When we make something by moulding normally we need a release agent or a lubricant to extract it from the mould. It is a condition common to almost all type of materials: rubbers, plastics, concrete,metals, baked foods. Die casting release agents are called in foundy world also lubricants because they must have also a very good lubricating power. Are commonly water based and applied at high dilution rates to use the great water evaporation heat to cool the moulds. We do here a short but general overview on these materials.
The necessity of using the
so called Release Agents when we produce moulded items is a need common to all types of
materials like, for instance, rubbers, plastics, building concrete and metals,
each one with
its peculiar release requirements, easy or difficult to satisfy.If we consider in general
the great world of release agents from the point of view of the intrinsic
notice that there are some of them that are common to all kind of products that
they must fulfill to reach the
target of giving a good release effect.In other words a good
release agent must have the following properties- Be inert toward the
material to demould. In fact if it is absorbed, it cannot be a good barrier
mould and the material to demould.This condition has another
Being inert means also to avoid any interference, chemical or physical, with the surface of the piece moulded to avoid defects of any kind like porosity, stains, flow marks and others.Must adhere to the mould and be resistant to the flow of cast material. If the release agent film is removed, even in a few points, the release is compromised because the moulded piece sticks to the mould and production is slowed or even stopped. Also when it is possible to demould the piece the sticking damages its surface to a certain extent and leads to rejects.
Must have some lubricating effect and help the cast material flow in the mould.
Must have lubricating properties to help the piece be extracted easily.
Must leave no residuals in the mould which are difficult to remove.
In the die casting field we work at very high temperature. A specific condition is the thermal resistance,good enough to allow the release agent to work well in difficult conditions. I means it should resist at the mould temperature first, to form a film stable enough to survive the time between the application and the metal injection in open air that is an oxidizing situation; then at the aluminium temperature to a
certain extent to provide a barrier and lubricating effect.
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