Effects of CNC/SiO_2 composite colloid on properties of waterborne poly acrylic acid coatings

ZHAO Guomin;PAN Mingzhu;College of Materials Science and Engineering,Nanjing Forestry University;

waterborne poly acrylic acid coatings;;cellulose nanocrystal;;nano-SiO_2;;abrasion resistance;;interfacial properties

Waterborne poly acrylic acid( PAA) coating is a waterborne environment-friendly coating and has been widely used in wooden furniture finishing,glass coating and automotive finishing because of its excellent corrosion resistance,weathering resistance and good film-forming properties. However,the waterborne PAA film is easy to be abraded,which not only reduces the gloss but also brings a sense of insecurity during the application. The main modification method to improve the abrasion resistance of waterborne PAA coating is the physical blending with inorganic nanoparticles,such as nano-SiO_2. However,nano-SiO_2 is aggregated easily,resulting in reduced compatibility with the waterborne PAA coating. In order to improve the dispersion of nano-SiO_2 in waterborne PAA coatings,the cellulose nanocrystal(CNC)/SiO_2 composite colloid was prepared by the sol-gel method. In this method,the CNC was used as the template,ethyl orthosilicate was utilized as the silicon source,and nano-SiO_2 was synthesized in situ polymerization on the surface of the CNC. Then,the CNC/SiO_2 composite colloid was used to modify waterborne PAA coatings. The effects of the CNC,nano-SiO_2 and CNC/SiO_2 composite colloid on the modification of waterborne PAA coatings were investigated. The results showed that the dispersion of nano-SiO_2 in PAA coatings,and the interface compatibility between SiO_2 and PAA were improved by adding the CNC/SiO_2 composite colloid prepared by the CNC template. After the addition of CNC/SiO_2 composite colloid,the hydrogen bonding and a small amount of ester were formed in CNC/SiO_2/PAA modified coatings. Compared with the CNC and SiO_2,the CNC/SiO_2 composite colloid improved the physical and mechanical properties of waterborne PAA coatings. When the addition of CNC/SiO_2 composite colloid was 5%,the hardness and adhesion of the PAA coatings increased to 6 H and the first level quality,respectively.The viscosity of the PAA coatings reduced from 979.3 mPa·s to 480.8 mPa·s,and the surface drying time increased from 60 min to 130 min.