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The Influence of Carboxylic Acid in Packaging Materials

Mattisson, Jonas LU (2016) KTE720 20161
Centre for Analysis and Synthesis
Abstract
Tetra Pak delivers food packing services world-wide and uses multilayer packaging materials to protect the food product from being affected by the environment. Loss of adhesion between the polymer and the aluminium layer in Tetra Paks packaging materials has proven to be a serious problem casing the package to lose its integrity and the food product to spoil. The problem is relatively unstudied but has shown to be connected to fatty and acidic products indicating a connection to the presence of carboxylic acids.
This master thesis was conducted to identify the core mechanism of the delamination phenomenon and to create a base from which further studies can be conducted. Two basic hypothesis were provided by Tetra Pak for further study... (More)
Tetra Pak delivers food packing services world-wide and uses multilayer packaging materials to protect the food product from being affected by the environment. Loss of adhesion between the polymer and the aluminium layer in Tetra Paks packaging materials has proven to be a serious problem casing the package to lose its integrity and the food product to spoil. The problem is relatively unstudied but has shown to be connected to fatty and acidic products indicating a connection to the presence of carboxylic acids.
This master thesis was conducted to identify the core mechanism of the delamination phenomenon and to create a base from which further studies can be conducted. Two basic hypothesis were provided by Tetra Pak for further study and evaluation. One is connected to the surface chemistry of the interface and the other is connected to changes in the mechanical properties of the polymers at the interface.
A literature study was conducted and the work was delimited to the most basic carboxylic acid; acetic acid as well as the most commonly used polymer; low density polyethylene. The study indicated a connection between the presence of water and the delamination phenomena in agreement with the aluminium-water system.
Three experiments where performed using two similar packaging materials produced at different times. These were exposed to food simulants containing different amounts of water to study the impact this would have on the delamination. The different experiments were then analysed using various methods to determine the mode of failure and connect these to the hypothesis.
Results from peel testing showed a greater, or at least faster, loss in adhesion for the packaging materials that were exposed to food stimulants with high concentration of water. The FTIR measurements revealed interesting results for the simulant with average concentration of water showing a thin layer of polymer on the al surface at the highest peel force. This correlates with the hypothesis that the mechanics of the polymer would have changed. The FTIR measurements at the lowest peel force for the simulant with highest concentration of water however showed lower amounts of LDPE, supporting the theory that the delamination is due to surface chemistry. The FTIR findings were further supported by microscopic surface studies which showed a clearer fracture surface with less LDPE for the delaminated samples.
The conclusion of this thesis shows that the setup used behaves according to the mechanism of the Al-water system which was strongly indicated by the formation of hydrogen gas and the lacking amount of polymer on the aluminium surface. The Al-water system in turn correlates with the hypothesis provided by Tetra Pak that the delamination phenomenon is due to surface chemistry. (Less)
Popular Abstract (Swedish)
Inte hur förpackningen påverkar din mat, utan hur din mat påverkar förpackningen.
Resultatet av detta arbete kan komma att ligga till grund för miljövänligare förpackningar som ger maten längre hållbarhet och förbättrar möjligheterna för att transportera mat över hela världen. Tetra Pak har länge arbetat med att leverera ett smartare och miljövänligare sätt att förpacka mat med sina pappförpackningar. I själva verket är det inte en simpel pappförpackning som skyddar maten utan ett flertal lager av plaster, lim och aluminiumfolie som alla har sin skyddande egenskap. Plast består av långa kedjor av atomer - man kan föreställa sig dem som en massa kokta spagetti.
I dagens samhälle blir vi allt noggrannare med vad vi får i oss och vad som... (More)
Inte hur förpackningen påverkar din mat, utan hur din mat påverkar förpackningen.
Resultatet av detta arbete kan komma att ligga till grund för miljövänligare förpackningar som ger maten längre hållbarhet och förbättrar möjligheterna för att transportera mat över hela världen. Tetra Pak har länge arbetat med att leverera ett smartare och miljövänligare sätt att förpacka mat med sina pappförpackningar. I själva verket är det inte en simpel pappförpackning som skyddar maten utan ett flertal lager av plaster, lim och aluminiumfolie som alla har sin skyddande egenskap. Plast består av långa kedjor av atomer - man kan föreställa sig dem som en massa kokta spagetti.
I dagens samhälle blir vi allt noggrannare med vad vi får i oss och vad som kan lossna från förpackningar och köksredskap och hamna i vår mat. Men något som många inte tänker på är hur maten kan påverka förpackningen. Denna studie undersökte ett sådant problem där mat innehållande fettsyror såsom ättiksyra, smörsyra och mjölksyra, efter en längre tid visar sig påverka förpackningen så att dess skydd bryts ned och hållbarheten på maten försämras.
