Effect of emulsion polymerization conditions of vinyl acetate on the viscosity fluctuation and gelation behavior of aqueous poly(vinyl alcohol) solution

Poly(vinyl alcohol) (PVA) was prepared by emulsion polymerization of vinyl acetate (VAc) at 40, 50, and 60 degreesC. PVAs of various molecular paramet ers were dissolved in water at concentrations of 3, 5, and 7% (g/dL) and ag ed at 30 and 60 degreesC. The effects of the molecular weight and polymeriz ation temperature on the viscosity fluctuation and gelation behavior of aqu eous PVA solutions were investigated. Viscosity was increased with increasi ng molecular weight when other parameters were held the same. PVA of superi or molecular regularity due to the lower polymerization temperature of VAc had higher relative viscosity. Viscosity and its fluctuation of PVAs with a ging time varied with the polymerization temperature of the precursors, con centration of the aqueous solutions, and aging time. For PVA with a number- average degree of polymerization of 2800 prepared from poly(vinyl acetate) polymerized at 40 degreesC, a sharp increase in viscosity was observed afte r 500 min of aging at a concentration of 7%. (C) 2001 John Wiley & Sons, In c.