纤维素纳米晶体/SiO_2纳米复合胶体对水性丙烯酸涂料性能的影响

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

为改善纳米SiO_2在水性聚丙烯酸(poly acrylic acid,PAA)涂料中的分散性,以纤维素纳米晶体(cellulose nanocrystal,CNC)为模板,正硅酸乙酯为硅源,通过溶胶凝胶法在CNC表面原位聚合形成纳米SiO_2,制备CNC/SiO_2复合胶体,并以复合胶体改性水性PAA涂料,探讨了CNC、纳米SiO_2以及CNC/SiO_2复合胶体对水性PAA涂料的影响规律。结果表明,以CNC为模板负载SiO_2制备得到的CNC/SiO_2复合胶体加入水性PAA涂料中可以有效提高SiO_2在PAA涂料中的分散性,改善了SiO_2与PAA的界面相容性。经CNC/SiO_2复合胶体改性后,PAA涂料中形成了氢键和微量的酯基。相比CNC和SiO_2,CNC/SiO_2复合胶体改善了水性PAA涂料的物理力学性能。当CNC/SiO_2复合胶体添加量为5%时,PAA涂料的硬度由H增大到6H,附着力由四级提高到一级,黏度由979.3 mPa·s减小到480.8 mPa·s,表干时间由60 min延长至130 min。

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 re- sistance, weathering resistance and good film-forming properties. However, the waterborne PAA film is easy to be ab- raded, which not only reduces the gloss but also brings a sense of insecurity during the application. The main modifi- cation method to improve the abrasion resistance of waterborne PAA coating is the physical blending with inorganic nanoparticles, such as nano-SiO2. However, nano-SiO2 is aggregated easily, resulting in reduced compatibility with the waterborne PAA coating. In order to improve the dispersion of nano-SiO2 in waterborne PAA coatings, the cellu- lose nanocrystal （CNC）/SiO2 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-SiO2 was synthesized in situ poly- merization on the surface of the CNC. Then, the CNC/SiO2 composite colloid was used to modify waterborne PAA coatings. The effects of the CNC, nano-SiO2 and CNC/SiO2 composite colloid on the modification of waterborne PAA coatings were investigated. The results showed that the dispersion of nano-SiO2 in PAA coatings, and the interface compatibility between SiO2 and PAA were improved by adding the CNC/SiO2 composite colloid prepared by the CNC template. After the addition of CNC/SiO2 composite colloid, the hydrogen bonding and a small amount of ester were formed in CNC/SiO2/PAA modified coatings. Compared with the CNC and SiO2, the CNC/SiO2 composite colloid improved the physical and mechanical properties of waterborne PAA coatings. When the addition of CNC/SiO2 com- posite colloid was 5%, the hardness and adhesion of the PAA coatings increased to 6H and the first level quality, re- spectively. 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.