Type And Choice Of Mold Release Agent

Update:2020-08-11 10:50

The  Mold release agent   is used to prevent the molded composite product from adhering to the mold, and an isolation film is used between the product and the mold so that the product can be easily released from the mold while ensuring the surface quality of the product. And the mold is intact.


There are two types of release agents: internal lubricity and external lubricity. The former is mainly to improve the lubricity of the polymer molecule itself, and the latter needs to have a certain degree of affinity or compatibility with the resin polymer. The latter is to improve the lubricity between the mold and the polymer.


Explanation: Ensure that the surface quality of products and molds is intact


Features: Improve the lubricity between the mold and the polymer


Advantages: can be used at a temperature of about 180°C


Commonly used release agents mainly include the following categories:


(1) According to the purpose of release agent, it can be divided into external release agent and internal release agent. The external release agent directly coats the release agent on the mold. The internal mold release agent is a compound whose melting point is slightly lower than the normal molding temperature. It is added to the resin during the thermoforming process and is compatible with liquid resins but incompatible with cured resins. Under certain processing temperature conditions, it will ooze from the resin matrix and form a barrier film between the mold and the product.


(2) According to the state of the release agent, there are film type (mainly polyester, polyethylene, polyvinyl chloride, cellophane, fluoroplastic film) and solution type (mainly hydrocarbon, alcohol, carboxylic acid and carboxylic acid ester), Metal salts include carboxylic acids, ketones, amides and halogenated hydrocarbons), pastes and waxes (including silicate esters, HK-50 heat-resistant grease, cylinder oil, gasoline and asphalt solutions, and waxes). The wax release agent in the base material is the most widely used type of release agent. It is cheap, easy to use, non-toxic and has a good demoulding effect. The disadvantage is that the surface of the product will be stained with oil, which will affect the surface paint. Make demolding difficult. For large products with complex shapes, it is usually used in combination with a solution-based release agent.


(3) According to the combination of release agents, there are single type and compound type release agents (including the combination of components and the method of use).


(4) According to the use temperature of the release agent, there are room temperature and high temperature release agents, such as room temperature wax, high temperature wax and stearate.


(5) According to its chemical composition, there are inorganic release agents (such as talc, kaolin, etc.) and organic release agents.


(6) According to their multiplexing time, there are a single release agent and a multiple release agent.


Due to the excellent adhesion of epoxy resin to other materials, mold release agents are encountered when using molds to mold epoxy resins. In order to smoothly remove the cured product from the mold, it is necessary to apply a release agent on the working surface of the mold. On the one hand, it can make the surface of epoxy resin products smooth, on the other hand, it can protect the mold from damage.


Therefore, it is very important to choose it. The general requirements of the release agent are as follows: easy to use, short drying time; safe and non-toxic operation; uniform and smooth, good film forming; no corrosion to the mold, no effect on the resin curing; low adhesion; it is easy to prepare and cheap .


In fact, it is difficult to fully meet the above requirements and can only be selected according to specific circumstances and conditions. Commonly used external lubricant release agents are as follows:


1. Film: such as polyethylene, polypropylene, polyvinyl chloride, polyester film and other plastic films. This plastic film release agent is easy to use and has good anti-sticking properties. But the disadvantage is that it is poorly laid, and is usually used for products with simple geometric shapes.


2. Solution: Polyvinyl alcohol, silicone oil, silicone grease, liquid or emulsified paraffin are commonly used. For example, the release agent made of silicone grease and toluene solution has good film-forming properties and good release effect, and can be used at a temperature of about 180°C. The disadvantage is that the mold should be baked at about 200°C after coating with silicate solution, otherwise it is not easy to form a film. Usually used for high temperature forming metal molds. It is also possible to spray suspended polytetrafluoroethylene or polyperfluoroethylene propylene on the metal mold, but this method is expensive and requires sintering.



3. Ointment, paraffin wax, stearic acid: but it is inconvenient to use and difficult to apply evenly, which affects the peeling effect. It is divided into four categories: molded products after wax is directly melted; emulsified products; molded products mixed with other substances; finished products after chemical reaction.


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