Self-Catalytic Two-Component Waterborne Polyurethanes with Amino Polyols from Biomass Based Epoxy Resin

Abstract

In order to improve the crosslinking reaction rate of two-component waterborne polyurethanes (2K-WPUs) in the absence of ungreen external catalysts, waterborne polyols containing different tertiary amines in molecular structure were synthesized from a turpentine-based epoxy resin (TME) and secondary amines (N-benzylethanolamine and diethanolamine). Then self-catalytic 2K-WPUs were prepared with the waterborne amino polyols and a hydrophilically modified hexamethylene diisocyanate tripolymer. The structure and micromorphology of TME based polyols were identified using nuclear magnetic resonance (1H NMR, 13C NMR), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy techniques. The crosslinking reaction of 2K-WPUs was monitored using differential scanning calorimetry (DSC) and FT-IR methods. Kinetics analysis from DSC showed the activation energy of the crosslinking reaction of 2K-WPUs reduced obviously by using amino polyols, which indicated the tertiary amines chemically bonded in the polyols could self-catalyze the crosslinking reaction of 2K-WPUs without adding small molecular toxic catalysts. Small steric hindrance of the tertiary amines led to high catalytic activity. The properties of the crosslinked products of the waterborne TME based polyols were investigated by DSC, thermogravmetric analysis and dynamic mechanical analysis (DMA). The results showed high hydroxyl value of the polyol and aromatic ring in the polyol structure resulted in high storage modulus (G′) and glass transition temperature (Tg) of the crosslinked products. More C–N bond content of the crosslinked products of the waterborne amino polyols decreased the thermal stability in the first degradation stage of the products.