Preparation Of PMMA/Nano-TiO₂ Composite Particles And Their Application In CNR Coating

Nano-titanium dioxide has excellent photocatalystic and UV-shielding properties. Functional polymer materials with the characteristics of both inorganic nanoparticles and organic polymer can be prepared by adding nano-TiO2 in polymer materials. However, the principal problem coming up in the preparing process is how to improve the compatibility between nano-TiO2 and polymer matrix materials. Surface grafting with strong chemical bond between polymer chains and inorganic particles can effectively solve this problem; in addition, the polymer chains with appropriate thickness grafted in the nano-particles can serve as interfacial buffer layer. In this paper, we started with the pretreatment of nano-TiO2 by silane coupling agent KH-570, to introduce unsaturated double bonds as active sites for surface grafting. And then environmentally friendly emulsion polymerization was carried out and PMMA/nano-TiO2 composite particles with high grafting rate were prepared through optimizing the conditions of polymerization system. Finally, the composite particles were used in CNR coating, and the influence of nano-TiO2 on composite coating was investigated.First of all, surface treatment of nano-TiO2 was dealt with silane coupling agent KH-570 after hydrolysis in water emulsion system. The influence of different pH value and emulsifier (SDS) concentration on hydrolysis rate and hydrolytic stability was investigated to set the conditions for hydrolysis. The coupling coating rate of nanoparticles was determined by calcinations, and the affect of hydrolysis and coupling conditions on coupling effect was studied. Results show that the appropriate conditions of hydrolysis and coupling were SDS concentration 0.1%, pH value 3.5, KH-570 concentration 2.0%, hydrolysis in ambient temperature, and coupling for 2 hours under 80℃.FTIR analysis indicates that chemical bonding was generated between the coupling agent and hydroxyl group around the nano-TiO2 surface, TEM shows that the nano-TiO2 after surface treatment can be uniformly dispersed in organic solvent.Secondly, PMMA/nano-TiO2 composite particles based on chemical grafting were obtained by emulsion polymerization. The interaction between polymer and nano-particles was analyzed with FTIR and TGA. The results show that two kinds of interaction forms, chemical grafting and physical coating, occurred between PMMA and nano-TiO2 before composite particles being extracted by acetone. After 72 hours of acetone extraction, when PMMA that physically adhered on the surface of composite particles was all removed, it can be seen through comparing the FTIR spectrum of PMMA/M-TiO2 with that of PMMA/TiO2 tKD It'V tKH "EUGgH' HIHFt SURvLGHJ Ey Foupling molecules that connected PMMA and nano-TiO2 together. The influence of polymerization conditions on polymer grafting rate and polymerizing stability was also investigated. Comparatively low gel content and grafting rate of 62.7%can be achieved under conditions of KH-570 concentration 2%,SLS concentration 0.1%,APS concentration 0.05%,and MMA/nano-TiO2 content ratio 10:5.TEM shows that dispersity of composite particles was improved after polymer grafting, and the particles stay at nano-level.Finally, PMMA/nano-TiO2 composite particles were added in CNR coating as to prepare nano-TiO2/CNR composite coating. Through general performance testing, heat sea-water resistance and antibacterial experiment of composite coating, we can found that the properties of coating, hardness and adhesion, corrosion resistance and antibacterial ability, were improved by filling nano-TiO2 with appropriate content. Antibacterial rates of composite coating against E.coli and staphylococcus aurous were 89% and 90%,respectively,as nano-TiO2 content is 3.0%. Considering all the properties, we can get a conclusion that composite coating with 3.0% nano-TiO2 shows the best overall performance.This paper studied the application of PMMA/nano-TiO2 composite particles in CNR coating, basing on the research of polymer grafting modification of nano-TiO2.lt revealed a new idea for nano-particles using in anticorrosion coating.