Although heat-curable thermosetting resins such as B-stage polyesters and acrylics may be employed, the preferred resins are thermoplastics such as polycarbonates, polyacrylates and rubber-modified polyacrylates, polysyrenes and rubber-modified polystyrenes, acrylonitrile/butadiene/styrene interpolymers (ABS), linear polyethylene, etc.