News Coatings Technologies
Isosorbide-based water-borne NIPUs improve adhesive performance
Researchers have synthesised a series of water-borne non-isocyanate polyurethanes from bio-based isosorbide and dimethyl carbonate, designed as polymeric adhesion coatings. The hexamethylenediamine variant achieved the highest hydrogen-bond density and a well-balanced combination of strength, toughness and interfacial adhesion.
Conventional isocyanate-based polyurethane adhesives raise toxicity and environmental concerns. To address these issues, researchers designed a series of isosorbide-based water-borne non-isocyanate polyurethanes (INIPUs) through a green polycondensation route. The synthesis combined bio-based isosorbide and dimethyl carbonate with various polyamines, including ethylenediamine, 1,4-butanediamine, hexamethylenediamine, isophoronediamine and diethylenetriamine, alongside trimethylolpropane triglycidyl ether to form polymeric adhesion coatings.
FTIR and ¹H NMR analyses confirmed the successful formation of urethane linkages. Peak deconvolution of the carbonyl region revealed that the polyamine structure strongly influenced the hydrogen-bond density, thermal behaviour and adhesive performance of the resulting materials.
Event Tip: Polyurethane Coatings
Uncover the versatility and durability ofpolyurethane coatings in industrial applications. This tutorial will explore polyurethane chemistry, advancements in hybrid formulations, applications in automotive and aerospace sectors, and sustainability considerations. Join in to deepen your knowledge of this resilient coating technology.
Hexamethylenediamine variant delivers balanced performance
Among the samples, the INIPU prepared with hexamethylenediamine (HMDA-NIPU) showed the highest hydrogen-bond content (Xb = 73.16 %) and the highest initial decomposition temperature (T5% = 212 °C). All variants displayed glass-transition temperatures below room temperature, indicating good chain flexibility; the HMDA-NIPU recorded a Tg of –21.69 °C.
Mechanically, the HMDA-NIPU achieved a 180° peel strength of 1.576 ± 0.097 N·mm⁻¹, a lap shear strength of 1.057 ± 0.029 MPa, a tensile strength of 7.123 MPa and an elongation at break of 909.0 %. It also exhibited the lowest adhesion activation energy (Ea = 73.19 kJ·mol⁻¹). The authors attribute this performance to a dynamic physical crosslinking network combining linear aliphatic segments with strong hydrogen-bond associations, enabling efficient energy dissipation through reversible bond dissociation and reformation. The study offers a strategy for designing high-performance water-borne INIPU adhesives via synergistic control of polymer structure and hydrogen bonding.
Source: Liang, G. & Ye, D., Waterborne epoxy-hybrid non-isocyanate polyurethanes based on isosorbide via dimethyl carbonate polycondensation with improving adhesion and cohesion properties. Progress in Organic Coatings, 110134 (2026).
