The use of wood fibres as filler in polymers dates back to the early 1900s. With the introduction of thermoplastics, the first commercial application of wood polymer composite (WPC) appeared in the mid-1950s, with the production of a wooden flooring tile made of PVC and wood flour. The most common technologies for producing WPCs today are extrusion and injection moulding, although some other technologies are also emerging. Several academic institutes along with some leading companies have been pooling their scientific and technical resources with the objective of developing the specific properties of wood products for various applications, leading to an increase in their use and the upgrading of their former “low-tech” image in the market.
Part of a car-door (photos: Mondi)
Oil price movements and shortage of oil supply strongly influence polymer prices, which can be both a threat and an opportunity for the WPC industry. Rising polymer prices can lead to the substitution of pure polymers with filled polymers, for example.
The most frequent application of WPC in North America, Europe and now in Asia is decking. Wooden decking is a new idea in Europe; stone has been the traditional material in its gardens. Tropical wood has the majority market share at present, followed by domestic timber and pressure-treated wood. WPC decking is gaining market share throughout Europe and many producers have been seen to have switched to the production of solid profiles, which offer a number of advantages in processing and installation, despite their weight.
The European WPC market currently amounts to about 175,000t/a. The markets for WPC siding, fencing and railing are still in the initial stages. The market showed steady growth until 2010, followed by two to three years of stagnation. Growth in this market has now resumed and it is expected to reach about 220,000t/a in 2015. The North American market currently amounts to about 1,500,000t/a and the rising Chinese market is currently for around 700,000t/a.
WPCs are used in a wide variety of applications in Europe, from decking and siding to sophisticated musical instruments, furniture, watches, pencils, tableware, toys, decoration and pallets.
WPCs are used in a wide variety of applications in Europe; here in a crate
Injection moulding is used more and more for the production of low-proportion natural fibre composites (NFC) – materials with up to 50% a content of natural fibres by weight. A number of other applications are currently undergoing commercial assessment, with the main focus on automotive applications (see picture below), where WPC materials have to compete with the talcum and glass fibre-filled compounds currently in use, as well as compression-moulded NFCs.
In automotive applications WPC materials have to compete with the talcum and glass-fibre -filled compounds currently in use, and compression-moulded NFCs; here part of a car-door made of WPC
Europe lags behind North America in marketing and brand development for NFC. Deeper penetration into the various different markets will require companies to increase their efforts to make the advantages and performance of this class of materials clear to both decision-makers and consumers. A study of the differences in the expectations of consumer and experts was presented by Wood K plus. It should also be noted that the definitions of “biocomposite” can be quite confusing, for consumers in particular.
Recycling
Recycling is a wide field and has to be divided into different topics: the use of recycled materials for the production of WPC/NFC; the use of process waste (in-plant recycling); and the use of the WPC/NFC after their lifetime, for example, thermal disposal is a further possible area of study.
The use of recycled materials as raw materials in the production process has to satisfy various requirements, on sourcing in particular. Sorted recycling materials, such as bottle caps, have to be differentiated from post-consumer materials. Both have to offer consistent standards, for high-quality products in particular. For example, the clarinet made of grenadill composite was developed by Fasal Wood and manufactured from the production waste of solid grenadilla wood clarinets. In-plant recycling does not normally present any problems, because the materials can be processed several times without significant deterioration. Tests conducted by Wood K plus showed that ten regrinding and injection moulding cycles led to only small changes in mechanical properties and a colour change in lighter composites can be observed after several cycles. So, a partial substitution of virgin materials should not be a problem. The use of sorted recycling material and post-consumer materials in particular will have to be demand-tested for various requirements.
Clarinet made from the production waste os solid grenadilla wood clarinets (photo: Fasal Wood)
The use of post-lifetime WPC/NFC is more critical as these materials will have been exposed to weathering and can also be contaminated. Testing will be required for each potential application and high quality products are probably not possible.
With the exception of formulations based on PVC, waste removal and the thermal disposal of decking materials do not cause any problems. In the case of low-percentage composites the materials have an advantage compared to traditional materials, such as PP filled with talcum or glass fibres, in that no residual ashes incur.
Summary
European WPC markets are again on an upward trend, but at a lower rate; stable growth for WPC production is forecast until 2015. Although Europeans are very cautious toward new materials, large WPC producers could change this through joint marketing activities. As this industry comes to recognise the performance range and production processes of this material class, progressively more applications will emerge, with benefits for the whole market.
Marketing is currently taking place at a low level, through the use of different quality signs, for example. WPC/NFC is a raw material that is based on renewable resources but this is not well-enough known either to decision makers or end-users. Current market data have been presented at various congresses in Europe.
In the case of recycling, many questions remain to be answered and the knowledge necessary for clear statements has to be generated. It is important to avoid repeating the mistakes made in the past, such as promises, for instance, “maintenance-free” that cannot be kept.
www.kplus-wood.at
Author: Dipl-Ing Dr Andreas Haider, Key Researcher at Wood K plus
