Recovery of glass fibers from glass fiber reinforced plastics by pyrolysis

Fiber-reinforced plastic sheets containing unsaturated polyester cross-linked with styrene, CaCO3 and glass fibers as fillers were pyrolyzed in a helium and steam atmosphere in order to recover glass fibers and valuable organic pyrolysis products. Glass fibers were separated from CaCO3 and CaO by dissolving calcium salts in hydrochloric acid. Residual organic material was burnt afterwards. Best results were obtained at a pyrolysis temperature of 600 and 700 A degrees C, resulting in a large liquid fraction high in styrene, leaving little residual organic material on the surface of the glass fibers. At a pyrolysis temperature of 500 A degrees C, the degradation of the polymer matrix was incomplete, and at 900 A degrees C, glass fibers were destroyed in the presence of CaO, leaving CaSiO3 as a product.