crystalline melting or or is it (xx) should we focus the interest more on the properties of the amorphous phase </S2>
<S1> of course there are many many polymeric materials which can act as as hot melt material er in in page three i er made some basic requirements for the for the hot melt adhesive and er as a reference material i i always er carried out er E-V-I-based based hot melt adhesive which is like er i told in the introduction lecture is the most used material er within the packaging area er for the structural requirements in general i tried to concentrate to to , to er find a suitable hot melt formulation based on polylactic acid and of course in in that way there are also fields that are uncovered </S1>
<S2> sh- should we . think that er that the adhesion is based er mainly on mechanical locking or secondary chemical interactions or even primary chemical bonds </S2>
<S1> er it cannot be solely said so that er that er this one factor that affects to the bond strength but normally it's a combination of all all this this and and and er , er with with the adhesive adhesive as a first requirement must wet the surface and and then then it's er it's possible to to have good bond through mechanical er mechanical attachment or or or by by , oth- othe- other chemical forces </S1>
<S2> yeah but er do you expect the chemical primary bond formation in these in these polymers </S2>
<S1> no no it's not the main main mechanism </S1>
<S2> okay </S2>
<S3> my question is also on the this hot melt melt adhesives and the the way they usually are defined the the the typical ones and i i had some papers that try to say that you could make a a analogy with human with human er body to to define this erm er hot melt adhesives and they basically say that they are constituted by four different things which are the polymers and the polymers are the kind of the the human skeleton then you have the the resins that are like let's say the the the muscles in that will provide the strength to to our to our body then you have waxes waxes or something like that that you feel kind of the water you know human body that are there to plasticise and to to provide some bulk and solidity to to the structure and then you have the kind of er antioxidants that are let's say our vitamins that are there to provide for the health and <S1> yeah </S1> so what i would like you to do is to to to try to see in your systems which which thing would be what so where is your polymer your resin your wax and your [antioxidant] </S3>
<S1> [okay] that that is true what you what you said and er also this E-V-A-based adhesive is is not solely er consisting of E-V-A but it also has has lower er molecular weight resins and also waxes in in in in the composition er in in my system er it's totally different system in in in that way because it's it's one one basic polymer which doe- does [all all all this kind] </S1>
<S3> [so it's clear that you have you have the polymer in there] <S1> yeah </S1> it's also clear that you have the let's say the the antioxidant will be your treatment for stabilising the [polylactide] </S3>
<S1> [yeah] yeah and all- also if you can er describe it so that maybe maybe maybe the caprolactone is is the the <S3> the wax </S3> or or the resin phase of the </S1>
<S3> and that's and that's the and that's the point that's what that was the question that i was <S1> yeah </S1> expecting you to say so you have a kind of let's say a human body without water <S1> yeah </S1> if you don't consider the wax </S3>
<S1> and an interesting topic which is not covered here is is mi- might be in the in the future considered a blending of of <S3> yeah </S3> of of this system </S1>
<S3> don't you think you you could use some plasticides or or something like that </S3>
<S1> yeah with with the plasticisers it might be might be er , the problem might be that er that you make the adhesive too too soft and and maybe towards er pressure sensitive [adhesive] </S1>
<S3> [mhm] of course you could play with the amount of polycaprolactone and the plasticisers </S3>
<S1> yeah yeah and and also also because available of of the as as er professor <NAME S2> said in the introduction phase the available of of the polylactide for for this kind of bulk purposes is is very limited at the moment so so it might be useful to think think of er blending some biodegradable <S3> mhm </S3> er components to to the system </S1>
<S2> yeah i think we go on more or less page by page and and we both er said er the questions we have found here er in in my case er small and and and and small things and and more general things because even the small things in a dissertation should be correct er one one thing i was looking where this figure two where as a polymer person i am used to find the compositions er and find the monomer units in the polymeric change er , here i don't find er vinyl acetate nor nor i find ethylen units , is is this really the way to to to present the composition </S2>
<S1> mhm , i presented it it that way here but er of course there might be different possibilities to to make it make it more more clear </S1>
<S2> ye- yes , th- th- the the correct atoms are there but maybe you don't find the correct er monomers and and if you if you wish to to define the polymer composition by using N and M values it's not so straightforward er by using this figure that is a minor thing but er but er as a polymer person i would er make a different er looking er figure two er another important thing is when we speak of E-V-A is the , is is the point that er there is one reference material the- there are not too many er actual research examples either but there is only one reference material er which is , if i understand right not very thoroughly characterised it is just said that this is E-V-A er and and as in in the last er discussion became evident there are some additives or or small molecu- molecules present w- w- why is it w-hy was this reference not er completely described in in this thesis </S2>
<S1> er of course i i didn't try to characterise the E-V-A-based material i used it er as as as a typical commercial reference material for for this kind of er packaging purposes and and er and er it has several components besides E-V-A but er but er they are not not er so deeply characterised </S1>
<S2> mhm but it's very difficult to draw conclusions if you don't know what is the ma- er benchmarking er material </S2>
<S1> yeah but the benchmarking was the performance of the of the materials </S1>
<S3> yeah my my question is also related with the choosing of of of the material for the study , so if i understand it well what you want is to have er er hot melt melt adhesive that is er biodegradable is cheap and is from renewable resources that's the basic if you can if you can then trigger the properties to be exactly the same or better than the the E-V-A yeah that's your and and so if if if that is the case why did you went for PLA and you don't stay with something like starch-based materials </S3>
<S1> [yeah that's er] </S1>
<S3> [because] are going to make renewable material from from with a starch origin why don't you start with starch </S3>
<S1> yeah that's a good question i i also have done er considerable amount of tests er with with starch-based materials but the but the on the performance-based er er i i chose the polylactic acid as as based adhesive as starting material as as you know one problem with starch is is that it is not thermoplastic as such <S3> mhm </S3> and it it needs needs er some other other components and al- also the moisture content in the air is very strongly affecting the properties of the starch-based adhesives so so er according to my tests er er i chose the polylactic acid based adhesive as as [more interesting one] </S1>
<S3> [but but you try] you tried starch alone or you tried some er blend because you also can find in the market blends of starch with polycaprolactone </S3>
<S1> yeah i i tried tried that with er polycap-caprolactone and al- also with some plasticisers er the problem according to my test with polycaprolactone was that er as in in the blend you needed quite a lot of synthetic non-renewable polycaprolactone material to get reasonable performance </S1>
<S3> yeah in a commercial brand you would like about 70 per cent of polycaprolactone <S1> yeah </S1> so it's a lot </S3>
<S1> yeah </S1>
<P:05>
<S2> yes maybe er well while while while while speaking of er caprolactone , one should mention clearly that it is not a biomass-based crude material do you agree </S2>
<S1> i- i'm sorry </S1>
<S2> ca- caprolactone is not a bio based [material] </S2>
<S1> [yeah] yeah (xx) </S1>
<S2> is it er bio-degradation </S2>
<S1> er there are , are , so it's it's fairly fairly known that polycaprolactone bio-degradates so </S1>
<S2> yeah it is slowly [er (xx) yes] </S2>
<S1> [with with more more more slowly than polylactic acid] </S1>
<S2> that's right so we can regard it as a a biopolymer al- although it is synthetic <S1> mhm </S1> i have a well some comments or criticism on on two figures namely er figure number three for a chemist is is maybe not er accurate and i , wonder if it if this reference is the primary reference for this figure er <P:05> w- w- what the what is the message of the of the figure three </S2>
<P:05>
<S1> er well well the message is is the er hydrolysis of of aliphatic polyesters but i i agree that er that er this picture could be more more clearly defined </S1>
<S2> i- i- i- yeah chemi- chemically i mean mass balances and and things like that should should be maybe correct it's it's qualitative of of it's nature another figure is figure five which you showed already in your lecture er by reading this one could understand that er there are two alternative routes for converting er parallel alternative routes to to convert lactic acids to er polylactic acids with the N value from 700 to 15,000 er , now er , molecular weights are , from 50,000 to to one million grams per mole is it possible to produce 50,000 grams er per mole polylactic acid er through direct polycondensation </S2>
