UNSATURATED MONOMER COMPOSITION WITH POLYUNSATURATED CROSSLINKER

摘要

Described herein are compositions and processes for preparing molded articles wherein shrinkage is substantially avoided by providing a thermosetting composition which foams during cure, resulting in articles with very smooth surfaces and which are weatherable. In one aspect, the invention comprises a thermosettable composition comprising: (A) from about 20% to about 70% by weight, based on said composition, of an unsaturated monomer; from about 1% to about 50% by weight, based on said composition, of(B) a thermoplastic polymer soluble in said unsaturated monomer; and from about 10% to about 40% by weight, based on said composition, of (C) a polyunsaturated crosslinking monomer, the amount of (C) being sufficient to cause the cured thermoset resin molded under heat and pressure from said composition to have an optically heterogeneous appearance due to foaming during cure, and a density significantly less than the theoretical density if unfoamed. Also provided is a process for preparing fiber-reinforced foamed thermoset moldings comprising the steps of (? preparing a composition comprising from about 20% to about 70% by weight, based on said composition, of (A) an unsaturated monomer; from about 1% to about 50% by weight, based on said composition, of (B) a thermoplastic polymer soluble in said unsaturated monomer; from about 10% to about 40% by weight, based on said composition, of (C) a polyunsaturated crosslinking monomer; and (D) a fibrous reinforcing agent selected from the class of materials consisting of fiberglass, sisal fibers, asbestos fibers, cotton fibers, nylon fibers, polyester fibers, polypropylene fibers, quartz fibers, beryllium fibers, boron fibers and carbon fibers; and then (2) curing said composition at a temperature ranging from about 200.degree.F to 350.degree.F and under pressure in a mold; the amount of component (C) in said composition being sufficient to cause foaming, substantial reduction of density below theoretical density, substantial absence of shrinkage, and reduced fiber prominence. Articles made from the aforesaid composition can be used without finishing or sanding steps and without the necessity of applying a protective coating.