The Study Of Preparation And Properties Of Environment-friendly Waterborne Polyurethane-urea Dispersion

The development of environment-friendly materials has become one of thefocuses in the material field today. Being a environment-friendly material used inmany fields, waterborne polyurethane （WPU） has become an important fine chemicalat home. By selecting different types of raw materials and controlling structure ofpolyurethane macromolecule, WPU can be synthesized to meet different requirements.The technology and properties of WPU, which was synthesized with aliphaticpolyesters of different molecular weight, amine chain extenders, isocyanate andsulphonate chain extender as raw materials, were carefully investigated.By the help of the prepolymerization, the prepolymer was first synthesized withpolybutylene adipate glycol （PBA） and isophorone diisocyanate （IPDI）, extended withaliphatic diamine sulphonate （AAS） after reducing the viscosity of the prepolymerwith acetone, and further extended with diamine chain extender. The above mixturewas dispersed in the deionized water. The dispersion of WPU was obtained afterremoval of acetone. Under the fixed IPDI, AAS and ethylenediamine, the technologyand properties of WPU and its film performance were investigated, respectively. Theresults were as follows.（1） When the prepolymer was synthesized with PBA1000orPBA2000, the viscosity of the system was low and the less amount of acetone wasadded in order to lower the visocity of the propolymer, but the stability and film-forming of its dispersion was inferior to that of the prepolymer synthesized withPBA3000.（2） When the-SO₃Na mass content in WPU macromolecule synthesizedwith PBA3000and extended for30min was among1.1wt%¹.7wt%, the stabledispersion of WPU can be obtained. With increasing of the-SO₃Na content, theapparent state of WPU changed gradually from opaque white to translucent blue, andto transparent khaki, and the dispersions were very stable at higher temperature andwere unstable at freeze-thaw temperature. Tensile strength, hardness and waterabsorption of the films of WPU increased with increasing of-SO₃Na content, but elongation at break was vice versa.when-SO₃Na mass of WPU macromolecule was1.3wt%, the tensile strength of WPU film was17MPa, elongation at break584%,hardness （Shore A） up to90.（3） When the content of-SO₃Na groups in WPU was1.3wt%or1.7wt%, latex particles in WPU dispersions existed at ball or rod shape, andthere were obvious crystallization and non-crystalline areas between latex particles.（4）The thermal stability of WPU film was higher and its initial thermal decompositiontemperature was above300℃.On the basis of the above experiments, the new dispersion of WPU wassynthesized with low molecular weight amine terminated polyether （D230） instead ofethylenediamine at the second expanding chain. The results showed that:（1） When themolar ratio of IPDI and PBA （R value） was2.0, WPU dispersion was stable and goodat the film-forming. Moreover, the tensile strength of the film was proportional to the-SO₃Na content and the elongation at breakand was vice versa. When-SO₃Na masscontent of WPU macromolecule was1.5wt%, the tensile strength of the filmwas12MPa, the elongation at break302%.（2） the size of latex particles in WPUdispersion was about50nm, and the interface among latex particles was obvious.（3）The thermal stability of WPU film was higher and its initial thermal decompositiontemperature was above357℃.