Enhanced flame retardancy of carbon fiber-reinforced poly(phenylene sulfide) thermoplastic via co-coating of graphene and zinc borate

The use of polymer matrix thermoplastic composite materials in the aviation sector has been increasing due to the superior properties. Materials used in airplanes are expected to have good fire resistance properties, and so composite materials offer an advantage to engineer properties. In this study, the surface of a commercially obtained 50% carbon fiber (CF) reinforced polyphenylene sulfide (PPS) composite plate was coated using a spray coating method with reduced graphene oxide (r-GO) and zinc borate, both known for their flame-retardant and green properties. The structural characterization, contact angle measurements, surface morphology determination, combustion analysis, thermal analysis, and mechanical analysis of both coated and uncoated samples were conducted. The limit oxygen index (LOI) value of the uncoated 50CF/PPS composite plate was measured as 59.2 ± 0.25%. The LOI value of the r-GO coated sample was increased to 61.0 ± 0.25%, while the LOI value of the sample coated with both r-GO and zinc borate was increased to 61.8 ± 0.57%. Thus, it was concluded that co-coating of r-GO and zinc borate synergistically enhances the LOI value of the composite material. The results of the study are believed to be industrially applicable.