a structural laminate comprises at least one planar facing sheet comprised largely of glass fibers but not having micro - glass as a filler . the facing sheet is self adhered to a rigid thermosetting plastic foam core . the non - glass filler material is chosen from a group consisting of clay , mica , talc , limestone , gypsum , aluminum trihydrate , antimony oxide , cellulose fibers , and plastic polymer fibers . the non - glass filler material improves containment of liquid plastic thermosetting polymer , and offers economic and safety advantages .