(A) study on the cure kinetics, phase separation and RIM process of rubber modified epoxy resin

Abstract

The reaction kinetic equations considering the vitrification effect were newly derived for the neat and rubber modified epoxy systems through the dynamic DSC technique. These newly derived reaction knetic equations could describe the change of reaction rate at both glassy and rubbery state during the vitrification process. In order to describe the vitrification effect, a modified WLF equation was introduced to the reaction kinetic equations. The relationship between glass transition temperature ($T_g$) and extent of reaction (X) was established by Di Benedetto``s equation and used to consider the change of reaction rate during the vitrification process. An autocatalytic reaction mechanism was found to describe adequately the reaction kinetics of neat and rubber (ATBN) modified epoxy curing reactions and its overall reaction rate order was assumed to be 2. The several reaction kinetic parameters were determined from the dynamic DSC experimental data through the Marquardt``s multivariable nonlinear regression method and Runge-Kutta integration technique. In order to constitute the RIM process as well as to observe the rheological effect on the phase separation behavior, the relationship between viscosity and chemical conversion was establish from the viscosity data measured by RMS for the curing reation of ATBN 10wt% added epoxy system. The phase separation behavior occurred during the curing reaction of rubber modified epoxy system was investigated by the light scattering experiments, the turbidity measurements, and the morphology of SEM, TEM, and OM (optical microscope). ATBN-DGEBA system showed UCST behavior and the UCST curve shifted to higher temperature region and became bimodal form as the chemical conversion increased. The scattered light intensity with time showed the formation of the dispersed rubbery domains and the mechanism of phase separation dynamically. The domain correlation length decreased as the isothermal curing temperature was increaded and ...