THERMOREVERSIBLE COVALENT CROSS-LINKING OF MALEIC ANHYDRIDE GRAFTED BUTYL RUBBER WITH GLYCEROL

Abstract

ABSTRACT The formation of thermoreversible hemi-ester cross-links of maleic anhydride grafted butyl rubber (MAn-g-IIR) using glycerol as a cross-linking agent in the absence of catalyst was studied in the present work. The effects of the molar ratios of glycerol to anhydride, the amount of the mixed solvent, the reaction temperature, and the reaction time on the percentage conversion of anhydride to ester were determined. The maximum percentage conversion calculated from the Fourier transform infrared spectroscopy spectra was 52.11. Reaction temperature played the most important role on the percentage conversion, followed by reaction time. Compared with the original MAn-g-IIR, tensile strength of the hemi-ester cross-linked MAn-g-IIR was significantly improved. These macromolecular regular clusters acted as strong and multiple cross-linking points that led to impressive mechanical properties. This confirmed the formation of hemi-ester cross-links. The covalently cross-linked MAn-g-IIR was reprocessable via compression molding at 179 °C and higher, indicating that the cross-links were indeed thermoreversible. The cross-linked materials could be repeatedly compression molded at 179 °C into homogeneous films for at least three cycles.