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Influence of polymer thickness, adhesive composition and layer structure on dielectric breakdown in laminated carton based packages

Brofelth, Malin LU and Alskär, Moa LU (2013) MTT920 20131
Packaging Logistics
Abstract
High voltage test equipment is used to measure the dielectric breakdown of polymeric material in order to detect defects in laminated carton based packages. The departments New Material Design and Applied Material Design at Tetra Pak in Lund wanted to understand how structural differences in polymeric material influence the dielectric breakdown of the material. The structural differences investigated were thickness, adhesive composition and polymeric layer structure. The master thesis was done in collaboration with Tetra Pak and the department of Packaging Logistics at Faculty of Engineering at Lund University, LTH.
The measurements were performed on the polymeric inside of laminated carton based packages. Since polymeric materials are... (More)
High voltage test equipment is used to measure the dielectric breakdown of polymeric material in order to detect defects in laminated carton based packages. The departments New Material Design and Applied Material Design at Tetra Pak in Lund wanted to understand how structural differences in polymeric material influence the dielectric breakdown of the material. The structural differences investigated were thickness, adhesive composition and polymeric layer structure. The master thesis was done in collaboration with Tetra Pak and the department of Packaging Logistics at Faculty of Engineering at Lund University, LTH.
The measurements were performed on the polymeric inside of laminated carton based packages. Since polymeric materials are dielectrics they are poor electric conductors. The high voltage test equipment used applies an electrical field to the material tested and the voltage is ramped up until the material cannot withstand the applied field and dielectric breakdown of the material occurs. The dielectric breakdown will start in weak points of the material, such as pores and cracks, where a lower voltage is required.
To examine the correlation between dielectric breakdown and thickness, the thickness of the polymeric inside of the material needed to be determined. The polymeric inside of the commercial laminated carton based package has thickness variation. It is therefore difficult to determine the polymer thickness in an exact and reproducible way where the dielectric breakdown of the material was measured. Since the high voltage tests are destructive it is not possible to measure the thickness afterwards.
To determine a correlation between material thickness and dielectric breakdown measurements were done on specially extruded material with varying thickness. Measurements were also done on material where depressions were created to give thickness variation and to control the position of the dielectric breakdown measurements. By measuring on material consisting of adhesive with different amount of polar groups but with the same thickness a correlation with dielectric breakdown was studied. At last the dielectric breakdown for material with different layer structures but with the same thickness was also investigated.
When performing measurements with the high voltage test equipment, problems with the hard- and software occurred. It was also difficult to isolate the test area properly. The conclusion of the method development was to move the computer and logger as far away from the test chamber as possible. Teflon tape was used to isolate the test area. Due to surface roughness of the material the use of a plate electrode with smaller diameter lowered the probability of measuring holes and major weaknesses in the material.
From the performed quantitative study a linear trend between dielectric breakdown and material thickness could be seen. No significant difference between materials with different amount of polar groups in the adhesive could be determined. From the measurements on materials with layer structural differences no significant difference in dielectric breakdown could be concluded. More measurements on materials with different layer structure and polymer composition are needed to draw conclusions on their impact on the dielectric breakdown. To compare the effect of different amount of polar groups in the adhesive, specially extruded material with lower amount of polar groups in the adhesive needs to be manufactured and measured. In order to determine the correlation between dielectric breakdown and thickness, more measurements on material where depressions have been created are needed. (Less)
Abstract (Swedish)
Ett högspänningsinstrument används för att mäta den dielektriska nedbrytningen av polymera material i syfte att hitta defekter i laminerade kartongförpackningar. Avdelningarna New Material Design och Applied Material Design vid Tetra Pak i Lund ville få förståelse för hur strukturella skillnader i polymera material påverkar materialens dielektriska nedbrytning. De strukturella skillnader som undersöktes var lagertjocklek, klisterlagersammansättning och den polymera lagerstrukturen. Examensarbetet gjordes i samarbete med Tetra Pak och avdelningen för Förpackningslogistik vid Lunds Tekniska Högskola.
Mätningarna utfördes på den polymera insidan av laminerade kartongförpackningar. Eftersom polymera material är dielektriska så har de dålig... (More)
Ett högspänningsinstrument används för att mäta den dielektriska nedbrytningen av polymera material i syfte att hitta defekter i laminerade kartongförpackningar. Avdelningarna New Material Design och Applied Material Design vid Tetra Pak i Lund ville få förståelse för hur strukturella skillnader i polymera material påverkar materialens dielektriska nedbrytning. De strukturella skillnader som undersöktes var lagertjocklek, klisterlagersammansättning och den polymera lagerstrukturen. Examensarbetet gjordes i samarbete med Tetra Pak och avdelningen för Förpackningslogistik vid Lunds Tekniska Högskola.
Mätningarna utfördes på den polymera insidan av laminerade kartongförpackningar. Eftersom polymera material är dielektriska så har de dålig elektrisk ledningsförmåga. Under försöken användes ett högspänningsinstrument där spänningen höjdes tills materialet förlorade sin isolerande egenskap, detta kallas för dielektrisk nedbrytning. Eftersom det krävs lägre spänning om materialet har en svaghet kommer mätningen av den dielektriska nedbrytningen alltid ske i den svagaste punkten.
