Some Examples of Mold-Release Agents

and silicones are used as mold-release agents. Pareiffin waxes are not very convenient, since they are removed from mold walls by plastic materials. Their chemical structure is such that their adhesion to metals is weak. 

Soaps offer a better adhesion to metals because of the polar part of their molecules. However, they also can be removed by plastic materials, since they have a long and bulky nonpolar chain that is weakly attached to the metal surface by only one point. 

Silicones, mainly polydimethylsiloxane, are excellent mold-release agents. Their chains contain numerous polar groups that adhere strongly to the metal surface, and their methyl groups, pointing away from the surface, facilitate the flow of the melt plastic material. Silicones function thus as a permanent separation layer. Their heat stability is relatively high (around 300°C) and no carbon film is formed when they decompose. However, their presence creates some problems when impression or metallization is to be done afterward on the surface of products. 

Mold-release agents are used in the form of powders, oils or jellies, solutions, sheets, or films. As sheets, cellophane, PVAL, CA, and so on, are used. 

Some lubricants and mold-release agents with some specific applications are listed in Table 2.2. 

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