Processing and characterization of single polmer composites using electrospun nanofibres
Matabola, Kgabo Phillemon
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This study describes the preparation and characterization of single polymer composites of poly(methyl methacrylate) (PMMA) reinforced with electrospun nanofibres. These single polymer composites, which refer to composites in which both the matrix and reinforcement are from the same polymer, have specific economic and ecological advantages and can be recycled. The nanofibres used as reinforcements in this study were produced by an electrospinning process. The interest in the nanofibres over traditional fibres was motivated by the large specific surface area to volume ratio, the smaller diameter and superior mechanical properties. The effect of the electrospinning parameters on the morphology and diameters of the electrospun high molecular weight PMMA (PMMAhigh) was investigated in order to obtain suitable diameters for the reinforcing fibres. The electrospinning parameters investigated were the polymer solution concentration, applied voltage and spinning distance. The results showed that the polymer solution concentration influences the diameter of the electrospun nanofibres more than the spinning voltage and the spinning distance. Furthermore, SEM analysis of the PMMAhigh nanofibres showed that the fibres had a smooth regular and cylindrical morphology with no beads and junctions. Effects of the processing temperature on the preparation of the single polymer composites of PMMA via a film stacking method were investigated. PMMAhigh nanofibres, with diameters ranging from 400-650 nm, were used as the reinforcement and a low molecular weight PMMA (PMMAlow) as the matrix. The results indicated that a processing temperature of 150 °C yielded the best composite with distinguishable physical phases and adequate melting of the matrix material. The effects of the different nanofibre diameters, fibre loading and processing temperature on the thermo-mechanical properties of the PMMA SPCs were investigated. Dynamic mechanical analysis showed a pronounced improvement in the storage moduli, loss moduli and tan δ of the composites compared to the matrix. This behaviour is the result of a positive reinforcing effect of the PMMAhigh nanofibres. The possibility of using the PMMAhigh nanofibres to improve the thermal stability of the PMMA SPCs was also investigated. The results indicated that the thermal stability of the neat PMMAlow matrix is unaffected by the composites formation. This is probably the result of the lower thermal stability of the PMMAhigh nanofibres. Characterization of the mechanical properties of the PMMA single polymer composites revealed that the flexural and impact properties improved upon composite formation whilst the tensile properties remained unchanged.