<S1> mhm . the purpose of of of this er figure was only to to er simplify -fy the pro- two alternative processes er , i have not calculated actually what the N values mean mean in in molecular weight . <S2> ye- yeah </S2> . but but anyhow the purpose was was was to show to the reader that er that er erm <SIGH> . let's say direct polycondensation is a- alternative let's say attractive alternative in in in the adhesive manufacturing process </S1>
<S2> maybe in the in the even in the lactide route you first oligomerised <S1> yeah yeah </S1> and and so they are not parallel routes they are complementary routes and er </S2>
<S1> but but also also making making may- eh the the ring-opening route even more complex when when when you [include the polycondensation phase] </S1>
<S2> [yeah that's right that's right yeah yeah] and and and frankly speaking 50 700 N 700 corresponding roughly 50,000 grams or more it's very hard to get through direct polycondensation you need some er (other) (xx) distillation at very specific procedures <S1> mhm [yeah] </S1> [but] you easily reach er let's say 10,000 grams per mole </S2>
<S1> yeah and according to our our tests that was <S2> yeah </S2> also so </S1>
<S2> er well may- maybe i before i give words to my colleague er . i only make the the the general comment that er in this thesis er , with er and maybe to the audience it's good to , to say that er formally this this summary part in this case more or less 30 pages is considered as the dissertation work as such and the papers are attachments to the dissertation and now in this case you have a o- i would say only six pages er theory part is that enough </S2>
<S1> well i i tried to make make a a very very , er let's say very dense thesis so so so er of course i could have more alternatives for potential polymers as as adhesive a- alternative but er i on the other hand i only wanted to concentrate on the on the let's say and give a basic description of of of these materials i have used er there are also er descriptions in the original er publications </S1>
<S2> of course , but as an opponent i have to say that this is very general and very short @@ that's my opinion , please @@ </S2>
<S3> that was also my comment that the beginning the the the the theoretical part could be much better i think so i agree with that </S3>
<S1> well can i co- comment <S3> [yes] </S3> [that er] o- on the other hand i i wanted to er concentrate on on those er references which were accurate er in the adhesive field so it it would er be fairly easy to get lot of references in the biomedical field so but but i i wanted to have only these accurate references </S1>
<S3> that that that's clear but my point was more for instance for somebody that is reading the thesis and is not expert on er on hot melt adhesives it would be good for instance if you if you just read all the other alternatives that that (xx) that you don't have just E-V-A okay for instance speaking something on polyamides or something on (the acrylates or) (xx) the the other types of systems that you could have or the other polymers that are alternatives </S3>
<S1> yeah in the in the packaging hot melt adhesives so so E-V-A-based polymers are are are , let's say almost without exception , [used] </S1>
<S3> [in mo-] in most systems but you can find very easily papers that say that for instance polyamides are better on (tensile) strength </S3>
<S1> yeah yeah yeah but normally they are not er er <S3> [(xx)] </S3> [targeted] for packaging applications </S1>
<S3> but some some comments on that on the thesis would be nice for us to to to understand the point and moving now to to the experimental part so page seven my first question is about the choosing of the materials for for this i think you i would like you to explain better why you went for for PLA PLLA and not for instance PLDA because it would be maybe at the beginning the the the choice will be more (xx) material because you you see there will be problems of degradation and crystallisation er er if you go for PLLA and also why you choose this er 81 19 molar ratio because there is no comment whatsoever on the </S3>
<S1> okay er first of all about the the er D- DL-polylactide is is er dealt in the in the paper four and and er it seems to be so that the er the adhesive properties of of DL-based polylactide is are are more more or less suitable for other type of hot melt applications for for example this kind of er er disposables or tapes or like pressure sensitive applications so so the cohesive strength of the DL wa- was was not e- enough for for packaging purposes , er a- as as you know the PLLA as such is is too rigid polymer for the adhesive so so that's why why polycaprolactone was chosen as as as other other component in in the in the adhesive er there are quite many publications in in the , er about the ho- how the content of er PCL affects to the er properties of of the copolymer er for example elongation which is very important in this thesis er and and the on the on the other hand as professor <NAME S2> mentioned the the caprolactone is is er synthetic polymer and and er er the intention was use that as er as low content as as possible er the 91 19 er was er proven to be let's say insuitable range for adhesive applications i i i don't say it's exactly correct er because there was also tested other other mhm compositions er but er we can say that if the amount of PCL varies between 14 to 20 per cent the adhesive characteristics are quite quite good </S1>
<S3> okay yeah that's okay but that that's what i think you you should you should have explained on on on the thesis okay so not to say i used 81 19 blend without saying why and consider all the things that you are that you are explaining us now and and also i know that you have a a paper (then) with PD with PDLA but but it would be good to from the beginning to say which one you choose and then you try the other one you understand what i mean because , from just the rational of somebody that is going to start to work <S1> mhm </S1> if i was going to do the work i would choose the PL- PDLA </S3>
<S1> but of of course there are a lot of lot of er writing in the let's say the main writing is in the or- ore- original papers and and er this is more or less summary of of of the publications </S1>
<S3> mhm and also the the the the the the the the choosing of putting 19 or 14 or 20 of polycaprolactone is very important because of the costs , because the the the point is not the cost of the polycaprolactone but to to put this into into an industrial application like packaging you have to have very big production of the polymers okay so if you think about now there will be big manufacturing of PLA from (xx) but there will be no not a big manufacturing of PLLA with 19 per cent of polycaprolactones so that cost will still be very very high for this type of application <S1> mhm [so the] </S1> [so my] point is how do you imagine to solve the problem because i could agree with if you find the system that is just based on polylactides that there will be no problem of taking this into the market because maybe we can go to very low costs <S1> mhm </S1> but when you put 19 per cent of polycaprolactone and you know that (xx) is not going to manufacture that at least for now it will be a completely different [(xx)] </S3>
<S1> [but] but a- as as you know also also with polylactide there are no er there there are al- also expectations about the er price levels so so it's not not so straight forward that you can </S1>
<S3> but at least there are expectations </S3>
<S1> @yeah@ yeah but on on the other hand er polycaprolactone is is er let's say existing commercially available er polymer for this purpose , but er i- in the future studies er i think it's i- important also consider this this point </S1>
<S3> yeah because the the point is er what what you say makes sense if you if you are doing the blending of PLA with polycaprolactone because you could buy both and you mix them and it would be okay but the problem is you have to synthesise something like that in big scale in order to get it cheaper <S1> yeah </S1> and nobody is doing that [(xx)] </S3>
<S1> [yeah and] and er let's say the whole thesis was based on on on that expectation that er polylactide will be the er let's say the price level will will be reasonably close to the commercial [synthetic polymers] </S1>
<S3> [yeah but er i] understand that er <S1> yeah </S1> that is quite clear for me but the point is the whole thesis should be based that PLLA polycaprolactone in a a 81 19 ratio should be close to the bulk prices you understand @@ what i mean <S1> mhm </S1> which is a completely different thing <S1> mhm . but er </S1> i i i understand the (xx) no problem whatsoever on what i'm saying but it's i- it's good for you to see to to see them yeah </S3>
<S1> yeah and this this is er of course considered in the in the future future studies when when er we hope to make a commercial adhesive out of out of this </S1>
<S2> yes i wish er still to stay on page seven in the to to better understand the selections of the materials that have been studied er er . what is the reason that er , as you (originally) stated star-shaped polymer was er chosen </S2>
<S1> er reason for for that </S1>
<S2> for for the w- why why to have star-shaped polymer instead of linear one </S2>
<S1> er i i think er it's er it's er or or the ba- basis for that was more or less less that er star-shaped er structures are known to known to have interesting properties which could be advantage er in in the hot melt adhesive process for example better er melt strength and also lower application viscosity </S1>
