Overview of recycling of the hottest waste plastic

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Overview of recycling and utilization of waste plastics

polymer materials are widely used in daily life, all walks of life and advanced technology fields because of their light weight, easy processing, beautiful and practical characteristics. However, while bringing people huge material civilization, the generation of waste also poses serious problems

about 20% to 30% of the plastic products produced every year in China belong to plastic packaging products and plastic agricultural films with short service life. After use, some of these plastic products become municipal solid waste and enter the garbage treatment system, while the other part is discarded at will. According to statistics, the annual output of urban domestic waste in China has reached 120 million tons, of which waste plastics account for 2-4%; In addition, according to the survey of Beijing, the daily production of garbage in Beijing is 16000 tons Among them, waste plastic accounts for 5% (about 800t/D), and the total amount of plastic waste produced each year is about 290000 tons. From the perspective of resource utilization, it is also valuable. When working, the temperature rise of the former is much lower than that of the latter. The recycling of waste plastics has important social and economic significance for saving energy, reducing the volume of waste plastics, reducing the harm of waste plastics to the environment and curbing the increase of oil prices

plastics can be divided into thermoplastics and thermosetting plastics according to their processing properties. Thermoplastics mainly include polyolefins, PVC, PS, pet, etc. (thermosetting resins are not introduced in this book). At present, thermoplastic waste plastics are the main waste plastics needed in plastic wood technology

polyolefins (including PE and PP) are widely used in films, packaging products, injection products (such as turnover boxes, parts, etc.) and plastic pipes. The service life of agricultural film is generally short. For example, the service life of the existing greenhouse film in China is usually 1-2 years. After use, the discarded agricultural film enters the environment and becomes an important part of plastic waste

polypropylene film is also one of the main application fields of polypropylene resin. PP film can be divided into cast PP film, blown polypropylene film and biaxially stretched polypropylene film (BOPP). The production scale of BOPP film is the largest, accounting for 60% of the total PP film. The application form of PP film also includes secondary processing products, such as metal plating film, composite film such as bopp-pe, bopp-pvdc, etc. PP film is mainly used for the packaging of food, textiles, washing supplies, drugs, etc., and also for electrical insulation film

another major use of polyolefins is woven products, including woven bags and woven fabrics, of which polypropylene woven products account for 60% - 70%. In China, due to the lack of paper and jute resources, plastic woven bags can be widely used. In addition to general woven bags, there are paper plastic composite bags, eye bags, etc., which can be used for the packaging of chemical fertilizers, cement, mineral products, resin, raw salt, sugar, grain, cotton, wool and so on

polyolefin resin is also the main raw material of plastic pipes, and its dosage is lower than PVC, ranking second. The products include water pipes, well pipes, micro irrigation pipes, corrugated pipes, composite pipes, gas pipes, etc., which are used for rural drinking water and agricultural irrigation, as well as the transportation of materials and media in chemical, food, beverage, pharmaceutical and other industries, and can also be used as urban gas and natural gas pipelines In addition, polyolefin is also used as the packaging of various containers, such as milk, edible oil, cosmetic crystal, household chemical crystal, drugs, chemical products, etc. Calcium plastic corrugated box is also a kind of kitchen, which is mainly corrugated sheet rolled by HDPE, calcium carbonate and various additives. It has the characteristics of high strength, light weight, moisture resistance and corrosion resistance, and has the advantages of both cartons and wooden boxes

the disadvantage is that it is slippery and cannot pack large or overweight goods

polyolefins are widely used, and the amount of waste plastics in different fields is increasing year by year. Therefore, in plastic wood technology and its products, polyolefin recycling material is the most important plastic raw material according to the force value of the impact testing machine in the tested range

PVC, commonly known as PVC, is one of the four general-purpose resins. It has the characteristics of high mechanical strength, good insulation performance, excellent flame retardancy, corrosion resistance, easy processing and so on. It is widely used in the fields of construction, packaging, electronic appliances and automotive industry, and its consumption ranks second in synthetic resins. At present, the annual average volume of waste PVC products in China is about 260000 tons. Among the recycled waste plastics in China, PVC recycling accounts for about 40% to 50% of the total recycling, mainly agricultural film, bottles, packaging film and other household waste, so that more people can wear other products. In 1994, the recycling volume reached 130000 tons. The Recycled PVC is mainly used to make recycled pipes, plates, slippers, floors and other products

in addition to the above general plastics, there are also a large number of thermoplastic composites and engineering thermoplastics

engineering thermoplastic is a kind of functional thermoplastic with good heat resistance, cold resistance, mechanical property, dimensional stability, electrical insulation, chemical resistance, weather resistance, conductivity, UV radiation resistance and adhesion. These properties of engineering thermoplastics enable them to be used in harsh environments, especially in the fields of electronics, electrical, automotive, medicine, optics, sports and construction. Engineering thermoplastic has maintained a good momentum of development since it entered the market due to its wide range of applications

with the increase of the consumption of engineering thermoplastics, its waste is also increasing. Among the recycled waste plastics, engineering thermoplastics are often mixed, so it is difficult to sort them out. Wood flour and this kind of waste plastics are blended and extruded, which basically has no impact on the service performance of plastic wood products. However, sometimes we need to pay attention to the control of the processing temperature of the extruder, because the processing temperature of engineering thermoplastic is generally high. When this kind of plastic is mixed more, the processing temperature should be appropriately increased

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