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Greenhouse film refers to a special plastic film used for facility agricultural production and construction. Its light transmittance, thermal insulation , the tensile and aging resistance properties are better than ordinary agricultural films.

There are four main types of greenhouse films commonly used in my country: the first is polyvinyl chloride (PVC) greenhouse film; the second is polyethylene (PE) greenhouse film; and the third is ethylene-vinyl acetate. Polymer greenhouse film; the fourth type is dimmable agricultural film.

These types of shed films have similarities and differences in properties, so their use effects are also different.

(1) Polyvinyl chloride (PVC) shed film has good thermal insulation, light transmittance and weather resistance, is soft and easy to shape, and is suitable as an outer covering material for greenhouses, greenhouses and small and medium-sized sheds. The disadvantage is that the film has a specific gravity (1.3 grams/cubic centimeter), and the coverage area of ??a shed film of a certain weight is 1/3 less than that of polyethylene film (PE), which increases the cost; it becomes hard and brittle at low temperatures, and it is easy to soften and relax at high temperatures; After the additives are precipitated, the film surface will absorb dust, which will affect the light transmission. The remaining film cannot be burned because chlorine gas will be generated. The main products of polyvinyl chloride shed film are:

① No anti-aging additives are added during the film making process of ordinary PVC shed film, and the service life is only 4-6 months. It can produce one season of crops and waste energy. , increased employment and investment, and are also being gradually eliminated.

② PVC anti-aging film is made by adding anti-aging additives to the raw materials and rolling them into a film. The effective use period is 8-10 months. It has good light transmittance, heat preservation and weather resistance. It is the main material for covering greenhouses and small and medium-sized sheds. It is mostly used for cultivation in early spring and late autumn.

③PVC drip-free anti-aging film (PVC double anti-shedding film) has both anti-aging and dripping properties, good light transmittance and thermal insulation, drip-free lasting 4-6 months, safe to use It has a lifespan of 12-18 months and is widely used. It is the first choice covering material for high-efficiency and energy-saving solar greenhouses. It is more effective as a greenhouse covering material.

④ In addition to the weather-resistant dripping performance, the PVC weather-resistant drip-free dust-proof film has a treated film surface, which results in less plasticization and less plasticization. It is lighter in dust absorption and improves the light transmittance. It is suitable for solar greenhouses and greenhouses. Cultivation in winter and spring is more beneficial.

(2) Polyethylene (PE) shed film is light in texture (specific gravity is about 0.96 g/cubic centimeter), soft, easy to shape, has good light transmittance, and is non-toxic. It is suitable for making various shed films, Mulch film is the main agricultural film variety in my country. Its disadvantages are: poor weather resistance and thermal insulation, and difficult to bond. If you produce greenhouse films, you must add anti-aging agents, drip-free agents, heat preservation agents and other additives to meet the production requirements. The main products are:

① Ordinary PE shed film (also known as PE blown agricultural film) is a white film produced directly from raw materials by blow molding without adding anti-aging and other additives. It is widely used in greenhouses and small and medium-sized sheds. , generally closed in spring and autumn, the use period is only 4-6 months, and only one season of crops can be grown, which wastes energy, increases labor, and is gradually eliminated in production.

②PE anti-aging film (also known as longevity film, anti-aging film) is made by adding anti-aging additives to PE resin and blowing it into a film. This kind of greenhouse film has a thickness of 0.08-0.12 mm and a service life of 12 to 18 months. It can be used for crop cultivation for 2-3 seasons. It not only extends the service life, reduces costs and saves energy, but also greatly increases the output and output value. It is Agricultural film varieties that are mainly promoted in facility cultivation.

③PE drip-free anti-aging film (also known as double anti-film, long-life dripping film) has dripping properties, weather resistance, light transmittance and thermal insulation at the same time, and the anti-fogging effect can be maintained for 2- 4 months, with an aging resistance life of 12-18 months. It is a comprehensive agricultural film variety that is widely used. It can not only be used in greenhouses and large, medium and small greenhouses, but is also suitable for early spring cultivation in energy-saving solar greenhouses.

④PE insulation shed film is a covering material that can prevent infrared radiation from radiating into the atmosphere, can increase the temperature of the greenhouse by 1-2°C, and has good application effects in cold areas.

⑤PE multi-functional composite film has various functions such as drip-free, heat preservation, weather resistance, longevity, etc. Some of them have ultraviolet blocking function to reduce the transmission of ultraviolet rays in the shed. Some can inhibit the formation of Sclerotinia ascus discs and Botrytis cinerea conidia. The service life can be up to 12-18 months.

(3) Ethylene vinyl acetate polymer (EVA for short) greenhouse film: (adding a certain proportion of eva), EVA resin is a new agricultural film material used in agriculture in recent years. The agricultural film made of it has better light transmittance, heat preservation and weather resistance than PVC or PE agricultural film. EVA agricultural film covering can increase yield by about 10% compared to other greenhouse films, can be used continuously for more than 2 years, does not deform before aging, can be easily recycled after use, and is not likely to cause soil or environmental pollution.

(4) Dimmable agricultural film is a dimmable film made by adding rare earths and other functional additives to PE resin, which can selectively transmit light and make full use of solar energy. Compared with other greenhouse films, it is a new type of covering material that has good warming and insulation effects in the greenhouse and strong biochemical effects on crops. It has the functions of early maturity, high yield, and improved nutritional content for different crops. Rare earth can also absorb ultraviolet rays, extending the use of agricultural films. life. Among them, the special purple film for leafy vegetables (leek film) is made by adding purple masterbatch and weather-resistant, heat-insulating, and drip-free masterbatch into the film, and then blowing it into a film. The film is slightly bluish-purple in color, reducing strong light, increasing temperature, advancing the growth period, and achieving high quality and high yield. Suitable for the cultivation of leeks and various green leafy vegetables.