Coating Modification And Application Development Of Functional Polysesquisiloxane

The polymethylsilsesquioxane（PMSQ）microspheres have a highly crosslinked network structure,and the microspheres have uniform dispersibility and good sphericity;the silicone elastomer（SE）,containing Si-O-Si segements,is also a crosslinked network structure.In this paper,according to control various influence factors,methyltriethoxysilane（MTES）was used as a raw material,and alkali was used as a catalyst,the PMSQ microspheres with good sphericity and narrow particle size distribution were prepared via hydrolysis-condensation in water-base system.In order to meet the higher demands,the smoothness of microsphere CPMSQ was improved by physical coating mothod.At the same time,PMSQ nanoemulsion was prepared.In view of its outstanding hydrophobicity,it was applied to aqueous phenolic resin to improve the wettability.The specific research details are as follows:（1）PMSQ microspheres with uniform particle size distribution and good sphericity were prepared by hydrolysis-condensation using MTES monomer as raw material and NaOH as catalyst.The optimum preparation process was obtained by exploring the preparation conditions:reaction temperature,amount of emulsifier,water,and NaOH;and the resultant were characterized by infrared spectroscopy（IR）,laser particle size analyzer,transmission electron microscope（TEM）,atomic force microscope（AFM）,scanning electron microscopy（SEM）,X-ray diffraction（XRD）and thermogravimetric analysis（TGA）.The results showed that when the monomer MTES mass was 30g,m（MTES）:m（H₂O）=1:4,the reaction temperature was 50°C,the NaOH concentration was 4.6%,the stirring speed was 300r/min,the reaction time was 10h,and the emulsification was performed.When the amount of the agent was 4.5%,PMSQ microspheres with uniform dispersion and good sphericity were obtained,and the average particle diameter was 2μm,and the yield was about 33.1%.（2）Using PHMS,VTES and VSO as raw materials,and complexing platinum as a catalyst,and a transparent solid silicone elastomer SE was obtained via hydrosilylation.The structure was characterized by SEM and IR.The effects of reaction conditions on SE yield and smooth degree were explored.When the VTES was 8%and the content of silicon hydride in PHMS was 0.18%,the yield of transparent elastic solid SE was improved.When the molecular weight of vinyl silicone oil VSO was 3000,the smoothness of the elastomer powder optimal.The SE was dispersed in heptamethyltrisiloxane（SMS）at a certain mass ratio and uniformly mixed,and then the PMSQ suspension and the prepared SEE were mixed in a certain mass ratio,and placed in an ultrasonic disperser for several minutes.After ultrasonication,and the product obtained by suction filtration is dried in an oven at 110°C to obtain a fine silicon powder having a good smooth degree,noted CPMSQ.It was characterized by SEM,TEM and so on.The coating conditions were explored.The results showed that when preparing CPMSQ,the silicone elastomer emulsion（SEE）was used as a surface coating agent to coat and modify the PMSQ microspheres.When the setting temperature was 110°C,m（SEE）:m（PMSQ）=1:10,a CPMSQ microsphere with better smoothness was obtained.（3）Using MTES monomer as raw material and NH₃·H₂O as catalyst,PMSQ nanospheres with uniform particle size distribution and good sphericity were prepared by hydrolysis-condensation.The PMSQ nanospheres were characterized by IR,laser particle size analyzer,TEM and SEM.The optimum preparation process was obtained by exploring the preparation conditions:reaction temperature,reaction time,amount of MTES,surfactant,water and NH₃·H₂O.The results show that when the catalyst NH₃·H₂O was 8g,monomer MTES was 25%,and the surfactant was 1.10 mmol/L,the obtained PMSQ nanospheres were uniformly dispersed with good sphericity,and the average particle size was about200nm.The water contact angle was 146°.The reaction time,temperature and pH of the system have specific influence on the hydrophobicity of PMSQ film.When the pH of the system was less than 7,the contact angel was very small.When the pH of the system was greater than 7,the contact angle increases sharply.The addition of hydrophobic PMSQ nanoparticles improved the hydrophobicity of the polymer surface.The PMSQ nanoparticles and the hydrogen-containing silicone oil emulsion were introduced into the aqueous phenolic resin,and the coating changed from hydrophilic to hydrophobic,and the water contact angle increased from 65.6°to 120°,which proved that the hydrophobic property was improved.