Whatever you call it, synthetic, synthetic leather, PU leather, or just PU, this material is another must-have for modern sports shoes. This class of material offers the shoe designer a huge variety of colors, textures, and features at a wide range of prices. It was once considered to be cheap junk not suitable for high-quality shoes, but times have changed! These man-made materials are often a composite made of two layers, being a backing layer made of woven or non-woven polyester fibers, combined with an external surface by “dry” lamination process or by liquid “wet” processes. Many of the least expensive synthetics have a fibrous woven backing with PVC skin made by a wet process. The surface on these may not be 100% smooth and the shoe will show wrinkles and creases. This material is the cheap stuff found on inexpensive shoes.
High-end leather starts with a water-resistant microfiber PU backing. This backing has a smooth surface, cuts cleanly, and can be dyed to match the surface materials. A microfiber style backing can be ordered in .5 to 2.00mm thicknesses, has some stretch, and can have a water-resistant treatment. On top of this backing, the skin can be applied.
Polyurethane plastic film .2 to .5mm thick is made in a separate operation and the two layers are then rolled together with heat and pressure. PU outer skin is then printed, embossed, scuffed, or polished to create one of the millions of surface options. The largest PU maker has hundreds of different embossing patterns that can be applied to hundreds of different surfaces. If you can meet the order volume required, you can pick any color you want! Synthetics will be reviewed in-depth in their own article.