<S2> er , yes i agree that one could expect the , modified rheological properties erm erm by the way that the class of property should have been mentioned already on the page three if you consider that was the key point er for the polymer selection <S1> mhm </S1> i would add rheological or viscoelastic properties <S1> yeah </S1> the </S2>
<S1> i i think at the pa- page three they are also also @@ me- mentioned undirectly </S1>
<S2> i i couldn't find it i couldn't understand your @@ but the- there are lots of options to modify the aliphatic polyesters' linearity er , or or branch their structure from star-shaped to to to er comb-like structures and even these polyglycerine that we have used as (xx) enables highly branched er structures it to my mind it would have been very interesting to to to study the the the correlation of the of of these geometrical forms of the mo- er molecules to the er applications properties but it's not been done , why , why not why didn't you have linear reference sample </S2>
<S1> er . of course like er like er i i also explained in the be- beginning that er er this this er work is is not er not er related to the structural properties of the polymers but but its intention was was to touch the adhesive properties of the of the [polymers] </S1>
<S2> [but] but but but aren't they depending on the structures </S2>
<S1> mhm er and and the synthesis er part was was was done done that way that er that er we believed that er er this star-shaped structure was was the best alternative er i i , have also done some work work with the with the other other structures for example trying to blend PLA -A to to with PCL but but er this proved to be more er let's say most attractive alternative </S1>
<S2> wh- wh- what what else could be affected through the , branch er formation i mean er . that might be ve- a of very great importance er for the adhesion application is there any any other influence of the (branched) structures than just the rheological modifications </S2>
<S1> er mo- mostly i considered those to be <S2> yeah </S2> be the most [(xx)] </S1>
<S2> [i would] expect er if you have a look on these kinds of er branched er structures er er you add er end er group functionalities to the polymer very very dramatically when you're branching [so] </S2>
<S1> [yeah of course] it can can have effect also [to adhesive] </S1>
<S2> [so so even] hyperbranch or dendrimers are are are known to have very high er functionality and that might be of course i don't know but in this case that might er be operative for the for the adhesion properties , but er but er i don't know if you considered this aspects er one on page seven i was missing badly missing by the way and or a- a- and even in the whole whole work the information of er the molecular weights or or melting temperatures of er the polycaprolactone component is was that measured and do you have information on that </S2>
<S1> er you mean the polycaprolactone pre-polymer <S2> yeah </S2> er , mhm the molecular weight was er was er measured in the in in paper four </S1>
<S2> so how how large were the </S2>
<S1> so that was roughly 9- 9,000 . but on er other otherwise it was not not characterised </S1>
<S2> and then then you you progressed er , in in the way that er in the second second stage you oligomerised lactic acids to to to (rather) low molecular weight er linear polymer is that right <S1> yeah </S1> of molecular weight around how much </S2>
<S1> er on the second s- or or the olig- , or the polycondensation of the polylactic acid was was until molecular weight of 2,000 one or 2,000 was obtained </S1>
<S2> and it was erm MN or MW </S2>
<S1> er it was M eh W i would say </S1>
<S2> yeah if yeah if if you <S1> yeah </S1> you should mention that and units are by the way grams per mole and then in @@ on the tenth line @@ on this page you have er you say that molecular weight of er 1,000s to 2,000 was obtained for the PLLA is that right </S2>
<S1> mhm i'm sorry which er line </S1>
<S2> it's er , fro- four from ch- first chapter it's fourth line from the bottom . on page er seven , it's tenth line from above from the bottom </S2>
<S1> yes oh that that was the molecular weight for [polycondensation (xx)] </S1>
<S2> [yeah but i- is it really] PLLA <S1> yeah </S1> but it was er condens- it it was er not polymerised er through lactide </S2>
<S1> no no it was direct polycondensation </S1>
<S2> is it then polylactide </S2>
<S1> yeah i i guess [that it yeah yeah yeah yeah] </S1>
<S2> [if polylactic acid a- according to the (xx) used] to to </S2>
<S1> that's correct </S1>
<S2> i don't know if you have a abbreviation PLA , the , poly- . well <P:08> i mean the general message and and criticism er from my side is that er er a more thorough understanding of the of the true geometrical form of the molecules would have been needed we i rel- i'm very confident that you that the polycaprolactone pre-polymer is star-shaped that that that is that and and in in the that publication i refer to we also have found the same but , then you continue with the polycondensation reaction you have macro-monomer first linear macro-mono- monomer having O-H and carboxylic ends and and that that is , if i understood right condensation through condensation linked to the caprolactone-based er star-shaped er bipolymer <S1> yeah </S1> is that right how how do you feel how how does this reaction occur is it very complete </S2>
<S1> well er in in paper four er the structure of of this polymer is is er quite well discussed and and er er it seems to be so that it's quite , let's say why- er quite complex er polymer so involving er er blend of of er this copolymer to to with with polylactic acid </S1>
<S2> so you you report even er ring-formation it's [(xx)] </S2>
<S1> [er] ring-formation was not er proven but er but on the other hand it was not er disproven either so it it was discussed in in in paper four </S1>
<S2> okay but certain uncertain uncertain the remains regarding the the shape of the <S1> [mhm yeah] </S1> [final polymer] that is that that there is most probably deviation er distribution in the in the (i mean) in the form </S2>
<S1> yeah but er al-also also there are are fields that er are uncovered in in in this thesis </S1>
<S3> <WHISPERING> (xx) </WHISPERING> </S3>
<S2> yeah <P:05> maybe we have discussed <S3> okay </S3> yes </S2>
<S3> so moving . moving a bit now to to some er experimental details it's again the same line of question if you go to page nine let's say the the adhesive films were prepared by melting the polymer for 15 minutes at 160 degrees C why is why is 15 minutes why is 160 degrees you try the other temperatures <S1> [er] @@ </S1> [you try the other times] why 600 microns and not 1,000 microns </S3>
<S1> yeah of course you must chose some some values 15 minutes was chosen because er , according to my experience it was time needed to to to melt this kind of sample and and er of course all all the samples er were done with the similar manner so so if there was any melt degradation so so the 15 minutes er time was very exact </S1>
<S3> but the the the this this type of que- of questions is important just because if somebody wants to follow your work let's say i understand that if you are writing a paper you will write just like that but on on on on a thesis you should discuss more of experimental details otherwise you just have to give the papers <S1> erm </S1> what you just told me should be written here or something like that because otherwise of course in a in a scientific publication we'll just say they were melt for 15 minutes at 160 degrees <S1> yeah </S1> C but that's why you have this initial part . it's in a in a in our portuguese thesis it's the same kind of thing if you want to do the detail er experimental part you should put much more details than you have in the in the papers otherwise you don't need this experimental part in here because you already have everything in in in </S3>
<S1> yeah but but the the parameters were only chosen er according to practical conditions </S1>
<S3> that was that was enough this time and what's cho- chosen according to practical conditions that would make , and in the in same line of of questioning is now moving to the page 10 and about the the degradation the degradation media what what's the rationale for choosing to make experiments in a buffer solution for this kind of </S3>
<S1> er as as you know it's a standard solution and and er we wanted to have a a let's say controlled er environment for for for to study study the hydrolysis of course they are not er er the conditions er which are in the repulping process [er as such] </S1>
<S3> [that's what i (wanted)] </S3>
<S1> but er but on the on the other hand they are very hard to er standardise so so you have to have some some er standard which you start </S1>
<S3> of course of course i understand that but </S3>
<S1> bu- bu- [but] </S1>
<S3> [does] it give you any useful information from a practical point of view let's say because what you want to understand is (xx) will degrade at 6 degrees 60 degrees C and the (xx) at PH-10 <S1> [yeah yeah] </S1> [yeah it's] basically the repulping conditions <S1> but </S1> there's nothing to do with making a test on static conditions at PH-7 in a buffer solution </S3>
<S1> er i i'm disagree on on that because it it's tells us us us the basic information about the the er , er hydrolytic degradation of of these polymers er er they are only one one conditions that can be used in the repulping process as as such so </S1>
<S3> but why not do let's say stay with he buffer but do an additional test trying to simulate the repulping </S3>
<S1> yeah [well i i tr-] </S1>
<S3> [(xx) 60] degrees and [(xx)] </S3>
<S1> [i i] i tried to simulate the temperatures er by choosing two different temperatures because it is known that the repulping is done done let's say within normal temperature or or or let's say higher higher temperature range </S1>
<S3> but you you you don't agree that PH is also very important [because the] </S3>
