CHARACTERIZATION AND CORRELATION OF THE NETWORK CHAIN DENSITY TO THE PROPERTIES OF FLUOROELASTOMER RUBBER

Abstract

ABSTRACT The concentrations of triallyl isocyanurate (TAIC) in a peroxide-curable fluoroelastomer terpolymer containing 67 wt% of fluorine were varied to generate compounds of differing crosslink densities. Experimental analysis was undertaken using rheometry, hardness, stress–strain (Mooney–Rivlin), equilibrium solvent swell, and low-field nuclear magnetic resonance (NMR) using the double quantum (DQ) technique. Increasing the TAIC concentration caused a systematic rise in rheometry elastic torque, hardness, and tensile strength, whereas both elongation at break and swelling levels decreased. These results are concurrent with an enhanced overall level of crosslinking, which was confirmed by the steady increase of the Mooney–Rivlin C1 values. DQ NMR analysis using hydrogen and fluorine probes and subsequent application of fast Tikhonov regularization to the corrected intensity data were particularly useful in discerning the inhomogeneous nature of the compound morphology. The spatial distribution of the crosslink density suggests that the compound consists of small, highly crosslinked/entangled polymerized TAIC domains embedded within the elastic crosslinked matrix. A concentration of 3 phr of TAIC is optimal according to compression set testing.