Effect of Chemical Treatments and HDPE-g-MA on the physical and mechanical behaviour of HDPE/ natural fibre composites.

Abstract

Many authors have reported on the use of natural fibres (raw or chemically modified) as reinforcing elements for high density polyethylene (HDPE). These materials have generated a lot of interest due to their low cost and high specific properties. In this work, HDPE and maleic anhydride (MA) compatibilised HDPE were compounded with chemically modified flax and hemp fibres using twin screw extrusion. The physical and mechanical properties of the composite were studied to investigate the effect of chemical modification of the reinforcement fibres. HDPE-g-MA was produced by grafting MA to HDPE’s backbone in a twin screw extruder using a peroxide initiated reactive process. The two chemical treatments used in this study were sodium hydroxide (NaOH) and maleic anhydride (MA) treatments. A fixed fibre loading of 10 wt.% was used in all composites. Fourier Transform Infrared Spectroscopy (FTIR) was used to examine the effects of the chemical treatments on the fibres and it was found that non-cellulosic material had been removed. The mechanical properties of the composites exhibited a significant increase in tensile strength and flexural modulus, whereas a significant decrease was recorded in Impact strength when compared to the virgin HDPE. It was also observed that the addition of the compatibiliser HDPE-g-MA significantly increased the tensile strength when compared with composites containing no compatibiliser. The tensile strength of the NaOH treated fibres reinforced HDPE also showed a significant increase compared with untreated fibre reinforced HDPE composites.Melt flow index analysis indicated that the material remained melt processable following compounding with the natural fibres. Additionally, the composites did not show any significant increase in weight due to water absorption following submersion in water for seven days. Furthermore, cost analysis revealed that the use of composites is advantageous in comparison to virgin HDPE in terms of raw material costs. From this series of tests it has been shown that chemically treatment and HDPE-g-MAcan be used to increase tensile strength and Young’s modulus properties of HDPE/ natural fibres composites.