Recycling Technology for Waste Glass Fiber Reinforced Plastics (GFRP) Using Pyrolysis with NaOH

Abstract

Glass fiber reinforced plastics (GFRP) are composite materials with high strength and flame retardancy, and the disposal process is expensive to cause illegal dumping. Therefore, new recycling technology of waste GFRP are desired. In this study, recycling of waste GFRP using pyrolysis with sodium hydroxide (NaOH) under an inert atmosphere was attempted by gasification and carbonization of resin and conversion of glass fiber into soluble sodium silicate. The pyrolysis behavior of GFRP, the characteristics of the obtained residue, the composition and the yield of generated gas, and the silica extraction into the solution were investigated. The gasification and carbonization of the resin and the conversion of the glass fiber into soluble sodium silicate were promoted by pyrolysis with NaOH. Further, it was found that the sample after the pyrolysis treatment can be pulverized into a powdery residue by washing the solution without mechanical crushing. It was confirmed that the gas yield, especially flammable gases (H₂ and CH₄), and the silica extraction increased and the residual ratio decreased, with increasing heating temperature, NaOH addition and heating time. When 1 M HCl was used for extraction, a decrease in residual rate, an increase in silica and calcium extraction, and an increase in specific surface area of the residue for using adsorbent were achieved, compared to using distilled water, HNO₃ and H₂SO₄.