Modification Of Aqueous Polyurethane Dispersions By Hydrophobic Segment: Synthesis And Characterization

Aqueous polyurethane dispersions have been used for a wide range of commercial applications, including adhesives, coatings for textiles, leather, rubber, and many polymeric substrates, because of their good strength and flexibility characteristics. Since they use of little or no organic solvent in aqueous polyurethane dispersions, they are nontoxic and nonflammable and do not pollute the air compared to their solvent-based counterparts.Aqueous polyurethane dispersion which is functionalized with hydrophilic side groups to render it self-dispersible in water offer outstanding stability and extraordinary film-forming properties. However, the disadvantage of this approach suffers from poor water resistance for introducing hydrophilic group in the bone of polyurethane molecular. It may be swelling for immersion in water and lost mechanical properties, and peeling off from substrates. In the sum of a great deal of literatures about various methods of modification of aqueous polyurethane, we provided a novel method to modify aqueous polyurethane by adding hydrophobic group to improve the ability of water-resistance. Our works include the following two parts:First, aqueous polyurethane was modified with Glycerol Monostearate during preparing prepolymer of polyurethane; aliphatic alkyl saturated containing seventeen carbons as power hydrophobic group is introduced in the side chain of polyurethane. Study shows the hydrophobic segments enrichment on the surface of the film ejects hydrophilic groups of carboxyl and urethane from surface, with the amount of increasing hydrophobic chains, the water absorption rate of the film is gradually reduced. That means modified polyurethane using our method has marvelous water resistance. Further research indicated the modified polyurethane have good pliability, relative outstanding mechanical properties.Secondly, we study on synthesis and characteristic of the aqueous polyurethane modified by unsaturated aliphatic alkyl. HTPB (hydroxyl-terminated polybutadiene) is introduced into the macromolecular of polyurethane. Studies indicate: 1. the particle sizes of the modified aqueous PU...