EFFECT OF TEMPERATURE ON THE RATES OF AQUEOUS POLYMERIZATION OF VINYL-ACETATE INITIATED BY SO4-CENTER-DOT- FREE-RADICALS PRODUCED FROM POTASSIUM PERSULFATE AND THE REDOX REACTION OF FERROUS AMMONIUM-SULFATE AND POTASSIUM PERSULFATE

The aqueous polymerization of vinyl acetate (VA) initiated by the redo x system, ferrous ammonium sulphate (FAS) and potassium persulphate (K PS) has been studied over a wide range of temperature, 5 to 65 degrees C. It is noted that the separating polymer phase is a stable colloid, milky white at or below 10 degrees C, but yellow at temperatures abov e 20 degrees C. It is deep yellow above 50 degrees C, but very faint y ellow between 10 to 20 degrees C. The colloidal stability (CS) of the latex solutions first decreases slightly and remains approximately con stant between 20 to 40 degrees C, and follows an increasing trend agai n above 40 degrees C. The rates of polymerizations have been found to be maximum at (25 +/- 2)degrees C, above or below which the rates decr ease. The purified polymer, polyvinyl acetate (PVA), is found to conta in iron and it is found to be insoluble in common solvents of PVA. Arr henius plot for the. activation energy (E(a)) of the aqueous polymeriz ation of VA in the system, FAS-VA-KPS, over the temperature range 5 to 65 degrees C, is a curved line. (E(a)) is about (+) 10.0 kJ/mol betwe en 5 to 20 degrees C, and about (-) 45.97 kJ/mol between 40 to 65 degr ees C. In the KPS-VA system, the initial rates of polymerization are f ound to increase with temperature (50 to 65 degrees C), but the (CS) d ecreases with temperature. The latex solutions are always white and do not change colour with temperature. WA is soluble in common solvents. E(a) for the formation of PVA in the KPS-VA system is (+) 108.18 kJ/m ol.