The development of polypropylene composites reinforced micro and nanoalumina filler from industrial waste

Abstract

Excessive source of bauxite ore has led to the relentless production of primary Aluminium (Al) globally. Environmental hazards caused by the Al manufacturing activities and high cost procedure of its scheduled waste safe disposal pose serious problems and demands sustainable solutions for the Al industries. Malaysia has abundant deposit of Al dross resulted from Al smelting process and easily available thermoplastic polypropylene (PP) from the oil industry. Effective use of local Al dross waste recycling to alumina (Al2O3) as filler in PP composite system is an interesting economic prospect, since Malaysia currently imports its Al2O3 requirements. The aim of this work is to synthesize micro and nano α-Al2O3 from Al dross using thermal decomposition and wet milling method; followed by analyzing the effect of micro and nano α-Al2O3 content on mechanical, morphological, wear and thermal properties as well as addition of maleic anhydride grafted polypropylene (MAPP) compatibilizer in PP composites. PP composites (without and with MAPP) based on various formulations (1, 3, 5 and 7 weight percentage (wt.%)) for both micro and nanosized α-Al2O3 particles were prepared through different processing method. The processes involved were compounding method using twin screw extruder machine followed by hot pressing. The mechanical properties of micro and nanocomposites are studied through tensile and impact tests. Mechanical properties showed improvement in tensile strength and modulus with increases micro and nano α-Al2O3 content from 1 to 5 wt.%. An optimum tensile strength was obtained by PP composite with MAPP filled 5 wt.% nano α-Al2O3 particles. These findings were supported by field emmision scanning electron microscopy (FESEM) where in the MAPP addition particularly, better dispersion of 5 wt.% nanocomposite was observed. Impact strength values however decreases with increases of α-Al2O3 loading from 3 to 7 wt.% which indicates improved stiffness of both micro and nanocomposite. The highest wear rate attained by 7 wt.% nanocomposite was significant as increased in nano α-Al2O3 content along with MAPP addition resulted in better wear resistance. Similarly, α-Al2O3 particles increment up to 7 wt.% increases the decomposition and melting temperature (Tm) of nanocomposite with MAPP compared to microcomposite. Thus, micro and nanoalumina particles produced from Al dross is an appealing alternative in utilizing the industrial waste efficiently besides enhancing the composites’ mechanical, wear and thermal properties.