Polyolefin Based Copolymers as Matrix Component in Coir Fiber Reinforced Composites

Abstract

Natural fiber reinforced polymer composites have attracted much attention in global market as they possess much advantageous characteristics over conventional composite materials in terms of eco-friendliness, light weight, low cost, good mechanical properties and biodegradability. Among natural fibers, the surface properties of coir fiber can be easily improved when the fiber is reinforced with polymer matrix. Therefore, the aim of the present investigation is to develop a coir fiber composite reinforced with polyolefin based copolymers (PCs) and investigate the influence of coir fiber loading on mechanical as well as on water absorption behavior of the composites. Three types of PCs were synthesized using different controlled radical polymerizations (CRP) techniques and used as matrix in composite preparation. Poly(ethylene-co-butyl methacrylate) synthesized via dual concurrent atom transfer radical polymerization (ATRP)-reversible addition fragmentation chain transfer (RAFT) polymerization as well as RAFT mediated miniemulsion polymerization and poly(1-octene-co-butyl methacrylate) synthesized via RAFT polymerization were used as matrix component to prepare the composite materials. The performance evaluation of these PCs in the prepared composites was also compared. The composites were prepared using compression moulding method by reinforcing with 65, 70, 75 and 80 wt. % coirfiber loading. Analysis by universal testing machine (UTM) showed that the tensile strength and flexural strength of composites were decreased with increase in the fiber loading. Highest tensile as well as flexural strength was observed for 65 wt. % coir fiber loading. Among the three types of PCs matrixes, poly(ethylene-co-butyl mehacrylate) synthesized by RAFT mediated miniemulsion polymerization showed highest tensile and flexural strengths in the prepared composite. PCs reinforced coir fiber composites showed the potential advantage over coir fiber composites with commercial Araldite 506 resin as matrix component in terms of tensile as well as flexural properties. The morphological study by scanning electron microscopy (SEM) analysis confirmed the good adhesion between the PCs matrixes and the coir fibers in the prepared composites. X-ray photoelectron spectroscopy (XPS) analysis demonstrated significant changes occurred on the surface of coir fiber due to reinforcement of PCs matrixes and X-ray diffraction studies showed the amorphous natures of the composites without any crystallinity. Thermogravimetric analysis results revealed that due to penetration of PCs matrix into the coir fiber, the thermal stability of composites were significantly increased. Furthermore, water absorption properties of composites were also investigated. Based on these results the synthesized PCs/coir composite materials are found to be suitable for its use as hardboards and in different household furniture materials.