What is PU - Polyurethane?
At its simplest, polyurethane (PU) is a chemical compound and a type of versatile plastic. It is the result of incredible scientific discoveries around the beginning of WW2 which opened up enormous opportunities for its use in its different forms in many varying industries including building, construction, automotive, furniture.
PU comes in more than 1 form and you can see its adaptations in many industries besides the PU fabric in apparel eg PU moulded parts in the construction, automotive and furniture industries. Indeed, in the apparel industry you can see PU in different fibre adaptations – spandex in socks, swimsuits, and athletic apparel.
The PU fabric used in apparel making as a substitute for genuine leather is the outcome of coating or laminating a synthetic base fabric (usually polyester but could also be nylon) with that chemical compound. The polyurethane coating is applied to a single side of the base fabric and it makes the fabric water resistant, light weight and flexible.
In some sense, the more correct term is ‘PU coated fabric’ because the actual fabric component is the underlying synthetic polyester or nylon.
But the generic ‘PU’ or ‘Polyurethane’ has become accepted as the descriptor for ‘imitation leather apparel’ items. Noting that some nations (such as Canada) have developed industry standards requiring more specification in labelling. For example, a requirement that labels contain the actual breakdown of PU and underlying fabric eg ‘75% PU, 25# Polyester’.
The PU fabrics used in leather-look apparel are durable and abrasion-resistant, yet soft, light and breathable. They have similar stretch, stiffness and permeability properties as leather. And groves similar to fingerprints can be mechanically pressed into the material to give it that ‘more real’ look.
Technology and smart people are developing leather-look fabrics from non-chemical bases. You can get leather accessories from mushrooms and from pineapples. These fabrics are not yet soft enough for apparel - but we're watching and we will adapt as soon as they are.
If you want to read more about polyurethanes in all their uses and glory, a good link is https://polyurethane.americanchemistry.com/Introduction-to-Polyurethanes and associated Chapters. It also outlines sustainability and recycling opportunities for polyurethanes for industry and consumers – and clearly raises the opportunities for apparel made using PU as well.