| Nano-SiO2/polymer hybrid material is a new type of composite materials obtainedby chemical bonding between inorganic nano-SiO2phase and polymer phase at thenanoscale. Generally, the polyhydroxy, vinyl and other functional siloxane monomer,and silane coupling agent are used as modifiers to improve the compatibility of SiO2nanoparticle and polymer, but there exists the following disadvantages:①due to theintroduction of polyfunctional monomers, cross-linking reaction is easily take place,which affects the viscosity and stability of the system, it is not conducive to thepreparation of the hybrid emulsion with high solids content;②because themolecular chain of the polyfunctional monomer is generally shorter, it is easilyshielded due to steric hindrance, leading to a lower grafting efficiency.In view of the above questions, in this study, nano SiO2/silicone/polyacrylatehybrid emulsion with high solid content was prepared by three-step method usingtetraethylorthosilicate （TEOS） as inorganic precursor, octamethylcyclotetrasiloxane（D4）, tetramethyl tetravinyl cyclotetrasiloxane （D4vi） as modifier and methylmethacrylate （MMA） and butyl acrylate （BA） as the polymer precursor:1. Nano-SiO2sol was prepared by sol-gel methodThe effects of catalytic method, catalytic time, the dosages of ethanol and water,and reaction temperature on the gel time were investigated. The results show that,when the acid-base two-step method is used to catalyze the hydrolysis andpolymerization of TEOS, and acid catalysis time is5min, the resulting nano-SiO2gelat50℃is conductive to the further in-situ fine emulsification polymerization.2. Nano-SiO2/silicone seed emulsion was prepared in situ under fine emulsionsystemThe effects of composition, dosage and feeding mode of emulsifier on the fineemulsifying effect, as well as catalysts on the polymerization were investigated. Theresults show that, selecting cationic emulsion system, excellent fine emulsifying effectcan be achieved through electrostatic interactions. Using anions catalyst to initiatepolymerization, the conversion rate is90.6%, and the structure, stability andmorphology of the resulting materials were characterized by FT-IR, SEM and DLS,the resulting nano-SiO2/silicone seed emulsion is homogeneous and stable.3. Nano-SiO2/silicone/polyacrylate hybrid emulsion was prepared by seed emulsion polymerizationUsing nano-SiO2/silicone emulsion as the core component, and acrylatemonomer as the shell component, the resulting nano-SiO2/silicone/polyacrylate hybridemulsion was prepared through seed emulsion polymerization. The effects of theemulsifier, the adding method, the swelling time were studied. With water-solubleammonium sulfate as catalyst, nano-SiO2/silicone/polyacrylate hybrid emulsion wasprepared by pre-polymerization and seed emulsion polymerization of the monomersmethyl methacrylate （MMA）, butyl acrylate （BA）, acrylic acid （AA）, and theconversion rate is94.4%. When the swelling time is up to15min, the swelling effectis good, When the acrylate content is increased to50%, the copolymerization rate ofnano-SiO2/silicone/polyacrylate hybrid emulsion is91.3%, and it still has exhibitedgood stability.4. Properties of nano-SiO2/silicone/polyacrylate hybrid materialsThe influence of the ratio of monomers, catalyst, polymerization conditions andtechnologies on the conversion rate, stability and viscosity were studied, furthermorethe curing, film-forming and mechanical properties. It is found that the solid contentof nano-SiO2/silicone/polyacrylate hybrid emulsion reached40%, the film-formingtemperature was5℃, the water absorption and resistance decreased with theincreasing of silicone content. And increasing polyacrylate content was beneficial toraise the adhesion level of the hybrid film, while increasing TEOS would enhance thehardness. |
PDF Full Text Request