Research and application of the hottest wood plast

2022-07-26
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Research and application of wood plastic composites since the establishment of the world trade organization, strict quarantine system (WTO/SPS Agreement) has been implemented for import and export packaging commodities. In 1998, the "longicorn incident" of China's export wood packaging and the implementation of environmental protection policies such as forest protection and returning farmland to forest further accelerated the development and application of wood plastic composites in China

development

wood plastic composite (WPC) is a thermoplastic material filled, reinforced and modified with wood fiber (or plant fiber). It has many performance advantages of wood and plastics. It is extruded (or pressed) into profiles, plates or other products to replace the application of wood and plastics

wood plastic composites have been studied for more than 80 years, but they have not been industrialized until 1985, when a small amount of them were used in sound-absorbing products. With the strengthening of the concept of environmental protection, the industrial departments of the United States, South Korea and Japan in 1990 promoted and accelerated the research and application development of wood plastic composites in order to seek the application of sawdust and waste wood chips, as well as the subsequent resource application. It is one of the most active fields in the extrusion industry to process wood flour filled blends into composites, and new applications and developments are emerging in endlessly. Many countries have invested human, financial and material resources to accelerate the pace of development and application, which has promoted the rapid development of the wood plastic industry

Farrel, a famous American wood plastic manufacturer, believes that the development of wood plastic composites is the result of the attention paid to environmental problems and the decreasing resources of the earth. Experts believe that the driving force for the development of wood plastic composites comes from the requirements of rational utilization of the earth's limited resources, reducing the consumption of raw wood, protecting forests, and recycling old wood powder and plastics. As far as the world is concerned, wood fiber is rich in resources, low in price, light in quality, little wear on equipment, good in dimensional stability, excellent in electrical insulation, non-toxic and harmless, and can be processed repeatedly. The thermoplastic waste plastics are mainly polyolefins such as PE, PP, PS and PVC, including new materials, recycled materials and their mixtures. Sufficient raw materials provide conditions for the development of wood plastic industry

since February, 1998, the United States has first implemented the new quarantine standards for wood packaging materials of China's export goods, requiring fumigation or high-temperature disinfection. Subsequently, Canada and European Union countries successively put forward requirements, otherwise they will refuse entry. At present, 95% of pallets in China are made of wood, and China's wood resource reserves are small, which can not meet the needs of the market. Resource constraints, market changes and environmental protection requirements determine that wood plastic composite products will develop rapidly

manufacturing

at present, the world's wood plastic composites are mainly manufactured by extrusion process. That is, the wood

powder is mixed with the molten resin and extruded. Its main production equipment is extrusion molding machine. At present, there are two commonly used types: one is the high-speed, high-energy "mixing" type co rotating parallel twin-screw extruder. Generally, it is a combined screw, which can adjust the length diameter ratio of the screw, the angle and number of kneading blocks, the combination mode of different kneading blocks, flexibly set the degassing port, and can directly process wood flour (or plant fiber). After drying, the wood flour is mixed with the molten resin and then continuously extruded. That is, wood powder drying and resin melting are carried out separately, so it is often composed of a "two-stage" extruder. Generally, the water content of waste sawdust is 4% ~ 7%. This process requires a large amount of wood flour that meets the requirements of water content. It is generally called "wood extruder". Similarly, wood flour with water content of 6% ~ 8% is added to the main feed port of the extruder. The front section of the extruder is used as the extruder for dehydration, and then the plastic resin is added through the side feeder. Therefore, the extruder is relatively long, and the length diameter ratio (L  D) can be as high as 46. Andex company of the United States takes the lead in this field and has obtained 8 patent production licenses in Europe, the United States, Canada and Japan. In addition, Italian ICMA company, American druppw & P and other companies are also famous for producing co rotating double screw

rod extruders

the other kind of equipment is the counter conical twin-screw extruder, which is generally called "profile

material" equipment with low speed and low energy consumption, and is a non combined screw. Compared with the general cone-shaped twin-screw machine, in order to meet the needs of heat sensitive resin processing, the screw is designed to adapt to a wide processing range, with less cutting effect on wood fiber, and even dispersion when the resin is small. Due to the small specific gravity and large filling amount of wood flour, the volume of the feeding area is larger and longer than that of the conventional model. If the amount of wood powder (plant fiber) is large and the rigidity of the molten resin is large, it is also required to have a high back pressure resistant gearbox. The screw with short metering section is used to ensure that the wood fiber has a short residence time and prevent its fracture and deterioration. The main manufacturers of the equipment include extrusiontekmilacron of the United States and Cincinatti branch of SMC of Germany. It is reported that the former is very experienced in the manufacturing of wood plastic composites and enjoys the reputation of "king of wood plastic" in the world

