Synthesis And Properties Of Water-Swellable Polyurethane And Its Blends

Two series of water-swellable elstomers, which were polyester polyurethane and polyether polyurethane, were respectively synthesized from polyester polyol or polyether polyol, isophorne diisocyanate (IPDI), dimethylol propionic acid (DMPA), trimethylolpropane(TMP) and ethylenediamine(EDA) by self-emulsified method. The structure of the water-swellable polyurethane was characterized by fourier transform infrared spectroscope (FTIR). The effects of the molar ratio of NCO/OH, the content of DMPA, the content of TMP on the basic properties of the emulsion were discussed. The effects of these factors on mechanical properties and swellable properties of the samples were also discussed. The results showed that, with the increase of the molar ratio of NCO/OH, the particle size of the emulsion and the tensile strength of the samples enlarged, but the viscosity of the emulsion and the elongation to break of the samples were decreased. The volume expansion rate of the sample was higher when the molar ratio of NCO/OH was smaller (1.3and1.4), while it was lower when the molar ratio of NCO/OH was larger (1.5and1.6). With the increase of the DMPA content, the particle size of the emulsion kept invariant, but the viscosity of the emulsion and the tensile strength of the samples went up. The volume expansion rate of the samples enlarged with the increase of the DMPA content, while the tensile strength retention rate of the samples after immersing water and the volume expansion rate retention rate of the samples immersed water again were decreased. Adding TMP could improve the tensile strength retention rate of the samples after immersing water and the volume expansion rate retention rate of the samples immersed water again, but the volume expansion rate of the samples was decreased with the increase of the TMP content. Changing trends of the effects of the DMPA content on properties of polyether polyurethane samples were similar with ones of polyester polyurethane samples. Compared with polyester polyurethane samples, although the tensile strength retention rate of the polyether polyurethane samples after immersing water and the volume expansion rate retention rate of the samples immersed water again were higher, the tensile strength and the volume expansion of polyether polyurethane samples were lower.The second part of the thesis is the sdudy on prepareation and properties of polyurethane/polyacrylic (PUA) water-swellable elastomers synthesized by the core-shell emulsion copolymerization of the aqueous polyurethane modified with acrylic copolymer. The structure of PUA was characterized by FTIR, and the thermal stability of the samples was analysised by TGA. The result showed that PUA had better thermal stability than polyurethane. With the increase of PA content, the tensile strength and the volume expansion rate of the samples were decreased, while the elongation rate at break, the tensile strength retention rate of the samples after immersing water and the volume expansion rate retention rate of the samples immersed water again were enlarged. With the MMA content in PA increased, the tensile strength of the samples enlarged, though the elongation rate at break and the volume expansion rate of the samples were decreased. With the addition of TMP, the mechanical properties and performances for repeated use were improved, but the volume expansion rate was decreased.