Graft copolymerization of methacrylonitrile on kenaf fibers by cerric ion-toluene redox pair

The graft copolymerization of methacrylonitrile onto kenaf fibers by a cerric ion-toluene redox pair was investigated in aqueous media. Graft yield of up to 212% was found, but the grafting efficiency was not greater than 17.6%. At varying concentrations of toluene, the conversion in graft yield passed through a maximum and thereafter decreased by as much as 46% for a two-half increase in the concentration of toluene. Similarly, acetic acid showed an initial increase in graft yield in the concentration range of 0.58-1.17M and a reduction to zero graft at a 11.67M concentration of the acid. Under identical reaction conditions, acetic acid and its derivatives decreased the graft yield in the order trichloroacetic acid > monochloroacetic acid > acetic acid > formic acid. The effect of the chlorinated acids was considered as a composite consisting of normal transfer reactions and a hydrolytic effect, as strong acids, on the grafted polymers. The percentage graft yield showed a normal temperature dependence over the range 30-60 degrees C with a calculated activation energy of 6.52 kcal mol(-1). The amount of grafted polymer increased with monomer concentration, but the average molecular weight decreased with the latter, suggesting an enhanced utilization of more grafting sites on the fibers. The water-retention capacity of the graft copolymer showed an 85% reduction in its value over a threefold increase in the graft yield. (C) 1996 John Wiley & Sons, Inc.