TOUGHENING EPOXY-RESINS WITH POLYEPICHLOROHYDRIN

Polyepichlorohydrin (PECH) rubbers were found to toughen epoxy resins based on the diglycidyl ether of bisphenol A (DGEBA) and cured with pi peridine. The degree of toughening depends on the molecular weight of the PECH and on the curing temperature. Best toughening was achieved w ith PECH of the highest nominal molecular weight of 3400 (Hydrin 10 X 2). Hydrin 10 X 1 (nominal molecular weight 1700) did not toughen the epoxy resin unless bisphenol A was also added, whereas Hydrin 10 X 2 t oughened it in the absence of bisphenol A. Curing resins containing bi sphenol A and Hydrin 10 X 1 at 160-degrees-C resulted in a slightly mo re brittle resin than when cured at 120-degrees-C. In contrast, curing resins containing Hydrin 10 X 2 at 160-degrees-C gave a significantly tougher resin than when cured at 120-degrees-C. The effect of PECH ru bbers on the T(g), modulus, and hot/wet properties is similar to that of carboxy-terminated butadiene-acrylonitrile rubbers (CTBN). Dynamic mechanical thermal analysis (DMTA) and scanning electron micrographs ( SEM) of fractured surfaces show that the PECH separates as a discrete phase during curing.