Using a very low concentration of potassium persulfate as initiator, acrylamide could be efficiently grafted onto potato starch under microwave irradiation and for the grafting O2 removal from the reaction vessel was not required. Under optimal conditions, grafting and efficiency observed were 160% and 89%, respectively. Grafted starch was characterized by using Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and thermogravimetric analysis (TGA). It was observed that the microwave irradiation could significantly accelerate the synthesis of starch‐graft‐poly(acrylamide), because under identical conditions no grafting was observed in a conventional procedure. Viscosity, shear stability and water/saline solution retention of the microwave‐synthesized grafted starch were studied and compared with that of the parent starch.
Abstract. Potato starch-graft-poly(acrylonitrile) could be efficiently synthesized using small concentration of ammonium peroxydisulfate (0.0014 M) in aqueous medium under microwave irradiation. A representative microwave synthesized graft copolymer was characterized using Fourier Transform Infrared Spectroscopy, X-ray Diffraction, Scanning Electron Microscopy and Thermogravimetric Analysis. Under microwave conditions oxygen removal from the reaction vessel was not required and the graft copolymer was obtained in high yield using very small amount of ammonium peroxydisulfate, however using the same amount of ammonium peroxydisulfate (0.0014 M) on thermostatic water bath no grafting was observed up to 98°C (even in inert atmosphere). Raising the concentration of the initiator to 0.24 M resulted into 10% grafting at 50°C but in inert atmosphere. The viscosity/shear stability of the grafted starch (aqueous solution) and water/saline retention ability of the microwave synthesized graft copolymer were also studied and compared with that of the native potato starch.
The combination of carbohydrates with silicon-based ceramic materials offers attractive means of production for high performance materials. Present article describes the synthesis of novel nanocomposites out of SiO 2 and saponified guar-graft-poly(acrylonitrile) (SG). Tetraethoxysilane was used as the precursor for silica and growth of SiO 2 phase was allowed concurrently in the presence of SG. The material so obtained was thermally treated at 808C, 1608C, 5008C, and 9008C to study the effect of thermal curing on its properties. During the curing process, silanol surface groups of silica globules reacted to create the reinforced SiO 2 -SG substance. It was observed that at 9008C, the SiO 2 phase crystallized out in tetragonal shape (similar to Cristobalite form of silica) in presence of SG. The chemical, structural and textural characteristics of the composites were determined by FTIR, XRD, TGA-DTA, SEM and BET studies. The materials were also evaluated as efficient Zn 2þ metal binder.
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