Daegu, South Korea – Bio-based polyols have made inroads into the market in recent years, while green diisocyanates are lagging behind, making fully bio-based PUs more of a challenge to make. Now, a team at the Daegu Gyeongbuk Institute of Science and Technology has found a way to produce green thermoplastic PUs that are either partially or fully biobased.
They used a one-shot polymerisation process to make the TPU. This used a combination of sebacic acid polyestser polyol, 1,4-butanediol derived from renewable sources, and a diisocyanate. The diisocyanate was a bio-based aliphatic one, pentamethylene diisocyanate (PDI), the petrochemical-derived aromatic diisocyanate MDI, or a combination of the two.
The bio-based carbon content of the TPU could be increased to about 97% if the PDI was used; this also increased the pyrolysis onset temperature. Conversely, an increase in MDI increases the complex viscosity, tensile strength, and strain. The tensile strength and elongation were comparable for the two.
The researchers suggest that either partially or fully biobased TPUs have potential as replacements for MDI-based materials, and they could have industrial applications.
The work has been published in the Journal of Applied Polymer Science.