Daegu, South Korea – Scientists at the Daegu Gyeongbuk Institute of Science and Technology have found a way to make a thermoplastic polyurethane with 97% bio-based content. It was made using biomass-based monomers in place of petroleum-based materials.
A one-shot polymerisation process was used to make the TPU, from a sebacic acid polyester polyol and 1,4-butane diol, plus an isocyanate. Sebacic acid is a fatty acid isolated from castor oil. For comparison purposes, they tried out the reaction with both bio-aliphatic pentamethylene diisocyanate (PDI) and petroleum-based MDI, and also a combination of the two.
The TPU made using the bio-PDI had an average molecular weight of about 120,000g/mol, a tensile strength of 20MPa, and tensile elongation of 587%. These properties, the team said, are comparable to those of fossil-based TPUs. Complex viscosity, tensile strength and strain all increased as the MDI content rose but, they said, the fully bio-based TPUs showed potential.
The materials have potential applications such as industrial sheets, screen protection films, cases, footwear, artificial leather and other textiles for clothing. The work had support from the Korean ministry of trade, industry and energy as part of its material component technology development project.
The work has been published in the Journal of Applied Polymer Science.