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Non-isocyanate polyureas: sustainable synthesis with tunable properties
A new melt polycondensation route enables the production of non-isocyanate, semi-aromatic polyureas with mechanical properties ranging from soft elastomers to high-modulus thermoplastics.
Non-isocyanate polyureas are an environmentally and health-conscious alternative to conventional polyureas as they eliminate the use of toxic isocyanate monomers. A research team has now developed a solvent-free melt polycondensation process combining bio-sourceable urea with linear primary diamines and aromatic diamines. This approach enables the direct incorporation of aromatic diamines – a step that has proven challenging in earlier non-isocyanate routes.
By adjusting the aromatic diamine content (5–20 wt%), the researchers created polyureas with high thermal stability (decomposition temperature Td,5 % > 318 °C) and a wide range of mechanical properties.
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From elastomers to high-performance thermoplastics
Remarkably, Young’s modulus spanned three orders of magnitude – from 3 MPa in soft elastomers to 1.1 GPa in high-modulus thermoplastics. Although atomic force microscopy and X-ray scattering revealed amorphous morphologies without distinct nanoscale phase separation, ductile films still exhibited excellent mechanical performance. This was attributed to the urea functionalities, whose associative bidentate hydrogen bonding acts as physical crosslinks.
The study demonstrates that high-performance, semi-aromatic polyureas with tunable properties can be produced using greener synthesis methods without compromising performance.
Source: Polymer Chemistry, Issue 29, 2025
