Melt density and volume flow rate of polypropylene/Al(OH) _3/Mg(OH)_2 flame retardant composites

摘要

Polypropylene (PP) flame retardant composites filled with aluminum hydroxide (Al(OH)_3), magnesium hydroxide (Mg(OH)_2) as well as zinc borate (ZB) were prepared with a twin-screw extruder. The melt volume flow rate (MVR) and density of the composites were measured by means of a melt flow rate instrument under experimental conditions with temperature of 180°C and load varying from 2.16 to 5 kg, to identify the effects of the particle size and content. The results showed that MVR of the composites decreased with an increase of the filler weigh fraction (φ_f) when φ_f was more than 10 phr. The MVR decreased first and then increased with an increase of the filler diameter (d). The melt density (ρ_m) of the composites increased linearly with an increase of φ_f and decreased linearly with the increase of d. In addition, the ρ_m increased with an increase of load. Under the same experimental conditions, the MVR decreased slightly while the ρ_m increased somewhat with addition of ZB for the PP/Al(OH)_3/Mg(OH) _2 composite systems.