The investigation of flammability, thermal stability, heat resistance and mechanical properties of unsaturated polyester resin using AlPi as flame retardant

The influence of aluminum dialkylphosphinate (AlPi) on the flammability, thermal properties and mechanical properties of unsaturated polyester resins (UPRs) was investigated. A series of flame-retarded UPR loading with AlPi were prepared. The flammability and thermal stability of these UPR composites were investigated with limiting oxygen index (LOI), UL-94 vertical burning and themogravimetric analysis test. The structure and morphology of char residues were examined with Fourier transform infrared and scanning electron microscopy (SEM). Additionally, thermomechanical property of cured composites was characterized by dynamic mechanical analysis (DMA). The results showed that the AlPi excellently improved the flame retardancy of UPR, the LOI increased from 21 to 29.5 with the increasing of AlPi and UPR-AlPi25 (25 %) passed V-0 classification. The char residue of UPR-AlPi25 at 700 °C was 11.17 % in nitrogen and 20.83 % in oxygen, suggested that interaction between AlPi and UPR strengthened the char-formation ability and the thermal stability of the UPR/AlPi systems. The SEM showed that the surface of the char for UPR-AlPi25 was strong and dense and flexural fracture surfaces of UPR/AlPi composites showed a homogeneous morphology. The DMA curve indicated the Tg was greatly improved with the increasing of AlPi.