Preparation And Properties Of Waterborne Polyurethane/Polyacrylate Self-healing Materials

With the increasingly stringent requirements of national environmental laws and regulations and people's demand for a better life,the preparation of high-performance multifunctional coatings with environmentally friendly waterborne and functional modified materials has gradually become a research hotspot in the coating industry at this stage.Water is used as dispersion medium,which makes waterborne polyurethane non-toxic and green environmental protection.However,single WPU has the problems of low solid content,poor water and solvent resistance,and high production cost.Polyacrylate(PA)coating has the characteristics of excellent light resistance,aging resistance,water resistance,film forming and color retention,but it has the defects of "hot adhesion and cold brittleness" when used alone.The coating materials with high solid content and excellent comprehensive properties can be obtained by the organic combination of WPU and PA.The mechanical damage such as friction,scratch and crack will lead to structure damage,coating function loss and service life shortening.Therefore,the research and development of waterborne polyurethane/polyacrylate with self-healing function to realize the self-healing of material cracks,cross-section and surface is of great significance to enhance the durability of products and extend the service life of coating products.In this paper,from the perspective of molecular design,we first introduce reversible dynamic chemical bonds into WPU molecules to give WPU damage self-healing performance,and then modify WPU with PA to accelerate the movement of molecular chain under certain conditions and improve the self-healing efficiency.This paper mainly is composed of the following three aspects:(1)Firstly,polytetrahydrofuran ether diol(PTMEG)and isoporone diisocyanate(IPDI)were used as reaction monomers,dibutyltin dilaurate(DBTDL)was used as catalyst,2,2 dihydroxymethylpropionic acid(DMPA)and 1,4-butanediol(BDO)were used as chain extenders,hydroxyethyl acrylate(HEA)as capping agent,water based polyurethane aqueous dispersion with double bond(WPUA)was prepared.Then,WPUA was used as emulsifier and reactive seed emulsion to copolymerate acrylic monomers.The core-shell structure of high solid content crosslinked waterborne polyurethane/polyacrylate(AWPUA)composite was obtained.The optimum process ratio was obtained by orthogonal design.The microstructure and thermodynamic properties were studied by FT-IR,TGA,TEM,SEM and mechanical test.The results showed that the AWPUA polymer emulsion was homogeneous monodisperse system,the emulsion size was 153.3 nm,the latex particles showed a core shell structure,the AWPUA film had high thermal stability,and the water resistance and solvent resistance were significantly improved.Compared with the WPU film,the water contact angle of AWPUA increased from 79.2° to 91.5°,and AWPUA had a certain self-foaming property.(2)PTMEG and IPDI were used as monomers,DBTDL as catalyst,DMPA,BDO,HEDS were used as chain extender,waterborne polyurethane containing aliphatic disulfide bond(WPUS)was synthesized.A series of waterborne polyurethane/polyacrylate composites containing different aliphatic two sulfur bonds(AWPUS)were prepared by physical blending with PA emulsion.The effects of different ratios of PA/WPUS on the self-healing properties of the films were investigated.The structure,transmittance,mechanical properties and self-healing properties of the products were characterized by FT-IR,Raman,UV-vis,SEM,polarizing microscopes,and mechanical tests were characterized.The results showed that the self-healing efficiency of PA/WPUS composite was significantly improved,and the self-healing efficiency increased from 73.4%in 6 h to 81.7%in 2 h at 60?.When the PA/WPUS ratio was 0.30/0.70,the tensile strength and tensile strain were 16.8 MPa and 704%,respectively.The stress recovery rate was 84.3%after 5 loading unloading cycles,which has good thermal stability,reprocessability and excellent comprehensive properties.(3)Waterborne polyurethane containing aromatic disulfide bond(WPUD)was prepared by using PTMEG and IPDI as monomers,DBTDL as catalyst,DMPA,BDO and 2,2 '-diaminodiphenyldisulfide(4-AFD)as chain extenders.A series of waterborne polyurethane/polyacrylate composites containing aromatic two sulfur bonds(AWPUD)were prepared by physical blending and PA emulsion.Raman,TGA,DSC,polarizing microscope and Ultra depth of field microscope were used to characterize the structure,thermal stability,mechanical properties and self-healing properties of the products.The effects of PA/WPUD ratio on the self-healing properties of the film were investigated.The results show that the self-healing efficiency of PA/WPUD composites is significantly improved,and the self-healing efficiency increases from 74.6%to 98.2%in 2 h at 60?.When the PA/WPUD ratio is 0.30/0.70,the tensile strength and tensile strain are 16.1 MPa and 544.2%,respectively.Meanwhile,the stress recovery rate is 66.2%after 5 loading unloading cycles.In this paper,the preparation of polyacrylate modified waterborne polyurethane,self-healing waterborne polyurethane/polyacrylate and self-healing properties of coatings were studied systematically.The prepared waterborne polyurethane/polyacrylate material has the characteristics of good water resistance,solvent resistance and high self-healing efficiency.With the help of the complementary advantages of waterborne polyurethane and polyacrylate composite materials to realize the resource utilization of coating materials.It has a certain theoretical significance and practical application value for promoting the green and sustainable development of the coating industry,the design of ecological and self-healing coatings.