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Introduction To WPC(Wood- Plastic Composites)
- May 17, 2017 -

Wood-plastic composite materials (Wood-Plastic Composites, WPC), is booming in recent years, a new type of composite materials, refers to the use of polyethylene, polypropylene and polyvinyl chloride, instead of the usual resin adhesive, and More than 35% -70% of wood flour, rice husk, straw and other waste plant fiber mixed into a new wood material, and then by extrusion, molding, injection molding and other plastic processing technology to produce the plate or profile. Mainly used for building materials, furniture, logistics and packaging industries. The plastic and wood powder by a certain percentage of mixed after the hot extrusion molding of the plate, called the extruded wood-plastic composite sheet.
 
Introduction
    Wood-plastic composite material contains plastic, which has a good elastic modulus. In addition, due to the inclusion of fiber and fully mixed with the plastic, which has a comparable hardwood and hardwood, bending and other physical and mechanical properties, and its durability is significantly better than ordinary wood materials. Surface hardness is high, generally 2 - 5 times the wood.
Processing Introduction
Some of the artificial zeolites can be added to the polymer. This aluminosilicate molecule captures the powder to absorb the odor in the material. Through the powder in a large number of crystal voids, the adsorbent can capture the odor of organic small molecules. Molecular trapping adsorbents have been successfully applied to polyolefin extruded tubing, injection and extrusion blown containers, isolated packaging materials, extruded packaging and sealing materials. The molecularly adsorbed powder can also be added as a dehumidifier to the plastic to remove water vapor.
Extruded products of different sizes and shapes increase the diversity of wood-plastic composites
When the profile is not required to have a continuous sheet structure or the parts have a complex structural design, the wood mold can be molded by injection or molded. Processors are sometimes faced with the problem of how the wood-plastic material is fully charged during processing. To solve this problem, they need to reduce the amount of wood fillers to increase the melt flow.
Since 200 ° C is the upper limit of the operating temperature of the wood-plastic composite, some resins with a melting point of more than 200 ° C, such as PET, can not be used in wood-plastic composites.
Water vapor will degrade the properties of the composite and also contribute to the breeding of microorganisms, so water vapor must be removed before using wood fillers. Before processing the wood filler to be dried, the general requirements of the treated water vapor content is less than 1 ~ 2%.
Now the wood-plastic composite processing machinery is equipped with feeding equipment, drying equipment, extrusion equipment and molding equipment, there are some necessary downstream equipment such as cooling water tanks, traction equipment and cutting equipment.

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Appropriate additives are required to modify the surface of the polymer and wood flour to enhance the interface affinity between the wood powder and the resin.

The high-filling wood powder has poor dispersibility in the molten thermoplastic, making the melt flow poor and difficult to be extruded. The surface treatment agent can be added to improve the flowability to facilitate extrusion molding.
Plastic matrix also need to add a variety of additives to improve its processing performance and the use of its products performance.
Feeding process
Wood flour fluffy structure, not easy to feed the extruder screw, especially wood powder contains more water often appear "bridge" and "pole" phenomenon.
Unstable feeding can lead to extrusion fluctuations, resulting in reduced extrusion quality and yield. Feeding interrupted, the material in the barrel to stay longer, resulting in material charred discoloration, affecting the inherent quality of products and appearance.
Using a forced feeding device and a reasonable way to transport to ensure the stability of extrusion.
Processing exhaust
The small molecules of volatile matter and water contained in the wood flour are highly prone to defects in the product, and the pre-treatment can not completely remove them. So the wood-plastic composite extruder exhaust system design than ordinary plastic extruder to give more attention, if necessary, can be multi-stage exhaust.
To a large extent, the better the exhaust effect, the better the quality of the extruded product.
Screw configuration design
In the process of extrusion of wood-plastic composites, the configuration of the screw plays a very important role. Reasonable screw structure can reduce the friction between the screw and the wood fiber, produce appropriate shear and dispersion, so that a large amount of wood powder material system can be a good uniform plastic.
Mold design and cooling stereotypes
In addition to ensuring a smooth transition of the runner design and a reasonable flow distribution, the wood-plastic composite material has a higher demand for the construction pressure and temperature control accuracy.
To achieve good fiber orientation and product quality is necessary to ensure that the nose has enough pressure and long positioning section, even in the compression section and stereotypes using double taper structure.
Wood-plastic composite thermal conductivity is poor, and its products are mostly profiles, cooling stereotypes more difficult, more water-cooled stereotypes. The cooling runner is designed to ensure efficient cooling


