Tamarix - and other invasive species as wood plastic composites

Wood-plastic composites from invasive
species
The rapid growth of wood–plastic composites (WPCs) in the
United States, especially in large-volume exterior products,
provides an outlet for significant quantities of wood processing
residues and also has the potential to use invasive species.
These composites are becoming increasingly popular
with consumers because of their inherent durability and low
maintenance requirements. The greatest growth in WPCs
has been in exterior building products such as decking and
guardrails. Invasive species would be an excellent raw material
to manufacture panels using both injection molded and
extrusion methods.
Particles of salt cedar, one-seed juniper, and eastern redcedar
were used to manufacture WPC samples (Winandy et al.
2005). Raw material was hammer-milled using 13- and 0.8-
mm screens. The largest particles were removed by sifting
the wood flour using a screen with 0.4 mm openings. The
wood flours were dried for at least 4 h at 105ºC. Each wood
flour batch was blended with an injection-molding grade
of polypropylene (PP) in a 32-mm compounding extruder.
For comparison, commercial pine wood flour was also compounded
with PP. Each blend contained 40% wood flour
by weight. The compounded blends were then dried, and
test bars were molded using a reciprocating screw injection
molder. Flexural, tensile, and impact tests were conducted
based on ASTM standards (ASTM 2003a,b). Results of the
mechanical tests are summarized in Table 2. Figure 3 illustrates
profile extrusion of a salt cedar–HDPE (high-density
polyethylene) composite. Laboratory and field evaluations
are ongoing.