Bio-Based 2K PU Coating for Durable Textile Applications

Polyurethane (PU) coatings are often applied on high added value technical textiles. To date, most PU textile coatings are solvent based or water based. Recent advances are made in applying high solid and two-component (2K) PU on textiles. Currently, polymers made from renewable raw materials are experiencing a renaissance, owing to the trend to reduce CO2 emissions and switch to CO2-neutral renewable products. There is also the tendency towards the “bio, eco, natural” consciousness-awakening of the end consumer and the market-driven question to implement renewable materials. However, the application of bio-based coatings on textiles is limited. In this regard, the present study is conducted to develop bio-based 2K PU coating specifically designed for waterproof textiles. A 2K PU coating formulation, composed of bio-based polyol and bio-based isocyanate Desmodur Eco N7300, was made and directly applied on a polyester fabric prior to thermal curing in an oven. The coating was characterized via Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The coatings were not thermoplastic and had a glass transition temperature of approximately 50 °C. Since a bio-based pentamethylene diisocyanate trimer (PDI-trimer), Desmodur Eco N7300 was used as an isocyanate source and not a diisocyanate derivative, and the resulting bio-based 2K coating was a thermoset instead of a thermoplastic. The effect of the additives and content of isocyanate on the elongation and stress at break was studied by performing tensile tests (ISO 13934-1) on 50 µm 2K PU films and comparing the obtained values. The performance of the coating was studied by evaluating the resistance to hydrostatic pressure initially and after washing, the Q-panel Laboratory UltraViolet (QUV) aging and the hydrolysis test. The developed bio-based 2K PU coating had excellent hydrostatic pressure, QUV aging resistance, hydrolysis resistance and wash fastness at 60 °C.