A theoretical analysis and a morphological prediction of polyacrylate (PA)/ polysiloxane (PSi) latex particles with core/shell morphologies were first conducted based on interfacial tensions and relative volumes of the two polymers in the latex system. The results indicated that the normal core/shell morphology particles (PSi/PA), with hydrophobic polysiloxane as the core and with hydrophilic polyacrylate as the shell, can be easily formed. Although the inverted core/shell morphology particles (PA/PSi) with polyacrylate as the core could not be formed in most cases, even if the fraction volume of polysiloxane was larger than 0.872, which is the smallest value of forming a PA/PSi particle, the PSi/PA particles were unavoidably formed simultaneously with PA/PSi particle formation. The synthesis of PA/PSi particles containing equal amounts of polyacrylate and polysiloxane was then carried out using seeded emulsion polymerization. Before the cyclosiloxane cationic polymerization, 3-methacryloyloxypropyl trimethoxysilane (MATS) was introduced into the polyacrylate seed latex to form an intermediate layer and chemical bonds between the core and the shell polymers. The characterization by transmission electron microscopy (TEM) demonstrated that the perfect PA/PSi core/shell particle is successfully synthesized when both the core and the shell polymers are crosslinked. The experiments showed that both the hardness and water adsorption ratio characteristics of latex films of the PA/PSi particles are in good agreement with those of the polysiloxane film.

No abstract

Polymer microspheres with narrow size distribution and with carboxyl groups on their surfaces were synthesized by soap-free emulsion polymerization of methyl methacrylate (MMA), ethyl acrylate (EA), and acrylic acid (AA), and the distribution of -COOH in the latex was determined by conductometric titration. Effects of ingredients on polymerization, latex particle size (D p ), and its distribution, and the distribution of -COOH were investigated. Results showed that monomer conversion and the amount of embedded -COOH (E a ) decreased, and D p increased with increasing amounts of NH 4 HCO 3 . The amounts of surface -COOH (S a ) and water -COOH (F a ) and the number of -COOH on each square centimeter of the particles' surface (S d ) increased with increasing amounts of NH 4 HCO 3 and AA. With the increase of initiator (APS) and AA, D p deceased. E a increased with the increase of AA. F a increased and then remained constant, and S d decreased with the increase of initiator.

ABSTRACT:Copolymer latices of styrene-butyl acrylate-silicone were prepared using a semicontinuous addition process and batch and monomer emulsion addition processes. The results showed that a stable latex with narrow particle size dispersion and a high monomer conversion can be obtained only by the semicontinuous addition process. The simultaneous free-radical and ionic copolymerization mechanisms were discussed. 3-Methacryloyloxypropyl trimethoxysilane in this work was used as a coupling agent to form a chemical bond between vinyl polymer and polysiloxane. It was found that the copolymerization reaction and the properties of latex and latex film were obviously influenced by silicone content. When the silicone content was less than 25 wt %, copolymerization proceeded readily and a stable latex could be prepared. With increasing silicone content, monomer conversion, latex stability, film hardness, and tensile strength decreased, whereas the water resistance and impact strength increased. Results of Soxhlet extraction, silicon analysis, and dynamic mechanical properties of latex polymer confirmed the occurrence of copolymerization.

No abstract

No abstract

No abstract

No abstract