För att undersöka korrelation mellan dielektrisk nedbrytning och tjocklek behövdes tjockleken av materialets polymera insida bestämmas. Den polymera insidan av de kommersiella materialen har en tjockleksvariation. Detta gör att det är svårt att på ett exakt och reproducerbart sätt bestämma polymertjockleken där den dielektriska nedbrytningen av materialet mättes. Då mätningar med högspänningsinstrumentet är destruktiva går det inte att mäta tjockleken i efterhand.
För att bestämma ett samband mellan materialtjocklek och dielektrisk nedbrytning mättes specialextruderat material med varierande tjocklek. Mätningar gjordes även på material där fördjupningar skapats för att få tjockleksvariation och styra var den dielektriska nedbrytningen mättes. Genom att mäta på material med klisterlager innehållande olika mängd polära grupper men med samma tjocklek kunde ett samband med dielektrisk nedbrytning undersökas. Slutligen studerades även den dielektriska nedbrytningen hos material med olika typer av lagerstruktur men samma tjocklek.
När mätningar gjordes med högspänningsinstrumentet uppstod problem med hård- och mjukvaran. Det var dessutom svårt att isolera testområdet ordentligt. Därför utfördes en metodutveckling där slutsatsen blev att flytta datorn och loggaren så långt bort som möjligt från testkammaren. För att isolera testområdet användes teflontejp. Genom att använda en plattelektrod med mindre diameter minskades sannolikheten att mäta hål och större svagheter i materialet.
Från den kvantitativa studien kunde en linjär trend mellan dielektrisk nedbrytning och materialtjocklek påvisas. Ingen signifikant skillnad i dielektrisk nedbrytning kunde konstateras mellan material innehållande klisterlager med olika mängd polära grupper. Inte heller mellan material med olika lagerstruktur kunde någon signifikant skillnad påvisas. Fler mätningar på material med olika lagerstruktur och polymer-sammansättning behöver göras för att kunna dra slutsatser av deras påverkan på dielektrisk nedbrytning. För att kunna bestämma korrelationen mellan dielektrisk nedbrytning och tjocklek behöver fler mätningar göras på material där fördjupningar gjorts. (Less)
Please use this url to cite or link to this publication:
author
Brofelth, Malin LU and Alskär, Moa LU
supervisor
organization
course
MTT920 20131
year
type
H2 - Master's Degree (Two Years)
subject
other publication id
13/5110
language
English
id
3971668
date added to LUP
2013-08-13 14:03:18
date last changed
2013-08-13 14:03:18
@misc{3971668,
  abstract     = {High voltage test equipment is used to measure the dielectric breakdown of polymeric material in order to detect defects in laminated carton based packages. The departments New Material Design and Applied Material Design at Tetra Pak in Lund wanted to understand how structural differences in polymeric material influence the dielectric breakdown of the material. The structural differences investigated were thickness, adhesive composition and polymeric layer structure. The master thesis was done in collaboration with Tetra Pak and the department of Packaging Logistics at Faculty of Engineering at Lund University, LTH.
The measurements were performed on the polymeric inside of laminated carton based packages. Since polymeric materials are dielectrics they are poor electric conductors. The high voltage test equipment used applies an electrical field to the material tested and the voltage is ramped up until the material cannot withstand the applied field and dielectric breakdown of the material occurs. The dielectric breakdown will start in weak points of the material, such as pores and cracks, where a lower voltage is required. 
To examine the correlation between dielectric breakdown and thickness, the thickness of the polymeric inside of the material needed to be determined. The polymeric inside of the commercial laminated carton based package has thickness variation. It is therefore difficult to determine the polymer thickness in an exact and reproducible way where the dielectric breakdown of the material was measured. Since the high voltage tests are destructive it is not possible to measure the thickness afterwards.
To determine a correlation between material thickness and dielectric breakdown measurements were done on specially extruded material with varying thickness. Measurements were also done on material where depressions were created to give thickness variation and to control the position of the dielectric breakdown measurements. By measuring on material consisting of adhesive with different amount of polar groups but with the same thickness a correlation with dielectric breakdown was studied. At last the dielectric breakdown for material with different layer structures but with the same thickness was also investigated. 
When performing measurements with the high voltage test equipment, problems with the hard- and software occurred. It was also difficult to isolate the test area properly. The conclusion of the method development was to move the computer and logger as far away from the test chamber as possible. Teflon tape was used to isolate the test area. Due to surface roughness of the material the use of a plate electrode with smaller diameter lowered the probability of measuring holes and major weaknesses in the material.
From the performed quantitative study a linear trend between dielectric breakdown and material thickness could be seen. No significant difference between materials with different amount of polar groups in the adhesive could be determined. From the measurements on materials with layer structural differences no significant difference in dielectric breakdown could be concluded. More measurements on materials with different layer structure and polymer composition are needed to draw conclusions on their impact on the dielectric breakdown. To compare the effect of different amount of polar groups in the adhesive, specially extruded material with lower amount of polar groups in the adhesive needs to be manufactured and measured. In order to determine the correlation between dielectric breakdown and thickness, more measurements on material where depressions have been created are needed.},
  author       = {Brofelth, Malin and Alskär, Moa},
  language     = {eng},
  note         = {Student Paper},
  title        = {Influence of polymer thickness, adhesive composition and layer structure on dielectric breakdown in laminated carton based packages},
  year         = {2013},
}