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ABSTRACT Multilayer packaging is commonly used in the food industry to improve product preservation by combining materials with specific properties for optimal protection. Ethylene vinyl alcohol (EVOH) is highly valued for its barrier properties against air and moisture. The mechanical properties of EVOH films are influenced by both the ethylene content, which affects crystallinity and barrier performance, and the thickness of the EVOH layer, which affects the film's mechanical strength. This study develops mathematical models to explore the relationship between EVOH film thickness, ethylene content, and mechanical properties, such as tensile strength, elongation at break, and elastic modulus. Using RSM with I‐optimal design, the optimal conditions for EVOH films are identified at a thickness of 0.03 mm and 48 mol% ethylene content. The model predicts values of 25.178% for elongation at break, 3077.865 MPa for elastic modulus, and 97.444 MPa for tensile strength. These predictions are validated through ANOVA, confirming the statistical significance of the model. Experimental results show achieved values of 27.119% for elongation, 3437.811 MPa for elastic modulus, and 107.308 MPa for tensile strength, demonstrating model accuracy. To further validate these findings, EVOH films are characterized by SEM, FTIR spectroscopy, and TGA, providing valuable insights into the structural and functional properties for food packaging.
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This content will become publicly available on February 1, 2026
Probing the thermo-oxidative degradation of ethylene vinyl alcohol (EVOH) by time-resolved rheology and NMR spectroscopy
EVOH’s excellent gas barrier properties have enabled its continued market growth in numerous applications including food packaging, fuel tanks, and construction. However, EVOH’s susceptibility to thermo-oxidation limits its ability to be reprocessed. While it is generally known that EVOH degradation leads to cross-linking, detailed degradation rates and mechanisms are not well established. Understanding EVOH degradation has been elusive because readily accessible thermal and spectroscopy methods do not reveal significant changes. Moreover, gel permeation chromatography requires specialized solvents and columns. We report that measuring changes in viscoelasticity with time-resolved rheology (TRR) is a facile way to monitor the temporal dynamics of EVOH degradation. TRR was performed on EVOH grades with ethylene copolymer contents of 27, 32, 48 mol%. As expected, the grade with the highest ethylene content was the most stable. However, with time, all the EVOH grades transitioned from a Carreau-like fluid to a power law fluid and no longer exhibited terminal behavior. Cole-Cole plots also revealed that EVOH relaxation evolved from rapid process into a long, complex process consistent with network formation. The mechanism of degradation was further elucidated by using 13C distortionless enhancement of polarization transfer (DEPT-135) nuclear magnetic resonance spectroscopy. These results showed that degradation occurred by ring-opening of lactone terminal groups that led to cross-linking. This enhanced understanding provides a foundation for developing methods to probe and mitigate EVOH degradation.
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- Award ID(s):
- 2132093
- PAR ID:
- 10562255
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Polymer Degradation and Stability
- Volume:
- 232
- Issue:
- C
- ISSN:
- 0141-3910
- Page Range / eLocation ID:
- 111099
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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