Effect of extrusion screw speed on biocomposite thermo-mechanical properties

Thermo-mechanical, optical and physical properties of polypropylene (PP)/lignocellulosic fibre-filled/maleated PP composites were studied as a function of extrusion screw speeds. All materials were extruded at four screw speeds and injection moulded as dogbone specimens. The density, yellowness index (YI) and Fourier-transform infrared spectra were determined for the processed specimens. Tensile properties and coefficient of linear thermal expansion (CLTE) were also determined. The densities of the composites remained constant within the same composition. YI and absorbances of carbonyl, vinylidene and hydroxyl groups, which are indicators of thermo-oxidation, decreased with a shorter extruder residence time. The CLTE and tensile properties showed peak properties at intermediate screw speeds. The analysis suggested optimising the residence time assisting in achieving a balance of properties