Generation of natural fibre reinforced thermosets by means of corotating twin screw extruder

A new type of etherified melamine resin has been reinforced with flax fibres. The kinetics of this resin is optimised in such a manner that the compounding process can be carried out by means of a corotating twin screw extruder. However, the incorporation of unmodified flax fibres causes a shift of the ruling pH value to an acidic range and therefore, small temperature variations can initiate cross-linkage within the extruder. Moreover, formation of covalent bonds between fibres and resin is impeded under acid conditions. Therefore, several acid scavengers were analysed regarding their interaction with flax fibre reinforced melamine resins. It was found that a fibre modification with borax solution prevents a catalytic impact of flax fibres and improves fibre matrix adhesion as well. The mechanical properties of the cured and shaped composites depend on the morphology of the moulding material. The morphology is influenced by fibre modification, screw configuration and process parameters. An optimised screw configuration combined with the use of innovative multicomb elements facilitates a homogeneous incorporation of fillers and additives as well as gentle fibre separation. Furthermore, the fibre modification improves the fibre separation.