Fabrication and characterisation of polypropylene nanofibres by melt electrospinning and meltblowing
Creators: name: Nayak, Rajkishore
Publisher: name: RMIT University
Year: 2024

description: This research achieved uniform nanofibres of polypropylene (PP) in melt electrospinning by using additives such as sodium oleate (SO) and sodium chloride (NaCl), which increased the electrical conductivity of the polymer melt. The average fibre diameters achieved by the use of pure polymers of 100, 300, 1000 and 2000 melt flow index (MFI) were in the range of 3.01-14.19 µm. The optimal amount of SO and NaCl were 7% and 5%, respectively for the fabrication of nanofibres from 1000 and 2000 MFI PP. The lowest average fibre diameters (achieved from 2000 MFI PP) were 0.371 ± 0.106 µm and 0.310 ± 0.102 µm corresponding to the optimum conditions of SO and NaCl, respectively. This research established the fact that there is no effect of the die shape on the cross-sectional shape of the meltelectrospun fibres. <br><br>This study also demonstrated the scope of fabricating nanofibres by meltblowing with the injection of various fluids such as air, nitrogen (N<sub>2</sub>) and water. The use of water worked better in terms of fibre morphology as compared to air and N<sub>2</sub> for the fabrication of nanofibres. The lowest fibre diameter of 0.438 µm was achieved from the 300 MFI PP with water. <br><br>This study also established the fact that the molecular weight was the predominant factor governing the fibre diameter in melt electrospinning. In contrast, the molecular weight was not the predominant factor governing the fibre diameter in meltblowing. The effective collector distances for nanofibre fabrication in the case of melt electrospinning were lower compared to the meltblowing. The polymer feed rate was substantially lower in the case of melt electrospinning (i.e. 0.64 g/hr) compared to meltblowing (i.e. 80 g/hr).<br><br>The results of energy dispersive x-ray (EDX) and Fourier transform infrared (FTIR) studies established the presence of additives in the melt electrospun fibres. Similar FTIR and NMR spectra of the polymer and the fibres indicated that there was no chemical change of the fibres fabricated by the application of various fluids and high temperature during meltblowing. The melting points of the fibres fabricated in melt electrospinning and meltblowing shifted to lower values compared to the initial polymer. This change was due to the thermal degradation caused by the high temperature during melt electrospinning and meltblowing. <br><br>The degree of thermal degradation was higher in the case of meltblowing. X-ray diffraction (XRD) studies showed that all the fibres fabricated by melt electrospinning and meltblowing contained low degree of crystallinity. The crystallinity, tensile strength and modulous of the meltblown fibres were increased with annealing. The fibres fabricated by melt electrospinning and meltblowing showed high values of contact angle indicating the hydrophobic nature. The additives SO, PEG and NaCl were washed away from the fibres fabricated by melt electrospinning. Hence, this research has achieved the goal of fabricating nanofibres and added new knowledge to the field of nanofibres.<br>