SOCIETAL BENEFITS OF PLASTICS - Plastics and Environmental Sustainability - page 203

5.4.4 Wood-Plastic Composites
Berge (2009) discussed trends in sustainability of building materials and
construction. There is growing interest in the construction industry to use
greener materials and in certifying construction projects as being “green”
or “sustainable.” Using more of low-impact materials such as wood is an
integral part of this effort. A material that benefits from this trend toward
“green” buildings is thermoplastic composites with bio-fiber fillers, called
wood-plastic composites (WPCs). The 2010 global market for WPC was 2.3
MMT and is expected 10 to grow to 4.6 MMT by 2016, given the short-term
projected growth rate of 13.8%. It is used in outdoor furniture and decking
as well as in the construction of bridges (see Fig. 5.5 ) . The longest plastic
bridge in the United States the 24.6 feet long and is the Onion Ditch Bridge
in Logan County, Ohio, is made of recycled plastic.
Figure 5.5 A deck made of wood-plastic composites.
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 lignocellulosic 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.