Raw materials for wood-polymer composites.

Abstract

To understand wood-plastic composites (WPCs) adequately, we must first understand the two main constituents. Though both are polymer based, they are very different in origin, structure, and performance. Polymers are high molecular weight materials whose performance is largely determined by its molecular architecture. In WPCs, a polymer matrix forms the continuous phase surrounding the wood component. These matrix polymers are typically low-cost commodity polymers that flow easily when heated, allowing for considerable processing flexibility when wood is combined with them. These polymers tend to shrink and swell with temperature but absorb little moisture and can be effective barriers to moisture intrusion in a well-designed composite. Wood itself contains polymers such as lignin, cellulose, and various hemicelluloses but has very different properties from the synthetic polymers with which it is most often combined. Wood is less expensive, stiffer, and stronger than these synthetic polymers, making it a useful filler or reinforcement. Though wood does not shrink and swell much with temperature, it readily absorbs moisture, which alters its properties and dimensions and can lead to biodegradation if not protected. In this chapter, we explore the basic structure and properties of polymers and wood individually to lay a foundation for a greater understanding of the composites made from them. Basic concepts and properties are briefly summarized with emphasis on materials common to current commercial technology. Sources of further information are listed at the end of the chapter.

Citation

Clemons, C. 2008. Raw materials for wood-polymer composites. Wood-polymer composites. Cambridge, U.K. : Woodhead Publication, Ltd. ; Boca Raton : CRC Press, 2008: p. 1.1-1.22: ISBN: 9781845692728: 1845692721.