Polyurethane is often used as a substitute for leather. It is an inexpensive substitute which can be made to mimic the appearance of leather, similar to Polyvinyl chloride (PVC), a form of vinyl also used for faux leather. Even though polyurethane is a strong artificial material, it is still vulnerable to the kinds of damage that can alter leather. If your polyurethane purse strap has been damaged, you can usually repair it to look like new.
Resew loose purse straps. Similar to leather, the stitching on polyurethane handbag straps can become loose with prolonged use. Carefully remove as much of the original stitching as you can with a seam ripper. A seam ripper is a small tool with a curved prong. Place the curved prong under the thread and pull to tear it out. Follow the original stitching holes to restitch the purse straps with a needle and thread. Since you are re-threading the strap through the original holes, you won't need a special needle. Use thick thread for greater support.
Apply clear shoe polish onto the polyurethane strap to cover shallow scrapes and scratches. Apply a dab of polish to the area and brush it in using a shoe polishing brush. Work the polish in using a back and forth motion. Buff the area until it is smooth with a dry rag.
Use a faux leather patching kit to cover deeper scratches. Choose a faux leather patching kit with a patching compound that matches the color of your purse. The patching compound is a thick liquid that can be squeezed out of the bottle and on to the area that needs to be patched. Apply the liquid compound to the area that needs to be patched. The patching kit should contain several different kinds of textured paper to match the texture of the faux leather being repaired. Choose the texture that best matches your purse.
Place the textured paper over the compound and press the paper down until the compound is flat. Heat the paper by blowing hot air over it using a hair dryer. Set the dryer on the hot setting. The heat will cause the compound to bond and to solidify. The textured paper will transfer its texture to the surface of the compound as it dries. After the compound has dried, remove the paper. You can just peel it off.