<S1> [PH is] very very important but er in the repulping conditions there are al- also variations of there there there are neutral PH conditions on the other hand there are alkaline conditions <S3> mhm </S3> but i i chose this er to to find out let's say the basic er basic er behaviour in the er hydrolytic environment </S1>
<S3> and er regarding the other type of degradation in the co- composting , have any idea what will be the effects of the degradation of PLA on the compost itself because everybody usually there's a a a composting test and forget that of course you should not kill the micro-organisms <S1> yeah </S1> that are in there and are go- are going to degrade your material <S1> yeah </S1> i i don't think there are many studies of PLA in this in this type of conditions </S3>
<S1> yeah yeah but that that's very very er sig- significant and also big field to study as such i i only wanted to see see what's the degradation in the in the normal er compost er would , would be for the for these samples <S3>  okay </S3> but it was not studied further </S1>
<S2> er still of the characterisation methods i would like to know what what what is your , opinion of the , errors or deviations regarding er er , these GPC measurements if i understand rightly were calibrated against poly (standard) standards </S2>
<S1> yeah and and al- also the values for er were were for P PLA A were chosen as linear values <S2> yeah </S2> so so they are not not er er absolute values er what i used the GPC measurements for were that er you you can see the difference in the between the samples and characterise the degradation as such but but er you are right that they are er not maybe maybe the correct <S2> mhm </S2> values </S1>
<S2> because what what what we have understood in our research is that easily 30 per cent er de- er errors might be <S1> mhm yeah </S1> in in regarding to the absolute values but i agree it's a large huge work to to to do really correct calibration for this and and when you you you are more interested to compare the samples <S1>  yeah </S1> maybe it is enough but of course er it has to be mentioned clearly and er ma- maybe i would have welcomed er the some er some estimation of the deviations between different er samples and and here you just say that they are averages from two measurements </S2>
<S1> mhm i i think er i agree mostly what you what you say on these GPC values er i i i also have have a the feeling that er er when when the experiments were done with the different GPC equipment also there was quite a lot of <S2> yeah </S2> variation in the in the values so so i i tried to to <S2> [yeah yeah] </S2> [concentrate the] comparisons </S1>
<S2> another , rather central method has been er thermal thermoanalysis DSC measurements er er you did use it for glass transition er measurements is DSC the right method for that </S2>
<S1> er yes because because er , er i i think er we er we got er er good values out of out of that <S2> yeah </S2> i i don't know if that is of course there are other methods that could be considered </S1>
<S2> yeah for example </S2>
<S1> er @@ </S1>
<S2> we use er we use DMTA <S1> yeah </S1> and er that is er scientifically usually used for TG measurements you you you see often TG values in DSC but er but er often not and and and and you see ma- even ma- not only TG but but you get er other kind of rheological information out of the DMTA i mean melting er mel- mel- information of the me- me- melting or softening er processes of the polymer so i would have welcomed very much in this kind of work er DMTA analysis , there are equipments even even in in in in in tampere and in helsinki and many places </S2>
<S1> yeah er i don't have so so erm big experience on that but er but er i i considered the DSC as as good measures in </S1>
<S2> but are you are you suggest- well in the future to to to to use that method and and see what extra information you might get out of that out of the properties er well i don't understand er clearly how how the DSC measurements for were were performed on on page 11 could you briefly describe er the procedure </S2>
<S1> so the samples were heated twice so so er and cooled rapidly between to get er this kind of amorphous er er structure to the polymer and and on the on the second run the er TG was er er er noticed </S1>
<P:05>
<S2> er . i understand this me- method er when you characterise the polymer materials property as such but er if you apply this for samples which were stored for a time and or or er yeah , to to to to reflect the changes er that occur in in the product is is that the correct method then </S2>
<S1> er well i i used this er DSC for example in in er in paper three to characterise the storage properties of the adhesive and there were variation er er if if if because this adhesive degraded quite rapidly and there were variations in in the time </S1>
<S2> but you sweep out the thermal history during the first melting and now you then you don't get any information of the post-crystallisation er things for example , isn't it so </S2>
<S1> yeah but er for example in paper three i i got the information that er if if the samples er were not er fully crystallised or or not if there was seen a crystallisation peak in the in the DSC measurements , after storage </S1>
<S2> but you you melted it er twice </S2>
<TRACK CHANGE>
<S1> yeah , but er from the first run you see the <S2> [yeah okay] </S2> [crystallisation peak] if if the sample had not [fro- fully crystallised] </S1>
<S2> [yeah yeah okay so] you used both er <S1> [yeah yeah] </S1> [information okay] . er w- w- while speaking of of er these er DSC measurements er (there) on page 13 er you you report , in table two some er melting temperatures and there for- formality is the symbol of melting temperature use MP in some articles you use TM which i would consider the the the correct one er but the the the question is erm why didn't you report crystallinities at all , and what is the another point is that that , er you report that there is er reduction of melting temperatures er through the addition of caprolactone units which is er okay it's really it's understandable but some information regarding the the the whole curve would have been very essential <S1> [er] </S1> [to see] if they had er separate peaks or not these two two two questions i have here </S2>
<S1> er yes they did have o- only one one peak which is also seen in in figure , er er er 18 A and er and the crystallisation was was er calculated in in in in paper two and er three </S1>
<S2> yeah . one one er thing in in this table two is er , that you don't announce the composition of the E-V-A it it's very strange because it it it even if it is just a reference sample it's so basic information that should be given [(xx)] </S2>
<S1> [er what] would you mean by composition the </S1>
<S2> er vinyl acetate er content </S2>
<S1> yeah well er like we have discussed before so the E-V-A reference was not er purely consisting of E-V-A so so the er E-V-A part the content was roughly 30 per cent </S1>
<S2> it should have been mentioned here </S2>
<S3> some more details on the experimental protocols erm i also agree that you you should have tried to use DSC for for making crystallinity for instance you could have done crystallinity as function of the degradation times (xx) if what you are saying about crystallisation is true or not you could use the DSC for that just comparing the enthalpies [of the (xx)] </S3>
<S1> [yeah yeah but i i] i have done that on on papers er [two] </S1>
<S3> [but not] counting the crystallinity just looking at the evolution of the of the the the peak </S3>
<S1> er there there was also calculation of the enthalpies </S1>
<S3> the enthalpies yes but what i mean is calibrate that to a full <S1> yeah yeah </S1> crystalline and have a a (real) figure and er also DMA would be very useful because you could look at (xx) the viscoelastic properties of of the materials looking at the storage models the loss models you could could even do tests inside solutions to have your sample inside the degradation solution and to look at what will happen as function of of the degradation that's a very nice method but my question is more about the weight loss i don't understand very well you didn't use er (thermometrical) analysis <S1> [no it was o-] </S1> [TG-A just] taking out the sample and </S3>
<S1> er the sample was heated er heated er between between some hours and and it was weighed bef- er between these [occasions] </S1>
<S3> [but why] was that you didn't have TG-A available or because TG-A you could do the [study as function of] </S3>
<S1> [yeah yeah] so it's more more easier to do that but unfortunately i didn't have have that available </S1>
<S3> moving now to to to the to the results , you have any other question on that (xx) </S3>
<S2> no i'm (xx) page four (xx) </S2>
<S3> (xx) yes this is my first comment that i told you in the general in the general comments that i think you have lots of problems with your graphs of the results and if you look page 14 is the first time this is figure eight and you are doing a graph like some guy that that some candidate that is taking an economics er degree or law school degree because the the distance between two and seven days is the same as between seven and 14 days or between 14 days and 28 days i don't think that is a an acceptable way of making graphs in a in a </S3>
<S1> but but on the other hand it makes clear it in the comparison [between] </S1>
<S3> [but but] you understand that you are not looking at the trend <S1> [yeah yeah of course] </S1> [and the real trend because that's] the of course the the time should be linear in this this is i i don't think if if i would be a referee of one of these graphs i would i would tell you to to change these graphs these graphs are not if you are making some some plot as function of time you of course you have to have to the the <S1> yeah </S1> [and you have many times this] </S3>
