Dielectric and thermal properties of flame retardant fillers in polypropylene/ethylene propylene diene monomer composites

The incorporation of zinc hydroxystannate, calcium borate, and a phosphorus-based nonhalogenated flame retardant fillers (with trade name of NP-100) in 50% polypropylene and 50% ethylene propylene diene monomer blends was investigated. The composites were prepared using an internal mixer and were molded using a compression mold to form test samples. Studies on the effect of filler loading (15, 30, 45, and 60vol%) on dielectric breakdown strength, dielectric properties, and thermal conductivity were determined. The flow properties analyzed using the melt flow index revealed that the addition of zinc hydroxystannate increased the melt flow index of the polypropylene/ethylene propylene diene monomer blends, whereas the addition of calcium borate and NP-100 decreased the melt flow index values. A study on the dielectric properties of zinc hydroxystannate, calcium borate, and NP-100-filled polypropylene/ethylene propylene diene monomer composites found that polypropylene/ethylene propylene diene monomer/NP-100 has higher breakdown strength compared with polypropylene/ethylene propylene diene monomer/zinc hydroxystannate and polypropylene/ethylene propylene diene monomer/calcium borate. The dielectric constant of the polypropylene/ethylene propylene diene monomer/calcium borate system is the highest, followed by polypropylene/ethylene propylene diene monomer/NP-100, and the least value of the dielectric constant is exhibited by polypropylene/ethylene propylene diene monomer/zinc hydroxystannate. For the dielectric loss of the composite, the polypropylene/ethylene propylene diene monomer/zinc hydroxystannate, polypropylene/ethylene propylene diene monomer/calcium borate, and polypropylene/ethylene propylene diene monomer/NP-100 blends recorded the lowest, medium, and highest values, respectively. The thermal conductivity of NP-100 is the highest, followed by calcium borate, and then zinc hydroxystannate. The polypropylene/ethylene propylene diene monomer filled with 15vol% of NP-100 is found to be the most suitable composition for electrical insulation compared with other volume composition percentages on account of low thermal conductivity, good flow ability, high breakdown strength, high dielectric constant, and low dielectric loss.