Anyone know how to rework scratched surface of plastics?

Question

any solution for rework the surface of plastic (polyurethene) after injection molding?

Answer 1

Very fine buffing compound and electric buffer with time and patience.

Answer 2

There are material called Buffing Compounds.

Usually, you start with some sandpaper, like 250-Grit, to removed mold marks.  You then go to progressibly finer grades of paper (the larger the grit number, the finer the grade) until all the scratches are gone.  1000 or 2000-Grit is usually a good end point.

You will also want to consider wet sanding with those finer grits.  In many cases they have a plastic backing (rather than paper) just for this purpose.

But the  sandpaper leaves you with a dull surface.  So you go to Buffing Compunds.  This is a pasty substance that you apply with a soft cloth, and rub it around with your fingers.  Again, the finer the grit the more "polish" you get.

For small areas, I will often use toothpaste instead of buying a special compound.  But toothpastes often contain sugar, and that leaves the surface sticky, so it needs to be washed with soap and water before you try to paint it (it that's your goal).