No abstract

ABSTRACT:The graft copolymerization of acrylic acid (AA) onto guar gum (GOH) was carried out by a peroxydiphosphate (PDP)-silver(I) system. Grafting ratio, efficiency, add-on, and conversion increase upon increasing the concentration of PDP and acrylic acid, whereas they decrease upon increasing the concentration of guar gum. Upon increasing the concentration of silver and hydrogen ions up to 2.0 ϫ 10 Ϫ3 and 4.87 ϫ 10 Ϫ2 mol dm Ϫ3 , respectively, the grafting ratio and efficiency increase but decrease upon further increasing the concentration. The increase in temperature from 30 to 45°C increases the grafting ratio but the conversion efficiency decreases. The optimum time period for graft copolymerization was found to be 2 h. The graft copolymers were characterized by infrared spectroscopy and thermogravimetric analysis.

Graft copolymerization of 4-vinylpyridine (4-VP) onto guar gum (GOH) using potassium monopersulfate (PMS)/thioacetamide (TAA) as a redox pair was studied in an aqueous medium under inert atmosphere. The concentration of potassium monopersulfate and thioacetamide should be 1.0 ϫ 10 Ϫ2 and 5.0 ϫ 10 Ϫ3 mol dm Ϫ3 , respectively, for highest grafting ratio and efficiency. Efficient grafting was observed at 19.25 ϫ 10 Ϫ2 and 4.87 ϫ 10 Ϫ2 mol dm Ϫ3 concentration of 4-vinylpyridine and sulfuric acid, respectively. The optimum temperature for grafting is 30°C. As the time period of reaction is increased, the grafting ratio increases, whereas efficiency decreases. The plausible mechanism of grafting has been suggested. A sample of guar gum and guar-g-4-vinylpyridine were subjected to thermogravimetric analysis with the objective of studying the effect of grafting 4-vinylpyridine on the thermal stability of guar gum.

A previously unreported graft copolymer of xanthan gum (XOH) with acrylic acid was synthesized and the reaction conditions were optimized using a potassium monopersulfate (PMS)/Fe 2ϩ redox pair. Grafting ratio, add on, and conversion increase with an increase in the ferrous ion concentration (2.0 ϫ 10 Ϫ3 to 5.0 ϫ 10 Ϫ3 mol dm Ϫ3 ) and PMS concentration (1.0 ϫ 10 Ϫ3 to 4.0 ϫ 10 Ϫ3 mol dm Ϫ3 ). It was observed that grafting takes place efficiently when the acrylic acid concentration and temperature were 5.0 ϫ 10 Ϫ2 mol dm Ϫ3 and 35°C, respectively. Samples of xanthan gum and xanthan gum-g-acrylic acid were subjected to thermogravimetric analysis with the objective of studying the effect of grafting of acrylic acid on the thermal stability of xanthan gum. The graft copolymer was found to be more thermally stable than xanthan gum.

No abstract

No abstract

ABSTRACT:The effect of reaction conditions on the grafting parameters during the grafting of acrylamide (ACM) onto guar gum (GOH) by using a Cu ϩ2 -mandelic acid (MA) redox couple was studied. On increasing the Cu ϩ2 ion concentration (0.5 ϫ 10 Ϫ2 to 1.0 ϫ 10 Ϫ2 mol dm Ϫ3 ), an increase in total conversion of monomer, grafting ratio, efficiency, and add on was observed. Grafting ratios increased with an increase in concentration of mandelic acid and reaches its maximum value at 0.8 ϫ 10 Ϫ2 mol dm Ϫ3 . It was observed that grafting onto guar gum takes place efficiently when monomer and hydrogen ion concentrations are 20.0 ϫ 10 Ϫ2 and 2.2 ϫ 10 Ϫ2 mol dm Ϫ3 , respectively. Optimum temperature and time for obtaining a maximum grafting ratio and efficiency was found to be 35 Ϯ 0.2°C and 2 h, respectively. The plausible mechanism of grafting was suggested. The graft copolymer was characterized by infrared spectroscopy and thermogravimetric analysis.

No abstract