MIXTURE DESIGN APPROACHES TO IPDI-H6XDI-XDI TERNARY DIISOCYANATE-BASED WATERBORNE POLYURETHANES

A systematic modelling analysis for polyaddition of poly(butylene glyc ol adipate) [PBA] to isophorone diisocyanate (IPDI), xylene diisocyana te (XDI) and hydrogenated xylene diisocyanate (H6XDI) ternary diisocya nate-based waterborne polyurethane (WPU) synthesized by a modified ace tone process was performed. Using a mixture of experimental designs, e mpirical models are fitted and plotted as contour diagrams, which faci litate revealing the synergistic/antagonistic effects between the mixe d 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, w hich possesses the highest tensile strength. The largest ultimate elon gation occurs at 1/3IPDI/1/3H(6)XDI/1/3 XDI ternary diisocyanate-mixed WPU. Particle size analysis shows that the larger particles are obtai ned in the dispersion IPDI-XDI binary WPU. Differential scanning calor imetry (DSC) results show that PBA polyol and its converted WPU show d oublet melting behaviour. A plot of 1/T-m(L) (lower melting temperatur e) against - lnX(IPDI) (mole fraction of IPDI in mixed diisocyanates) is approximately linear, indicating that the hard segments are randoml y distributed along the molecular chain. Wide angle X-ray diffraction (XRD) and polarized microscopy (POM) on these WPU films were also exam ined. (C) 1998 Elsevier Science Ltd. All rights reserved.