Thermal resistance of carbon fibres/carbon fibre reinforced polymers under stationary atmospheric conditions and varying exposure times

Recycling of carbon fibre reinforced polymer composites is a mostly unsolved problem. Thermal recycling (e.g. pyrolysis) is often described as a promising method for recycling of carbon fibre reinforced polymers (CFRP). Manageable technology, high throughput and relatively low energy demand make these methods attractive as possible solutions. However, the carbon fibre (CF) exhibits special behavior under thermal stress, which makes the thermal treatment a complex task. With this contribution, we examine the influence of the temperature on CFRP under thermal treatment. Raw CF's and pure epoxy resin are investigated separately and compared to the treatment of the compound material. The influence of exposure-times at various temperatures, as well as the texture of the treatment residues are examined. Our investigations are based on thermogravimetric analysis (TGA). In addition to standard TGA methods, we introduced hold times of about 10 min at defined temperatures (400, 600 and 800 °C). Particle sizes and hold times were varied. Damage on the fibre surface was examined by means of scanning electron microscopy (SEM). We found that the influence of the particle size was substantial. Different sizes led to considerably different times of decomposition and decomposition start temperatures. Analysis of the residue at 800 °C show damage and increased amounts of oxygen on the surface of the fibre. In addition, our results show that a trade-off between maximum temperature and hold time is possible up to a certain degree.