Thermal decomposition of PAG oil: chemical characterization, thermal stability assessment and lifetime prediction via accelerated life test
摘要
PAG oil offers excellent thermal and lubricating performance, but degrades at high temperatures, forming acidic compounds harmful to equipment. However, real-time monitoring of its degradation in practical systems is limited. To address this challenge, an accelerated life test was conducted over 56 days at 125, 135, and 150 °C to investigate the chemical and physical changes in PAG oil and to predict its lifetime. FT-IR analysis revealed that as oil degradation progressed, the distinctive peak representing a carbonyl bond (C=O) appeared at 1740 cm⁻1, and it was used as a degradation parameter at a molecular scale change. Through TGA analysis, a progressive decrease in decomposition temperature with aging was observed, indicating a reduction in thermal stability. GPC analysis showed a decrease in molecular weight over time and a transition from bimodal to unimodal distribution, confirming molecular breakdown. By integrating the results of these analyses, the degradation mechanism of PAG oil was proposed, involving both oxidative chain cleavage and secondary condensation reactions. Arrhenius equation was used as a predictive model, determining the reaction rate constants and activation energies for each temperature to establish the correlation between aging temperature and lifetime. It was found that at 110 °C, the oil has a lifetime of 128.6 days, while at 150 °C, it is reduced to 61.5 days.
Graphic abstract