Thermal ageing, degradation and swelling of acrylate rubber, fluororubber and their blends containing polyfunctional acrylates

Abstract

The thermal ageing and degradation behaviour of acrylate rubber (ACM) fluoroelastomer (FKM), and blends of ACM and FKM containing polyfunctional acrylates were studied in air and nitrogen atmospheres. The blends were also subjected to swelling in different solvents. Thermogravimetric analysis of the blends containing polyfunctional acrylate indicated higher thermal stability of the blends by shifting initiation of degradation to higher temperature. The ageing and degradation of FKM-containing blends resulted in elimination of hydrogen fluoride and formation of some lower molecular weight components. Polyacrylates with higher functionality showed multi-step degradation. Higher levels of polyacrylate in the blend resulted in an additional step of degradation compared to polyacrylate. Swelling studies indicated higher swelling resistance of ACM and FKM containing polyacrylate in solvents having different solubility parameters. Maximum swelling of the blends was observed with the solvents having solubility parameter values comparable to that of blends i.e. in the range of 9–10 MPa 1/2. The swelling index of the blends decreased with increasing level of polyfunctional acrylates. Higher functionality of polyfunctional acrylates decreased the swelling index.