Mechanism of Mold Release Agent :
1. Demoulding process
After spraying the mold release agent on the surface of the mold, the actual interface during vulcanization molding is shown in Figure 1. In Figure 1, the contact surface between the rubber compound and the release agent is the A side, the release agent side is the B side, the contact surface between the release agent and the mold is the C side; the release agent layer is the coacervate layer. At the time of mold release, it is called interface peeling when peeling on the A side and C side, and it is called coacervate failure when it peels off on the B side.
2. Transfer rate of release agent
The transfer rate of the release agent refers to the percentage of the release agent transferred to the molded product during the demolding process. :
① Peel off the mold from the A side, and the mold release agent does not transfer;
②The release agent is transferred by a small amount (about 22%) due to the peeling off on the A side and the destruction of the coacervate on the B side;
③ The mold is released only due to the destruction of the coacervate, and the release agent is transferred more (about 44% to 70%);
④ Demolition is caused by the peeling of B and C surfaces and the destruction of the coacervate, resulting in the transfer of a large amount of release agent (about 93%);
⑤ When the molded product is in contact with the release agent, mixing and bonding occur, and when it is barely demolded, the surface and interface of part of the molded product (product) will be damaged and demolded. The commonly used release agent is required to be peeled off on the B side or A, B2 side. The release caused by the coacervate has the best release effect.
3. Surface tension of release agent
The release agent's barrier properties depend on its surface properties, and the physical properties of surface non-wetting substances are derived from the concept of its critical surface tension (RC). The measurement method of RC is to drop droplets of several substances with different surface tensions on the surface of the tested substance and measure their contact angle θ. Use the surface tension of the substance to be tested and the cosine value cosθ of its contact angle θ to draw a straight line, extend this straight line and intersect the ordinate, the abscissa value corresponding to the intersection point is the surface tension value of the substance to be tested, also called the substance The critical surface tension RC. This value means: that when the liquid surface tension rL on the surface of the material is greater than the critical surface tension RC of the material, the liquid does not wet the surface of the material; when RL, the liquid will wet the surface of the material. Therefore, the material with small critical surface tension is used as the release agent, which is the release agent with the best isolation.