The use of lignocellulosics with thermoplastics, however, is a more recent innovation. Broadly defined, a thermoplastic softens when heated and hardens when cooled. Wood flour is a readily available resource that can be used as a filler in thermoplastic composites. Wood flour is processed commercially, often from post-industrial materials such as planer shavings, chips, and sawdust.
Several grades are available depending upon wood species and particle size.
Wood fibers, although more difficult to process compared with wood flour, can lead to superior composite properties and act more as a reinforcement rather than a filler. A wide variety of wood fibers are available from both virgin and recycled resources. Other materials can be added to affect processing and product performance of wood-thermoplastic composites. Several considerations must be kept in mind when processing wood with thermoplastics. Moisture can disrupt many thermoplastic processes, resulting in poor surface quality, voids, and unacceptable parts.