Solution and Suspension Polymerization of Vinyl Acetate and Continuous Alcoholysis to Poly (vinyl Alcohol)

Solution polymerization of vinyl acetate (VAc) was carried out in methanol, ethanol and isopropanol using azobis (isobutironitrile) (AIBN) as initiator under anatmosphere of nitrogen gas. The higher the molecular weight of the solvent used the lower of average degree of polymerization ( n P )obtained. Effect of catalyst types, solvent and amount of water on time of continuous alcoholysis of poly (vinyl acetate) (PVAc) reveald that the suitable catalyst is sodiumhydroxide in water. Increasing the initiator concentration and amount of solvent used decreased n P . Suspension polymerization ofVAc was carried out in water using poly (vinyl alcohol) as suspending agent and AIBN as initiator. Effect of temperature, suspending agent, and initiator concentration on the average degree of final alcoholysed poly (vinyl alcohol) (PVA) were studied. Increasing polymerization temperature (56-60oC) increased n P . However, increasing of the initiator and suspending agent concentration were decreased the n P of the polymerobtained. Average degree of PVA of 2200- 4550 were obtained using different polymerization and alcoholising conditions with alcoholysing percentage of 97-99.Scanning electron microscopy (SEM) study of PVAc obtained using suspension polymerization lead to spherical particles of different size with some small particles stick on the large particles. The particles are so hard which remain spherical even after milling. Thealcoholysis method used produced irregular morphological particles of the PVA.

کلیدواژه ها:

poly (vinyl acetate) ، poly (vinyl alcohol) ، alcoholysis ، solution polymerization ، suspension polymerization