Study On The Synthesis And Properties Of Organic Silicone Modified Waterborne Polyurethane

Water-borne polyurethane (WPU) is a transparent or opaque liquid prepared by dispersing polyurethane particles in the media of water. It not only inherits the excellent properties of solvent-borne polyurethane with abrasion resistance, good flexibility, low temperature resistance and good fatigue resistance, but also shows the advantages of nontoxic, non-flammable, environmental friendly and easy to be modified, etc. Therefore, WPU has attracted a great deal of interest from domestic and foreign researchers, and has been widely used in many fields such as coating of textile and leather, adhesive, fiber-reinforced composites. In particular, WPU can be used as thermoplastic resin to prepare ultra-high molecular weight polyethylene (UHMWPE) fiber reinforced composites which has been widely used in the fields of bullet-proof materials, cut resistant gloves, high strength ropes and so on. The main work and research results of the thesis include the following three aspects.(1) Toluene diisocyanate and polypropylene glycol are used as main raw materials, 1,4-butanediol andα,α-dimethylol propionic acid (DMPA) are used as chain extender, triethylamine is used as neutralizing agent, the polyether WPU with 30% solid content is prepared using acetone method. The effect of added DMPA content and NCO/OH molar ratio (R value) on the appearance, stability, particle size, viscosity of the WPU emulsion and water absorption of WPU film are discussed, as well as the effect of pre-polymer dispersion methods on the stability of WPU emulsion. The results indicate that with the increase of DMPA content, the appearance and stability of WPU emulsion are improved, the particle size decreases, the viscosity of emulsion and water absorption of WPU film increase, the optimal DMPA content is 5-6%. As the R value increases, the appearance and stability of WPU emulsion become worse, the viscosity decreases, the particle size of emulsion and water absorption of WPU films are both reduced preliminarily and then increase, the optimal R value should be controlled at 1.1～1.2. Emulsifying PU by dispersing pre-polymer into deionized water can prevent the emulsion from forming gels and the obtained WPU emulsion has better appearance and longer storage stability.(2) The silane modified polyester WPU emulsion is prepared by using anionic method with toluene diisocyanate and poly(diethylene glycol adipate) as main raw materials, and silane coupling agent as modifier. Owing to the introduction of silane to WPU macromolecules, the silane can react with water with a hydrolytic condensation reaction when the pre-polymer is emulsified in water and form cross-linked network in the WPU structure. The effects of added silane content on the properties of WPU are investigated. The results indicate that with the increase of silane content, the appearance and stability of WPU have little changes, but when the silane coupling agent content exceeds 5%, the appearance and stability of emulsion become worse. As silane content increases, the particle size, emulsion viscosity and the water absorption of WPU film are all reduced preliminary and then increase, the glass transition temperature, initial decomposition temperature and the mechanical properties of WPU film increase, the contact angle of WPU film with water is enlarged and surface tension is reduced accordingly, the wetting and adhesion properties of WPU emulsion to UHMWPE fibers are enhanced. The optimal silane coupling agent content should be controlled at 2-4%. Compared with adding silane in the emulsification stage, the obtained silane modified WPU emulsion has better appearance by adding the silane coupling agent during pre-polymerization stage.(3) The silane modified polyether WPU emulsion is prepared by using toluene diisocyanate and polypropylene glycol as main raw materials, and modified with silane coupling agent. The stability, appearance, particle size and viscosity of WPU emulsion are studied, the thermal and heat resistance, water absorption, contact angle with water and mechanical strength of WPU film are researched, as well as the wetting and surface adhesion properties between WPU and UHMWPE fiber. The results indicate that polyether WPU has the same changing trend as polyester WPU with increasing the content of coupling agent. The comprehensive properties of polyether WPU are better than that of polyester WPU after silane modification. Silane modified polyether WPU has better low temperature resistance, higher mechanical properties and better wetting and interfacial bonding properties with UHMWPE fiber. Therefore, silane modified polyether WPU is more suitable for the application in UHMWPE fiber reinforced composites.