Studies on graft copolymerization of N-vinyl formamide onto Guar gum initiated by bromate/ascorbic acid redox pair

摘要

An unreported graft copolymer of guar gum with N-vinyl formamide has been synthesized using potassium bromate/ascorbic acid redox pair.By studying the effect of the concentration of monomer,bromate ion,ascorbic acid,guar gum along with the effects of time and temperature on the grafting characteristics: grafting ratio (%G),add on (%A),conversion (%C),efficiency (%E),homopolymer (%H) and rate of grafting (Rg),the reaction conditions for optimum grafting have been determined.The maximum grafting ratio,add on,conversion,efficiency and rate of grafting were obtained at minimum concentration of N-vinyl fomamide (NVF) i.e.at l0x10~(-2) mol dm~(-3).The maximum values of these parameters were observed at minimum temperature (35deg C) and minimum reaction time (120 min).On increasing the concentration of ascorbic acid from 0.4xl0~(-3) to 2.0x10~(-3) mol dm~(-3) the above parameters show increasing trend while on increasing the concentration of bromate ion from 0.2 to l.8xl0~(-2) mol dm~(-3) the parameters show decreasing trend.Infrared spectra of Guar gum and guar gum-g-NVF has been investigated.Thermogravimetric analysis and differential scanning calorimetric analysis showed that guar gum-g-NVF was thermally more stable than guar gum.