oa Mechanical, morphological and thermal properties of LDPE/glass, MDPE/glass and HDPE/glass fibre reinforced composites

Three types of polyethylenes (low density: LDPE, medium density: MDPE, and high density: HDPE) were used to investigate the effect of chain branching on the dispersion and adhesion in glass fibre (GF) reinforced polymer composites. The compounding of LDPE/GF, MDPE/GF and HDPE/GF was carried out in a Brabender twin screw extruder. In each composite system, glass fibre was 20% weight and the main matrix was 80%. The mixtures were fed into hopper of the extruder, extruded, cooled and granulated. The compounded samples were prepared as test specimens by a PE 5 injection molding machine. Mechanical, morphological and thermal methods were used as the characterization techniques to study the interaction between the glass fibre and the polyethylene. Addition of glass fibres to the matrix enhanced the mechanical properties for all composite systems. The degree of enhancement, however, depended on the branching and crystallinity of each polymer. The long chain branching (LCB) in LDPE resulted in higher increase in modulus both in the melt and in the solid state. The higher crystallinity of HDPE was responsible for higher increase in tensile strength and less fibre pull-out upon addition of glass fibres. Scanning electron microscopy of LDPE/glass fibre reinforced composites showed more fibre pull out from the matrix. The addition of glass fibres also resulted in improved thermal stability of the various polyethylene samples. The main aim of this study was to understand the effect of the branching of polyethylene on adhesion of GF to the polymer chain and the results on mechanical, thermal properties of glass fibre reinforced composites.