F. Chu

High solid content multisized emulsion copolymerization of styrene, butyl acrylate, and methacrylic acid

Polymer lattices with a multimodal particle size distribution (PSD) polymer latex were prepared by introducing additional surfactants during the semicontinuous emulsion polymerization of styrene, butyl acrylate, and methacrylic acid. The polymerization was investigated by following the variation of the particle size, the size distribution, the number of particles, the Tg of the different particle sizes, and the total conversion at different steps of the polymerization process. The results show that bimodal and trimodal PSD polymer lattices can be obtained by this method and that the secondary generation of particles is greatly influenced by the nature and the amount of additional surfactants, as well as the moment when they are introduced. When the amount of additional surfactants is increased, the diameters of both the small and large particles decrease and the number of particles in each of the populations increases. Earlier introduction of these surfactants favors the generation and the growth of the small particles and thereby leads to a reduction of the relative fraction of large particles in the final latex. On introduction of 7 wt % of additional surfactants, based on the total monomers, 100% of the monomers of the second-stage polymerization were consumed to form the small particles. This fraction decreases with a decreasing amount of the additional surfactants. These results were further demonstrated by measuring the Tgs of both the large and the small particles of two lattices, in which the Tgs of the copolymers produced in each of the stages were different. High solid content (>65%), low viscosity, and coagulum-free lattices have been obtained through secondary nucleation, and a minimum in viscosity was found when the weight fraction of the large particles was around 80%.

Study of poly(St/BA/MAA) copolymer latexes with bimodal particle size distribution

A new strategy was developed for producing a polymer latex with trimodal particle size distribution by adding a second seed of polymer particles and some additional surfactants during polymerization. The polymerization was investigated by following the variation of the particle size, the size distribution, the number of particles, the surface tension and surfactant surface coverage at different stages of the polymerization process. The results showed that both the size and the size distribution can be easily controlled by varying the amount of additional surfactants and the second seed of polymer particles. The secondary nucleation was achieved when the surface coverage of particles was over 70%, and the amount of small particles formed increased with increasing amount of additional surfactants. The introduction of the additional surfactants had no significant effect on the size and number of middle particles, but reduced the size of large particles and caused the number of large particles to remain more stable because of the suppression of limited flocculation. Copyright

Mechanical Properties of Films from Hybrid Acrylic‐Polyurethane Polymer Colloids

A variety of polyurethane based on the polyaddition of isophoronediisocyanate and polypropyleneglycol has been used to prepare acrylic‐polyurethane hybrid polymer colloids, through either mini‐emulsion polymerization of their solutions in a mixture of monomers or seeded emulsion polymerization of this mixture from seeds of modified polyurethane containing dimethylolpropionic acid neutralized with triethylamine. The mixture of monomer is composed of 30% styrene, 30% methylmethacrylate, and 40% butylacrylate. The mechanical properies of films prepared through coalescence of these latexes where studied. The effect of various parameters such as the composition and the amount of polyurethane as well as the synthesis process are discussed.

Particle Size in Emmulsion Polymerization of Octamethyltetrasiloxane

Abstract In view of interest in the emulsion polymerization of octamethylcyclosiloxane, (D4), the stability of droplets of monomer D4 against Ostwald ripening was studied and shown to obey the LSW theory at room temperature. The emulsifier was sodium dodecyl benzylsulfonate and the mixture was initially sonicated for a few minutes. Upon polymerization, initiated with dibenzylsulfonic acid, the particle size, measured by dynamic light scattering (DLS), first increases, then rapidly decreases probably through some secondary nucleation process to become stable when the particles contain enough polymer, that can act as a stabilizer against the Ostwald ripening.