Classification and Process Introduction of Silicone Release Agent

Dec 9, 2020

Rubber and plastic products in the mold processing, rubber and plastic materials and mold surface contact, may be due to the mold surface concave and convex and other micro defects, rubber and plastic products from the mold stripping will have a certain friction resistance. In the process of injection or extrusion of rubber and plastics, negative pressure is often formed between the rubber and plastic materials and the mold, or the adhesion between them is caused by physical adsorption or chemical bonding, which makes it difficult to peel the rubber plastic products from the mold after molding.

In order to weaken the adsorption or adhesion between the product and the mold, mold release agent, which can form an effective separation film, is often used. The release agent is a layer of film that is used on two surfaces that are easy to adhere to each other, so that the adhesion between the adhesive and the sticky material can be isolated, so that the product can be easily stripped, making the product demoulding easier and more convenient.

There are many kinds of basic materials that can be used as mold release agent. The commonly used mold release agents are inorganic, organic and polymer. The common inorganic release agents include graphite powder, talc powder, mica powder, disulfide key and other powders. The common organic release agents include fatty acids, fatty acid soaps, waxes, glycol, etc, This kind of release agent has the function of lubricant. The polymer release agent mainly includes polyvinyl alcohol, cellulose acetate, organic fluorine polymer and silicone polymer, among which the silicone polymer is the most suitable release agent.

Silicone release agent is prepared from organosiloxane. It has the advantages of good heat resistance, moderate surface tension, easy to form a uniform isolation film, long demoulding life, non-toxic, good luster, and not compatible with resin. It is widely used in plastics, rubber and other occasions. The disadvantage is that there is a layer of oily surface on the surface of the product after demoulding, and the surface must be cleaned after secondary processing. Commonly used are silicone oil, silicone rubber, emulsified silicone oil and silicone grease.

Classification of silicone release agent
Classification by product composition and form
(1) Organosilane and its solution:
The base material of release agent is organochlorosilane or organoalkoxysilane. The direct use of organosilane as release agent has certain limitations. Organochlorosilane absorbs moisture in the air during the film-forming process, and the hydrogen chloride released is corrosive. Therefore, it is only suitable for glass, ceramic solution porcelain and other corrosion-resistant molds.
(2) Silicone oil, its solution and ointment:
The base materials of release agent are methyl silicone oil, methyl phenyl silicone oil and various modified silicone oil. Silicone oil type release agent is usually used to prepare silicone oil solution with silicone oil as the main component and toluene, gasoline and other organic solvents.
Semi solid paste type release agent can be prepared by mixing silica oil with silica, diatomite, mica powder and other solid components.
(3) Silicone rubber and its solution:
Liquid silicone rubber can be directly used as mold release agent, but it is more widely used to prepare silicone rubber solution with organic solvent, crosslinking agent, catalyst and other auxiliary components, and then coated on the mold surface to form a hydrophobic silicone rubber working film.
(4) Silicone resin and its solution:
The base material of release agent is silicone polymer which can be crosslinked and solidified, such as methylsilicone resin and methylphenyl silicone resin. Usually, the silicone resin is dissolved in ethanol, toluene, gasoline and other organic solvents to prepare silicone solution. The release agent is applied to the mold surface by spraying or dip coating process, and then the silicone resin is solidified into a working film by heating.
(5) silicone emulsion:
The emulsion is composed of silicone oil or silicone resin as the main component, emulsifier and water added. The water emulsion coated on the mold surface is formed after the moisture evaporates.
(6) Silicone aerosol:
Silicone oil as the main component, together with Freon, butane and other ejectors, is mixed and packaged in a sealed container. When applied with the release agent, the main component of the release agent is sprayed on the mold surface with the main component of the release agent. The spray agent volatilizes rapidly and the residue forms the working film of the release agent.
(7) Other types:

In addition, there are direct use of silicone rubber to make elastic mold, silicone rubber mold itself not only has good heat resistance, but also has excellent performance of anti adhesion and easy demoulding, especially suitable for forming demoulding of products with complex shape.

Classification by service life
(1) Temporary release agent:
During the working process, some components of the release agent are gradually consumed, that is, the release agent is transferred to the products. Temporary release agent is one-time application or one-time finishing for limited times. Silicone release agent based on various inert silicone oil is a typical temporary release agent.
(2) Semi permanent release agent:
The solidified film of release agent is firmly attached to the surface of the mold. During the process of product processing and after the product demoulding, the release agent does not transfer to the product and is not digested, so it becomes a semi permanent release agent.
Classification by application object or process conditions
According to the application object, such as polyurethane release agent, tire release agent.
According to the actual use of technology, such as: high temperature resistant release agent, acid and alkali resistant release agent, etc.
Characteristics of silicone release agent
Comparison of various silicone release agents

The application method of bulk silicone oil type and aerosol type release agent is the most convenient. It only needs to spray the release agent on the mold surface to carry out the processing operation, and the product demoulding is simple.The application of ointment type release agent is more complicated than the former, but after its working film, it is suitable for the mold with rough surface, and the frequency of sustainable and effective demoulding is relatively more.Compared with the aqueous silicone release agent, the water emulsion type does not pollute the environment because it does not use organic solution, but water emulsion.