Spring is a good season for watermelon growing. When using watermelon film, our main concern is its light transmittance and whether it can meet its growth needs. So how to improve the light transmittance of the watermelon special film, so that the watermelon can obtain more sufficient light effect, so that the watermelon can grow better?
Spring is a good season for all things to grow, and light is also very important for plants. In order to make the watermelon grow better, watermelon film should be used. Watermelon film, if used properly, can promote the growth of watermelon, but if used improperly, it will affect the growth of watermelon. So try to use a new watermelon film, the light transmittance of the old watermelon film is naturally poor, and there is no way to compare it with the new one.
When using, you should always wipe the dust on the outer layer of the watermelon special film. It was outdoors after all, as there was a lot of dust outside. If it accumulates for a long time, the outer layer of the watermelon film will be dirty, which will affect the light transmittance of the watermelon film, so wipe the dust outside.
Clean up the dew on the watermelon film in time to prevent it from affecting the light transmittance of the greenhouse film. Generally, there will be dew at night. If it is not cleaned during the day, it will greatly affect its light transmittance.
Because the light transmittance of the watermelon film is more suitable for the use of watermelon, it is necessary to adjust its external conditions and regularly clean the dust and dew on it to improve the light transmittance.
Watermelon special film is selected according to the season. The film is basically used in northern winter. This film is not only weather resistant, but also has strong light transmission and thermal insulation functions.
Greenhouses are covered with straw curtains or insulation covers, which are usually used for insulation. It separates the space into individual enclosed spaces to retain heat and prevent internal and external heat exchange. But the straw curtain just cuts out the movie. In order to keep the temperature in the greenhouse constant, the influence of the thickness of the special film for watermelon on the thermal insulation effect of the greenhouse was studied.
1. With the help of larger bonding force and film shrinkage, the goods are tightly fixed as a whole, so that the scattered fragments become a whole. Even in the dark, the goods will not loosen, separate, no sharp edges and stickiness to avoid damage.
2. Maintenance: Surface maintenance provides a bright maintenance surface for the goods to achieve the purpose of dustproof, oil-proof, moisture-proof, waterproof and anti-theft. Packaging can make the packaging material bear uniform force and avoid damage caused by uneven force, which cannot be achieved by traditional packaging methods.
3. Fastening: Use the shrinking force of the elongated film to pack the goods together to form a compact and space-free unit.
Watermelon mulch film is used every year in the watermelon planting season and off-season, which can reach the breeding temperature of watermelon seedlings and grow well. Watermelons come in different varieties and densities. Density can be used to identify the plastic, but since the density of the foam is not the true density of the material, the foam should be separated at this point. In actual industry, the density of plastics is also used to separate plastics.
The special film for watermelon should be a transparent film with high light transmittance, strong heat insulation, high pressure resistance, pesticide resistance, strong chemical resistance and high chemical fertility. The reclaimed site needs thick film every year, which can be replaced after 2-3 years of continuous use. No thick film is used, it can be harvested in a short time and changed every year.
Polyethylene and polypropylene are the most commonly used olefin plastics. Polybutene-1 and poly-4-methylpentene-1 are also used. Some copolymers of ethylene ethylene and polyisobutylene used for gaskets are also important polyolefin plastics. The easiest way to identify these plastics is by infrared spectroscopy. But some information can also be obtained from the melting temperature range
The host said: Polyethylene (related to density) 105~130℃ Polypropylene 160~170℃ Polybutene 120~135℃ Poly-4-methylpentene-1 more than 240℃
The reactions of the pyrolysis gases of these plastics and mercury oxide are different from each other. Therefore, first soak the filter paper with a sulfuric acid solution containing 0.5 g of yellow mercury oxide (1.5 ml of concentrated sulfuric acid added to 8 ml of water), and then put a small amount of dry sample into the cracking tube, cover the mouth of the tube with the above filter paper, and heat. If the steam causes golden spots on the filter paper, this indicates that these plastics may contain polyisobutylene, butyl rubber, and polypropylene (in small amounts it may take a few minutes for the color to develop). Polyethylene does not react. Natural rubber, nitrile rubber and polybutadiene can produce brown spots. Polyethylene and polypropylene produce waxy products during pyrolysis. Polyethylene has a paraffin-like odor, while polypropylene has a slightly aromatic odor.
Simple identification method of common plastics (2): polystyrene
The identification method of polystyrene and most styrene-containing copolymers is as follows: put a small amount of sample in a small test tube, add four drops of fuming nitric acid, and acid vapor will be released without destroying the polymer. The residue is heated on a flame for about 1 minute, the test tube is positioned so that the open end is slightly downward, and the mouth of the tube is covered with a piece of filter paper. The filter paper was treated by soaking with 2,4-dibromoquinoneimine in ether and drying in air. If you add a drop of ammonia on the filter paper, the filter paper turns blue indicating styrene.
If the sample still contains some free nitric acid, the test is completely affected and the filter paper turns brown to mask the blue color. This identification reaction is also useful for styrene-butadiene copolymers and abs (acrylonitrile-butadiene-styrene copolymers). The presence of acrylonitrile can be verified by assaying for ammonia.
Simple identification method of common plastics (3): chlorine-containing polymers
In addition to polyvinyl chloride (pvc), chlorinated polymers and various copolymers of vinyl chloride are: polyvinylidene chloride, chlorinated rubber, hydrochlorinated rubber, chlorinated polyolefin, polychloroprene and polytriene Chlorofluoroethylene. In addition to using the Bolstein test to detect chlorine, these polymers can also be identified by their color reaction with pyridine (see table).
First, the sample must be extracted with ether to remove the plasticizer. The sample can also be dissolved in tetrahydrofuran. Filter to remove possible insoluble components, add methanol to re-precipitate, after suction filtration, dry at below 75°C, and react with 1 ml of pyridine with a small amount of sample. Let stand for a few minutes, then add 2~5 drops of 5% sodium hydroxide solution in methanol. (1 g of sodium hydroxide dissolved in 20 ml of methanol). Note the color change just after adding the reagent, 5 minutes and 1 hour later
A further test was to boil a small amount of plasticizer-removed specimen with 1 ml of pyridine for one minute, then divide the solution into 2 portions, reheat to boiling, and immediately add 2 drops of 5% sodium hydroxide in methanol To one part of the solution, the other part is cooled first, then add 2 drops of sodium hydroxide methanol solution, observe the color and observe the color change after 5 minutes.