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Jaugusti (Mechanical) (OP)
5 Mar 12 15:07
Can anyone help me understand which plastics do well with Zinc Stearate or Calcium Stearte as mold release agents? Should these release agents be applied in a powder form or disolved in some sort of liquid? What plastics do well with Silicone or lecithin?

Thanks
patprimmer (Publican)
5 Mar 12 16:59
Most if not all plastics work with stearates, but it does not take much. Many already have them or something similar added at the compounding stage by the raw materials manufacturer and more can do harm.

To much reduces mechanical properties, gives splay marks or silver streaks and builds up on the mould surface as a mould deposit and even blocks air vents.

Regards
Pat
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Richar24 (Industrial)
19 Mar 12 4:31

It is always best to avoid anything that can contaminate the material. Operators add it in varying amounts creating bad knit lines, etc.

The best way to fix the problem is to fix what is wrong with part or mold design so that the parts don't stick. Sticking is usually a correctable condition between mold and part design changes.

Adding air vents that can be pressurized as the mold opens can sometimes work to keep the parts from sticking on the Hot Half of the mold, plus there are a number of other options.

If time and money doesn't allow for changes, speak to your material supplier and see if they have a lubricated grade of your resin available. This makes for more consistent parts and higher quality parts.
 

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