As a film blowing manufacturer, it is a common phenomenon to change the film formula and produce films of different specifications. In this process, various emergencies and on-site film blowing lead to quality problems due to various reasons. By collecting the most common faults and causes in the film blowing process, New Tianhe Plastics proposes the following points to solve production problems.
1. The film is too sticky and has poor opening
1. The type of resin raw material is wrong, it is not a film-blown low-density polyethylene resin, which does not contain an opening agent or the content of the opening agent is low;
2. The temperature of the molten resin is too high and the fluidity is too large;
3. The inflation ratio is too large, resulting in poor opening of the film;
4. The cooling speed is too slow, the film cooling is insufficient, and mutual bonding occurs under the action of the traction roller pressure;
5. The traction speed is too fast.
Second, the film transparency is poor
1. The extrusion temperature is low and the resin plasticization is poor, resulting in poor transparency of the blown film;
2. The inflation ratio is too small;
3. The cooling effect is not good, which affects the transparency of the film;
4. The moisture content in the resin raw material is too large;
5. The traction speed is too fast and the film cooling is insufficient.
3. The film is wrinkled
1. The thickness of the film is uneven;
2. The cooling effect is not enough;
3. The inflation ratio is too large, causing the film bubble to be unstable, swinging back and forth from side to side, and prone to wrinkles;
4. The angle of the splint is too large, and the film bubble is flattened in a short distance, so the film is also prone to wrinkles;
5. The pressure on both sides of the traction roller is inconsistent, one side is high and the other is low; 6. The axes between the guide rollers are not parallel, which affects the stability and flatness of the film, resulting in wrinkles.
4. The film has fog-like water marks
1. The extrusion temperature is low and the resin plasticization is poor;
2. The resin is damp and the moisture content is too high.
Fifth, the film thickness is not uniform
1. The uniformity of the die gap directly affects the uniformity of the film thickness. If the die gap is not uniform, some parts have larger gaps and some parts have smaller gaps, resulting in more or less extrusion. The thickness of the formed film is also inconsistent, some parts are thin, and some parts are thick;
2. The temperature distribution of the die mouth is uneven, with high and low, so that the thickness of the film after blowing is uneven;
3. The air supply around the cooling air ring is inconsistent, resulting in uneven cooling effect and uneven thickness of the film;
4. Inappropriate inflation ratio and traction ratio make it difficult to control the thickness of the film bubble;
5. The traction speed is not constant and changes constantly, which will of course affect the thickness of the film.
Sixth, the thickness of the film is thick
1. The die gap and extrusion volume are too large, so the film thickness is too thick;
2. The air volume of the cooling air ring is too large, and the film is cooled too fast;
3. The traction speed is too slow.
7. Thin film thickness
1. The die gap is too small and the resistance is too large, so the film thickness is too thin;
2. The air volume of the cooling air ring is too small, and the film cooling is too slow;
3. The traction speed is too fast, the film is stretched too much, and the thickness becomes thinner.
8. Poor heat sealability of the film
1. The frost line is too low, and the polymer molecules are oriented, so that the performance of the film is close to that of the oriented film, resulting in a decrease in heat sealing performance;
2. If the inflation ratio and the traction ratio are too large, the film will be stretched and oriented, thus affecting the heat sealing performance of the film;
Nine, film longitudinal tensile strength is poor
1. The temperature of the molten resin is too high, which will reduce the longitudinal tensile strength of the film;
2. The inflation ratio is too large and does not match the traction ratio, so that the orientation effect and tensile strength of the film in the transverse direction are improved, while the tensile strength in the longitudinal direction will be deteriorated;
3. The cooling rate of the film is too fast;
4. The pulling speed is slow, and the orientation of the film in the longitudinal direction is not enough, so that the longitudinal tensile strength is deteriorated.
10. The transverse tensile strength of the film is poor
1. The cooling speed of the cooling air ring is too slow;
2. The traction speed is too fast, and the difference with the inflation ratio is too large, which will cause fibrillation in the longitudinal direction, and the transverse strength will be deteriorated.
A big, plump grape on the market is mouthwatering. Growing sweet and plump grapes is exactly what most winegrowers expect. If grapes want to increase their yield and sweetness, they naturally cannot do without a special membrane for grapes. Choosing a good plastic wrap can not only improve the yield and quality of grapes, but also have a long service life and reduce the cost of buying plastic wrap. What are the specific benefits?
1. Larger than ordinary agricultural film grapes;
2. Sweeter. It has strong light transmittance, which is beneficial to grape photosynthesis and sugar accumulation. It is sweeter than ordinary grapes;
3. High output. The yield of grapes covered with ordinary agricultural film is higher.
This film is a kind of greenhouse film commonly used in grape cultivation. It does bring many economic benefits to farmers. So what are the advantages of the special membrane for grapes?
1. Droplet and defogging cycles are synchronized with the film
Generally, anti-aging non-drip film and anti-fog film can be used for 3-6 months after being used in the greenhouse. This product can not only prevent the generation of fog, but also form a water film on the inner surface of the shed film and flow down evenly. The utility model can realize the synchronization of the fog droplet defogging period and the aging resistance period, reduce the humidity in the greenhouse, reduce the incidence of diseases and insect pests, have high ultraviolet transmittance, good sterilization performance, reduce the dosage of medicines, and increase the working comfort of farmers in the greenhouse.
2. High strength
Due to the use of excellent polyolefin raw materials, the stretchability, abrasion resistance and wind resistance of the product have been greatly improved. It is suitable for the coverage of warm greenhouses in northern winter and greenhouses around the world.
3. Long service life and long aging resistance. According to the thickness, it can be used continuously for 2-4 years or even longer, which can save manpower to replace the shed film.