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Material properties
1. The product has the same processing performance as the logs, can be nailed, drillable, can be cut, bonded, fixed with nails or bolts, smooth and delicate surface, no sanding and paint, the paint adhesion is good, Like paint.
2. Products have better physical properties than logs, better stability than wood size, noisy cracks, warping, no wood knots, twill, adding colorants, coated or composite surface can be made of colorful Various products, so no need for regular maintenance.
3. Can be a variety of specifications, size, shape, thickness and other needs, which also includes a variety of design, color and grain of finished products, to customers more choices.
4. Products with fire, water, engage in corrosion, resistance to moisture, not insects, not long fungi, Naisuan Jian, non-toxic, non-polluting and other excellent performance, low maintenance costs.
5. Product use similar to the appearance of wood, plastic hardness than high, long life, can be thermoplastic, high strength, energy conservation.
6. Product quality Kennedy, light weight, insulation, smooth surface, free of formaldehyde and other harmful substances, non-toxic, non-polluting.
Five advantages of wood-plastic materials
(1) waterproof, moisture. Fundamentally solve the wood products on the wet and multi-water environment, moisture absorption after the moisture is easy to rot, expansion and deformation of the problem, you can use the traditional wood products can not be used in the environment.
(2) pest control, anti-termite, effectively prevent insects harassment, to extend the service life.
(3) Variety of colors to choose from. Both natural wood texture and wood texture, but also according to their own personality to customize the required color
(4) plasticity, can be very simple to achieve personalized modeling, fully embodies the personality style.
(5) high environmental protection, pollution-free, pollution-free, recyclable. Products do not contain benzene, formaldehyde content of 0.2, lower than the EO-class standards for the European environmental standards, can be recycled to greatly save the amount of wood for sustainable development of the national policy for the benefit of the community.
(6) high fire resistance. Can effectively flame retardant, fire rating to B1 level, the case of fire self-extinguishing, does not produce any toxic gases.
(7) can be machinable, can be set, can be shaved, can be saw, drillable, the surface can be painted.
(8) easy to install, easy construction, do not need complicated construction technology, saving installation time and cost.
(9) no crack, no expansion, no deformation, no maintenance and maintenance, easy to clean, save post-repair and maintenance costs.
(10) sound-absorbing effect is good, energy-saving, so that indoor energy saving up to 30% or more.
The application of wood
Wooden floor, floor coverings, the whole cabinet, wardrobe, wall hanging board, decorative hanging plate, hanging plate, outdoor floor, wood plastic fence, steel gazebo, garden guardrail, balcony guardrail, leisure benches, flower rack , Air conditioning planes, shutters, and so on.
Wood plastic materials, flexible application, can be used in any field of wood processing, wood is currently the best environmentally friendly materials; currently engaged in wood products in the development and production of enterprises: Guangzhou famous wood, Jiangsu tripod, Jiangxi three and Wood, Shandong Guoqiang Hardware Group, Shanghai Health of the wood, Ben Ben, Hong Tai (China) snow Deng, Linyi Green can Wood, Linyi Jinding Wood manufacturers.
At present, wood-plastic products in the country's low energy consumption played a vital role, is a recyclable product, the country's several major projects in the application of a more extensive, which in the construction of the Beijing Olympic Games and three plastic (China) snow Deng, the country wind wood, Bai love wood, Long Hao wood six wood for the Green Olympics made a great contribution. In the construction of the World Expo and three wood and plastic, Dabo plastic wood, the country of wood and other seven wood-plastic enterprises for the Expo building blocks.
Standard for wood and plastic
GB / T 24137-2009 "wood-plastic decorative panels"
GB / T 24508-2009 "wood flooring"
LY / T 1613-2004 "extruded wood-plastic composite"
Comparison of wood and pure wood
Although the wood-plastic composite material is more expensive than pure wood, but with the manufacturers to find more efficient processing methods, the relative high cost is gradually reduced. The use of recycled plastics in composites can also further reduce costs. Even in the face of the current cost structure, many consumers are still willing to accept the relatively high price because of the advantages of these composite materials.
 1, environmentally friendly:
Use of recycled materials (wood flour and plastic)
Do not need to be anti-corrosion treatment
 2, do not need routine maintenance, long life than the wood does not absorb moisture, tide, do not rot, pest control
Not broken, cracked, not deformed
Not sensitive to cold and hot environments
 3, polyolefin wood-plastic composite mechanical properties, and can be widely used for carrying structural materials;
 4, polyolefin wood-plastic materials 95% of the raw materials for renewable materials, so the cost is low, while the product can be 100% recycling;
 5, PVC wood-plastic composite material through the micro-foam to improve the impact strength, reduce the proportion of the real imitation wood.