Chen Huan-qin

Synthesis of TiO2 nano-particles and their photocatalytic activity for formaldehyde and methyl orange degradation

TiO2 nano-particles were synthesized by sol-gel technique and characterized by X-ray diffractometer (XRD) and transmission electron microscope (TEM). Their photocatalytic activities for formaldehyde (FA) and methyl orange (MO) degradation were tested using degradation rate (η) as an evaluation index. Based on the orthogonal test results, the optimal condition for TiO2 preparation was obtained. Results showed that particle sizes were in the range of 10–40 nm, and that prepared TiO2 had better photocatalytic activity than P25. A simplified model was developed to evaluate the apparent quantum efficiency (Φapp) of this photocatalytic reaction system.

The growth of latex particles during the Vac/BA copolymerization

The semi-continuous seeded emulsion copolymerization of vinyl acetate and butyl acrylate was carried out with hydroxyethyl cellulose as a colloid stabilizer. The morphology of the latex particle and the relationship between the reaction time and the average particle diameter and/or the conversion ratio during the polymerization were investigated. The experimental results show that the morphology of the latex particle possesses the stable steric construction. In the seeded polymerization, the average particle diameter of latex decreased while the conversion ratio increased. At the second term of the emulsion copolymerization (the growth stage of particle size), the latex particle average diameter increased with copolymerization continuously, but the instantaneous conversation ratio was not large, so it was very necessary to properly prolong the time during the holding temperature stage.

Effect of Polyvinyl Alcohol with a Thiol End Group on the Properties of Polyacrylic Dispersions and Spray-dried Powder

The emulsion polymerization of highly shear-stable copolymer dispersions of methyl methacrylate and butyl acrylate were carried out using poly (vinyl alcohol) with a thiol end group (PVA-SH) as protective colloid. The dispersions can be transformed into corresponding redispersible powder via a spray drying-cooling process. On-line FT-IR monitoring shows that grafting polymer of PVA-g-PMMA was formed mainly at the stage-1 of the emulsion polymerization. TEM images show, the PVA-SH shell was fragmentary when adding SDS at initial stage and integrated when adding at particle growing or final stage. The particle size turns to be smaller when delayed adding SDS surfactant. Triethanolamine, a co-regulator of PVA-SH, controlled the Mn to 50 000–70 000 and reduced the PDI to 1.5–1.7. The acrylic dispersions with 0.8wt%–1.5wt% PVA-SH1 can be spray-dried into super dispersible polymer powder (SDPP), which can easily disperse in water and form reconstituted dispersions with an average particle size smaller than 1 micron.