PREAPARATION OF CATIONIC LATEXES OF POLY(STYRENE-CO-BUTYL ACRYLATE) AND THEIR PROPERTIES EVOLUTION IN LATEX DILUTION

Cationic latexes were prepared through emulsion copolymerization of styrene （St） and butyl acrylate （BA） with a cationic surfactant, cetyl trimethyl ammonium bromide （CTAB）. Latex properties, including particle size, size distribution, （ potential, surface tension and monomer conversion, were determined for latexes prepared with different CTAB amounts. Evolution of these properties during emulsion polymerization was followed in order to understand the mechanism of the particles formation. Results showed that both particle size and 6＂ potential were function of polymerization time and latex solids. Parallel emulsion polymerizations with cationic, anionic charged initiator and charge-free initiators were also carried out, the latex properties were determined at different polymerization time. All these results were attentively interpreted based on the mechanisms of emulsion polymerization, surfactant adsorption and latex particle stabilization.

Heteropolyacids Catalysis in Synthesizing Butylacrylate

The catalytic activities of some heteropolyacids(HPAs) in synthesizing butyl acrylate are reported. It has been demonstrated that 12 tungstophosphoric acid is the most effective catalyst among more than 20 HPA(salts). Various factors concerned in this reaction have been investigated. The optimum conditions have been found, that is, the molar ratio of alcohol to acid is 1.2∶1.0 , the catalyst concentration 1%(mass fraction), the reaction time 2 h, the temperature 98—124 ℃ and a certain amount of polymerization inhibitor exists.

Acrylate Copolymers as Impact Modifi er for Epoxy Resin

P（BA-GMA）（PBG）, having various molecular weights, was synthesized by in situ polymerization of butyl acrylate（BA） and glycidyl methacrylate（GMA）, and further used as a modifier to improve the comprehensive properties of the epoxy curing system. The copolymers were characterized by gel permeation chromatography（GPC）. The effects of various molecular weights of copolymers on the mechanical properties, thermal performance, and phase behavior of the curing system were carefully evaluated. The experimental results of differential scanning calorimetry（DSC） and dynamic mechanical analysis（DMA） showed that glass transition temperature decreased and the tan δ peak shifted to a lower temperature with decreasing molecular weight of copolymer. Mechanical properties analysis of curing films showed that the impact strength and fracture toughness increased significantly upon the addition of PBG, indicating good toughness of the modified epoxy resins. From scanning electron microscopy（SEM） studies of the fracture surfaces of ER/PBG systems, the fracture behavior of epoxy matrix was changed from brittleness to toughness.

DMS AND ^(13)C NMR STUDIES ON THE COMPATIBILITY AND DYNAMICS OF LATEX BIDIRECTIONAL IPNS AND LATEX IPN OF PVAc/PBA

The compatibility and dynamics of latex bidirectional/nterpenetrating polymer networks (LBIPNs) and latex IPN(LIPN) of poly(vinyl acetate)(PVAc) and poly (butyl acrylate )(PBA) are investigated by means of dynamic mechanical spectroscopy (DMS) and nuclear magnetic resonance (NMR) techniques. The results of DMS show that the compatibility of the LBIPNs is much better than that of the corresponding LIPN and depends to, a large extent on the distribution of PVAc both in the core and in the shell. The results of NMR measurements indicate that the rotational correlation times of the side- groups of PBA in the LBIPN are longer than those in the LIPN. The relation between the ^(13)C linewidths of PBA and temperature is also discussed.

Synthesis of cationic styrene-acrylic acid ester copolymer emulsion for paper sizing

Surface sizing is an effective way to increase paper’s water-resistance and printability.The purpose of this study was to study synthesis process to develop an efficient cationic styrene-acrylic acid ester emulsion(SAE)for the surface sizing of paper.Dimethylaminoethyl methacrylate methyl chloride(DMC)was used as the cationic monomer,and cationic starch or native starch was used as the emulsion stabilizer to copolymerize with styrene and butyl acrylate.The results indicated that the SAE synthesized with cationic starch and DMC had a high cationic charge density and a high DMC conversion rate.Paper sized with the cationic SAE had higher surface strength and lower Cobb value than the paper sized with other surface sizing agents such as,anionic SAE,and cationic or oxidized starch.Scanning electron micrographs revealed that the paper sized with a combination of oxidized starch and cationic SAE had smoother surface morphology when compared to the paper sized with oxidized starch alone,or with oxidized starch and anionic SAE.