PHASE-SEPARATION DYNAMICS OF RUBBER EPOXY MIXTURES

Time-resolved light scattering has been employed to investigate the kinetics of phase separation in mixtures of carboxyl-terminated butadiene-acrylonitrile copolymer (CTBN) and diglycidyl ether bisphenol A (DGEBA) epoxy oligomers. The CTBN/DGEBA mixture reveals an upper critical solution temperature (UCST); i.e., the mixture phase separates upon cooling but reverts to a single phase upon heating. Several temperature- (T-) quench experiments with various quenched depths were undertaken on a 20 wt % CTBN mixture. The time evolution of scattering halo was subsequently followed as a function of quenched depth. At deep quenches, the phase separation process has been dominated by spinodal decomposition (SD). The general trend of SD is nonlinear in character. The evolution of the maximum wavenumber (qm) and the corresponding maximum intensity (Im) obey the power law (qm ~ t-φ and Im ~ tψ). The exponent φ exhibits quench depth dependence with the value varying from 1/6 to 1/3. The results were further tested with the dynamic scaling laws. © 1990, American Chemical Society. All rights reserved.