1. КК
  2. № 1 (47) / 2025
  3. Impact of Low Temperatures and Uv Irradiation on the Mechanical Properties of Polymer Films for Packaging

Impact of Low Temperatures and Uv Irradiation on the Mechanical Properties of Polymer Films for Packaging

КК.
2025;
Volume 1 (47), 2025, Number 1 (47)
: pp. 107 - 116
https://doi.org/10.32403/2411-3611-2025-1-47-107-116
Authors:
  1. V. H. Slobodianyk
  2. I. M. Nazar
  3. I. I. Koniukhova
  4. O. D. Koniukhov
1
Lviv Polytechnic National University,
2
Lviv Polytechnic National University
3
Lviv Polytechnic National University
4
Lviv Polytechnic National University

This study investigates the influence of low­temperature exposure (–18 °C) and ultraviolet (UV) irradiation on the mechanical properties of polymer films used in flexible packaging applications. The research focuses on widely used materials, including glossy and matte polypropylene (PP) and polyethylene terephthalate (PET) films of various thicknesses. Mechanical tensile tests were performed to evaluate the elasticity, tensile strength, and mechanical resistance of the films before and after exposure to cold and UV radiation.
The results show that exposure to –18 °C generally improves the mechanical per­formance of PP films, especially in terms of ultimate tensile force and elongation. This behavior is attributed to partial relaxation of internal stresses and secondary crystallization within the polymer matrix. Notably, the 35 µm thick glossy PP film demonstrated the highest resistance to cold, with a substantial increase in strength and plasticity in both longitudinal and transverse directions. PET films exhibited more stable but lower levels of deformation, reflecting the inherent rigidity and crystalline structure of polyester polymers.
On the other hand, UV exposure resulted in a significant degradation of mechanical properties across all film types, caused by photodegradation of polymer chains and oxidative processes. The decline in tensile strength and elasticity was more pronounced in thinner films. Among all samples, PET film exhibited the highest UV resistance, albeit with a lower overall elongation at break.
The findings underscore the dual nature of environmental influences on polymer films: while low temperatures can enhance strength and flexibility through structural reorganization, UV radiation leads to irreversible degradation. These insights are critical for the selection and design of packaging materials intended for environments involving freezing conditions or prolonged exposure to sunlight. Understanding such behaviors supports more accurate predictions of packaging material performance during storage and usage.

flexible packaging
polypropylene
polyethylene terephthalate
mechani­cal properties
tensile strength
film elongation
UV irradiation
low temperatures
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