Thermal degradation of naturally aged NBR with time and temperature

Abstract

Nitrile butadiene rubber (NBR) is a polymer widely used in pipe fittings as a sealing and damping element. The performance of the polymer materials degrades with time and temperature. The present work emphasizes the thermal degradation of NBR materials using thermogravimetric analysis (TGA) at heating rates of 5, 10, 15, and 20 °C min−1 in a controlled nitrogen environment. Model-free methods, namely the Kissenger, Kissinger-Akahira-Sunose (KAS), and Ozawa-Flynn-Wall (OFL) approaches, are used to determine the kinetic activation energy and frequency factor. The obtained values were used to calculate the lifetime of virgin NBR and the remaining life of naturally aged NBR. Fourier-transform infrared spectroscopy (FTIR) was used to detect changes in the functional groups of the NBR material with age. From the experimental data, it is concluded that virgin NBR has better thermal stability than naturally aged NBR. Furthermore, the activation energy of NBR is temperature-dependent, and oxidative aging has a significant impact on the degradation of kinetic parameters. At lower conversion rates, the activation energy of virgin NBR (79.39 kJ mol−1) and aged NBR (78.25 kJ mol−1) are almost the same, while at increased conversion rates, virgin NBR (529.77 kJ mol)−1 has higher activation energy than aged NBR (280.15 kJ mol−1).