Properties of Fire Retardant Thermoplastic Vulcanizates from NR/PP Blends Filled with Aluminium Trihydrate and Magnesium Hydroxide with Reference to the Effect of Mixing Methods

Abstract

Blends of natural rubber (NR) and polypropylene (PP) with composition of 60/40 %wt were prepared by using an internal mixer to obtain thermoplastic vulcanizate (TPV). Aluminium trihydrate (ATH) and magnesium hydroxide (MH) were used as fillers to improve thermal stability and fire retardant properties. Three different mixing methods were used to incorporate the fillers into the TPVs, which were (1) compounding of NR and filler followed by dynamic vulcanization of NR during blending with PP, (2) compounding of NR with a half part of filler (and oil) followed by dynamic vulcanization of NR when blending with PP before adding another half part of filler into the blend (3) melt mixing of PP, NR and filler followed by dynamic vulcanization during mixing. The incorporation of ATH and MH decreased tensile strength and elongation at break of the TPVs, but increased the thermal stability and LOI%. From this work, the mixing of filler with NR/PP blend by using method 3 provided better balance of tensile, thermal and fire resistant properties and processing cost reduction.