Performance Evaluation of PLA Based Biocomposites Reinforced with Photografted PALF

Abstract

In this study, biocomposites were fabricated through a compression moulding technique that used untreated and grafted pineapple leaf fibre separately with polylactic acid (PLA) as a matrix. For grafting, pineapple leaf fibre (PALF) was chemically modified using two different monomers, i.e. 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) solutions, in the presence of methanol (MeOH) and photoinitiator (Darocur-1664) under ultraviolet (UV) radiation with the aim of improving thermo-mechanical characteristics. Based on grafting efficiency and mechanical attributes, the intensity of UV radiation and monomer concentration were maximized. A series of solutions, created by varying the concentrations (10‒60%) of monomers in MeOH along with 2% photoinitiator, were prepared. Experimental results revealed that composites made of PALF grafted with 30% HEMA at the 15th pass and 40% MMA at the 20th pass of UV radiation achieved the optimum mechanical properties compared with an untreated PALF/PLA composite. The optimized solutions were further enhanced by adding various concentrations (0.5‒1.5%) of urea, with the best mechanical features achieved using a 1% concentration of urea. The chemical bonds formed due to photografting were viewed using Fourier transform infrared spectroscopy (FTIR). Degradation behaviour under heat was determined through thermogravimetric analysis, which found that photografted PALF/PLA showed significantly better thermal stability than the untreated composite sample. A water uptake test showed that grafting reduced the water retention capacity of the treated composite significantly. Crystallization characteristics were inspected using a differential scanning calorimeter, which showed that grafted PALF had a substantial effect on the degree of crystallization of PLA. In addition, scanning electron microscopy was used to monitor the interfacial bond, and revealed that interfacial adhesion was enhanced by the incorporation of photografted PALF into the matrix.

Keywords

• photografting
• PALF
• thermo-mechanical properties
• PLA
• UV radiation