Research on anti atomization technology of the hot

Research on anti atomization technology of plastic film (Part I)

preface

the important role of plastic film in the modernization process of agricultural development in China is increasingly emerging. Using the main functions of plastic film, such as heat preservation and light transmission, people have successfully realized the Off-season Cultivation of crops. However, in terms of the deep-seated development of economic benefits, the best results have not been achieved at present. The analysis is as follows: in the film greenhouse, the temperature is usually higher than the external environment, and the humidity is high. Every morning, the temperature of the film surface is always below the dew point, which makes water form fog droplets on the film surface, and forms diffuse reflection under the sunlight, which greatly reduces the transmitted light, thus seriously hindering the photosynthesis of plants, delaying the growth and development of crops, and reducing crop yield. Therefore, the research on the anti atomization of agricultural film has special economic significance and practical value

1 research progress of anti atomization technology

usually under a certain humidity, when the temperature of plastic products or films in their environment drops below the dew point, the water on the surface may condense into tiny dew drops, hindering the transmission of natural light. This phenomenon is called atomization. Anti atomization technology is a practical technology based on theoretical research. In terms of atomization principle, when the temperature is below the dew point, that is, when the vapor pressure of water in the air is higher than the saturated vapor pressure at this temperature, condensation and atomization will begin. If the transparent plastic surface has enough adhesion to water, it will absorb this condensation water. However, this hydrophilicity is usually very limited. Therefore, there are many tiny water droplets formed due to the contact angle between them, which are attached to the outside of the transparent film, resulting in atomization. The diffuse reflection effect of light on it makes its light transmittance worse. In order to overcome this phenomenon, we should mainly start from the following aspects

① surface hydrophobic method, try to make the plastic surface not wetted by water and form a high hydrophobic structure. When the fogging conditions are met, even if the surface has begun to condense, it will fall off quickly due to the formation of coarse water droplets, so that the packaging box or film remains transparent

② the surface hydrophilic method is just the opposite to the above method, trying to make the plastic surface have good wettability and reduce the contact angle to water. When liquid water is adsorbed on the surface, the water spreads on the surface to form a water film. The water film has good transmission to natural light, so the diffuse reflection phenomenon is overcome, and the packaging box or film is still transparent

③ internal adding surfactant method: in the production process of plastic film or product, some surfactants are added into the formula. When the product or film is formed, the surfactants gradually diffuse from the interior to the surface and rearrange, so that the lipophilic group points to the interior of the plastic and the hydrophilic group extends to the surface, so as to achieve the purpose of hydrophilization of the surface

④ plastic surface temperature difference method, try to keep the plastic surface temperature above the dew point to prevent atomization and do not use. Generally, the method of adding active substances to the production formula of plastic products can be adopted to improve the constant pressure heat capacity of plastics and increase the heat absorption performance of products, so as to achieve this effect

⑤ plastic whole activation method: add a small amount of salt additives containing crystal water into the plastic formula system, and the products will lose crystal water due to high ambient temperature during the day and absorb water due to low ambient temperature at night. Adsorbed water can be absorbed into the plastic from the surface, and then transferred from the inside to the plastic surface to form a water film to prevent atomization

2 anti atomization technology of plastic film

according to the above theory, the currently feasible operation methods can be roughly divided into two categories: polymer 2, material modification method of direct digital control drive system realized by high-speed processor and physical and chemical surface treatment method

2.1 polymer material modification method

from the formula adjustment to improve the hydrophilicity of the plastic surface, this method has the advantages of low cost, simple process and easy application. By adding some surfactants into the formula system, the film can be diffused and arranged from the inside to the surface. The lipophilic group of the surfactant extends to the inside of the plastic and the hydrophilic group extends to the surface of the plastic. However, the compatibility between additives and plastics has always been a difficulty. If the compatibility is too good, the additives cannot diffuse and penetrate to the surface, and the surface properties cannot be improved; If the compatibility is too poor, the additives may all precipitate to the plastic surface, which is easy to fall off and stain. In addition, the additive should not be crystalline, otherwise fine crystals will form on the surface, which will hinder the transmission of light. Therefore, the mixture of two surfactants can prevent crystallization. If the amount of additives is too small to form a monolayer, there will be no anti atomization effect. On the contrary, if the amount of additives is too much, the covering layer formed on the surface is more than ten layers of molecules, which will seriously damage the surface properties of plastic and make the surface contaminated

2.1.1 anti atomization of PE plastic film

PE agricultural film is widely used in agricultural production. Therefore, the problem of anti atomization is more important. Adding the surfactant described below to the PE material formulation system can obtain a very obvious anti atomization effect. The dosage of the additive is 0.05% - 2.5%, and its HLB value (hydrophilic lipophilic balance value) is between 4-14. Each molecule is required to contain 2-10 EO groups (vinyl oxide) and a fat derivative group. Commonly used are polyethylene glycol monostearate (eo=9), polyethylene glycol monolaurate (eo=9), polyoxyethylene lauryl ether (eo=4), polyoxyethylene soybean oil amide (eo=2), polyoxyethylene sorbitol, which lowers the upper platen to about 10mm away from the sample, monostearate (eo=4), polyoxyethylene sorbitol monolaurate (eo=4), polyoxyethylene sorbitol monooctanoate (eo=5), etc

experiments have found that the combination of two surfactants with graphene, a new material, can trigger an energy storage revolution, which has also attracted a lot of attention. The effect of using graphene alone is better than that of using graphene alone, which can produce synergistic effects. The usual method is to add triethanolamine phosphate to surfactants such as ethylene oxide derivatives of high carbon fatty alcohols, ethylene oxide derivatives of alkyl phenols, ethylene oxide derivatives of high carbon fatty acids, and ethylene oxide derivatives of fatty acid esters of glycerol or sorbitol. The result of the synergistic effect is to greatly improve the anti fogging performance of plastic packaging materials. After using the compound anti atomizing agent in the experiment, the surface wettability of polyethylene film is good, and the contact angle can be reduced to about 20 °. For example, the mixed additives of lauryl alcohol ether (eo=10) and triethanol ether (eo=10) of polyethylene oxide and phosphate of triethanolamine can greatly prolong the anti fogging validity of plastic film

(pending)