Maiju Hietala, researcher in Wood and Bionanocomposites, at Luleå University of Technology

Wood and plastic in perfect harmony

Published: 21 January 2013

Research at Luleå University of Technology presents a method where individual wood fibers can be used to enhance wood-plastic composites (WPC). Wood fiber serves as reinforcement and gives a stronger and stiffer material. The solution is described in a new doctoral thesis written by Maiju Hietala, PhD in Wood and Bionanocomposites.

– Today, wood fiber is seldom used in the manufacture of wood fiber composites because of difficulties in the process and higher costs, instead wood flour is being used. My research shows that it is possible to separate the wood from the wood chips in a single step process. The process is called extrusion and means that the material is pushed through a nozzle. To avoid destroying the wood fiber, it had to be moistened or exposed to chemical treatment, Maiju Hietala says.

Motivated by the environmental challenge

Interest in the use of renewable materials in biocomposites has steadily increased over the past 10 to 15 years. The main driving forces behind this development are lower material costs and increased environmental awareness. The environment is something that also motivates Maiju:

– I am an environmental engineer from the beginning and want to work with the development of more environmentally friendly materials. Wood is a natural material that we have plenty of in Sweden and Finland, and it would be good if we can expand its uses. In this case we can use residual waste that otherwise would be burnt. It would be possible to replace less environmentally friendly materials like fiberglass with more eco-friendly WPC, especially when the WPC is strengthened with wood fiber.

Reinforcement at the nano-level requires more research

Maiju also tried to use cellulose fiber to produce nanocomposites through extrusion. At the nano-level, components are so small that they are measured in nanometers (billionths of a meter), which makes it possible to give the material unique properties. Experiments with reinforcing plastic with cellulose nanofibers did not completely worked out, so more research is needed in this area.

Maiju Hietala's research has been conducted in collaboration with the University of Oulu where she also conducted fiber analysis. Maiju's PhD is the first dual doctoral dissertation from Luleå University of Technology and the University of Oulu.