This report deals with the chemically and the radiation-initiated emulsion polymerization of vinyl acetate. In experiments with potassium persulphate as initiator and sodium lauryl sulphate (SLS) as emulsifier the rate of polymerization is approximately proportional to the square root of initiator concentration and to the 0.25 power of the number of particles. The number of particles is proportional to the 0.5 power of the emulsifier concentration. The rate of polymerization is constant in the interval 15 to 70-85% conversion. The limiting viscosity number of the polymers produced is independentp of initiator concentration and number of particler. In experiments with the emulsifier sodium dodecylbenz ene sulphonate (SDBS) it is observed that the shape of the polymerization curve is entirely changed when the concentration of SDBS is increased from 2. 9 to 11. 5 g/1 H~0. At the high concentration the rate of polymerization declines already from 35-45% conversion. On the basis of the experiments with SLS as emulsifier it is suggested that the mechanism of vinyl acetate emulsion polymerization is similar to that of vinyl chloride. The linearity of the conversion versus time curve is explained as being due partly to adecrease in the desorption rate of radicals from the particles and partly to a decrease in the termination rate c > instant with the progress of the polymerization. The peculiar effect observed in experiments with the emulsifier SDBS is explained as being due to retardation caused by this compound. However, the data are insufficient to prove this hypothesis unequivocally. In experiments with radiation initiation, performed at dose rates of 62 and 301 krads/h in a recycle flow reactor system, the rate of polymerization is proportional to the square root of the dose rate. The effect of the number of particles and concentration of SLS is similar to that observed with chemical initiation. The rate of polymerization increases when the flow rate is increased from the beginning of the polymerization. At conversions beyond 40% there is no effect of flow rate. The rate of polymerization per unit volume of in-source reactor increases as the reactor volume is decreased, although the overall rate of polymerization increases with increasing reactor volume.
|Place of Publication||Roskilde, Denmark|
|Publisher||Risø National Laboratory|
|Number of pages||119|
|Publication status||Published - 1973|
|Series||Denmark. Forskningscenter Risoe. Risoe-R|
- Risø report 282