Investigation of hygrothermal aging on the polyurethane-based (PUB) adhesive: substantiating competition scenario between sub-aging thermo-oxidation and hydrolytic phenomena

In this work, the effects of accelerated thermo-oxidative, hydrolytic and hygrothermal aging on the mechanical and chemical properties of a polyurethane based (PUB) adhesive are presented. The adhesive is extensively used in automobile industry particularly as a glass sealant. PUB is inevitably exposed to the hygrothermal environment during service life and the integrity of matrix interface is most vulnerable. This study focuses on weighing and comparing effects of different aging environments on material behavior; it showed that hygrothermal aging is a competition between two sub-aging phenomena i.e., thermo-oxidation and hydrolytic aging. Samples were exposed to 0%RH, 80%RH and submerged condition in distilled water. Uni-axial tensile tests, Differential Scanning Calorimetry (DSC) analysis, Dynamic Mechanical Analysis (DMA), Fourier Transform Infrared Spectroscopy (FTIR) Analysis, Scanning Electron Microscopy (SEM), cross-link analysis and swelling tests were carried out on as-received and aged samples. Accelerated aging process was conducted at different temperatures (60 degrees C, 80 degrees C and 95 degrees C) and for different exposure durations of 1, 10, 30, and 90 days. This work confirms that the effect of hygrothermal aging is a result of competition between thermo-oxidation and hydrolytic aging environments. The total mechanical and environmental damage incurred by specimens is a collaborative effect of all exposure environments involved i.e., aging time, temperature, oxygen, water and humidity. The results are confirmed by chemical test outcomes as well.

Automated summary

This study explores the effects of accelerated aging on a polyurethane based adhesive, particularly focusing on the competition between thermo-oxidation and hydrolytic aging during hygrothermal exposure. Various tests were conducted on samples exposed to different environments, showing that the mechanical and environmental damage is a collaborative effect of all exposure environments involved. Chemical test outcomes confirmed the results obtained from mechanical tests.