Synthesis And Application Of Waterborne Polyurethane Modified With HP-PDMS

Waterborne polyurethane was a dispersible polymer in water medium. It possessed properties such as the security environmental protection, good suppleness, simple process, low cost. And it possessed some good characteristics as well as the solvent polyurethane. But waterborne polyurethane has poor water resistance, poor solvent resistance and low adhesion force, so it needed to be modified. Waterborne polyurethane modified by the polyether-polysiloxane would lose part of hydrophobic, because the polyether-polysiloxane owned water-solubility. Therefore, hydroxypropyl polysiloxane with hydrophobic property was synthesized at first, and it was used to modify waterborne polyurethane. Waterborne polyurethane emulsion modified with hydroxypropyl polysiloxane (HP-PDMS-WPU) was prepared, and it made the fabric good hydrophobic property, moisture permeability and soft handle. This paper was divided into three parts:Part one:The synthesis and characterizations of hydroxypropyl polysiloxane (HP-PDMS). The hydroxyalkyl polysiloxane(HP-PDMS) was synthesized through hydrosilylation with polysiloxane terminateed with hydrogen and allyl alcohol as raw materials and Platinum complex as catalytic agent. The influnence of reaction affect factors on the reaction conversion were studied, the synthesis conditions of HP-PDMS was optimized, and the structure of HP-PDMS was characterized with FTIR and1H-NMR.The result showed that the optimum synthesis conditions of HP-PDMS were that the amount of catalyst was15ppm, the reaction temperature was60℃, reaction time was4h, the reaction conversion was63%. The structure of product was comfirmed as hydroxyalkyl polysiloxane by FTIR and1H-NMR. The number-average molecular weight of HP-PDMS was1757, it accorded with molecular weight in theory. The hydroxyl value was63.9mg KOH/g, and it could dissolued in acetone.Part two:Synthesis and performance of waterborne polyurethane modified with HP-PDMS. The polyurethane pre-polymer was synthesized with isophorone diisocyanate (IPDI) and polyether (N210) as raw material, HP-PDMS instead of part of N210,2,2-bis(hydroxymethyl) propionic acid (DMPA) as a hydrophilic monomer. On this basis, HP-PDMS-WPU was synthesized with1,4-butanediol (BDO) as chain extender, trimethylolpropane(TMP) as cross-linking agent. The effects of different dosage and different molecular weight of HP-PDMS on the properties of HP-PDMS-WPU emulsion and its film were investigated. FTIR was used to characterize the structure of HP-PDMS-WPU, the properties of emulsion and its film of HP-PDMS-WPU were compared with that of WPU. The result showed that the stability of HP-PDMS-WPU emulsion was good, the particle size of emulsion was about75nm, the water absorption of the film was32.1%, the water contact angle of the film was106.2°, the tensile strength the film was15.61MPa, the elongation at break of the film was413.1%when the molecular weight of HP-PDMS was1757and the amount was6%. The FTIR analysis showed that the HP-PDMS had been grafted to the polyurethane molecular chains. Compared with the unmodified waterborne polyurethane, the water resistance, the water contact angle and the mechanical properties of HP-PDMS-WPU film were improved greatly.Part three:Study on the application performance of HP-PDMS-WPU. Self-made HP-PDMS-WPU was applied to coat the polyester fabric. The effects of finishing factors such as dosage of coating agent, curing temperature and curing time on the properties of coated polyester fabric were investigated, the coating process conditions were optimized, the performance of the coated fabric was tested, and compared with non-modified waterborne polyurethane and waterborne polyurethane modified polyether-polysiloxane. The results showed that the optimized conditions of coating process with HP-PDMS-WPU were that coating agent dosage was10g/m2, cured at150℃for60s, and the tear resistance of coated fabric was457.3N, the hydrostatic pressure was647mm. Compared with non-modified waterborne polyurethane, the softness and the hydrostatic pressure were improved. Compared with waterborne polyurethane modified polyether-polysiloxane, the engage angle was improved greatly and reached136.1°, and the softness, washing fastness, tear strength and other properties was comparable.The results of the study show that, compared with waterborne polyurethane modified with HP-PDMS with hydrophobic property, the film possessed high hydrophobic property and the coating fabric possessed high water repellency. The coating agent of HP-PDMS-WPU was more suitable for outdoor fabric coating.