PROCESSING OF INTRACTABLE POLYMERS USING REACTIVE SOLVENTS .3. MECHANICAL-PROPERTIES OF POLY(2,6-DIMETHYL-1,4-PHENYLENE ETHER) PROCESSED BYUSING VARIOUS EPOXY-RESIN SYSTEMS

The rather intractable polymer poly(2,6-dimethyl-1,4-phenylene ether) (PPE) can easily be processed by using epoxy resin as a reactive solve nt. In this reactive solution processing technique, PPE is dissolved i n epoxy resin at elevated temperatures and processed. After processing , the epoxy resin is polymerized and phase separation accompanied by p hase inversion is initiated and the reactive solvent is subsequently i ntegrated in the final material. In this paper, attention was focused on the possibility of tuning the properties of the in situ polymerized dispersed epoxy phase. A solvent system was studied which consisted o f epoxy resins and diamine curing agents, based on bisphenol and poly( propylene oxide). Both resins could be used as a solvent for PPE and t he resulting processable solutions exhibited upper critical solution t emperature behaviour. Upon increasing the poly(propylene oxide) conten t in the reactive solvent system the properties of the dispersed phase could be varied gradually from non-ductile glassy to completely rubbe ry, and consequently the properties of the PPE/epoxy could be controll ed over a broad range. The presence of a non-ductile glassy dispersed phase (with yield stress '' yield stress of PPE) resulted in an increa se in the yield stress of the material and was shown to constrain yiel ding of the PPE matrix. Reduction of the yield stress of the dispersed phase facilitated ductile deformation of PPE in tensile loading but r esulted additionally in a reduction in toughness. After changing the p roperties of the dispersed epoxy phase to completely rubbery a substan tial increase in toughness was obtained. Interestingly, the rubber wit h the lowest level of adhesion proved to be the most efficient impact modifier for PPE.