GE Plastics recently introduced a resin that will compete with solid surfacing products such as Corian and Avonite, and even ceramic or wood. Referred to as heavy Valox, it is made from polybutylene teraphthalate or PBT. About 65% of the material is a proprietary mix of mineral fillers. (Other solids as well as cultured marble and onyx also use –– filler specifically alumina trihydrate — see "Solid Surfacing Options," 11/90). The mineral filler gives the plastic weight, durability, flammability protection, and a certain "feel." Heavy Valox product manager, Blair Anthony, sees some advantages over other formulations. "It's easily thermoformed and can even be injection molded with standard tooling." This means it can be used in kitchens and baths not only for countertops and cast sinks but molded parts