Recovery of carbon fibres by the thermolysis and gasification of waste prepreg

This paper examines the recovery of carbon fibres from a composite used in the aeronautical industry, via a combined process of thermolysis and gasification in an air atmosphere. The waste was thermolysed at 500 °C, 600 °C or 700 °C in a pilot plant to determine the optimum thermolysis temperature. The solid residues produced – char covered carbon fibres – were characterized by SEM and XPS. The optimum time for the gasification of the char covering the fibres was determined in a combined thermolysis/gasification assay. After thermolysis at the optimum temperature (500 °C), 12 l/h of pure air were injected into the reactor and char gasification performed at 500 °C for 30–180 min. The optimum gasification time was 30 min. Longer gasification times led to the production of fibres of smaller diameter with oxidized surfaces and reduced tensile strength. The optimally recovered fibres showed about 70% of the tensile strength of virgin fibres and some 90–96% of their elasticity.