Abstract
Aluminium trihydrate (ATH) is being extensively added to polypropylene (PP) to make a fire retardant composite. Blends of PP/ATH composite are more fire resistant as compared to pure PP. Percentage proportion of both the constituents in the final composite depends upon the application. Improvement in the fire retardant properties of such composites have been studied and published in literature but effects on mechanical strength have not been addressed. The effect of concentration of ATH on the strength of PP/ATH composite was presented. The tensile, flexural and fracture properties were studied and discussed. Experimental tests, ASTM analytical formulae and finite element approach were used. It has been found that increase in ATH has an inverse effect on the mechanical strength.
1 Introduction
Thermal and fire retardant properties of polymers often can be altered through the introduction of particulate fillers. These fire retardant polymers have robust application in various fields, such as aerospace, automotive, marine, military [1,2]. Polypropylene (PP) is a thermoplastic polymer which is being used in various industries including textile, stationary, automotive, laboratory equipment, plastic parts and reusable containers of various types [3]. Different concentrations of ATH are commonly added to PP for different applications to increase its flame Refs. [4]. Thermal, electrical and fire retardant properties of ATH blended with different polymers including PP have already been published in Refs. [4−12], while not enough information is available on the mechanical strength and fracture toughness of these polymer composites.
7 Conclusion
Mechanical properties including tensile strength, elastic modulus and flexural strength of flame retardant PP/ATH composite are calculated using standard experimental tests and fracture toughness is calculated using finite element technique and ASTM standard formulae. The FE model is validated through the experimental results of three-point bending test and then used to calculate critical load for a notched specimen. After all experimental tests and FE analyses, the comparison graphs for different blends of PP/ATH composite are plotted and all values are tabulated. It is found that tensile strength, flexural strength and fracture toughness of the composite are decreasing with the increase of ATH in the blend. On the other hand, a slight increase in the elastic modulus of the composite has been noted with the increase of ATH. As evident in the literature, addition of ATH may improve the fire retardancy of the PP polymer, but this research has proved that increase in flame retardancy of the composite is on the expense of the mechanical strength.
