Evolution of lignocellulosic fibre lengths along the screw profile during twin screw compounding with polycaprolactone

Composites made of polycaprolactone reinforced by 20% hemp fibres were prepared by melt blending in a twin screw extruder (TSE). The influence of the extrusion parameters (feed rate and screw speed) on the fibre length evolution along the screw profile was investigated. The fibre length rapidly decreased after the introduction of the fibres and during the flow through the kneading blocks. Fibre fragmentation was increased at high screw speeds and low feed rates. The flow conditions along the TSE were calculated using Ludovic© software, focusing on the specific mechanical energy (SME) provided to the fibres. The fibre length evolution can be correctly estimated for various flow conditions using an exponential function of the SME.