title: Polymerization rate and mechanism of ultrasonically initiated emulsion polymerization of n-butyl acrylate.
abstract: The factors affecting the induction period and polymerization rate in ultrasonically initiated emulsion polymerization of n-butyl acrylate (BA) were investigated. The induction period takes only an instant in ultrasonically initiated emulsion polymerization of BA without any added initiator by enhancing the N2 flow rate. Increasing temperature, power output and SDS concentration, decreasing the monomer concentration results in further decreasing induction period and enhanced polymerization rate. Under optimized reaction conditions the conversion of BA reaches 92% in 11 min. The polymerization rate can be controlled by varying reaction parameters. The apparatus of ultrasonically initiated semi-continuous and continuous emulsion polymerization were set up and the feasibility was first studied. Based on the experimental results, a free radical polymerization mechanism for ultrasonically initiated emulsion polymerization was proposed, including the sources of the radicals, the process of radical formation, the locus of polymerization and the polymerization process. Compared with conventional emulsion polymerization, where the radicals come from thermal decomposition of a chemical initiator, ultrasonically initiated emulsion polymerization has attractive features such as no need for a chemical initiator, lower reaction temperature, faster polymerization rate, and higher molecular weight of the polymer prepared.
authors.affiliation: State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute, Sichuan University, Chengdu, Sichuan 610065, China.
authors.forename: Hesheng
authors.initials: H
authors.lastname: Xia
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.forename: Yongqin
authors.initials: Y
authors.lastname: Liao
authors.forename: Xi
authors.initials: X
authors.lastname: Xu
authors.forename: Steven M
authors.initials: SM
authors.lastname: Baxter
authors.forename: Robert V
authors.initials: RV
authors.lastname: Slone
authors.forename: Shuguang
authors.initials: S
authors.lastname: Wu
authors.forename: Graham
authors.initials: G
authors.lastname: Swift
authors.forename: David G
authors.initials: DG
authors.lastname: Westmoreland