Det finns två hypoteser för hur man tror att fettsyror i maten bryter sammanfogningen mellan plastlagret närmast maten och det aluminiumlager som ligger närmare förpackningens utsida. Den första hypotesen är att fettsyrorna från maten tränger in mellan kolkedjorna i plastlagret, och när de når limmet som håller fast plasten i aluminiumfolien lossnar detta och fettsyrorna hamnar mellan plastlagret och aluminiumfolien, lite som hur tomatsås lägger sig i botten av tallriken och skjuter undan spagettin som annars klibbar fast i porslinet. Den andra hypotesen är att man tänker sig att kolkedjorna i plasten ligger intrasslade med varandra likt nykokt spagetti. När fettsyror tränger sig mellan kedjorna blir där ett halt glidlager likt när man häller olja på spagettin för att denna inte skall klibba. På samma sätt som spagettin, glider då kedjorna mot varandra och håller inte längre ihop lika bra, och plastlagret förstörs men lämnar kvar en mycket tunn film på aluminiumfolien.
Genom att lagra lågt koncentrerad ättiksyra i kuvert gjorda av ett av Tetra Paks material kunde ättiksyrans påverkan på materialet över tid undersökas med en rad olika tester som bland annat mätte den kraft det krävdes för att separera plastlagret från aluminiumfolien och även undersöka vad för ämnen som bildats på de båda ytorna.
Slutsatsen var att det i detta fall var den första hypotesen som orsakade mest skada på förpackningen. Detta bevisades delvis av att då plastlagret lossnat kom aluminiumfolien i kontakt med vattnet i den utspädda ättiksyran och det började bildas vätgas, som i sin tur fick kuverten att börja svälla upp. Detta skulle inte kunna ha skett om där var kvar en plast film som i den andra hypotesen. (Less)
Please use this url to cite or link to this publication:
author
Mattisson, Jonas LU
supervisor
organization
course
KTE720 20161
year
type
H2 - Master's Degree (Two Years)
subject
keywords
food packing, Packaging Material, Carboxylic Acid, delamination, adhesion, polymer technology, polymerteknologi
language
English
id
8895445
date added to LUP
2016-12-13 11:16:55
date last changed
2016-12-13 11:16:55
@misc{8895445,
  abstract     = {Tetra Pak delivers food packing services world-wide and uses multilayer packaging materials to protect the food product from being affected by the environment. Loss of adhesion between the polymer and the aluminium layer in Tetra Paks packaging materials has proven to be a serious problem casing the package to lose its integrity and the food product to spoil. The problem is relatively unstudied but has shown to be connected to fatty and acidic products indicating a connection to the presence of carboxylic acids. 
This master thesis was conducted to identify the core mechanism of the delamination phenomenon and to create a base from which further studies can be conducted. Two basic hypothesis were provided by Tetra Pak for further study and evaluation. One is connected to the surface chemistry of the interface and the other is connected to changes in the mechanical properties of the polymers at the interface. 
A literature study was conducted and the work was delimited to the most basic carboxylic acid; acetic acid as well as the most commonly used polymer; low density polyethylene. The study indicated a connection between the presence of water and the delamination phenomena in agreement with the aluminium-water system. 
Three experiments where performed using two similar packaging materials produced at different times. These were exposed to food simulants containing different amounts of water to study the impact this would have on the delamination. The different experiments were then analysed using various methods to determine the mode of failure and connect these to the hypothesis. 
Results from peel testing showed a greater, or at least faster, loss in adhesion for the packaging materials that were exposed to food stimulants with high concentration of water. The FTIR measurements revealed interesting results for the simulant with average concentration of water showing a thin layer of polymer on the al surface at the highest peel force. This correlates with the hypothesis that the mechanics of the polymer would have changed. The FTIR measurements at the lowest peel force for the simulant with highest concentration of water however showed lower amounts of LDPE, supporting the theory that the delamination is due to surface chemistry. The FTIR findings were further supported by microscopic surface studies which showed a clearer fracture surface with less LDPE for the delaminated samples. 
The conclusion of this thesis shows that the setup used behaves according to the mechanism of the Al-water system which was strongly indicated by the formation of hydrogen gas and the lacking amount of polymer on the aluminium surface. The Al-water system in turn correlates with the hypothesis provided by Tetra Pak that the delamination phenomenon is due to surface chemistry.},
  author       = {Mattisson, Jonas},
  keyword      = {food packing,Packaging Material,Carboxylic Acid,delamination,adhesion,polymer technology,polymerteknologi},
  language     = {eng},
  note         = {Student Paper},
  title        = {The Influence of Carboxylic Acid in Packaging Materials},
  year         = {2016},
}