<S1> [but the but then you have the] the comparison message is quite quite clear according to this graph </S1>
<S3> yeah but for that don't do a graph like this do a bar graph or something that is not the problem is you are doing a a Y-X graph with the with the X completely out out of scale let's say so if you do a bar graph or something like that it would be okay but in something like this it's it's not okay because this is a number it's not <S1>  mhm </S1> it's not a <P:05> and moving to page er 15 , you you say and it was funny to see that there is no no need for pre-drying as as compared to to other works that even from from professor <NAME> that show that <S1> yeah er </S1> you need to make some drying and you you you (watch it) with that and i agree to the handling of of </S3>
<S1> i i i think there are differences also if you are talking about medical polymers <S3> yeah </S3> or or or this kind of bulk polymers er and according to the this the pre-drying was was not <S3> not needed </S3> needed </S1>
<S3> but you think in industry becau- it was not needed because you were controlling them handling very qui- er let's say your samples were already dry and because they were already dried there was no need for pre-drying you would agree with that </S3>
<S1> yes i agree and also i i think i also said in the in the in the paper one that the effect of pre-drying should not be , [(xx)] </S1>
<S3> [it's it's clear] you even say you even say that in this page 15 but but my question is is if you move this process to industry you think the handling will be the same or maybe we need to do the pre-drying </S3>
<S1> er w- well according to my test er also without pre-drying the adhesive er performed quite well </S1>
<S2> but er still on page er 14 and again still in in in the the figure but now in figure nine and er i make the same comment that i was a bit surprised there to see how different kinds of figures there are i mean dif- different formats and er i'm used to to er the system that you you report the parameter and the unit now you have only units here in in these figures and er have a look on on on figure nine it it er is ha- has has the text below it <READING ALOUD> changes in the elongation values  </READING ALOUD> well first of all @@ it's not changes it is it is some mega pascal values versus time and er another thing is that they are not elongations they are strengths , as are correctly mentioned in the article but here it's wrong </S2>
<S1> yeah that's an error </S1>
<SS> @@ </SS>
<S2> @yeah@ er okay that's formality but er then one should discuss a bit er of the behaviour of the samples er there you the these er these triangles th- sample three indicates er pretty dramatic increase er in in the in the strength with time and you in in the previous er on the previous page you you you state that slightly different polymer structure formed during the stabilisation process wha- what er that's not a scientific explanation it , any evidence of differences of the polymer structure and what kind of differences could they be </S2>
<S1> er in in figure er nine proves that er the the sample three er did not er did not erm degrade so rapidly as as the other other samples er . er in in page er 13 i'm <P:06> referring to the sample two which was the peroxide stabilised sample </S1>
<P:06>
<S2> and it if i it goes up first and then then it er comes down , er sample two </S2>
<S1> yeah because because er er the sample two was so brittle after after two weeks that there was no no strength values to be measured </S1>
<P:05>
<S2> but what kind of differences in polymer structure could be </S2>
<S1> er there are publications about this er peroxide modification and and er and er according to those publications there are differences for example it's er it's more amorph- amorphous <S2> (xx) </S2> polymer structure after peroxide modification </S1>
<S2> so you mean that the the reactions and er mod- er changes have occurred during the stabilisation process not with time </S2>
<S1> er i think the peroxide er stabilised sample behaved differently than than than the un- unstabilised er stabilised and end-capped samples </S1>
<S2> and and w- wha- what is the reason for changes in mechanical properties , finally </S2>
<S1> for peroxide stabilised samples </S1>
<S2> of for all of these </S2>
<S1> er so so the changes are are are because of the crystallisation of the samples , during time , and and the stabilised samples behaved differently than the unstabilised sample </S1>
<S2> okay . and this sample number . is it now one first sample it it goes down due to the i- it becomes very brittle , is is it so </S2>
<S1> yeah </S1>
<S2> one would have er er needed the information of er crystallinities somehow in this connection because if if you explain er this behaviour through post-crystallisation the the then of course that information would have been very essential in this connection </S2>
<S1> mhm , well like we discussed before that er it was also covered in paper three that er we we see clearly that there are differences in the crystallisation behaviour of of the different samples </S1>
<S2> what what what is the role of er , er water absorption to these er properties , with time </S2>
<S1> to which properties </S1>
<S2> mecha- er changes in in er mechanical properties may be well [(xx)] </S2>
<S1> [well of of course there] there are are differences because if the samples were in the this er hydrolysis solution so the mechanical strength went down er dramatically , fast </S1>
<S2> but do you assume that the the samples er absorbed water to the level of equilibrium </S2>
<S1> yeah i would say [so] </S1>
<S2> [how how] how how fast did that occur and and up to the what level </S2>
<S1> er that was not not studied </S1>
<S2> isn't well i would assume that it is very essential if you if you measure properties with time for example and or yeah . but it it did not er well come come to the research plans <S1> yeah no </S1> did did why not </S2>
<S1> @@ no er i i er tried to characterise with the with these these er these methods i have done done here and er </S1>
<S2> as easy as it would have been <S1> @@ </S1> to to to do and to my mind very essential </S2>
<S1> there are different methods [to to characterise] </S1>
<S2> [yeah well] yeah okay this @@ </S2>
<S3> moving to 16 and a general comment on on another statistical analysis and you don't have standard deviations in in any graph . and sometimes it's very difficult to see for instance this this graph that you have figure ten how many measurements you have for each one of these erm these figures that you have in the </S3>
<S1> mhm you mean the figure 10 </S1>
<S3> figure 10 like always </S3>
<S1> yeah yeah so <S3> just one measurement or </S3> it it was just one measurement like like like it was explained in the </S1>
<S3> mhm so it's </S3>
<S1> methods part </S1>
<S3> it's very difficult to say that if if we can really trust these figures and if when you say temperature is relevant and the other one are not relevant this this usually has to be based on more than one measurement and a statistical test to see if i don't know if 23 is very different from er the , 18 okay if 23,000 is very different from 19,000 <S1> mhm </S1> [(xx)] </S3>
<S1> [well well] let's say the basic information was was that er that er er this kind of hot melt adhesive has er can be applied with the existing equipment that er that er erm this er this erm , for example pre-drying conditions don't have <S3> (xx) </S3> so much effect </S1>
<S3> but why why higher temperature is so bad this they cannot be used with this er with this molecular weight </S3>
<S1> er let's say that it it differs of of those others and as as we know , from the other publication that higher temperature can be er very critical to this kind of adhesive , but of course we because of that reason we wanted to er process the hot melts as as well as possible </S1>
<S3> then in in figure 12 we have again of course the same problem that you have two hours four hours six hours and then 27 hours , but not speaking about that why you made all the weight loss at at 170 degrees and not at 160 degrees because it will make much more sense to use the same temperature prev- for much longer time </S3>
<S1> this this is this is a <S3> just to make it fast </S3> this is a standard for normal hot melt adhesives that er they are normally applied at 160 degrees but er just to be <S3> [fast] </S3> [because] there might be slight differences in the equipment er that's why the 170 degrees temperature is normally used to calculate weight loss </S1>
<S3> mhm okay and by looking at that graph how how can we comment these results is 24 per cent a big number 30 per cent is it a a big weight loss what what's the criteria for for saying that the , is there a figure that we can say we are going to say that this this er adhesive is not thermostable and this this one is <S1> er well </S1> so is 24 or 30 is it such a big degradation or not so important </S3>
<S1> when when you compare it to the reference sample er which has er three per cent weight loss after 24 hours of course it's very significant but but on on the other hand er er it is said in the text that er normally one or two hours processing [times are normal and and] </S1>
<S3> [yes that's not what i was going to say if you're] going to use one or two hours or in your case you you even <S1> yeah </S1> went to four hours in the last paper and <S1> yeah so s- </S1> so it's almost the same <S1> er </S1> for four hours or for two hours is almost the same for [(xx)] </S3>
<S1> [yeah yeah] and and er that was the message that er that within this normal time range ranges the these type of hot melts would be used in the application equipment </S1>
<S3> mhm </S3>
