Preparation And Coating Application Of Waterborne Polyurethane Modified With Hydroxypropyl Terminated Fluorinated Polysiloxane

Waterborne polyurethane was prepared with water as the dispersion medium, itscharacteristics were superior mechanical properties, abrasion performance, resistances to solvent,flexibility at low temperature as solvent based polyurethane and it was safe and environmental,good compatibility, and convenient to use. But the introduction of hydrophilic groups in theprocess of waterborne polyurethane preparation lead to poor water resistance, the applicationwas restricted. Polysiloxane has good flexibility and hydrophobicity, when it was introduced intowaterborne polyurethane, the hydrolytic of waterborne polyurethane would be improved. Inorder to further enhance the hydrolytic resistance of the waterborne polyurethane, fluorinatedpolysiloxane was synthesized with introducing the fluorinated groups into the polysiloxane, andshared the virtues of both polysiloxane and fluoropolymer. The hydrolytic resistance ofwaterborne polyurethane would be improved significantly, when the hydrophobic fluorinatedpolysiloxane was introduced into waterborne polyurethane. Hydroxypropyl terminatedfluorinated polysiloxane was synthesized at first, and waterborne polyurethane modified byfluorinated polysiloxane was synthesized by hydroxyl terminated fluorinated polysiloxane asmodifying agent, at last, the modified polyurethane was applied to coat the polyester fabric. Theresearch contents of this paper were divided into four parts:Part1: Synthesis and characterization of hydrogen terminated fluorinated polysiloxane.Hydrogen terminated fluorinated polysiloxane was synthesized via cationic ring-openingpolymerization by D4、D3Fand HMM as raw material, the effect of the dosage of catalyst, thereaction temperature and the reaction time on yield were discussed, the chemical structure ofsynthesis product was characterized by FTIR、1H-NMR and GPC. The results showed that theoptimal synthesis conditions of Hydrogen terminated fluorinated polysiloxane were that thedosage of catalyst was2%, the reaction temperature was50℃, and reaction time was4.5h. TheFTIR and1H-NMR results indicated the synthesis product was hydrogen terminated fluorinatedpolysiloxane. The GPC results indicated well-defined and lower MWD hydrogen terminatedfluorinated polysiloxane was successfully prepared.Part2: Synthesis and characterization of hydroxypropyl terminated fluorinated polysiloxane.Hydroxypropyl terminated fluorinated polysiloxane was synthesized via hydrosilylation by hydrogen terminated fluorinated polysiloxane and allyl alcohol as raw material andchloroplatinic acid as catalyst. Influence of the side reaction inhibitor, the dosage of catalyst,synthetic temperature and synthetic time on the double bond conversion were researched, thesynthesis conditions were optimized, the chemical structure of synthesis product wascharacterized by FTIR、1H-NMR and GPC, and the hydroxyl value was measured. The resultsshowed that the side reaction inhibitor could effectively prevent for the side reaction. Theoptimal synthesis conditions of hydroxypropyl terminated fluorinated polysiloxane were that thedosage of side reaction inhibitor was0.2%, the dosage of catalyst was60ppm, the reactiontemperature was75℃, and reaction time was4h. The FTIR and1H-NMR results indicated thesynthesis product was hydroxypropyl terminated fluorinated polysiloxane. The measuredmolecular weight accorded with molecular weight in theory, and its measured hydroxyl valuewas match with the hydroxyl value in theory.Part3: Preparation of waterborne polyurethane modified with hydroxypropyl terminatedfluorinated polysiloxane and its properties. Waterborne polyurethane modified by hydroxypropylterminated fluorinated polysiloxane was synthesized by polyether (N210) and isophoronediisocyanate (IPDI) as raw material, hydroxyl terminated fluorinated polysiloxane as modifyingagent, dimethylol propionic acid (DMPA) as the hydrophilic monomer, and trimethylolpropane(TMP) as the chain extender. The chemical composition of modified polyurethane wascharacterized by FTIR. The effect of the dosage of DMPA, the molecular weight and dosage ofmodifying agent on the properties of emulsion and its film were discussed. The results showedthat the stability of the emulsion increased, the particle size of the emulsion decreased, the waterabsorption rate of the film increased, the hydrophobicity of the film decreased，the tensilesteength of the film increased, the elongation at break of the film decreased as the dosage ofDMPA increased; The stability of the emulsion decreased, the particle size of the emulsionincreased, the water absorption rate of the film decreased, the hydrophobicity of the filmincreased, the tensile steength of the film first increased and then decreased, the elongation atbreak of the film increased as the molecular weight and dosage of modifying agent increased;When the dosage of DMPA was5%, the molecular weight of fluorinated polysiloxane was1712and its dosage was6%， the stability of emulsion was good, the particle size of the emulsion was45nm, the water contact angle of the film was106.8°, the water absorption of the film was 28.1%， the tensile steength of the film was8.43Mpa, the elongation at break of the film was739.58%; The FTIR results indicated the synthesis product was waterborne polyurethanemodified with hydroxypropyl terminated fluorinated polysiloxane.Part4: Application of waterborne polyurethane modified with hydroxypropyl terminatedfluorinated polysiloxane. Waterborne polyurethane modified with hydroxypropyl terminatedfluorinated polysiloxane was self-made and applied in polyester fabric finishing, the effect ofbaking temperature, baking time on properties of fabric were investigated, the coating conditionswere optimized, the water contact angle and tearing strength of coated fabric were tested, andcompared with the fabric coated with unmodified polyurethane and waterborne polyurethanemodified by polysiloxane. The results showed that the conditions of coating process withwaterborne polyurethane modified with hydroxypropyl terminated fluorinated polysiloxane werethat on the premise of pre-baked at90℃for5min, baking temperature was150℃, baking timewas90s, the water contact angle of the coated fabric was138.2°, the hydrostatic pressure was644mm. Compared with the unmodified polyurethane and waterborne polyurethane modified bypolysiloxane, the water resistance of the fabric coated with waterborne polyurethane modifiedwith hydroxypropyl terminated fluorinated polysiloxane was improved significantly.