Mixture design approaches to IPDI-H₆XDI-XDI ternary diisocyanate-based waterborne polyurethanes

A systematic modelling analysis for polyaddition of poly(butylene glycol adipate) [PBA] to isophorone diisocyanate (IPDI), xylene diisocyanate (XDI) and hydrogenated xylene diisocyanate (H₆XDI) ternary diisocyanate-based waterborne polyurethane (WPU) synthesized by a modified acetone process was performed. Using a mixture of experimental designs, empirical models are fitted and plotted as contour diagrams, which facilitate revealing the synergistic/antagonistic effects between the mixed diisocyanates. The results indicate that each component demonstrates different performances in either binary (IPDI-XDI, XDI-H₆XDI and IPDI-H₆XDI) or ternary (IPDI-XDI-H₆XDI) systems with the IPDI-based WPU, which possesses the highest tensile strength. The largest ultimate elongation occurs at 1/3IPDI/1/3H₆XDI/1/3XDI ternary diisocyanate-mixed WPU. Particle size analysis shows that the larger particles are obtained in the dispersion of IPDI-XDI binary WPU. Differential scanning calorimetry (DSC) results show that PBA polyol and its converted WPU show doublet melting behaviour. A plot of 1/T(m)(L) (lower melting temperature) against - 1nX(IPDI) (mole fraction of IPDI in mixed diisocyanates) is approximately linear, indicating that the hard segments are randomly distributed along the molecular chain. Wide angle X-ray diffraction (XRD) and polarized microscopy (POM) on these WPU films were also examined.