Demolding force

The necessary demolding stiffness can be adjusted with the temperature control of the mold. Demolding forces can be influenced by temperature control (shrinkage, stiffness, tendency to stick). 

Scaling (reactions of materials with gas) of metal parts is a type of corrosion that also occurs in injection molds. Examples are uncooled cores that turn blue when acquiring a scale layer. This scale layer changes the demolding force among other effects. 

Mold release effect—the demolding force required to eject a solidified part from the mold is reduced so that the finished article is ejected from the hot mold without deformation. External release agents are based on PE waxes, fluoropolymers or high molecular weight polymers (or a mixture of these) in a solvent solution or in a water emulsion. Many types are noninflammable. They are generally sprayed on the mold surfaces and consist of silicone compounds in traces. They affect adhesion of ink and paint. 

Testing of lubricants is based on the determination of the flow behavior of plastic melts (capillary viscosi-metry, spiral flow test, demolding force, by plasto-graph, extrusiometer, melt strength, roll-mill tests, etc.) or by finished part testing (gloss and smoothness, slip measurements, determination of static friction, etc.). 

Coating molds with Chemniflon (nickel containing polytetrafluoroethylene particles distributed evenly throughout the matrix) reduced the adhesive wear of the mold surface and resulted in a reduction of the demolding force by 35%. ... 

The installation of an indicating device for exact metering of the aqueous release agent minimized the formation of urea and resulted in decreased demolding force, improved product surface quality, and reduced production costs of material for automotive seats. 

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