FEATURE “Biocomposites” Applications g…/… Novel composites based on natural fibres and thermosets The higher the density of the moulded part, the better the flexural properties. The binder content has only a small effect. Please note the high values of flexural properties for pressed parts composed of this material that have a density of 0.9 g/cm3 and above: samples in production direction have a flexural MOE between 7-8 GPa and a flexural strength as high as 70-85 MPa. Samples perpendicular to this direction have a flexural MOE about 4.5 GPa and a flexural strength of about 50 MPa. Water uptake also depends on the density of the moulded composite (Figure 7). The water uptake decreases with increasing density of the moulded part. By choosing higher binder contents, water uptake is further reduced, especially at lower composite densities. Moisture-induced thickness swell of moulded composites depends only on the resin content, and not on the density of the moulded part. A higher binder content renders a composite more rigid against dimensional changes, and the fibres are better protected against water. Thus, despite a high water uptake, the thickness swell is not significantly affected. Since water uptake and thickness swell are critical, these properties were further improved by 50% upon application of 1.5% of a hydrophobizing agent. The advantages for the manufacturer of this composite material are (1) preparation of prepregs instead of impregnating the mats immediately before moulding, (2) the good storage stability of impregnated mats and (3) no risk of releasing harmful volatiles during processing. More information: www.kplus-wood.at Fig. 7: water uptake JEC Composites Magazine / No37 December 2007http://www.kplus-wood.at http://www.cpicfiber.com