Can the glossy finish of TPE overmolded parts be restored to matte through post-processing?

During production of TPE overmolded products, glossy overmolded layers often appear, deviating from the expected matte effect and compromising the product's visual quality. Can such TPE overmolding issues be improved through post-processing? This depends on the cause of glossiness, product structure, and aesthetic requirements, with specific treatment methods having limited applicability. Below, the Zhongsu Wang editorial team shares detailed insights.

I. Common Post-Processing Methods

Physical polishing is a direct and effective approach. Use fine-grit sandpaper or sponge sandpaper to lightly and evenly sand in one direction, reducing surface gloss. Follow with a secondary light polish using polishing cloth to enhance smoothness. This method suits flat or simple curved surfaces, but care must be taken to avoid damaging edges or exposing the base material.

Matte coating involves spraying TPE-compatible elastic matte paint over glossy surfaces. Clean oil and dust before application, applying one or two thin coats. Some coatings require low-temperature curing. Suitable for complex patterns or curved products, but ensure paint compatibility to prevent peeling or material corrosion.

Plasma treatment utilizes low-temperature plasma to alter the microscopic surface roughness of TPE overmolded products. This non-contact method can process complex structures without affecting material properties or tactile feel. However, it requires specialized equipment and is more cost-effective for batch processing. Its effectiveness is limited for certain high-gloss materials.

II. Processing Precautions

Regardless of the method chosen, always test on scrap samples or offcuts first to verify matte uniformity, product integrity, and compatibility. During processing, control pressure or parameters: avoid excessive force during grinding, manage coating thickness during spraying, and regulate time and power during plasma treatment to prevent material cracking, deformation, or reduced adhesion.

Note: 

When the overmolded layer is too thin, grinding may expose the base material. For food contact products, coatings are unsuitable. only physical grinding is permissible, ensuring no dust residue remains.

In summary, while post-processing can mitigate glossiness in TPE overmolding, preventive measures at the source are preferable. These include selecting low-gloss materials, adjusting injection molding parameters, or using textured molds with a matte finish. Post-processing increases costs and may slightly affect product feel or adhesion.

If issues arise, prioritize physical polishing based on product structure, appearance requirements, and cost. For complex structures, use matte coatings, consider plasma treatment for high-precision applications.