Graft Copolymerization Kinetics of Ethyl Acrylate onto Hydroxypropyl Methylcellulose Using Potassium Persulphate as Initiator in Aqueous Medium

Potassium persulphate (KPS) has been used as efficient initiator for graft copolymerization of the ethyl acrylate (EA) onto hydroxypropyl methylcellulose (HPMC) at 60 ± 0.1°C. Graft copolymerization of EA onto HPMC has taken place through the radical initiation process. The grafting parameters have been evaluated by varying concentration of EA from 0.097 to 0.376 mol/L, KPS from 1.772 to 5.316 mmol/L and HPMC from 0.117 to 0.468 mmol/L. Evidence of grafting was obtained from IR spectroscopic measurements, SEM, and TGA studies of the grafted and ungrafted HPMC. The rate of graft copolymerization has shown 1, 0.5, 0.5 order with respect to the concentrations of the EA, KPS, and HPMC, respectively. The graft copolymerization data obtained at different temperatures were used to calculate the energy of activation which has been found to be 41.7±1.2 kJ/mol within the temperature range from 50 to 65°C. On the basis of the experimental observations, initiating steps have been proposed and a suitable rate expression for graft copolymerization has been derived.