Synthesis and properties of novel high thermally stable polyimide-chrysotile composites as fire retardant materials

Abstract

Abstract Novel high thermally stable polyimide-chrysotile (PI-Chr) composites were synthesized. Firstly, Chrysotile (Chr) was modified with 3-aminopropyltriethoxysilane (APS). Poly(amic acid) solution was synthesized from pyromellitic dianhydride (PMDA) and 4,4′-diaminodiphenyl ether. Then, PI-Chr composites were prepared from poly(amic acid) solution and different ratios of modified Chr. Prepared PI-Chr composites were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray spectroscopy and thermal analysis techniques. Thermal analysis results showed that the PI-Chr composites have higher decomposition temperatures in comparison with the pure PIs. A 10% weight loss belonging to PI-Chr composites was observed between 489°C and 536°C in air atmosphere, but this value was 468°C in air for pure PIs. The glass transition temperatures (Tg s) of the PI-Chr composites were 373°C–384°C, depending upon the amount of the Chr. PI-Chr composites exhibited improved thermal stability. The activation energies (Ea s) of the thermal degradation reaction were calculated using the Kissinger method for pure PI and composites. The Ea s of the PI-Chr composites were found to be 77 and ∼117 kJ/mol. The fire retardant properties of Chr in the PI matrix were also tested by the total heat release test. The introduction of Chr in the composites leads to a slight increase in fire retardant properties thermal stability.