Under normal circumstances, the normal use of the grape greenhouse film has good light transmittance, but the old film is easy to adhere to the dust outside the film, and the inside is also dew due to the weakening of the droplet function, which affects the light and is not conducive to the formation of photosynthetic products. Yield and quality of small vegetables. How to maintain the transmittance of the film?
Demisting inside to avoid film condensation
After entering winter, the defogging performance of the film has a great influence on the humidity control of the greenhouse. The better quality plastic film can reduce the fog in the greenhouse to a large extent, and the better dripping performance can make the condensed water fall along the film, avoid directly dripping on the surface of the plant, causing pathogen infection. In addition to the quality of the film, what other factors will affect the dripping properties of the greenhouse film?
1. The whole shed is covered by plastic film.
Some vegetable farmers use plastic film to cover the entire greenhouse, so that the evaporated water in the greenhouse circulates in the space between the plastic film and the plastic film. As soil moisture continues to evaporate, there will be more and more moisture in this space, and dripping will become more and more serious.
2. Close contact between plastic film and steel wire and bamboo scaffolding.
In order to increase the stability of the new greenhouse, many vegetable farmers deliberately increase the density of steel wires and use steel pipes instead of bamboo poles. After replacing the grape greenhouse film, the steel wire spacing of the plastic film factory became smaller, or the film support was not strong. In strong winds, or during the process of retracting the insulation quilt, frequent friction between the shed film and the shed frame will cause the anti-fogging agent on the film to reduce or even disappear, and the dripping becomes worse. Of course, when the water droplets flow downward, obstacles such as steel wires will also gather more water droplets, which will reduce the dripping of the shed film.
3. Excessive use of sulfur and chlorine-containing chemicals.
It is understood that in the production of agricultural film, in order to increase the service life and use effect of greenhouse films, various additives are often added, such as antioxidants, ultraviolet absorbers, hindered amine light stabilizers, brighteners, nucleating agents, and hindered Burning agent, defogging agent, etc., make the film have good performance, anti-aging, light transmission, defogging and dripping. For example, hindered amine light stabilizers can change greenhouse films, but due to their alkaline chemical properties, if a large amount of sulfur and chlorine-containing chemicals are used in the greenhouse, acidic substances are easily formed on the surface of the greenhouse film, and alkaline hindered amines And light stabilizers, thereby reducing the performance of greenhouse films.
4. The angle of the shed surface is too small.
We have always advocated a ratio of ridge height to shed width of 1:2, which is to keep the shed surface more suitable. Once the width of the greenhouse is too large, the curvature of the surface of the greenhouse will be reduced, and the surface of the greenhouse will become straight, which will affect the fluidity of the water droplets on the membrane, so that the water droplets will not directly descend along the membrane flow.
In addition, different types of coverings can also affect the film droplets. On the contrary, it will increase the chance of friction between the grape greenhouse film and the scaffold, thereby affecting the film dripping.