<S2> yes i , was a bit wondering this er this figure 10 still which is in in the first er publication on page 2 22 er be- because the rather leave out these very exact molecular weight values nobody believes that you have true values with the <S1> yeah </S1> five significant er figures </S2>
<S1> o- of course we discussed about these GPC values and and and it is so that they are [not very acc- accurate] </S1>
<S2> [they are not not at all] that er accurate but erm the er . another point is that the degradation . how do you understand er the mechanism of stabilisation in this connection the- the- there is end-capping possibility and there is free radical stabilisation how w- what is the mechanism of of these </S2>
<S1> mhm , there are publications to to how how to er modify the melt stability er with peroxides and and er mechanism with with that is is to to effect with the er catalyst residuals and [and] </S1>
<S2> [er er] . how how w- w- with those but how , in which sense what happens with the catalyst </S2>
<S1> er er . i i think it's er it's the deactivation of the catalyst residuals <S2> yeah </S2> and and er with the end-capping there are also also several publication where where it has been proven to be also suitable me- method for for increase the melt stability </S1>
<S2> mhm but on the other hand you you state here that er er degradation of er polymer chains was a random process how does it fit er with the the idea of er for example end- stabilisation through end-capping </S2>
<S1> mhm er , maybe it's also reason that when when when this degradation starts also the end-capped sample er untreated chains are formed the end-capped er is is not effecting anymore <S2> mhm yeah </S2> but in the beginning beginning yes </S1>
<S2> okay it's erm they are difficult er processes and and of course to understand er the mechanisms er would have needed er lots of analysis understand very well that you can't do everything in one work er one thing however i , a bit er question here is the straightforward er statement that er that you state that poly- er polydispersity values remained unchanged and then you use this as a , motivation to state that this was a random er degradation process , is it so in theory </S2>
<S1> mhm in which [which] </S1>
<S2> [that] random process leads to stable polydispersity here on pa- page 16 er the fi- last sentence of first chapter </S2>
<S1> mhm yes this was er based on the actual trial we we did it with the industrial line and and er and er , and er er i i would think so that in theory [that's it's true] </S1>
<S2> [but it's namely] if if you think that that well i- i- it's simply thought that if we have long chains and you truly have a random schism it er it's more more probable that the long chains are broken than the short ones and it leads to narrowed polydisperities so if it is ideal system then then i would say that that er this er er stable polydispersity is is not an indication of er of of random process . er you know in (polar) technology so-called er (xx) braking is based just on this principle and it is used er to er to to modify the polydispersity </S2>
<S1> yeah may- maybe it was not very proven comment that i made </S1>
<S2> okay yeah please . may- maybe one thing before you <S3> yeah </S3> could you please er . shortly comment why why was this erm thermal er , weight loss measurement done it er did i understand right it is a standard procedure for hot melt er <S1> yeah yeah </S1> testing for to to be sure that there are no evaporative components <S1> yeah </S1> okay </S2>
<S3> moving to page 21 this paragraph that you have , it's when you are measuring adhesion is always a problem for any for any type of systems because you are measuring very small values let's say you are working with things like 0.4 up to 1.4 mega pascal , yeah so it's it's very important for us to to understand again if this is statistical relevant how many measurements you you did for this and what was the why you didn't use again standard deviation but also what was the the load cell that you used on the on the (xx) machine and why it's it's very difficult to for for us to understand if really a difference of 0.1 mega pascal is relevant or not what was the the load cell in the in the machine because that to my knowledge is not is not <S1> mhm yeah </S1> written here in any place and it's completely different to use a load cell of 50 kilo miltons or five kilo miltons or one kilo mil- </S3>
<S1> yeah if it is not stated in the publications i i cannot recall that but it was chosen [according to (xx)] </S1>
<S3> [it was small (xx)] </S3>
<S1> it it was small loading cell </S1>
<S3> and how many measurements for this </S3>
<S1> er there are five measurements </S1>
<S3> and so why you don't use standard deviation in these and try to use some statistics to say if this is different or not statistically significant </S3>
<S1> mhm er i i think the difference is quite quite clear anyhow in those those pictures and and a- </S1>
<S3> well from one from one B and three B to two B and four B but if it is from two B to four B i'm not sure from one B to three B </S3>
<S1> er yes they are not er not er significant differences i i i think the message was that er that er also the failure type was judged and and er it was clearly seen that that er er with DL DL type er of of polymer the adhesive failure happened within the adhesives so not or or the let's say cohesive failure <S3> failure </S3> in the in the adhesive so not not in the er material , er as it it er happened in the er lactic acid based formulation </S1>
<S2> mhm yes i i'm looking still er pa- page 19 as a minory comment i i i just have to say that the please use either decimal po- points or or other (xx) . points in in english language you have used er two different er co- systems in in on the same page and in in a dissertation is not acceptable but er on the next page page 20 you state that er <READING ALOUD> peroxide stabilisation had a negative effect on adhesion probably due to cross-links or en- entanglements formed during the stabilisation process </READING ALOUD> this is well rather loose statement er what what what what kind of structures and and by through which er reactions they they would occur and did you get any direct evidence of these </S2>
<S1> er it it was er surprising that the the adhesion rate with the peroxide modified sample er was was worse than than with the other samples er , this comment is is is maybe one one reason for for this but er i cannot er prove that very accurately er but anyhow the the , er reason to go on was was was to choose the end-capped and unstabilised sample , but er as as you know the peroxide stabilisation might have er many effects to the [structure] </S1>
<S2> [yeah] i agree more or less on on on on that but er how how do en- entanglements er reduce adhesion </S2>
<S1> mhm er maybe it was er thought that that the point that er that er er cohe- cohesive strength of the adhesive er went went up but er er on the other hand i know also that er that er with this kind of a peroxide content the those cross-links are not very likely to happen </S1>
<S2> (well) it remains a bit er well speculative er statement and and in a scientific er connection it er well creates more questions than than makes things clear er on page 21 er you state that er . the the last sentence i i'm looking at the the that the there is a loss of amorphous phase er . you you refer to . post-crystallisation </S2>
<S1> mhm er y- yes yes so so because the or or so the partially degraded amorphous regions <S2> yeah </S2> were crystallising </S1>
<S2> okay well if you have </S2>
<S3> it was briefly mentioned before the (section) (xx) in in er in page 22 you are looking at changes in crystallinity when you have the the end-capped sample at room and and low temperature yeah and i think it would it would be much better if you put as they are side by side the same scale for both otherwise again you you are losing on the compar- on the comparison because if you go to to the paper , you have something like like a heat flow of ten in one and heat flow of 14 on the other so if you want to show that something is bigger if you put the same scale it will help a lot to show that the (xx) peak has increased in , you understand what [i mean as the graphs are side by side it will make much more much more sense] </S3>
<S1> [mhm er yeah yeah but er but er i i] i think the the me- message was that the it had the er crystallisation peak </S1>
<S3> yeah but that that's what i'm saying to compare the crystallisation peaks <S1> yeah </S1> it would it would help and in the in the second graph what is that peak that you have at about 70 degrees C </S3>
<S1> so that is the crystallisation peak </S1>
<S3> this one </S3>
<S1> yeah and and the other is </S1>
<S3> [and this is and the other one] is the melting </S3>
<S1> [(xx)] yeah </S1>
<S3> so by looking at this at the beginning you would say that there is no no no crystallisation whatsoever at room temperature or not <S1> mhm </S1> because that's confusing <S1> [er so] </S1> [what you] what you are you are saying </S3>
<S1> okay so the the reason for this comparison w- was that the sample was storage at room temperature and after this storage the sample had crystallised so that it er was fully crystallised but when the sample was er kept at low temperatures er it was er minus 18 degrees so so it was not fully crystallised <S3> okay </S3> so they were o- only storage conditions </S1>
<P:08>
<S3> then on on page 25 <P:08> you say by the end that <READING ALOUD> the densile properties were lost more rapidly than expected  </READING ALOUD> so it's always a problem when when we make this type of sentences because what was expected what were you expecting <S1> er well @@ </S1> 50 per cent deduction 80 per cent deduction 90 per cent @@ </S3>
<S1> well well the expected er expected values were that er that er we were getting measurements after several days or let's say several hours but but er er these these samples er . degraded so rapidly that the the tensiles va- values were lost after [30 minutes] </S1>