properties

wood fiber and plant fiber were used as modified filling materials to improve the rigidity of plastics in the early stage. Wood plastic composite can make full use of resources and can be recycled. The waste Huaibei City has also increased investment and intelligence. Whether the waste materials can be recycled is the focus of the second green revolution. It has become an important consideration for the industry to replace paper packaging shopping bags. Therefore, the prospect of wood plastic composites is very promising

The main characteristics of wood plastic composites are as follows: ① good social economy, sustainable development, especially suitable for China's national policy of "forest protection"; ② Durable, long service life, similar to wood appearance, higher hardness than plastic; ③ It has excellent physical properties, better dimensional stability than wood, no cracks, warpage, no wood knots, twills, and can be made into colorful products by adding colorant, film covering or composite surface layer; It has the processability of thermoplastic and is easy to form. It can be formed with general plastic processing equipment or after a little modification. The new investment of processing equipment is less, which is convenient for popularization and application; ⑤ It has the secondary processability similar to wood, and can be cut, bonded, connected and fixed with nails or bolts; ⑥ It is good for decoration, can be painted and beautified, and the product specification and shape can be adjusted according to user requirements, with great flexibility; ⑦ Not afraid of moths, aging, corrosion resistance, small water absorption, no moisture absorption deformation; ⑧ It can be reused and recycled, biodegradable, and protect the environment; ⑨ In favor of environmental protection, waste wood chips, crop fibers and hr45n waste plastics can be used as materials; ⑩ Rich resources, low cost and low use cost. At present, the shortcomings and shortcomings of wood plastic composites are that the toughness is lower than that of parent plastics, and the processing equipment and downstream devices need to be adjusted and transformed accordingly. We believe that with the joint efforts of scientific and technological personnel from all over the world, the deficiencies will be improved in a short time

application

like aluminum-plastic composites, North America is the region with the largest consumption of wood plastic composites in the world. Pricipiapartners of the United States pointed out that in 2001, the consumption in the North American market alone reached 320000 tons, and it is expected that the consumption in 2005 will double that in 2001. Among them, the consumption of plates (including platforms, road slabs, platforms, backing plates), packaging backing plates and composite pallets account for more than 60% of the total consumption

in addition, decorative materials such as wall panels, ceilings, decorative panels, foot boards, wall panels, noise

partitions, and China's plastic machinery enterprise market will further open up the use of wood plastic composite panels for seaside floors, building templates, and moisture-proof boards. It can also be used to decorate frames, fences, courtyard handrails, furniture, cabin partitions, office partitions, storage boxes, flower boxes, movable shelves, shutters, etc

American strandex company pointed out that as wood plastic composites are environmentally friendly and green materials, the consumption of

pipes in Europe is not large at present, but because the processing plants are worried that the European community will effectively limit the use of PVC in the form of regulations, it is a huge market and opportunity for wood plastic window frames to replace PVC window frames. Therefore, experts believe that wood plastic products, which replace PVC and other plastic products, will grow as fast as plastic products and aluminum-plastic composites before, with broad application prospects

last year, the total output of plastic products in China reached 20million tons, ranking the second in the world. The output of packaging plastics in China has exceeded 3.8 million tons, accounting for more than 18% of the total output. The number of packaging waste plastics is huge. In addition, the output of garbage in China has reached a peak, with an annual output of 130 million tons, making China the country with the largest amount of garbage in the world. Sawdust and crop fiber need to find a way out, which also creates conditions for the development of wood plastic composites in China. Therefore, wood plastic composites will have a big market

in a word, the investment project of Xiangkou Township, Yunxi County, Hubei Province of wood plastic composite materials and other composite packaging materials, and the counterpart assistance of Wuchang District to Xiangkou township for three years, have raised a total of millions of yuan in funds (materials) to support the township to implement projects such as market road hardening, village road construction, and financial resource base construction, and have assisted in the construction of two hope primary schools and a commercial marketing chain store

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