Wood-plastic composite materials (Wood-Plastic Composites, WPC) is booming in recent years as a new type of composite material, refers to the use of polyethylene, polypropylene and PVC, etc, instead of the usual resin adhesive, with more than 50% flour, rice husk, straw and other plant waste wood fibers mixed into new materials, and then by extrusion, molding, injection molding and other plastic processing technology to produce the sheet, or profile. Mainly used for building materials, furniture, logistics, packaging and other industries. Plastic and wood powder mixed in proportion by hot extrusion of sheet, known as wood-plastic composite sheet extrusion.
 As Wood-plastic composite material containing plastic, so has good elastic modulus.  Furthermore, as containing adequate fiber and mixed with the plastic, which has the equivalent of hardwood compression, bending and other mechanical properties, and durability than conventional wood materials. High surface hardness usually is wood 2 - 5 times.  
Processing  
When the profile does not require a continuous sheet-like structure or structural components with complex design, wood profiles can be through injection molding or compression molding. Processing are sometimes faced with the processing of wood materials to complete filling of the problem, in order to solve this problem, they need to reduce the amount of wood filler to increase the mobility of the melt.  
As the 200℃ is the processing of wood-plastic composite materials maximum operating temperature, some exceed 200℃ melting point resin, such as PET, can not be used for wood-plastic composite materials.
Water vapor will deteriorate the performance of composite materials, but also can breed microbes; the use of wood filler must first be removed before the water vapor. Wood filler before forming processing to be dried, as generally require treatment, the moisture content to less than 1 ~ 2%.  
Wood-plastic composite materials are required equipped with a feeding machine, drying equipment, extrusion equipment and molding equipment, and some need to downstream equipment such as cooling water tanks, haul-off machine and cutting equipment.  
Produce
Should add appropriate additives to modify the surface of polymer and wood flour, in order to improve interface affinity.  
High amount of wood flour filled in melt thermoplastic will lead poor dispersion, poor melt flow, and difficultly extruding, should be added surface treatment agent to improve liquidity in order to facilitate extrusion. 
Plastic substrate is also necessary to add various additives to improve the processing performance and product performance.  
Feeding process  
Flour fluffy structure, is not easy for extruder screw feeding, especially flour contains more water often appears "rack bridge" and "pole" phenomenon. 
Feeding out of stability will lead to wave; the result is out of the quality and capacity.  Feeding interruption, the material to extend the residence time in the machine barrel, resulting in discoloration of materials burned, affecting the intrinsic quality and appearance of products.
Adopt reasonable force feeding device and transport to ensure the stability of extrusion.  
Exhaust in processing  
Wood flour with a few molecules and water is easy to bring deficiencies, while pre-treatment and can not completely remove them. Therefore, wood-plastic composite materials extruder exhausting system should design more than ordinary plastic extruder to give more attention as you can.  
Screw design 
Wood-plastic composites extrusion process, the screw configuration plays an important role. Reasonable screw structure can reduce the friction screw and wood fiber to produce an appropriate mix of shear and dispersion; so that the material contains a lot of wood flour can be a very good system, even plastics. 
Mould design and cooling  
In addition to the design to ensure the smooth flow and reasonable distribution of wood-plastic composite material as the ability to build pressure and temperature control accuracy have higher requirements.  
To obtain good fiber orientation and product quality should ensure that the die head has sufficient capacity and long-established stereotypes pressure section, even in the compressed section by section and setting the structure tapers.  
Wood-plastic composite materials has poor thermal conductivity, and its products mostly profiles and cooling more difficult, to use more water setting. 
Material Properties
1. Product has the same processing performance with the logs, can be nailed, drilled, cut, adhesive, nails or bolts used to connect a fixed, smooth and delicate surface without sanding and paint, the paint adhesion is good, can also be based on individual preference painting. 
2. Product is better than wood physical properties, good dimensional stability than wood, noise will crack, and warp, knot-free wood, twill, adding coloring agents, film or composite surface can be made of colorful a variety of products, so no need regular maintenance. 
3. Can meet a variety of specifications, size, shape, thickness and other needs, which also includes a variety of design, color and grain of the finished products to customers for more choices. 
4. Products have fire, water, carry out corrosion, resistant to moisture functions, and will not be moth-eaten, not long fungi, acid, no poison, no pollution and other excellent performance, low maintenance costs.
5. Wood products use a similar appearance, harder than the plastic, long life, can be thermoplastic molding, high strength, and energy conservation. 
6. Product quality is strong, lightweight, thermal insulation, the surface smooth, free of formaldehyde and other harmful substances, no poison, no pollution. 
Advantages of WPC materials 
(1) Waterproof, moisture-proof. Fundamental solution of the wood products and more humid environment in the water after absorbing moisture decay, expansion and deformation of the problem, you can use traditional wood products can not be applied to the environment.  
(2) Pest control, termite, insects effectively eliminate harassment, to extend the service life.  
(3) Colorful, many colors to choose from. Only has the natural wood texture and the wood texture, but also to customize according to their individual needs color 
(4) Plasticity, can be very simple to achieve personal style, fully reflect the individual style.  
(5) High environmental protection, pollution, pollution-free, can be recycled.  Material products are not benzene, formaldehyde content of 0.2, lower than the EO-level standards, environmental standards for the European classification, recycle a significant reduction in the amount of wood used for sustainable development policy for the benefit of the community.  
(6) High fire resistance. Effective flame retardant, fire rating to B1 level, fire extinguishing, does not produce any toxic gases.  
(7) Can be processed, and can be set can be planed, can be sawed, can be drilled, the surface can be painted.  
(8) Simple installation, construction convenient, does not require complicated construction process, saving installation time and costs.  
(9) Does not crack, no swelling, no distortion, no repair and maintenance, easy to clean, repair and maintenance costs savings later.  
(10) Good sound absorption, energy saving and good indoor energy-saving up to 30%.  
Application of Wood Plastic Composites Products 
Wood interior doors, flooring, baseboard, the whole cabinet, wardrobe, hanging wall plates, decorative hanging plates, hanging siding, outdoor flooring, wood fence, steel gazebo, garden fence, balcony fence, leisure benches, flower , air frames, blinds, and so on. 
Flexible application of WPC materials, can be applied to any field like wood, is the best environmentally friendly materials to replace wood. 
Standard of WPC
GB / T 24137-2009 <<wood decorative board>> 
GB / T 24508-2009 <<Wood Flooring>> 
LY / T 1613-2004 <<wood-plastic composite extrusion>> 

Comparative advantage with the pure wood 
Although wood-plastic composite materials are more expensive than pure wood, but as manufacturers find more efficient processing methods, their relative cost is decreasing. In the use of recycled plastic composite materials can further reduce costs.  Even in the present cost structure, because many consumers are still willing to accept the advantages of composite materials, to accept the relatively high price. 
★ 1. Environment-friendly: 
Use of renewable materials (wood flour and plastics) Do not need to be embalmed.  
★ 2. Does not require routine maintenance, longer service life than wood does not absorb moisture surge, and not rot, pest control Not rupture, cracking, deformation  
On cold and hot environment is not sensitive . 
★ 3. Polyolefin plastic composites mechanical properties can be widely used for bearing structural materials; 
★ 4. Polyolefin materials, 95% use renewable raw materials, cost is relatively low, while products can be 100% recycled; 
★ 5. PVC wood-plastic composite materials increased impact strength through the micro-foam, reduce the proportion.