SYNTHESIS, BY REACTIVE EXTRUSION, OF HIGH MOLAR-MASS EPOXY PREPOLYMERS CONTAINING RUBBER PREFORMED PARTICLES

High molar mass epoxy prepolymers containing rubber dispersions based on carboxyl-terminated butadiene-acrylonitrile random copolymer (CTBN) were prepared from initially miscible solution of low molar mass epox y prepolymers, bisphenol A and CTBN-based rubber. During chain extensi on inside a twin-screw extruder due to epoxy-phenoxy and epoxy-carboxy reactions, a phase separation process occurs. Epoxy-phenoxy and epoxy -carboxy reactions were catalyzed by the triphenyl phosphine. The effe ct of reaction parameters (temperature, catalyst, reactant stoechiomet ry) on the reactive extrusion process were analyzed. The structure of the prepolymers showed low branching reactions (2-5%). Low molar mass prepolymers have a Newtonian rheological behavior. Cloud-point tempera ture of different reactive liquid butadiene acrylonitrile random copol ymer (RLP)/epoxy resin blends were measured for different RLP concentr ations. It was shown that rubber particles remain insoluble in a range of temperature from room temperature to 180 degrees C, typical of tem peratures used for epoxy curing reactions. Prepolymers containing diff erent rubber concentrations were cured using dicyandiamide as the hard ener. The practical adhesion of the issued networks to an aluminium al loy increased with rubber concentration. (C) 1997 John Wiley & Sons, I nc.