Low Gloss Plastics and processing techniques - Help Please

Hi Everyone. I am currently designing a product where I want a low gloss finish to the outer surfaces. A look much like that of a Black soft-feel paint.

However, I am trying to achieve this without using paint due to the additional environmental impact this brings.

I have been in touch with the big plastics companies (such as GE Plastics) and they do have a Low Gloss ABS+PC mix range. I have some sample plaques - The gloss is low. However, I was wondering if anyone had any specific experience using these low gloss plastics and if they’d like to share some info?

The Plaques I have display some pretty bad flow lines. I have been assured that this is purely due to the machine setup. Is this a common theme with the low gloss plastics?

I was thinking that to achieve the high diffusion appearance that the soft feel paint gives we would need a tight grain etching to our tool. I can’t be sure the effect this will give me. Does anybody have any experience with this and can anyone recommend a particular grade of plastic?

Thanks for your time.

The cheap way to accomplish this is to use HIPS (high impact polystyrene) which is naturally dull. Then put a vapor hone finish on your tool surface to assure a consistent matte finish. You may still have flow lines depending on your gate layout. Run a mold flow simulation to test this.

People use the soft touch paint to get a perfect surface on top of an imperfect surface. We looked at using that paint and discovered it costs over US$75 per gallon.

Good luck.

maybe this is a silly question, but have you explored Mold Tech, Yick Sang, etc textures. Rubber paints are more expensive and do have a tendency to get dirty and also wear off.

Mold flow is definitely an issue…but a simple EDM finish gives you a matte sandblast texture. Similar to Mold-tech, but inherent in the mold making process.

Hi Guys,

Thanks for the feedback. I have got a Mold Tech grain book and we’ve already identified the graining we want with the customer. We too found the paints to be expensive, and this product is intended for automotive applications so the wear and tear aspect is an issue.

Past experience has shown us that we cannot easily control the grain regularity with EDM finishes. For this product where there is high value on the aesthetics we prefer to use a more controlled process.

Thanks again.

Hi. First, I will confirm what you say in your last post above: Moldtech or similar photochemical applied textures are more manipulable than EDM and also more consistent on die pull surfaces.

A caution though, applicable if you are using a very fine texture to simulate a satin/matte rubber like finish. These molded surface finishes on ‘engineering grade’ polymers are very easily scuffed; drag a fingernail across leaves a shiny trail that is not removable (similar visual effect as suede clothing). This is why you don’t regularly see molded plastic surface finish between high gloss and standard Moldtech 11020 (business machine light stipple - easily EDM copied). Materials wise, I have experienced this with ABS, polycarbonate, polyesters, and various blends of the above, filled and unfilled. One popular midwest molder thought they could control this issue via process control varying core/cavity temperatures. They could, but not consistently within a run and between personnel shifts.