Study On The Synthesis And Modification Of Aquenous Polyurethane

Different factors such as hard segment and -COOH content, soft segment, chain extender, technics of preparation influence on the properties of aqueous polyurethane and their films have been studied. Three type of hybrid emulsions of PUV, EPU and PUER have been prepared when the aqueous polyurethane were modified by acrylate and epoxy respectively. Properties of the hybrid emulsions and films have been compared.Results showed that aqueous polyurethane main-chain and the acting force between the main-chain changed with hard segment content and soft segment. These changes result in transformations of properties of aqueous polyurethane and their films at the same time. Aqueous polyurethane made from prepolymer mixing process has some cross-linking structure, otherwise, made from MEK process are linear thermoplastic resin. So there are several differences between these two types of resins.When the aqueous polyurethane was modified by acrylate, particles size and viscosity of core-shell type acrylic-polyurethane hybrid aqueous emulsion changed with the acrylate content in the core-part. Resistance of PUA films to water and organic solvent are improved simultaneously.When the aqueous polyurethane was modified by epoxy E44. Films from this hybrid aqueous dispersion present favorable properties, especially the resistance to water and organic solvent, however, the hybrid aqueous dispersion has a poor reserve stability. Another way of modification by epoxy indirectly through VER resin which was prepared (PUER) by the reaction of epoxy E44 with acrylic acid was studied, results showed that films of PUER have enhanced a lot compared to PU, especially the reserve stability has improved obviously, resolved the limitation of EPU dispersion.In order to control the crystallinity of hard and soft segment, 1,2-PG and PNA, which containing dissymmetrical and symmetrical side methyl groups separately, were incorporated to hard-segment and soft-segment respectively. Relationships between crystallinity of soft and hard-segment and micro-phase separation with mechanical property and adhesive strength were studied.