WIDE-ANGLE X-RAY-SCATTERING, FOURIER-TRANSFORM INFRARED-SPECTROSCOPY,AND SCANNING ELECTRON-MICROSCOPY STUDIES ON THE INFLUENCE OF THE ADDITION OF LIQUID FUNCTIONAL RUBBER INTO EPOXY THERMOSET

Sophisticated analytical methods (viz. wide-angle X-ray scattering, Fo urier transform infrared spectroscopy, and scanning electron microscop y have been applied to investigate the mechanism of toughening of epox y cresol novolac resin due to the addition of carboxy-terminated polyb utadiene (CTPB) liquid functional rubber. The average molecular interc hain spacing < R > in Angstroms of neat epoxy and epoxy-rubber blends were calculated from the strong maximum in the diffraction scan using established equations. The half-width < HW > of the maximum was used t o qualitatively describe the distribution of < R >. An increase in < R > value signifies formation of a separate packing order, as well as a n increase in the free volume which, however, varies with the extent o f compatibilization between epoxy cresol novolac and CTPB. Fourier tra nsform infrared studies convincingly establish the crosslinking betwee n the oxirane group of epoxy and the carboxyl group of CTPB as reflect ed in the characteristic peak shifts in the blends, compared with indi vidual polymers. The merger of several peaks of individual polymers, a s well as the appearance of minor peaks elsewhere, were also evident. Scanning electron microscopy studies have also been undertaken to stud y the phase morphology development, as well as changes in the fracture surface topography with varied CTPB content. (C) 1998 John Wiley & So ns, Inc.