Evaluation of polylactic acid polymer composites strengthened with chopped vetiver fiber and pearl millet-derived- nano silica towards environmental sustainability

Abstract

In search of lightweight materials, polymer (biodegradable) composites are considered across the globe in engineering applications that suit their requirements towards environmental sustainability. In this study, the biodegradable polylactic acid (PLA) based polymer composite is fabricated by reinforcing chopped vetiver fibers (VFs) of varying proportions of weight (5, 10, 15, 20 and 25 wt.%) along with 2 wt.% addition of nano-silica (nSiO₂) derived from pearl millet using injection moulding. The fabricated PLA + VF composite is characterized by its mechanical, wear and thermal behaviour as per ASTM guidelines. Micrographs show an even distribution of nSiO₂ and chopped VFs in the PLA matrix which can impact the properties of composite. Results show that, with the inclusion of VFs in the PLA matrix the density and porosity increase proportionally. Similarly tensile, impact and flexural strength increases until 20 wt.% addition, afterwards a decreasing trend is observed due to poor interfacial bonding of fibers with the matrix. Water absorption nature decreases with the inclusion of nSiO₂, but increases with the inclusion of VFs. The heat deflection temperature of PLA + nSiO₂ + VF increases whereas the coefficient of linear thermal expansion decreases with the inclusion of VFs till 20 wt.%. Wear resistance gets improved due to the incorporation of nSiO₂ and VFs which possess certain self-lubricating properties. Thermal gravimetry analysis (TGA) and differential scanning calorimetry (DSC) assessments exposed that, the addition of VF (20 wt.%) and nSiO₂ increases the heat-withstanding capability as the matrix softening occurs in the 57°C-80.7°C range, with a heating value of 99.4°C, the residual mass obtained is 99.6%.