The impact of the manufacturing process on the surface quality of polyethylene terephthalate optical film

Seaman, Amy Margaret Christine (2023). The impact of the manufacturing process on the surface quality of polyethylene terephthalate optical film. University of Birmingham. Eng.D.

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This study aims to understand the ways in which the conditions of the manufacturing process of polyethylene terephthalate film can affect the surface quality of clear optical films. The purpose of gaining this understanding was to improve on existing cleaning methods and processing conditions that are currently insufficient and lead to a decrease in surface quality over time.

Flexible electronics is a growing industry within the technology sector. This growth drives demand for screens which are both flexible and scratch resistant. DuPont Teijin Films (DTF) focuses on rapid innovative product development and aspires to produce high quality, optically clear film for flexible electronic applications. An obstacle to development is the requirement for impeccable surface quality. Through this work it has been confirmed that the presence of contamination on the surfaces contacting the film within the manufacturing line is the key culprit for exacerbating surface defect formation. The project is split into three distinct parts that all aimed to deliver a deeper understanding of this problem.

The first stage of this work was to characterise the debris found on the manufacturing line to confirm the hypothesised formation pathways. Debris was analysed using a variety of analytical techniques and found it to be primarily composed of the products of PET hydrolytic and oxidative degradation.

Next, this work measured the adhesive forces present between the interacting surfaces on the line and aimed to recommend an appropriate cleaning strategy based on an understanding of these interactions. The adhesive force was measured by colloidal probe atomic force microscopy, but no consistent results were found. This is hypothesised to be due to the contributions of surface roughness and humidity making repeatable results a challenge to acquire.

Finally, this work aimed to understand how the presence of contamination impacts surface defect formation. New lab-based models for scratch modelling at the micro-scale and for creating pseudo-dirtied surfaces were developed. Topographical and friction measurements revealed that contamination was affecting the frictional properties of the rollers by modifications to both topography and surface energy of the surfaces.

Overall, this work was able to solidify and unify much of the historical and anecdotal hypotheses within DuPont Teijin Films of how contamination plays a role in surface defect formation. Armed with this understanding now allows the business to move towards solutions that target the root of the problem.

Type of Work: Thesis (Doctorates > Eng.D.)
Award Type: Doctorates > Eng.D.
Licence: All rights reserved
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Chemical Engineering
Funders: Engineering and Physical Sciences Research Council
Subjects: Q Science > Q Science (General)
Q Science > QD Chemistry


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