Study On Modification Of Environmentally Friendly Waterborne Polyurethane Polymer Materials

In the past few decades,traditional solvent-based polyurethanes have been widely used in automotive paints,foams,plastics,and packaging materials because of their flexibility,adhesion,weatherability,and corrosion resistance.However,the conventional solvent-based polyurethane uses organic solvents such as benzene and toluene as dispersing agents,which are harmful to the human body and the environment.Due to the severe limitations of volatile organic compounds(VOCs)and the increasing environmental awareness,waterborne polyurethanes have attracted much attention due to the use of water as a dispersing agent.Most waterborne polyurethanes are a onecomponent linear thermoplastic polymer.For ease of emulsification in water and good dispersion stability in water,the aqueous polyurethane backbone contains hydrophilic groups and low crosslink density.Factors lead to poor adhesion,mechanical properties,water resistance and thermal stability。In order to overcome these shortcomings,the physical modification,chemical modification and composite modification of aqueous polyurethane were studied by using siloxane materials.In addition to organic structures such as C-C and C-H,the siloxane molecular chain also has an inorganic structure such as Si-C and Si-O-Si,so that the siloxane has the characteristics of a machine-inorganic compound.This paper uses isophorone diisocyanate,polycarbonate diol,2,2-bishydroxymethylpropionic acid,1,4-butanediol,triethylamine,3-aminopropyltriethoxysilane.A series of different siloxanes were synthesized as the main raw material,hexadecyltrimethoxysilane and N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane as modifiers.The modified aqueous polyurethane dispersion was characterized by infrared spectroscopy,particle size measurement,thermogravimetric analysis,contact angle,mechanical test and water absorption.In this paper,different content of cetyltrimethoxy-amino terminated polyurethane was synthesized by physical blending.The results show that when the addition amount of hexadecyltrimethoxysilane is 2wt%,the mechanical properties of the mixed film are the best,the tensile strength reaches 9.64 MPa,and the thermal stability,hydrophobicity and water resistance of the film are improved.But the improvement is not high.Then,the synergistic action of cetyltrimethoxysilane and 3-aminopropyltriethoxysilane is used to compositely modify the aqueous polyurethane.The results show that the composite modification can significantly improve the surface hydrophobicity of waterborne polyurethane.When the amount of HDTMS is 3wt%,the contact angle of water reaches 105 °,but the mechanical properties are reduced.Finally,N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane was used as a chain extender to copolymerize WPU.The results show that the copolymerization modification is better than the physical modification.Moreover,the siloxane can be introduced into the WPU side chain and the chain end by chemical modification,and the addition amount could significantly improve the properties of the aqueous polyurethane.