The Study Of Nano-TiO₂Effect On The Structure And Performance Of Waterborne Polyurethane For Synthetic Leather

In this paper, the nano-TiO₂was added into the aqueouspolyurethane emulsion to prepare modified nano-TiO₂/WPU compositesby the methods of direct particle blend dispersion and powder grafting.And the composite materials for the film and application experimentswere done. The main contents and results are as follows:Two crystal style nano-TiO₂were made by the method of gel-sol.FT-IR, XRD, SEM and grading analysis results demonstrated thatcrystal form of products were rutile and anatase, the grain size is about50nm. The dispersants screening experiments show that CMC wassuited for rutile type nano-TiO₂in water solution and SHMP was suitedfor anatase type nano-TiO₂suit in water solution. The optimum amountof dispersant were0.3%（wt） and0.2%（wt）respectively.Nano-TiO₂/WPU composite films were made by direct dispersionmethod of nanoparticles, researching the effect of nano-TiO₂crystalstyle （rutile and anatase） on performances of composite films. Viscosityanalysis demonstrated that rutile type nano-TiO₂increases the betteradhesion effect. Grain size, SEM and AFM analysis showed that addingnano-TiO₂make no effect on the stability of PU emulsion, compositeparticles is still nanoscale, two crystal style nano-TiO₂both disperseduniformly in composite film and had no effects on the flatness of it.When adding rutile and anatase TiO₂mass fraction of3%and4%, thetensile strength of Nano TiO₂/WPU composite films compared with thepure film increased by26.8%and29.49%, the elongation ratioincreased by17.4%and20.6%, the vapor permeable increased by9.6% and13.4%, the permeability increased by16.7%and17.4%.With theincrease of two types nano-TiO₂content, the both contact angle of thecomposite film first increased and then decreased, as the rutile andanatase TiO₂mass fraction of3%, the maximum contact angle of thecomposite film were77.5°and75.1°. The mechanical property and theanti-bacterial tests showed that added anatase type nano-TiO₂had bettermechanical and anti-bacterial properties.Anatase nano-TiO₂was modified with grafting method and addedto the polyurethane prepolymer, while adding the inorganic dispersantSHMP in the process of emulsification, at last got modified nano-TiO₂／WPU composite materials. The effect of nano-TiO₂on the structure,particle size, solid content, water resistance, mechanical property,stability and other performance of waterborne polyurethane. Theexperiment results show that: the particle size and solid content ofcomposite emulsion increased significantly after adding modifiednano-TiO₂, particle size mostly between100²00nm; Following withthe increase of modified nano-TiO₂, the water absorbing quality ofcomposite film was decreased first and then increase, contact angle ofcomposite film was increase first and then decrease, moreover when thecontents of modified nano-TiO₂is2%, water absorbing is least andcontact angle is84.1°and largest. The largest tensile strength andelongation at break respectively increases30.1%and21.2%than blankfilm, the mechanical property of composite film is best when thecontents of modified nano-TiO₂is2%³%; IR and XRD analysisshowed that the KH550successfully grafted onto the surface ofnano-TiO₂particles, there had chemical bonding between modifiednano-TiO₂and WPU, the crystallinty of polyurethane has basically nochange. SEM and AFM images can be seen that the nano-TiO₂uniformly distribute in the composite film and the surface of compositefilm was smooth.Nano-TiO₂／WPU composite materials be used in synthetic leathercoating, inspecting its practical application performance in theproduction of synthetic leather. Research showed that adding nano-TiO₂ had certain advantages in improving material appliced performance, itcan greatly improve the wear-resisting property of WPU coating.