Application and Chemical Principles of Die Casting Release Agents

Water based release agents should generally be preferred for die-casting release agents because they have the characteristics of low cost, easy volatility, and can not only play a role in demolding, but also regulate the mold temperature during demolding, and are easy to prepare. 
 

When using release agents, whether by spraying or brushing, they should not be too thick and the thickness should not be uniform. The mold can only be closed and die cast after the diluent evaporates, thus avoiding the increase of gas volume in the mold cavity or pressure chamber and the possibility of gas holes in the casting, and avoiding the formation of high back pressure due to the increase of gas, which makes forming difficult. During use, the exhaust system should be cleaned at all times to avoid the exhaust system losing its function due to blockage by release agent. At the same time, it is necessary to avoid turning points and accumulation of release agent at convex corners to prevent unclear contour of the die-casting.

Chemical principle of die-casting release agent:

1. Polar chemical bonds interact with the surface of the mold to form a regenerable adsorption film;

2. The silicon oxygen bond in polydimethylsiloxane can be regarded as a weak dipole (Si+- O -). When the release agent spreads in a single orientation on the surface of the mold, 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 alkyl groups; But when the alkyl group occupies a large steric hindrance, the stretching configuration is limited, and the demolding ability will decrease;

4. The molecular weight and viscosity of the release agent are also related to its demolding ability. When the molecular weight is small, it has good spreading ability but poor heat resistance.