Gloss for plastic injection parts

Gloss is defined as the amount of light that is reflected off a surface. The rating used for gloss is based on how much light is reflected at different angles and the degree of light that is scattered. Parts with high gloss reflect the majority of light with very low scatter. Low gloss is low reflection at differing angles with large scatter. The correct amount of gloss is determined by the requirements of the end-use application. Here are some causes and solutions below for gloss of plastic injection parts.

Cold melt temperatures provide low gloss on untextured surfaces. Solutions: If higher gloss is needed, processing at higher temperatures is needed. In some cases, too hot a melt temperature can also cause low gloss. In this case, additives that are mixed in with the base resin, such as plasticizers or some flame retardants, can bloom on the surface. Reducing the melt temperature may help in this situation.

Low packing pressure is another cause of low gloss, since the plastic material is not fully packed onto the cavity surface and does not replicate the surface. Solutions: Increasing pack pressure will allow the melt to pick up all the details of the mold cavity.

Injection speeds that are too slow will reduce the gloss on the surface since these also may cause the melt not to replicate the mold surface. Solutions: Increasing injection speed will raise the melt temperature and pack out the part.

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