Flame retardant polypropylene (PP) composites were prepared by combining random polypropylene with uncoated and surface-treated forms of magnesium hydroxide filler and elastomeric modifiers, with and without maleic anhydride functionalization. Four types of magnesium hydroxide (MDH) with different surface treatments were compounded at amounts up to 60% by weight to PP/polyolefin elastomer (POE) matrix resin to obtain a series of composites. The tensile strength and elongation at break were measured. MDH coated with polymeric material was found to give a high elongation at break value compared with the values obtained with uncoated and vinyl silane and amino silane coated MDH. Two types of POE, i.e., neat and maleic anhydride grafted POE (POEgMA), were used to investigate the stress whitening of composites in bending deformation. POEgMA used composites showed no stress whitening while neat POE used composites showed whitening when bended.
Nanocomposites of polypropylene-based RTPO with organically modified clays were prepared by melt compounding of three components, that is, polypropylene-based RTPO, maleic anhydride-grafted polypropylene oligomer (PPgMA), and organically modified clay. Their morphologies, tensile behaviors, and flammability properties were investigated. In the clay nanocomposites, the silicate layers were dispersed at the nanometer level, which was confirmed by X-ray diffraction and transmission electron microscopy. The tensile yield strength of nanocomposites containing 10 wt % clay exhibited 2.8 times higher value compared with that of neat resin. The combustion behavior of the nanocomposites was evaluated by measuring the heat release rate (HRR) using cone calorimetry. The peak HRR was lowered greatly and the char yield was very high compared with those of neat resin. However, these flame retardant properties of clay are not sufficient as a flame retardant used alone in cable applications.
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