Preperation And Properties Of Poly (Vinylidene Fluoride) Functional Coating On Synthetic Leather

The function of polymer materials represents its development direction in the future,which will greatly promote the advanced manufacturing.Synthetic leather,as an important polymer material,has gained wide market demand in various fields.In recent years,synthetic leather industry has also grown towards conduction,damping and electrochromic field.So,it is important to study the ferroelectric,dielectric and pyroelectric coatings of synthetic leather for the purpose of widening its applications.Poly?vinylidene fluoride??PVDF?is an important ferroelectric and dielectric polymer material,which exhibits the properties of universal polymers and fluororesin.However,the dielectric constant of PVDF coating is low,and the adhesion strength to synthetic leather base is also weak.In order to solve above problems,PVDF,PVDF/poly?butylene adipate??PBA?and PVDF/ionic liquid composites were choosen as main research objects,the effects of PBA and[BMIM]PF₆ on the crystallization behavior of PVDF were studied.Then,the relation between crystal structure and ferroelectric and dielectric properties of PVDF has been further investigated.In addition,the oriented PVDF/PBA double layer composite thin films and the oriented PVDF/[BMIM]PF₆/PBA ternary composite thin films were prepared by epitaxial crystallization method.The interfacial structure between the oriented PVDF and PBA was studied by GIXRD.The main research contents and conclusions are as follows:?1?The POM and SEM morphological results show that PVDF and PBA are thermodynamically compatible.In their blends,the PBA melt is mainly distributed between the PVDF spherulites.With increasing the content of PBA,the ring spacing of?-form PVDF spherulites becomes larger,but its size increases initially and then decreases,indicating that a large amount of PBA hinders the growth of PVDF crystals.DSC results show that the thermodynamic behavior of PVDF is also influenced by the PBA content and its crystallization temperatures.Given enough annealing time,PBA in the composites can promote PVDF to form more stable crystals.FTIR results show that the above-mentioned thermodynamically more stable PVDF crystals are?-form crystals.The electrical properties results show that the addition of PBA can enhance the ferroelectricity of PVDF,increase the coercive field and the maximum polarization,which helps increasing the switching ratio of the composite as a memory.?2?Oriented PVDF/PBA bilayer composite films were prepared by epitaxial crystallization method.The POM characterization results show that the PBA came into spherulites when crystallized on glass sbustrate.However,the PBA crystallized on the oriented PVDF film formed tiny crystals instead of large spherulites.The crystallization temperature of PBA in the oriented PVDF/PBA composite system was higher than that of pure PBA,which indicated that the oriented substrate has strong heterogeneous nucleation effect on PBA.The XRD results show that on highly oriented PVDF substrate,the PBA lamellae are well aligned and more thermodynamically stable?-PBA crystals are formed.The GIXRD analysis results show that there is a good lattice matching relationship between the?020?crystal planes of?-PBA and the orientation molecular structure of PVDF.?3?PVDF/[BMIM]PF₆ blend solution was prepared by solution blending method and then casted into film.The POM shows that the addition of[BMIM]PF₆ results in the reduction of crystallization rate.While the crystallization growth rate was reduced in the composites.FTIR and XRD results show that the crystallization temperature has less effect on the crystal structure of PVDF,large amount of polar phase structure can form in a short time.[BMIM]PF₆ change the microstructure of PVDF as well as improves its hydrophilicity and dielectric properties.?4?Oriented PVDF/[BMIM]PF₆/PBA ternary composites were prepared by epitaxial crystallization.The POM characterization results show that the PBA crystallizes on the oriented PVDF film and form tiny crystals instead of large spherulites.The crystallization temperature of PBA in the oriented PVDF/[BMIM]PF₆/PBA ternary composites system is higher than that of pure PBA,which indicated that the oriented substrate has strong heterogeneous nucleation on PBA.The XRD results showed that on highly oriented PVDF and PVDF/[BMIM]PF₆ substrate,the PBA lamellae are well aligned and more thermodynamically stable?-PBA crystals are formed.Compared with the oriented PVDF/PBA bilayer composite system,it is found crystal structure of PBA is not affected by[BMIM]PF₆ and the crystal structure of the PVDF substracte plays an important role in the crystallization process of PBA.It is further illustrated that there is a good lattice matching relationship between the orientation PVDF and PBA,which deepens the understanding of the epitaxial system and the interface structure.