The main types of greenhouse film at present
At present, the structure of the shed film product should be developed to multi-layer composite, and the performance tends to be developed in the direction of functional integration such as high light transmission, high insulation, high strength, long life and continuous flow drip period, anti-fog period and dustproof period. According to the different production materials, the development of shed film has generally experienced four stages: the first is polyethylene (PE) shed film; The second is polyvinyl chloride (PVC) shed film; The third is ethylene-vinyl acetate copolymer (EVA) shed film; The fourth is the PO film, and the fifth-generation five-layer co-extruded film that is under development.
The main characteristics and differences of various types of shed film
PVC(polyvinyl chloride) shed film. This kind of film has good light transmittance, the new film has a full light transmittance of more than 85%, excellent moisture retention, small thermal conductivity, large tensile strength, and strong wind resistance. Good chemical stability, acid and alkali resistance. The disadvantage is that the film ratio is significant, and the same area of greenhouses, its use is increased by 1/3 than polyethylene, resulting in increased costs; Secondly, it becomes hard and embrittlement at low temperature and easy to soften and relax at high temperature. After the additive precipitation, the film surface vacuuming, generally use a month after the light transmission is very poor, residual film on the soil pollution, can not be burned treatment, due to the production of chlorine gas caused environmental pollution, the current use gradually reduced.
PE shed film. PE shed film texture light, soft, easy modeling, good light transmission, non-toxic, suitable for a variety of shed film, film, is the main agricultural film varieties in our country. According to the needs of farmers, different product types such as PE aging resistance (single protection), PE aging resistance flow drop (double protection), PE aging resistance flow drop fog removal (three protection) can be produced, and it has good aging resistance and flow drop fog removal. Its disadvantages are: poor weather resistance, poor thermal insulation, and not easy to bond. Learned from Manager Song that the current market is more used for PE grout film,
The grout film is based on the original polyethylene shed film, and is processed again. The inner surface of the agricultural film is treated by coating method. In this way, the treated shed film, the functional flow atomizer is tightly attached to the inner wall of the shed film, and a layer of pharmaceutical layer is formed on the inner surface of the shed film. As soon as the moisture in the shed contacts the inner wall of the shed film, it will form a layer of water film, and then it will flow down the slope of the shed due to its own gravity, so as to achieve the effect of eliminating fog and dripping. The essential difference with the previous shed film is that the functional agent exists independently outside the shed film, so the time of the fog and drip function depends entirely on the control of the coating process and the quality of the coating agent as well as the service life of the agricultural film, which can generally reach more than one year.
Of course, there are also individual defects in the grout film. First, the anti-fog droplets are attached to the surface of the agricultural film, so that its adhesion is not so strong. External forces are easy to cause damage to the coating, so it is easy to cause water dripping in the damaged area. For example, when the shed is on, the friction between the inner wall of the shed and the steel frame on the shed, and the high crop encounters the agricultural film will occur. At the same time, crops that like high temperature and high humidity are not easy to use grout film, such as cucumber, bitter melon, melon and so on. However, the defects do not obscure, even if the above situation, the overall effect of agricultural film is still more obvious than the traditional agricultural film. Because this product has obvious advantages in the effect of fog and drip, and the cost is relatively low, its per square meter is about 1.1-1.3 yuan, compared with the price of EVA film, the input cost is less, so it is favored by many vegetable farmers. The current grout film due to different filling levels, product quality is uneven, vegetable farmers in the purchase of various products to inspect, choose a regular company to buy.
EVA membrane. EVA shed film is currently used in a large number of greenhouse plastic film, this film has super light transmission, light transmittance of more than 92%; It has excellent droplet fog removal, and the droplet period is more than 4-6 months. It has excellent thermal insulation, dust resistance and super aging resistance (more than 18 months). Three-layer EVA film can be widely used in the production of high-grade economic pollution-free vegetables, such as cucumber, tomato, pepper, bitter melon and so on. The disadvantage is that the price is higher, according to the thickness specifications are different, the current market price is: 0.08mm in general 2.05-2.1 yuan/square meter, 0.09mm in 2.15-2.2 yuan/square meter.
In addition, PO film is also a new type of film developed in recent years, this kind of film is a high-grade functional polyolefin agricultural film produced by polyolefin, its light transmission, continuous fog elimination, drip, heat preservation, etc., in the shed film in a leading position, cost-effective, is the most promising type of film. At the same time, due to the influence of many domestic brands of PO film production technical reasons, the quality of PO film produced by many companies will be unstable, and farmers need to identify well-known brands when purchasing.