PROCESSING OF INTRACTABLE POLYMERS USING REACTIVE SOLVENTS .1. POLY(2,6-DIMETHYL-1,4-PHENYLENE ETHER) EPOXY-RESIN

A new processing route for poly(2,6-dimethyl-1,4-phenylene ether) (PPE ), an intractable polymer on account of its thermal and oxidative sens itivity, was explored. PPE can be dissolved at elevated temperatures i n epoxy resin and these solutions can then be processed at temperature s as low as 175 degrees C. For solutions of PPE with a molecular weigh t of 10, 20 and 30 kg mol(-1), the phase diagram and the flow curves i n the homogeneous region were determined. The upper critical solution temperature (UCST) cloud point curves intersect the glass transition-c omposition lines at a PPE content of similar to 70 wt%. Below this com position, thermoreversible gelation is observed upon cooling which pre vents complete phase separation. Curing of the homogeneous solutions, using diethyltoluene diamine, resulted in virtually complete phase sep aration. In the composition range that was studied (30-70 wt% PPE), th e chemically induced phase separation is accompanied by phase inversio n, yielding a final morphology of epoxy spheres dispersed in a PPE mat rix. Thus, after processing, the (reactive) solvent is converted into a dispersed phase. The mechanical and thermal properties of the final materials, such as toughness and glass transition temperature, are dom inated by the continuous PPE matrix.