Leather & Polyurethane


Whenever we talk about a footwear ,Be it lifestyle, fashion or Industrial. The first thing which comes to our mind is LEATHER.

Leather is a durable and flexible material created by tanning animal raw hide and skins. The most common raw material is cattle hide. It can be produced at manufacturing scales ranging from artisan to modern industrial scale

Leather is used to make a variety of articles, including footwear, automobile seats, clothing, bags, fashion accessories, and furniture. It is produced in a wide variety of types and styles and decorated by a wide range of techniques. The earliest record of leather artefacts dates back to 2200 BC.

Leather is produced in the following grades .

  • Top-grain leather includes the outer layer of the hide, known as the grain, which features finer, more densely packed fibres, resulting in strength and durability. Depending on thickness, it may also contain some of the more fibrous under layer, known as the corium.
  • Full-grain leather contains the entire grain layer, without any removal of the surface. Rather than wearing out, it develops a patina during its useful lifetime. It is usually considered the highest quality leather. Furniture and footwear are often made from full-grain leather.
  • Corrected grain leather has the surface subjected to finishing treatments to create a more uniform appearance. This usually involves buffing or sanding away flaws in the grain, then dyeing and embossing the surface.
  • Nubuck is top-grain leather that has been sanded or buffed on the grain side to give a slight nap of short protein fibres, producing a velvet-like surface.
  • Split leather is created from the corium left once the top-grain has been separated from the hide, known as the drop split. In thicker hides, the drop split can be further split into a middle split and a flesh split .
  • Bi Cast Leather is a split leather that has polyurethane or vinyl layer applied to the surface and embossed to give it the appearance of a grain. It is slightly stiffer than top-grain leather but has a more consistent texture.
  • Patent Leather is a leather that has been given a high-gloss finish by the addition of a coating.
  • Suedeis made from the underside of a split to create a soft, napped finish. It is often made from younger or smaller animals, as the skins of adults often result in a coarse, shaggy nap.
  • Bonded Leather also called reconstituted leather ,Is a material that uses leather scraps that are shredded and bonded together with polyurethane or latex onto a fibre mesh. The amount of leather fibres in the mix varies from 10% to 90%, affecting the properties of the product.


Majority of the footwear soles ,Be it lifestyle, fashion ,sports or industrial footwear are made from POLYURETHANE which is more commonly known as PU.

Polyurethane Elastomers are used in application where toughness, flexibility, strength, abrasion resistance and shock absorbing qualities are required ,Which is why  Polyurethane is the most preferred & popular sole making material in the footwear industry

Polyurethane is obtained by mixing ingredient chemical isocyanate and polyols, in predetermined proportion, which further react to form the polymer.

Otto Bayer in Germany discovered and patented the chemistry of polyurethane in 1937.

Some of the leading manufacturers of polyurethane globally are Basf ,Huntsman and Dow Chemicals.

The simplest PU is linear in which the hydroxyl compound and the nitrogen compound each have a functionality of two. This can be represented by the following

Isocyanate + Polyol = Polyurethane

This is a exothermic reaction, as liquid isocyanate and polyol react to form PU, the mixture becomes increasingly viscous eventually forming a solid mass.

The important processing characteristics of the system will include viscosity, pot life, reactive mix ratio control, time and process temperature.

Polyurethane is any polymer consisting of chains of organic units joined by urethanes links

Polyurethane can be made in a variety of textures and hardness by varying the particular monomer used and adding other substances.

They are best known to us in the form of flexible foams, mattresses, earplugs, chemical resistant coating, specialty adhesives, sealants ,furniture, automotive seating and footwear soles.