Wood compatibilizer

One outlet for polypropylene, polyethylene, and polyvinyl chloride waste is plastic lumber. These materials, often containing more than one polymer and a wide variety of additives, provide superior weather resistance in humid environments when compared to natural wood. To manufacture these materials, the compound incorporates compatibilizers, which allow dissimilar polymers to mix evenly, Additionally, they assist in the incorporation of fillers and additives, such as wood flour, calcium carbonate, and pigments. 

Caulfield, D.F., Koutsky, J.A. and Quillen, D.J. (1993). CeUulose/polypropylene composites the use of AKD and ASA sizes as compatibilizers. In Wood Fiber/Polymer Composites Fundamental Concepts, Processes, and Material Options, Wolcott, M.P. (Ed.). Forest Products Society, pp. 128-134. 

This chapter reports successful initial efforts to bond wood in the presence of hydrophobic plastic material [polystyrene (PS)] using well-defined and tailored cellulose-polystyrene graft polymers as compatibilizers or interfacial agents. The synthesis of these tailored cellulose graft polymers is also presented. 

Figure 1. Exploded view of the use of graft polymers (GP) to compatibilize the linking of wood (W) and polystyrene (PS) materials.

The potential use of cellulose graft polymers to compatibilize the linking of a natural polymer (wood) with a synthetic polymer (polystyrene) is based on... 

Encouraging results on the bonding of plastics to wood using tailor-made cellulose-polystyrene graft polymers as compatibilizers or interfacial agents may offer a new approach to the engineering of wood-plastic products with improved mechanical and physical properties for a variety of applications. It also holds the potential of opening up new markets for renewable resources in the form of woody materials. For example, polystyrene production is currently 3.9 billion... 

A parallel lecture treats all these processes from the point of view of compatibilization [16], Here we cite some of our earlier results using recycled wood waste, talc and calcium carbonate to bond together all these components by a modest dose of radiation, in presence of a limited amount of reactive additive [17],... 

U.S. Pat. No. 6,942,829 [72] discloses a method of forming a polymer-wood composite material comprising 20-80% by weight of cellulose filler such as hardwood fiber, softwood fiber, hemp, jute, rice hulls, and wheat straw, 20-80% of a thermoplastic polymer such as polypropylene, polyethylene, polyamides, polyesters, and other polymers, 0.1-10% of a blend of a nonionic compatibilizer and a lubricant. 

D. Feng and A.R. Sanadi. Effect of compatibilizer on the structure-property relationships of kenaf fiber-polypropylene composites. In Fourth International Conference on Wood-flber-Plastic Composites, Madison, WI, May 12-14, 1997, pp 157-160. 

H. Nitz, P. Reichert, H. Romling, R. Mulhaupt, Influence of compatibilizers on the surface hardness, water uptake and the mechanical properties of poly (propylene) wood flour composites prepared by reactive extrusion. Macromol. Mater. Eng. 276, 51-58 (2000)... 

Since the early 2000s, plant-derived biobased fibrous fillers have been frequently used for the reinforcement of PLA-based materials. A well known and frequently used plant-derived fibrous filler is kenaf. Like the case of pollen as an additive, the wettability between PLLA and kenaf should be improved by the addition of a compatibilizer. Other fibrous materials are cellulose fibrous materials or fibres [383,384], cellulose whiskers [385], recycled cellulose fibre [386], cotton fibre [387], sugar beet pulp [388], flax [389], bamboo fibre [390], kenaf [391-393], papyrus [394], hemp fibre [395], cuphea and lesquerella [396], ramie [397], rice straw fibre [398], red algae fibre [399], miscanthus fibre [400], abaca fibre [401], milkweed [402], wood fibre [403] and recycled newspaper fibre [404], Poly(L-lactic acid) fibre can also be used to reinforce soft plastics such as PCL [405],... 

More recently [22], a poly-(aminoamide-epichlorohydrin)/stearic anhydride compatibilizer system was developed to optimize the interface between pine flour and polyethylene in the corresponding composites. FTIR spectra showed that the compatibilizer had indeed been grafted to the wood particles and the decrease in water uptake by the composite corroborated the interest in using this novel system. 

The treatment of wood fibres with isocyanate-bearing molecules and their incorporation into polyethylene were also recently studied [44]. In particular, the use of poly-(diphenylmethane diisocyanate) (XV) increased both the modulus of rupture (MOR) and the modulus of elasticity (MOE) of the ensuing composites. The use of stearic anhydride (XVI) as a novel compatibilizer further improved both MOR and MOE and enhanced the water resistance of the composites. 

The performance of wood-polyethylene composites was found to improve by an appropriate compatibilization with different MAs and the additional incorporation of organo-clay particles [47] consisting of natural mont-morillonite modified with quaternary ammonium salt. The thermal expansion coefficient and the heat of deflection values indicated that these materials displayed an improved interfacial adhesion. 

The plastic fraction used in WPC is usually recycled PE, PP, PET, PVC PS, or a mix of these. Wood fiber as well as other natural lignoceUulosic fibers can be used as the filler the characteristics of fibers that are good candidates are shown in Table 5.9. Being of natural origin, a given type of fiber can have a large variation in properties (Kouini and Serier, 2012). The use of compatibilizers or pretreatment of the wood fraction is often employed to ensure good dispersion of filler in the plastic matrix. 

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