Characterization of In-Situ Reinforced Polymer Composites

Abstract

This study investigates a novel technique for the fabrication of well dispersed carbon particle reinforced polymer composites. The technique is based on the in-situ generation of the particles during polymer melt processing through the incorporation of a carbon-rich precursor of low thermal stability. During processing, the precursor is decomposed, leaving behind carbonaceous char within the polymer matrix. The potential of reinforcing polypropylene (PP) with carbon particles through the above described in-situ process is proven. In this study 44 µm reinforcement carbon particles are created through pyrolysis of carboxymethylcellulose (CMC) at a processing temperature of 270 °C. Five different concentrations (2.5, 5, 10, 15, 25 wt%) of CMC powder were mixed with polypropylene and pyrolysed through successive extrusion compounding cycles, before being injection moulded. CMC is a soluble polysaccharide with a wide application in food and biomedical applications. Studies report the pyrolysis of CMC at high temperatures beyond 400 °C to obtain activated carbon for use in pollution treatment, and biomass gasification. In contrast, this study noticed, amongst other aspects, low temperature pyrolysis ranging between 260 and 300 °C producing micro sized carbon suitable for further use as filler material in PP based composites. Necessary pyrolysis and processing conditions were defined through preliminary thermal analysis of PP and CMC using isothermal and dynamic Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) methods. Observations reveal that a minimum holding temperature of 260 °C is required for pyrolysis, at which the process is terminated after around 26 minutes. Increasing exposure temperature reduces pyrolysis time. Resulting char was analysed using X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Visual inspection using scanning electron microscopy (SEM). CMC char particles were found to be composed of functionalized amorphous carbon of spherical shape, having an average particle size of 44 µm, which is applicable for composite filling purposes. Pyrolysing CMC during polymer processing resulted into well dispersed carbon particle filled polypropylene composites without any agglomerations, as evidenced by scanning electron microscopy (SEM). Thermogravimetric