Wood-polymer composites (WPC) - a composition comprising a polymer (of natural or chemical origin) and the organic filler modified by chemical agents. Wood-polymer composites consist of the following components:
- organic filler ;
- or a synthetic thermoplastic organic polymers or mixtures thereof; it’s possible to use recycled materials;
A set of special chemical additives (modifiers) that enhance consumer and technological properties of the initial mixture and the finished product.
The first specialized enterprises for the production of WPC appeared in Sweden in 1977. At that time for reducing the final cost approximately 30% of finely ground sawdust was added to the final product based on PVC mixture. This experiment didn’t bring much success - the demand was insignificant, and the wear process equipment, on the contrary, very high. Therefore, the development in this field resumed only in the 90s in such countries as Finland, Sweden, Germany, Italy, the Netherlands, Japan and the United States. Modern equipment and technology have led to a more acceptable performance of the manufacturing process, and wood fibers, previously regarded as a defective filler, have now become the main component of the composite material.
Nowadays the global market for wood-polymer composites is close to 3 billion. USD. The popularity of the material can be attributed to several factors, among which are the key:
- shortage of initial materials - wood and polymers and dependence of polymer market on oil prices;
- environmental programs development within which it is necessary to process waste products;
- high aesthetic and physical-mechanical properties of wood-polymer composites, a material with unique design properties;
Wood-polymer composites can be classified according to different criteria: depending on the composition, method of processing, builders, etc. The most important types of WPC grouping are listed in the following table. The term does not impose any restriction on the type of organic filler. Various agricultural waste and waste of consumption can be used instead of wood.
Table 1. Classification of wood-polymer composites
|1. Composition and components of the mixture|
|2. Type of processing||
|3. Filler type||
|4. Wood component aggregation state|
|5. By type of thermoplastic polymer binder||
|6. By physical and mechanical propertiesм|
|7. By density||
|8. By strength||
|9. By flammability||
|10. By resistance to water, light, biological and other influencesм||
|11. By external look|
|12. By design||
|13. By surface type||
Variety of classification indicates that the term wood-polymer composite combines a large group of materials which, on the one hand, has a single basic properties and, on the other hand, have their own unique characteristics. This is due to a variety of formulas used, i.e. change in the ratio of filler and binder, use a variety of modifiers and processing agents.
In the following paragraphs of the report the basic properties of wood- polymer composite will be described, as well as features for preparation of various formulas of the composite compound.