The polymerizable liquid, i.e., monomer such as diallyl orthophthalate and the like, polyphenylene ether polymer, catalyst and where desired an allylic prepolymer and modifying ingredients such as dyes, pigments, iillers, glass coupling agents, inhibitors and so forth are mixed together and used to impregnate a fibrous non-Woven mat or a woven fabric; where glass mats or fabrics are used it may be