Exploration of dynamic mechanical analysis for studying degraded polymers: dynamic mechanical changes after ultraviolet exposure

Published

September 30, 2025

Author(s)

Hsiuchin Huang, Donald Hunston, Li Piin Sung

Abstract

Many techniques, including surface and bulk measurements, have been used to study the changes in mechanical properties of polymers induced by photodegradation. This study employed dynamic mechanical analysis (DMA) as a less-destructive method to examine the bulk mechanical changes of ultraviolet (UV)-exposed polyesters. The measurements were conducted in the temperature range from glassy state to half of glass transition. Different degrees of photodegradation were carried out on the polyesters using NIST SPHERE (Simulated Photodegradation via High Energy Radiant Exposure). These polyesters underwent post-exposure treatment by being stored in an ambient environment after exposure. Significant changes in viscoelastic properties during post-exposure storage, particularly within the first 24 hours, were detected. At the early stage of glass transition, both stiffness and the onset temperature of loss modulus decreased with storage time, with the decrease rate depending on the degree of degradation. The molecular response to high-frequency oscillatory strain was less sensitive relative to the unexposed polyesters. On the other hand, the effect of high frequency changed with the incremental post-exposure storage, allowing the degree of degradation and the material rigidity to be differentiated. Photodegradation also led to chemical changes and alteration of molecular structure in the UV-exposed polyesters. These changes affect the resulting mechanical properties. Fourier transform infrared spectroscopy (FTIR) was conducted to study the chemical changes.

Citation

Polymer Degradation and Stability

Volume

242

Pub Type

Journals

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Keywords

DMA, mechanical property, polyester, UV, accelerated weathering, post-exposure treatment

Citation

Huang, H. , Hunston, D. and Sung, L. (2025), Exploration of dynamic mechanical analysis for studying degraded polymers: dynamic mechanical changes after ultraviolet exposure, Polymer Degradation and Stability, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=959807 (Accessed March 28, 2026)