Accelerated Aging Behaviors and Mechanism of Fluoroelastomer in Lubricating Oil Medium

• Published in: Chinese journal of polymer science 2020-08, Vol.38 (8), p.853-866
• Main Authors: Wang, Qi-Long, Pei, Jing-Ke, Li, Gao, He, Xi, Niu, Yan-Hua, Li, Guang-Xian
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Cleavage; Condensed Matter Physics; Coupling (molecular); Crosslinking; Fluoropolymers; Glass transition temperature; High temperature; Industrial Chemistry/Chemical Engineering; Lubricating oils; Polymer Sciences; Reconstruction; Temperature; Temperature dependence; Tensile strength; Thermal stability
• ISSN: 0256-7679; 1439-6203
• DOI: 10.1007/s10118-020-2410-1

The aging behaviors and mechanism of fluoroelastomer (FKM) under lubricating oil (FKM-O) and air (FKM-A, as a comparison) at elevated temperatures were studied from both physical and chemical viewpoints. The obvious changes of mechanical and swelling performances indicate that the coupling effect of lubricating oil and temperature causes more serious deterioration of FKM-O compared to that of FKM-A. Meanwhile, much stronger temperature dependence of both bulk properties and micro-structures for FKM-O is found. Three-stage physical diffusion process is defined in FKM-O due to the competition between oil diffusion and elastic retraction of network. FTIR results reveal that the dehydrofluorination reaction causes the fracture of C-F bonds and produces a large number of C-C bonds in the backbone. The coupling effect of oil medium and high temperature could accelerate the scission of C-C bonds and generate a series of fragments with different molecular sizes. The TGA results, crosslinking density V e , and glass transition temperature T g derived from different measurements coherently demonstrate the network destruction in the initial stage and the simultaneous reconstruction occurring at the final stage. The newly formed local network induced by reconstruction cannot compensate the break of the original rubber network and thus only provides lower tensile strength and thermal stability.