Cellulose/polypropylene composites: the use of AKD and ASA sizes as compatibilizers
Daniel F. Caulfield, Research Chemist, USDA Forest Service, Forest Products Lab., Madison, Wisconsin James A. Koutsky, Professor, Chemical Engineering, University of Wisconsin, Madison, Wisconsin Daniel T. Quillen, Graduate Research Assistant, Materials Science Program, University of Wisconsin, Madison, Wisconsin
Abstract Alkylketene dimer (AKD) and alkenyl succinic anhydride (ASA) were used as compatibilizers in both solution and emulsion forms to treat 100 percent cellulose and 70/30 wt.% cellulose/polypropylene composite sheets made by both an air-formation technique and traditional wet handsheet formation. In all cases, the air-formed sheets had poorer mechanical properties than did the handsheets. While the treatments appeared to have a visible effect on the spreading of polypropylene over cellulose, the effects of the treatments on mechanical properties was almost always negative. Annealing the wet-formed handsheets for 5 minutes at 130°C before pressing gave control sheets with improved modulus, strain-to-break, and burst strength, but had a slight negative effect on air-formed sheet properties. The effect of treatments on the water durability of the airformed sheets was minimal or adverse, while for the wet-laid handsheets, the treatments were slightly beneficial if the sheets had been annealed, but detrimental if they had not. Introduction It has been widely noted that a key to good composite properties lies incompatibility between matrix and filler. In the wood fiber-polyolefin system, the highly polar nature of the cellulosic surface does not lend itself to strong interactions with the non-polar polymer. Modification of the cellulose surface, either by chemical coupling agents or grafting, has proven to be beneficial in improving the strength and modulus, as well as the water resistance of these composites (4,7,8,11,12,14,15,17,19). In the realm of paper...