Gate Blush

The tendency of a plastic to turn white or chalky in areas that are highly stressed (viz., gate blush). 

Gate blush (gate splay) n. A blemish or disturbance in the gate area of an injection-molded article. It occurs when the melt fractures as it emerges from the gate due to sudden release of large elastic stresses. 

Injection molding Uniform melt flow, enhanced physical properties Reduce gate blush Reduced jetting Can reduce flow lengths if too high... 

These are usually self-adhesive, precut, printed patterns on a substrate that are simply adhered to the surface of a product. Decals generally use a transparent plastic film while labels are usually on an opaque plastic, metallic and multilayer sandwich base. Labels of sufficient thickness are useful for hiding unavoidable appearance problems such as gate and sprue removal areas, sink marks, blushes, splays, and weld lines. 

Injection molding machines Resin should be dried < 0.02 %. Do not use resin that has been out of the dryer for > 20 min. Cold molds are difficult to fill and require higher injection pressures. Hot molds, generally, give better finish and less molded-in stress. Melt temperature is very sensitive to very small changes in rpm or back pressure despite sensor or controller set point. Measure with hand held pyrometer or laser sensor. Need slower fill rate for spme-gated parts to prevent blush, splash or jetting. If the walls are > 5 mm, then slow fill helps reduce sinks and voids. 

PC provides average scratch resistance and clarity, and faceshields made with PC can also be coated with anh-fog and anh-scratch sealants, though a primer is frequently required prior to processing. The solvent system used for the coating process can, however, cause blushing around gates and joints. 

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