Bio-based water-borne polyurethanes for coating applications
Belgian researchers performed bio-based water-borne polyurethanes (WPU) from two commercially available partially or fully dimerised fatty acid polyols of similar hydroxyl values, close to those of petro-based polyols used for coating applications.
Similarly to the conventional WPU, they were synthesised using a solvent-based process at a constant isocyanate index INCO of 110. The effect of hard segment content made of ionic dimethylolpropionic triethylammonium salt (DMPTA) and both aliphatic diisocyanates isophorone diisocyanate (IPDI) or 4,4′-methylene bis(cyclohexyl isocyanate) (H12MDI) as coupling agents was investigated on the behaviour of WPU dispersion in water and the thermal and mechanical properties of the films obtained after casting and drying these WPU dispersions.
Increase of hard segment
As expected, the results highlighted that the increase of hard segment yielded an increase of hardness and a decrease of thermal stability in relation with the presence of hard segment moieties in the range of 18–26 wt%. More interestingly, the nature of the polyols strongly affected the final properties of the materials. Indeed, the WPU based on “Veopur” exhibited elastomeric behaviour with values of strain at break superior to 600%, while “Priplast”-based WPU showed a brittle behaviour with strain at break less than 50%, especially when synthesised from H12MDI as coupling agent.
The study is published in: Progress in Organic Coatings, Volume 97, August 2016, Pages 175–183
