The Rapid Emulsion Polymerization Of Vinyl Monomer By The Initiation Of Potassium Persulfate-Sliver Ammonia Complex

Harkins established the emulsion micelle theory in 1947 for the first time, which qualitatively descripted the polymerization mechanism, Smith and Ewart made it quantitatively. Gardon, Rose, Fitch and Tsai, and others had been re-calculated and extended on the classical theory. Priest, et al found that water-soluble monomer sometimes could polymerize without emulsifier, then put forward the theory of homogeneous nucleation. Gradually revised and improved model has greatly promoted the theory and practice of emulsion polymerization.How to control the nucleation process and clarify the mechanism of nucleation was the focus of research of emulsion polymerization in the last 10 years. At present, domestic and foreign research on the nucleation mechanism of polymerization was very active, emulsion polymerization theory continued to be explored and perfected.This paper used potassium persulfate-sliver ammonia complex initiator to initiate the emulsion polymerization of vinyl monomers styrene, methyl methacrylate monomers. The potassium persulfate-silver ammonia complex was designed and used to initiate the emulsion polymerization of the non-polar styrene as a new initiator.Compared with the conventional emulsion polymerization initiated by potassium persulfate, research results from polymerization kinetics showed that under the complex initiation system, the emulsion polymerization of styrene was very greatly accelerated and denonstrated high efficiency:the maximum rate of the complex stystem under the same temperature was six times as the conventional emulsion polymerization when the polymerization temperature was 70℃or 80℃, the maximum rate was 1.2 mo1·L-1·min-1,0.68 mo1·L-1·min-1 respectively; one the other hand, the polymerization rate at 40℃was 0.1 lmo1·L-1·min-1, which was comparable with the maximum rate at 70℃in the system initiated by Potassium persulfate. Laser dynamic light scattering and TEM results showed that the polymer latex diameter had uniform particles morphology with the diameter of 60nm smaller than the conventional system. In addition, the molecular weight measured by GPC derived from only 3/5 of conventional emulsion polymerization while with similar molecular weight distribution. Particles type, size and evolution during the reaction was great difference between conventional emulsion.When the potassium persulfate-silver ammonia complex initiation system used to initiate the polar monomer methyl methacrylate, polymerization kinetics also showed similar high-speed and high efficiency characteristics, there was no constant rate period, when the reaction temperature was 70℃, the maximum temperature of the polymerization rate was 3 times more than conventional emulsion polymerization; one the other hand, the polymerization rate at 55℃was comparable with the maximum rate at 80℃in the system initiated by Potassium persulfate. Laser dynamic light scattering results showed that the polymer latex diameter had uniform particles morphology with the diameter of 30nm smaller than the conventional system. In addition, the molecular weight measured by GPC is only 3/5 of conventional emulsion polymerization while with similar molecular weight distribution.Based on the experimental results, it was obviously that the reaction mechanism for the potassium persulfate-silver ammonia complex initiation was different from the classic.The addition of ammonia silver had a dual role which not only promoted the decomposition of potassium persulfate but it may also interreaction with the vinyl monomers to form "chelate", so that its polymerization mechanism deviated from the classical emulsion polymerization mechanism. 'silver ammonia complex-styrene monomer' complex was the main polymerization nucleation sites, and showed a continuous nucleation characteristics.