Potential of carbon particle reinforced polypropylene formed in-situ through the pyrolysis of carboxymethylcellulose

The potential of reinforcing polypropylene (PP) with carbon particles through an in-situ process is investigated. In this technique 44 µm reinforcement particles are created through pyrolysis of carboxymethylcellulose (CMC) during compounding. CMC is a natural cellulose polymer that decomposes at 270 °C - the processing temperature of PP. CMC was mixed with polypropylene and pyrolysed through successive extrusion compounding cycles, before being injection moulded into samples. This technique results in good dispersion of the carbon particles without any agglomerations, as evidenced by scanning electron microscopy (SEM). Thermogravimetric analyses reveal a carbon content of 4-28 vol% when initially mixing 2.5-25 wt% CMC into the PP matrix. Mechanical testing of the carbon reinforced PP results in an improvement in impact strength by 69%, however, at the cost of a 14% drop in tensile strength, both associated with a weak particle-matrix interface as evidenced by SEM and mathematical modelling of the interface. This, in addition to the prolonged processing time are outcomes calling for the optimisation of the compounding and pyrolysis process in future work. However, this study definitely shows the potential of reinforcing thermoplastic polymers through the pyrolysis of another carbon-rich polymer of low thermal stability.