Natural fiber composites are made with a thermoplastic or a thermosetting polymer matrix. The thermoplastics can be PE, PP, PS, PVC or PLA, while the thermosetting polymers are mainly acrylate, epoxide and phenol resins. The most important natural fibers used are flax, hemp, jute, kenaf, sisal, abaca and cotton. Other frequently used materials include wood fiber, sawdust and rice husks. In many cases, optimal bonding of the matrix and fibers is ensured by using adhesion promoters.
Indispensable for natural fiber composites compounding is perfect dispersive and distributive mixing at low product temperatures, in order to process the additives and typically high content of 30-70% natural fibers according to product specifications without thermally damaging the fibers. Also required are multiple feed points and if necessary the injection of liquid adhesion promoters at predetermined positions.
The BUSS Co-Kneader’s specific capabilities really come to the fore in these applications. Due to the operating principle of natural fiber composites compounding, the enormous number of mixing cycles at moderate and uniform shear rates enables unsurpassed mixing efficiency and product quality at maximum throughput rates. As a side effect of the moderate shear rates, wear and tear is significantly lower than with other kinds of screw extruders. The process chamber is modularly designed by in-house experts according to specific applications.