Transparent plastic film, sheet or sheet, in a humid environment, when the humidity reaches below the dew point, it will condense a layer of fine water droplets on the surface, causing the surface to be fogged and fogged, hindering the transmission of light waves, for example, using film packaging products. At the same time, the contents are also invisible due to fogging, and the generated mist droplets are liable to cause damage to the contents.

Antifogging agents are a class of additives used to prevent the above-mentioned fogging phenomenon. They are surfactants with hydrophilic groups that can be oriented on the surface of the plastic, with the hydrophobic groups inward and the hydrophilic groups outward, so that water can easily wet the plastic surface, and the condensed fine water droplets can rapidly diffuse to form extremely thin water. The layer or large water droplets flow down the film. In this way, the atomization caused by the light scattering of the small water droplets can be avoided, and the condensed water droplets can be prevented from falling onto the packaged object, thereby damaging the packaged object.

According to the manner in which the antifogging agent is added to the plastic, the antifogging agent can be classified into an internal type and an external type. The internal anti-fogging agent is added to the resin during the compounding, and is characterized in that it is not easy to lose and has long lasting effect, but it is difficult to obtain good anti-fogging property for the polymer having higher crystallinity; the anti-fogging agent is soluble in the outer coating type. After being applied to the surface of the plastic film in an organic solvent or water, it is easy to use, low in cost, but poor in durability, easy to be washed away or wiped off, and only used when the anti-fogging agent is ineffective or when it is not required to be durable. .

The effectiveness of anti-fogging agent can be divided into four types: initial anti-fog, long-lasting anti-fog, low-temperature anti-fog and high-temperature anti-fog. It is difficult to combine four effects with anti-fog, often based on film anti-fog. For the effect requirements, choose several combinations.

The chemical composition of the antifogging agent is mainly a partial esterified product of a fatty acid and a polyhydric alcohol. Commonly used polyols are glycerin, sorbitol and anhydrides thereof. Commonly used fatty acids are saturated or unsaturated acids of C11 and C12, and fatty acids having 24 or more carbon atoms can also be used. In general, esters of medium-chain fatty acids have good initial anti-fog effects; long-chain fatty acids have good long-lasting anti-fog effects. In fact, antifogging agents are often mixed esters of various acids. Many fatty acid esters of polyhydric alcohols lack hydrophilicity. By adding ethylene oxide, hydrophilicity can be improved, initial antifogging properties and low temperature antifogging can be increased. Sex.

Antifogging agents should have the following properties:

1. High anti-fog performance, rapid effect and good durability;

2. It has good thermal stability, is not easily decomposed by heat, and the decomposition product does not cause degradation of the polymer;

3. Good compatibility with other additives, does not hinder the function of other additives;

4. Does not affect the transparency, electrical properties, adhesion, stain resistance and other functions of the film.

Several typical antifogging agents are described below.

Glycerol monooleate white wax, can be used as an internal anti-fogging agent, has good initial anti-fog and low temperature anti-fog, suitable for food packaging film, the general dosage in polyethylene is 1~1.5 The fraction is 0.5 to 1 part in the polyolefin. The sorbitan monopalmitate is a yellow granule and is an internal anti-fogging agent. It is effective and long-lasting, and is used in the amount of 1 to 1.7 parts in the polyvinyl chloride.

Sorbitol monostearate is also an anti-fogging agent. It is a yellow granular solid with a melting point of about 60 ° C. It has a long-lasting effect. It is commonly used in agricultural films. It can also be used as a food packaging material. It is used in polyvinyl chloride. The amount used is generally 1.5 to 1.8 parts, and is 0.7 to 1 part in polyvinyl acetate.

Polyethylene oxide (20) glyceryl monostearate is also an internal antifogging agent that is extremely effective and has good initial and low temperature antifogging properties. It is a light yellow liquid with antistatic properties and is suitable for food packaging films. It is generally used in an amount of from 1 to 1.5 parts in the polyvinyl chloride and from 0.5 to 1 part in the polyolefin.

Constant Force Spring

Constant Force Spring,Constant Force Spring Model,Constant Force Springs,Constant Force Spring Processing

Dongguan Jiufukai Hardware Products Co., Ltd , https://www.jfkspring.com