Die-casting mold release agents should generally be water-based mold release agents, because it has the characteristics of low cost, volatile, and can also play a role in adjusting the mold temperature in addition to the role of mold release, and easy to prepare Wait.
When using the release agent, whether it is spraying or brushing, it should not be too thick and the thickness should not be uniform. The die can be closed and die-cast after the diluent volatilizes, thereby avoiding the increase in the amount of gas in the cavity or pressure chamber and the occurrence of pores in the casting Possibility to avoid the formation of high back pressure due to the increase of gas, making forming difficult. In use, the exhaust system should be vented at any time to avoid the failure of the exhaust system due to the blockage of the release agent. At the same time, avoid turning and accumulation of the release agent at the convex corners to avoid unclear contours of the die castings.
The chemical principle of die casting release agent:
1. The polar chemical bond interacts with the mold surface to form a regenerative adsorption film;
2. The silicon-oxygen bond in polysiloxane can be regarded as a weak dipole (Si+-O-). When the release agent is spread on the mold surface into a single orientation arrangement, the molecule adopts a unique extended chain configuration;
3. The free surface is covered by alkyl groups in a densely packed manner, and the demolding ability increases with the density of the alkyl group; but when the alkyl group occupies a large steric hindrance, the stretching configuration is limited and the demolding ability will be reduced;
4. The molecular weight and viscosity of the release agent are also related to the release ability. The molecular weight is small and the spreadability is good, but the heat resistance is poor.