The influence of expandable graphite on the thermal, flame retardant and mechanical characteristics of short carbon fiber reinforced polyamide composites

Abstract

The fire retardant performance of carbon fiber (CF) reinforced polyamide 6 (PA 6) composites plays an important role in their novel application fields. Thus, expandable graphite (EG) is integrated into CF containing PA 6 composite system to donate halogen-free flame retardant property based upon intumescence. The effect of EG amount on the thermal, flame retardant, and mechanical properties of CF reinforced PA 6 composites is examined. The properties of the composites are investigated using thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94 V), mass loss calorimeter (MLC), tensile, and impact tests. According to the test results, thermal stability reduces as the added amount of EG increases. The addition of EG improves fire performance and reduces the flammability characteristics of CF containing PA6 composites. The highest LOI value (36.4%), UL-94 V rating (V0), and the lowest peak heat release rate (pHRR) (74 kW/m2), total heat evolved (THE) (23.9 MJ/m2) values are observed with the inclusion of 30 wt% EG. The impact strength increases at 10 wt% EG addition, whereas negligible change is observed at higher EG loadings with respect to the reference sample. The increase in tensile modulus and the reductions in tensile strength and percentage elongation are observed as the added amount of EG increases. In brief, CF reinforced PA6 composites gain multifunctional characteristic with the help of interaction between EG and CF based on condensed phase fire-proofing behavior.