<S3> [but you were not] expecting that or why you were [not expecting] </S3>
<S1> [no i i i] wasn't expecting </S1>
<S3> so much </S3>
<S1> that that much </S1>
<S3> er and regarding the hydrolysis again i i would like to have seen something like doing in a in a in a basic PH to have an idea what happens to the materials at PH-10 and also the effect of (xx) because you speak on one of the papers <S1> mhm yeah </S1> on this autocatalytic degradation and you don- you know that can change completely the (xx) on on </S3>
<S1> yeah yeah i i i think according er to these studies the degradation in the repulping conditions or let's say full degradation in the repulping conditions is is not not proven so so there must be be more more tests to to be done </S1>
<S2> yes i i still @@ stick to the figure 18 er er did i understand right that the the B curve there is a single measurement </S2>
<S1> yeah </S1>
<S2> where you have the melting , peak is a bit yeah and and this is the- then you come down with temperature and you you you receive the the the er (expected) </S2>
<S1> no it was er in the first run </S1>
<S2> first run and what is the what was the small peak downwards </S2>
<S1> so it was the crystallisation peak </S1>
<S2> at that temperature <S1> yeah </S1> okay , you you don't see TG indications in in these </S2>
<S1> no no not not in these so TG was was er judged er after after cooling and and then heating in the second run </S1>
<S2> okay <P:06> i come back still to maybe to the first question of the of the features of an ideal hot melt adhesive , and and i have in my mind er the rheological long term properties of these hot melts did you is it is it expectable and did you see cold drawing of the adhesive layer </S2>
<S1> no i i i don't think the rheological characteristics er of of er hot melts are are so important because because the applications conditions they differ significantly from the er for example from the extrusion coating process so there are not not so high (shear) forces involved in the hot melt application process </S1>
<S2> e- e- even not in er at higher temperatures </S2>
<S1> er as as long as as we concentrate with this normal temperatures <S2>  yeah </S2> hot melts are applied </S1>
<S2> yeah but do you need er . because this property to to my mind i- i- is dependent on crystallinity and on the on the er degree of crystallinity and and . what is your opinion based on these results do you need certain minimum crystallinity in your er successful hot melts </S2>
<S1> yeah yeah because i i think the the hot tack and and and the strength values are are are better </S1>
<S2> strength values er based on cohesive failure or adhesive failure </S2>
<S1> er ba- based based er that the strength value of the adhesive must exceed the er cohesive value of the of the packaging material and er adhesion failure happens when when the adhesive layer er separates from the from the material </S1>
<S2> okay is that the reason why . er (xx) polylactide is is not successful [as you mentioned already] </S2>
<S1> [yeah that that that that was] that was the reason because lack lack of er crystallinity in those polymers </S1>
<S2> on page 24 er , there is a , again a loose statement er in the er second line in chapter 4.4 is you state that that apparently due to crystallisation er did did you measure the crystallisation <S1>  er </S1> or changes in the crystallinity </S2>
<S1> the enthalpy changes were measured in the [(xx)] </S1>
<S2> [how] how much did er did er crystallinity increase roughly </S2>
<S1> er in it was in paper paper two so the er changing er table two so the changing of the me- melting enthalpy during the hydrolysis </S1>
<S2> and i- i- i- i- your opinion i- is er or or w- what is your opinion is it er is the crystallisation based on true post-crystallisation under hydrolytic conditions or is it based on the increased fraction of crystalline phase due to er (xx) of amorphous phase </S2>
<S1> mhm i i i think the er reason for crystallinity or the increase of crystallinity was that the the amorphous phase was lost and and and also the er amorphous phase was able to re-crystallise during the degradation </S1>
<S2> er did you in this connections now measure the the the water absorption in in hy- in connection to hydrolysis measurements </S2>
<S1> er in hydrolysis er the weight loss and and of the sample was was measured </S1>
<S2> yeah but er but of course the sam- <S1> no no </S1> yeah because that that would have to my mind would have been rather interesting </S2>
<S1> er about the statement er which er which you referred at the beginning was was that er that was based only on the visual judgement of the samples </S1>
<S2> yeah maybe now you have to keep in in in in the mind that er caprolactone as a component is er pretty hydrophobic so it it it not only er brings certain crystallinity and er slower degradation rate et cetera but it also brings with it er certain hydrophobicity maybe not maybe these er concentrations are rather low for through hydrophobicity but but to my mind that now that is an interesting property and possibility for caprolactone and and er now you have had only one composition in case you would have changed the composition and then er studied more thoroughly these er phenomena even the hy- rate of hydrolysis you have i'm sure you have er would have er seen pretty interesting er correlations , but okay it's not done in in this this work , maybe if you wish you continue </S2>
<S3> and then page 26 . you forgot to put all the that i mentioned bars in the in the S-E-M pictures in the in this part you have that in the papers but you don't have it in these ones that's important because you don't have any idea on the magnification well you know the magnification is 150 times [but you don't know (the dimension)] </S3>
<S1> [yeah yeah that's true the scale basis] are are missing missing in in </S1>
<S3> they are in the paper so you can go to the paper but they should also be here and that it a question that i didn't ask before is about why you didn't try to do the the hydrolysis test at at 60 degrees instead of the 43 <S1> yeah </S1> because i would go to the maximum temperature let's say that the the materials will (stand) </S3>
<S1> yeah but er </S1>
<S3> also because of the TG of the polymers and to have to to have a look on what will be the difference that you get if you do that at 60 </S3>
<S1> of course the TG of the polymers was very very low er but but er but er as we discussed before the actual er repulping conditions they vary a lot so so they are between 20 to 60 degrees so the 40 er 3 degrees might be good good starting point also </S1>
<S3> okay and in the next page you have again one of these sentences that is difficult in the second in the second section you say <READING ALOUD> the glue lines from cardboard pieces had disappeared </READING ALOUD> that that was by looking or </S3>
<S1> yeah that was only by by [visual examination] </S1>
<S3> [but you should] maybe state that that was just an observation or something because one one sentence like that [is always] </S3>
<S1> [yeah i i thought] it was quite clear <S3> @@ </S3> but maybe not </S1>
<S3> and er the in the last in the last er the the sentence before last you speak about the enzymatic activity in the compost and again is very important that you have enzymatic activity in the compost and it would be very important to understand if the degradation of these of these materials in there will not in some way interact with the enzymatic activity because then not only we don't have these materials being degraded but maybe nothing is being degraded as er as it should be because we just add some adhesive in the </S3>
<S1> i i think the it was little surprising that in the compost en- environment er the the end-capped sample which have be- been most stable in the in the other conditions so so it degraded faster but i i think the biggest reason for that was was that the conditions of the compost are anyhow er always uncontrolled so there might be <S3> mhm yeah </S3> unknown factors to that </S1>
<S2> yeah i i was looking er the same er feature in this report you rather straightforward refer to enzymatic degradation one have ha- has to keep in mind that er there is usually very (xx) conditions as well so it's not only <S1> mhm </S1> enzymes that function there </S2>
<S1> yeah but the statement was based on on on on that that er erm maybe speculating the reasons for for the faster degradation of the end-capped sample </S1>
<S2> yeah okay in some other connections we have seen pretty fast enzymatic degradation of er some er polyesters so it is truly interesting er field and and there are possibilities to to to get er i mean controlled er degradation through enzymes when you when you wish the polymer to be degraded </S2>
<S1> mhm but but in the in the compost environment i i think er er in in in this er test there w- were unknown factors that that er cannot be explained </S1>
<S2> in fact i was a bit er missing er references to or in in in at least some comments in the text er on the truly standardised and er and and controlled er degradation tests because the the there are laboratories <S1> yeah </S1> that have developed <S1> yeah </S1> these tests and they they would be the means to to get an idea of true microbiological er degradation or even truly enzymatic er [degradation] </S2>
<S1> [mhm but] i i i think it was also interesting to know that er how how these samples actually er behave in the in the let's say no- normal municipal compost </S1>
<S2> for sure but but now this remains as more or less as er a demonstration <S1> mhm </S1> and and and if if one would truly like to do more deeper and scientific research on this then then definitely he would er would would end up to this er controlled er degradation </S2>
