Preparation, processing and characterization of biodegradable wood flour/starch-cellulose acetate compounds

A novel biodegradable material was prepared by compounding, in different pr oportions, pine wood flour (WF) and a commercial starch-cellulose acetate b lend on a configurable co-rotating twin screw extruder. After pelletizing, the compounds were injection moulded and the mechanical and rheological pro perties of the mouldings determined. As the content of wood flour increases up to 50% (wt/wt), the tensile strength and the modulus improve significan tly, whereas the toughness drops gradually. The effect of the wood flour co ntent on the shear viscosity is complex, being impossible to establish a li near relationship between the two. The shear viscosity decreases with shear rate, but for a level of 40% and 50% of WF there is evidence of a quasi-Ne wtonian behaviour, irrespective of the test temperature. Compounds with 50% WF present the highest tensile strength and modulus but are difficult to p rocess. However, the processability can be improved by using glycerol as pl asticizer, without paying a too severe penalty in mechanical properties. In fact, by adding 15% glycerol (wt/wt), compounds with 50% WF can be success fully injection moulded into specimens with good mechanical properties. (C) 2001 Kluwer Academic Publishers.