Study On The Synthesis And Characterization Of Waterborne Polyurethane Emulsion Modified By Acrylate

Waterborne polyurethane (WPU), as an environmental friendly andfilm-forming matereals, has been widely used in coatings, adhesives, textile anddyeing and other manufacturing industries. However, WPU was limited itsapplication on some situations because of its high prices and low waterresistance. Therefore, WPU modified with other components become hotresearch direction. It is well know that polyacrylate (PA) behaves good waterresistance, weather resistance, high gloss and other characteristics. WPUmodified with PA can take advantage of the two kinds of polymer respectively,which is synergistic to prepare the high quality and low price of compositeemulsion (PUA). Meanwhile, the compatibility of both has played a decisiverole for the synergy effect. In this research, the functional vinyl monomers wereused to improve the interaction among the molecular chain segments of PUA.Ultimately these ways achieve the design of particle and the excellentperformance of emulsions. The main contents are as follows:1. N-acryloylmorpholine (AMCO) and2-ethylhexyl acrylate (2-EHA) wereused to modify PUA emulsions by a hybrid synthesis technology. Various characterization methods were used to investigate the effect of2-EHA andACMO content on the properties of the hybrid emulsions and their resultantfilms. The research results show that the spherical particles exhibit asemi-interpenetrating network structure. Modification with AMCO, the hybridemulsions show decreased average particle size and increased viscosity.However, the2-EHA content has little effect on the latex average particle sizeand the viscosity. The hydrogen bond interaction increases with an increase inthe ACMO content. Therefore, tensile strength and adhesion on substratesincrease, but the water resistance and elasticity decrease. It has been found that2-EHA and ACMO have a synergistic effect on the properties of PUA.2. A serious of waterborne hydroxyl-functional PUA emulsions fortwo-component coatings was prepared. The results showed that increasing theweight ratio of HEA/BA led to a decrease in the average particle sizes andnarrow in the particle size distribution, but increase the viscosity and the specificsurface of particle of emulsion. Emulsion particle morphology showedcore-shell structure, even multinuclear structure. Meanwhile, their films showedincreased thermal resistance, adhesion on substrate and tensile strength, butworsen water resistance. When the emulsions were applied in two-componentcoatings, hydroxyl groups of PUA can not only engage in the intra-molecularand/or intermolecular hydrogen bonding, but also form covalently cross-linkednetworks with polyisocyanate in their films. The film of their glass transitiontemperature and water resistance were greatly improved 3. A series of the epoxy-modified PUA emulsion were prepared, and theirfilm properties were investigated. It can be found that, when the amount ofglycidyl methacrylate (GMA) used no more than5wt%, the emulsion has goodstability. With increasing the amount of GMA, emulsion particle size increases,but it still mountain the core-shell particle structure. Since the reaction of epoxygroups and carboxyl groups and epoxy groups among themselves, forming athree-dimensional network structure, the crosslinking rate of films, waterresistance, chemical resistance and mechanical properties improved significantly,but the elongation at break decreased.4. The effect of the amount of allyl polyoxyethylene ether (APEG) on filmand adhesive properties of PUA emulsions was investigated. The results showthat: with the increase of the amount of APEG the emulsion particle size, incontrast to emulsion viscosity, after decreases and then increases. When thecontent of PA in PUA arrives at50wt%, becaused of introducing APEG, theemulsion can remain stable. APEG have a greater impact on the amount of PUAfilm performance. With increasing APEG dosage, water absorption andelongation at break of the film increased, tensile strength and hardness of thefilm decreased, and increase thermal resistance first and then decreased. APEGreduced activation temperature of the PUA film, to improve its bonding strengthand wettability of the substrate. The best performance of peel strength, which is2.63N/cm, was obtained while APEG content was8wt%.