Recently, scientists at the Kyungpook Institute of Science and Technology in Daegu, South Korea, have found a way to make thermoplastic polyurethane (TPU) with 97 percent bio-based content. It is made using biomass monomers instead of petroleum-based materials.
This TPU is made from sebacate polyester polyol, 1,4-butanediol and isocyanate in a single polymerization process. Sebacic acid is a fatty acid isolated from castor oil. For comparison, they tried reactions with bio-based aliphatic pentamethylene diisocyanate (PDI) and petroleum-based MDI, as well as combinations of the two.
The average molecular weight of TPUs made with bio-based PDI was about 120,000 g/mol, with a tensile strength of 20 MPa and a tensile elongation of 587%. The team says these properties are comparable to fossil-based TPUs. Composite viscosity, tensile strength and strain all increased with increasing MDI content. They say it is possible to make a fully bio-based TPU.
These materials have potential applications such as industrial sheets, screen protectors, bags, footwear, artificial leather and other apparel textiles. This R&D work was supported by the Korean Ministry of Trade, Industry and Energy as part of its Material Component Technology Development Program.
