Preparation and characterization of polypropylene/rubber powder blends containing two flame retardant systems intended for the automotive industry

Abstract

Two series of polymer blends based on post-consumer materials, i.e. postconsumer polypropylene (rPP) and rubber dust (Rd) under the trademark ECOPLASTOMER® PP70 with a mutual ratio of components 70/30 wt.% containing 10, 20, and 30 wt.% of flame retardants, have been prepared using a twin-screw

eco-friendly system based on melamine phosphate (MP), aluminum hydroxide oxide (AC), and peanut shells (PS), used as flame retardant agents on the mechanical, thermal, and flammability properties of polymer blends was assessed. The incorporation of ATH-sil results in the appearance of peaks related to OH groups, with higher intensity for increased ratio of filler; similar observations are made for the MP-AC-PS system, although mainly finding the P-OH from MP, Al-O from AC. DSC analysis revealed that the inclusion of the selected flame retardants did not impact the melting and crystallization temperatures of the polymer matrix. Conversely, an attenuation in the melt flow rate ofthe composites was observed with increasing proportions ofboth additives, leading to enhanced rigidity, elevated elastic modulus, and diminished elongation at break following a similar pattern. Tensile strength experienced a minor decrease, particularly in composites containing more than 20% of the flame retardants, while hardness remained unaffected by their integration. Both flame retardants diminished the combustibility of the modified polypropylene/rubber powder blends; nevertheless, the most favorable outcomes were achieved with ATH-sil, especially when employed ata minimum of 30wt%. The formulated MP/AC/PS system proved more adept at diminishing combustibility and smoke emissions at lower levels of flame retardants.