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; the third is ethylene-vinyl acetate copolymer greenhouse film; The four types are light-adjustable agricultural films.
PE agricultural film is widely used in agricultural production. Therefore, the problem of its anti-fogging becomes more important. By adding the surfactants described below to the PE material formulation system, a very obvious anti-fogging effect can be obtained. The dosage of the additive is 0.05% to 2.5%, and its hlb value (hydrophilic-lipophilic balance value) is between 4 and 14, and each molecule is required to contain 2 to 10 eo groups (oxyethylene groups) and an aliphatic derivative. group. Commonly used polyglycol monostearate (eo=9), polyglycol monolaurate (eo=9), polyoxyethylene lauryl ether (eo=4), polyoxyethylene soybean oil amide (eo=2), polyoxyethylene sorbitan monostearate (eo=4), polyoxyethylene sorbitan monolaurate (eo=4), polyoxyethylene sorbitan monocaprylate ( eo=5) and so on.
Experiments have found that the combination of two surfactants is better than using one alone, and it can produce a synergistic effect. The commonly used methods are ethylene oxide derivatives of high-carbon fatty alcohols, ethylene oxide derivatives of alkylphenols, ethylene oxide derivatives of high-carbon fatty acids, ethylene oxide derivatives of fatty acid esters of glycerol or sorbitol, etc. In the surfactant, the phosphate of triethanolamine is added, and the result of synergistic effect is to greatly improve the anti-fogging performance of plastic packaging materials. After using the composite anti-fogging agent in the experiment, the surface wettability of the polyethylene film is good, and the contact angle can be reduced to about 20°. For example, the mixed additives of lauryl ether (eo=10) and triethanol ether (eo=10) of polyethylene oxide and phosphate of triethanolamine can greatly extend the validity period of anti-fogging of plastic films.
In order to prolong the service life of agricultural plastic film and achieve greater economic benefits, it is necessary to make reasonable choices, correct use, and good care and maintenance according to the actual situation of the region. The following is a brief introduction to the knowledge of selecting, using and maintaining agricultural plastic films.
The choice of agricultural plastic film
There are different varieties and specifications of plastic films according to the original family, molding method, application, width and thickness. When purchasing plastic film, a reasonable choice should be made according to the climatic conditions and usage of the region. For example, thick plastic film is suitable for use in the area north of the Yellow River; thin plastic film is suitable for use in the area south of the Yangtze River; 0.1 mm thick plastic film is suitable for the outer covering of plastic film greenhouses; 0.065 mm or 0.075 mm thick The plastic film is suitable for raising rice seedlings; the plastic film for covering is preferably wide; the plastic film for packaging is preferably a blown film with a thickness of 0.1 mm or more.
When choosing plastic films, you should also pay attention to the safety performance of plastic films. Generally, agricultural plastic films do not produce harmful gases, and there is no adverse impact on the contact with humans, animals, and crops. It can be said to be safe. However, if the plastic film manufacturer inadvertently uses some volatile auxiliary materials during production, such as adding diisobutyl phthalate to polyvinyl chloride plastic, during the use process, it will gradually change from plastic to plastic. Harmful gases are volatilized from the film, causing crops to be "poisoned", plants grow slowly, and leaves appear yellow and white spots and wither. At this time, it is necessary to quickly ventilate the greenhouse, water the crops with water, and replace the "toxic" plastic film in time to avoid the spread of vegetarianism. The solution to this problem is that, first of all, the manufacturer must strictly control and carefully select auxiliary materials to prevent "toxic" plastic film from leaving the factory; the total number of users should be checked frequently, and the growth and changes of crops in the plastic film greenhouse should be paid attention to. Take immediate action when something goes wrong. In addition, agricultural plastic films are directly used in agricultural production and should not be used to package food, beverages, medicines, etc.
Protection of agricultural plastic film
During the use of plastic film, under the action of light, heat, machinery, chemicals, microorganisms, etc., it often becomes soft and hard, the light transmission performance decreases, and the color gradually changes to brownish yellow. When it is rubbed into pieces, this phenomenon is called "aging" of the plastic film. The longer the plastic film is resistant to aging, the longer its service life. The aging resistance of plastic films is of course determined by the film formulation and processing technology of the manufacturer. However, practice has proved that the same plastic film, in a similar climate environment, due to different use and maintenance methods, aging resistance. The time is also different. It can be seen that correct use and proper maintenance are two important links to prolong the service life of plastic films.
The agricultural plastic film is mainly used for crop breeding, and the manufacturer mainly considers its formula, processing technology and quality standards based on the conditions of use of this plastic film. If this plastic film is used as a "universal film", it can be used as a straw mat when drying crops, used as a raincoat and tarpaulin in rainy days, and used as a sail when sailing, and it will be damaged in a short time. Therefore, each plastic film must have a certain range of use, and pay attention to its correct use. For example, when building a greenhouse with plastic film, the scaffolding should be as smooth as possible, the spikes and protruding parts on the skeleton should be cut off, and the scaffolding material should be moderately soft and hard. When tying the scaffolding, do not use iron wire, but use materials such as straw rope, yarn rope or plastic rope to avoid puncturing the plastic film. The entire scaffolding should not be uneven, and the distance between each bracket should not be too long (generally one to two meters is appropriate) to prevent the plastic film from being scratched by strong winds. When covering the greenhouse, the plastic film should be leveled (but not too tight to avoid tearing) to prevent water accumulation. During the entire use period of the plastic film greenhouse, there should be a special person to manage it. If the shackle is broken, the water accumulates after the rain, the rope is loose, and the film is perforated, it should be maintained and repaired in time.