Synthesis And Characterization Of Polyurethane-Acrylate/Nano Silica Composite Emulsion

Waterborne polyurethane has many advantages, such as no pollution, safe and reliable, excellent mechanical properties, good bio-compatibility, easy modification, etc. Waterborne polyurethane resin has gradually replaced solvent polyurethane and become an important direction of development of polyurethane industry. Waterborne polyurethane can be widely used in coating, adhesive, coated fabric and finishing agent, paper surface treatment agent, leather finishing agent and fiber surface treatment agent. But, inevitably, waterborne polyurethane has brought the problem of poor water resistance. What’s more, bad weathering resistance and gloss also limit the promotion and application of waterborne polyurethane material. Therefore, the modified waterborne polyurethane is especially important. At present, the common methods of modification are acrylic modification, nano modification, epoxy resin modification, organic silicon modification, organic fluorine modification, etc. Polyacrylate has excellent water resistance, weathering resistance and light resistance and low price. These just can make up the defects of waterborne polyurethane. Nano silicon dioxide has many characteristics, such as high strength, good stability and good hydrophobic. Nano silicon dioxide can make up the poor water resistance of waterborne polyurethane. Therefore acrylate and nanometer silicon dioxide were used to modify waterborne polyurethane. The main content is divided into three parts:(1) Polyurethane-acrylate/SiO2composite emulsion prepared by in situ polymerizationNano silica (SiO2) sol was synthesized through a sol-gel process. Then nano silica sol was modified by KH-570. Polyurethane-acrylate/SiO2composite latex (S-SPUA) with core-shell structure was synthesized with modified nano silica, acrylate and polyurethane prepolymer end-capped by double bond by in situ polymerization. The structure of the copolymer was characterized by Fourier transform infrared spectrometer (FTIR). The particle morphology of the SPUA latex was observed through transmission electron microscopy (TEM). Tensile testing machine, scanning electron microscopy (SEM) and thermo gravimetric analyzer were performed on the film to test the physical properties, the fracture surface appearance and the thermal properties of the SPUA films. The results indicated that, with increasing the mass fraction of modified nano silica, the thermal stability and the physical properties of the films were improved obviously. When the mass fraction of modified nano silica was8%in the film,the temperature for the maximal thermal mass-loss rate was413℃,water absorption was4.1%, the tensile strength of the S-SPUA film was17.7MPa and the hardness was93.(2) Waterborne polyurethane-acrylate/nano SiO2synthesized through a sol-gel procedurePolyurethane-acrylate/SiO2composite emulsion were synthesized by compound in situ with sol-gel method. In the process of experiment, ethyl orthosilicate(TEOS) was used as precursor, and y-methacryloxypropyltrimeth-oxysilane (KH-570) was used as silane coupling agent. The particle morphology of the G-SPUA emulsion was observed through transmission electron microscopy (TEM). The structure of the copolymer was characterized by Fourier transform infrared spectrometer (FTIR). Tensile testing machine, scanning electron microscopy (SEM), shore durometer and thermo gravimetric analyzer (TGA) were performed on the film to test the surface appearance, the thermal properties, hardness, and physical properties of the G-SPUA films. The results indicated that, with increasing the mass fraction of TEOS, the physical properties of the films were improved obviously. When the mass fraction of ethyl orthosilicate (TEOS) was8%, the water absorption was5.8%, the tensile strength of the G-SPUA film was16.8MPa, the shore hardness was94, and the temperature for the maximal thermal mass-loss rate was416℃.(3) Synthesis and characterization of different ionic polyurethane/nano-SiO2composite emulsionAnionic hydrophilic monomer (ASPU-15), cationic (CSPU-15) and nonionic (NSPU-15) polyurethane/nano SiO2composite emulsions were synthesized by2,2-dihydroxy methyl propionic acid (DMPA) and methyl diethanolamine (MDEA) bind and nonionic polyethylene glycol (YMER N-120), respectively. SEM、TGA、 FTIR、DSC、XRD and tensile testing machine were performed on the film to test the surface appearance, thermal properties, the structure and mechanical properties of the composite films. The impact on the state of emulsion and film properties with different TEOS mass fraction was discussed. The results showed that the particle size of nonionic polyurethane/nano SiO2composite emulsion was bigger. Intensity of crystalline:NSPU-15>CSPU-15>ASPU-15; Tensile strength and shore hardness: ASPU-15>CSPU-15>NSPU-15. Anionic hydrophilic monomer and cationic nonionic (NSPU-15) polyurethane/nano SiO2composite films have better thermal properties, water resistance and mechanical properties; nonionic (NSPU-15) polyurethane/nano SiO2composite films have better flexibility, alkali resistance and acid resistance. Therefore, different types of composite materials can be chose according to different requirements in the practical application.