<S1> yeah but i i think the one of the aims of these demonstrations was to show that that er these adhesives degrade very rapidly when you you also see see from the samples that still the er cardboard part was was left after [adhesive is (gone)] </S1>
<S2> [one one] demonstration , could also have been done and it is , some proof of acceptable eco-toxicological properties w- can you comment th- that </S2>
<S1> er i would er think that er this this components which are quite well known that er there are no problems in that that way but er er on the other hand it was not considered in in this work </S1>
<S2> for example erm if i remember right you used er ten octane <S1> yeah  </S1> in a concentration of 0.1 er weight percentage for (xx) <S1> yeah that is </S1> it's quite much it's it's by far more than is the customary in in biomedical (upgrades) <S1> mhm </S1> but er , in our own research we have seen er some er surprises in in eco-toxicological tests and er but er i agree , one could think that these are very well behaving and and acceptable components as such but i suggest that , some sort of testing is done in in that regard . well any other @@ comments [from our side] </S2>
<S3> [last last last] last comments yeah on on the conclusions page you you comment a bit that there will be an decrease in the impact strength for increased crystallisation of that's what that's what (you are) everybody would expect but maybe it would have been good for this to test er adhesives also in impact impact conditions just to make two or three tests and to have an idea if that is really the case what happens to the materials <S1> mhm </S1> when they are , what do you think of that </S3>
<S1> yeah also the ela- elasticity or or the (xx) values </S1>
<S3> but but on dynamic and only [impact conditions because it's different from (xx)] </S3>
<S1> [yeah yeah i i] think i have also stated that somewhere </S1>
<S3> yeah that's @@ important that and then on on conclusion two , i i don't seem to have demonstrated that these er hot melt adhesives will cause no problems in the physical environment for this kind of package what you prove this they will degrade on those conditions <S1> mhm but the </S1> there is no proof that , you understand my comment </S3>
<S1> yeah er like like er we discussed before i i said that it is not not proven but on the on the other hand er er it was proven that er these kind of adhesives will not er er retain these kind of sticky residuals because they they tend to form very hard (portal) structure in the hydrolysis </S1>
<S3> yeah okay so that's it's more in that sense and you you also conclude the last conclusion that you could use standard equipment for using this er adhesives and this is very good but if you have to design a system now yourself to use these these materials let's say you will make changes from the standard industrial , <S1> er </S1> do you think if if somebody starts a factory and wants to use these adhesives you will make the machines like they are now or there will be some some difference in the </S3>
<S1> of course it it would be maybe interesting to to see what er er what er this kind of extrusion type of equipment where you get very fast changing of the adhesive er might be good for this kind of er adhesives but on on the other hand it's very very big advantage that er it can be used as such in the existing equipment </S1>
<S3> mhm okay </S3>
<S2> er you end with questions yeah i see yeah okay maybe we , come come to the last metres of of the questions but er . i'm looking on still on paper what is this now four it must be the one we already have spoken about and from my side i i find er er just this paper pretty interesting although it's different from the others because it er tries to and discusses the the the structures and correlations there is in table two of the parameter yield used how do you define yield in this case , it's attachment on on of of the </S2>
<P:11>
<S1> mhm , er in in this paper like er like i told you i have done the adhesive part er part of of </S1>
<S2> so it's er <NAME> and others who have done [(xx) yeah] </S2>
<S1> [er <NAME> <NAME> has done the synthesis] er at the moment i cannot explain </S1>
<S2> well i yeah okay . i understand it's it reflects er if if i understand correctly that that is my point the the fraction of er of the oligomers connected to caprolactone </S2>
<S1> erm it might be , i cannot recall if that was [explained in the text] </S1>
<S2> [yeah because it's it's pretty] important to to to know and understand the . since the values are pretty low and and then then of course it reflects er heterogeneous nature of the of the samples <S1> mhm </S1> but er okay maybe my final er specific comment or well no it is general comment is i that i have to say regarding the last attached paper is that this paper is very general it is of course a demonstration of of er successful formulation in an industrial process and of course from that po- perspective it is valuable but it is it is not er in a way it's not not a scientific paper er as as i'm used to see in dissertations </S2>
<S1> mhm er i agree that it was very important to to to develop and actually prove that this kind of hot melt will also perform in in the industrial conditions </S1>
<S2> yeah but it is only one run if i understand </S2>
<S1> it is only one run but er er of course with this kind of polymers it's not very easy to make make very thorough [experience] </S1>
<S2> [of course that's right yeah] <P:07> from my point i . we could discuss of many details for for hours and hours but maybe we have together now covered er the main and most important er er points in this dissertation and er i would like to make the the the final statement from the opponents' side . er <READING ALOUD> the dissertation of <NAME S1> lactic acid based hot melt adhesives preparation and er properties er deals with one of the er central research and development areas in polymer science and technology namely the development of environmentally degradable polymers and products based on renewable crude materials , er in this case the work has focused on the synthesis of lactic acid based polymers and their use in large scale applications like in packaging materials , the dissertation is a bundle type of its composition consisting of 30 page summary and five attached publications the candidate has been in central role in producing the scientific contents of the joint publications and he is the first author in four of them all the attached publications as already mentioned have passed the referee criticism . the first publication reports studies on properties and er stability of lactic acid based polymers for hot melt applications er the publication is rather limited in it's er scientific contents but the results are are logical and er well presented , the second article reports more deeply on the hydrolytic er decomposition and degradation in composting conditions er properties in industrial polymer samples have been studied and reported , molecular weight measurements electro-microscopy and (xx) preparation chromatography have er been the most important er structure property corr- er er important er methods , er str- structure property correlation to some extent but more wide sets of samples and deeper insight in to the basic phenomena would have been er welcomed erm in a work intended to be a part of a doctoral dissertation er the publication number three investigates the applications la- lactic acid based hot melts erm adhesion properties and er storage stabilities have been researched in packaging applications erm m- mainly based on thermo analysis and molecular weight measurements conclusions are drawn er er re- regarding the er changes of different er kinds of samples er adhesion has been tested and fracture mechanisms reported er based on qualita- qualitative and er erm . analysis and and same microscopy publication number four reports the behaviour of lactide caprolactone copolymers er and blends of polylactides in hot melt applications the polymer synthesis has been carried out by specialists in <FOREIGN> åbo akademi </FOREIGN> and the application oriented research has been carried out by the candidate erm er of course as we have a lot discussed an interesting feature is the er controlled and branched structure of of the copolymers , the fifth er appended publication reports the behaviour of a lactic acid based hot melt formulation in an industrial lamination process er the article er although it has passed the referee system of a journal is apparently based only on one experimental run thus one could question the scientific er relevance of the article as part of a scientific differtai- dissertation er although of course the the value of the article lies in the fact that it demonstrates er the technical and industrial relevance of the research and the the developed er formulation , as a whole we can summarise that the dissertation of er <NAME S1> is well organised er clearly reported and written all its parts connect well together er forming a good evolutionary research approach leading to an industrially significant result er at the end , er scientifically one er could state that the research could have been more to- er thorough in several details especially regarding structure property correlations and and structural analysis er we have a pleasure to congratulate the candidate for selecting a highly interesting topic guiding the research in a good manner to a significant result and er also we congratulate the of the performance today er thus we are glad to recommend that the dissertation will be accepted </READING ALOUD> </S2>
<S1> <READING ALOUD> er i thank the opponents professor <NAME S2> professor <NAME S3> for for your comments and criticism if anyone in the audience has a question please request the <FOREIGN> kustos </FOREIGN> permission to speak </READING ALOUD> </S1>
