Sharif Digital Repository

A novel superabsorbent hydrogel composite based on gelatin has been prepared by graft copolymerisation of acrylic acid and acrylamide in the presence of kaolin powder, using methylene-bisacrylamide (MBA) as a crosslinking agent and ammonium persulfate as an initiator. The synthetic variables affecting the water absorbency of the resulting superabsorbent composite were studied and the composite structure was confirmed using FT-IR spectroscopy. A new absorption band at 1728 cm-1 in the composite spectrum confirmed the presence of a kaolin-organic polymer linkage. The effect of kaolin content and MBA concentration showed that increasing these parameters decreased the water absorbency of the... 

In this work, we synthesize a novel protein-based superabsorbent hydrogel and study its swelling behavior. The crosslinking graft copolymerization of acrylic acid (AA) onto the hydrolyzed collagen as a protein backbone was carried out in a homogeneous medium. Potassium persulfate (KPS) as an initiator and N,N′-methylene bisacrylamide (MBA) as a crosslinker were used. The product's structure was established using FTIR spectroscopy. We were systematically optimized the certain variables of the graft copolymerization (i.e. the monomer, the initiator, and the crosslinker concentration) to achieve a hydrogel with maximum swelling capacity. Under this condition, maximum capacity of swelling in... 

In this article, we synthesize a novel gelatin-based superabsorbent hydrogel via graft copolymerization of mixtures of acrylic acid (AA) and acrylamide (AAm) onto gelatin backbones. The polymerization reaction was carried out in an aqueous medium and in the presence of ammonium persulfate (APS) as an initiator and N,N-methylene bisacrylamide (MBA) as a crosslinker. The hydrogel structures were confirmed by FTIR spectroscopy. The effect of grafting variables, i.e. concentration of MBA and APS, AA/AAm weight ratio, and reaction time and temperature, was systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The swelling behavior of these absorbent polymers... 

In this contribution we have developed a collagen-based highly porous hydrogel by neutralizing the grafted poly(acrylamide-co-acrylic acid) after gel formation. Preparation of the hydrogels involved free radical polymerization of a combination of hydrolyzed collagen, acrylic acid (AA), acrylamide (AAm) and distilled water, in appropriate amounts and contained a crosslinking agent called N,N′-methylene bisacrylamide (MBA). The chemical structure of the hydrogels was characterized by means of FTIR spectroscopy, DSC and TGA thermal methods. Morphology of the samples was examined by scanning electron microscopy (SEM). Systematically, the certain variables of the graft copolymerization were... 

This article reports the first oil-absorbent cross-linked copolymer consisting of modified multiwalled carbon nanotube (MWCNT) and showing high oil absorbency. Also, to investigate and evaluate the effective parameters on oil absorbency, cross-linked dodecyl methacrylate (DDMA)-diphenylacrylamide (DPAA) and DDMA-butyl acrylate (BA) copolymers were synthesized. DDMA was copolymerized with different mol% of DPAA or BA and cross-linked using azobisisobutyronitrile as the initiator and various weight percentages of 1,4-butandiol dimethacrylate, methylene bisacrylamide, or vinyl group-modified MWCNT cross-linkers. The effects of monomer feed composition, cross-linker concentration, and the... 

Inclusion of nano-clays into hydrogels is an efficient approach to produce nanocomposite hydrogels. The introduction of nano-clay into hydrogels causes an increase in water absorbency. In the present work, Nanocomposite hydro-gels based on kappa-carrageenan were synthesized using sodium montmorillonite as nano-clay. Acrylamide and meth-ylenebisacrylamide were used as monomer and crosslinker, respectively. The structure of nanocomposite hydrogels was investigated by XRD and SEM techniques. Swelling behavior of nanocomposite hydrogels was studied by varying clay and carrageenan contents as well as methylenebisacrylamide concentration. An optimum swelling capacity was achieved at 12% of sodium... 

Gelcasting is a novel forming method in fabricating complex three dimensional ceramic parts, and has many parameters and characteristics required to be specified. Up to now, few articles have been published on determination of the idle time of gelation precisely. In this work the chemorheology of gelation in aqueous solution of acrylamide and N, N′ methylenebisacrylamide monomer, and zirconia (PSZ) suspensions of this solution was investigated. As the viscosity of gel system increases abruptly in gelation point, idle time can be determined precisely by measurement of viscosity against time. Idle time can also be determined through temperature measurement against time since the reaction of... 

A novel optimized chelating hydrogel was synthesized via graft copolymerization of acrylamide and 2-hydroxyethyl methacrylate (as two-dentate chelating co-monomer) onto salep (a multicomponent polysaccharide obtained from dried tubers of certain natural terrestrial orchids) using N,N′-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. Reaction parameters (N,N′-methylenebisacrylamide and ammonium persulfate amounts as well as acrylamide/2-hydroxyethyl methacrylate weight ratio) affecting the water absorption of the chelating hydrogel were optimized using a systematic method to achieve a hydrogel with high swelling capacity as possible. Heavy metal ion adsorption... 

A series of biopolymer-based superabsorbent hydrogels based on carboxymethyl cellulose has been prepared by free-radical graft copolymerization of acrylamide and 2-acrylamido-2-methylpropan sulfonic acid (AMPS) in aqueous solution using methylenebisacrylamide as a crosslinking agent and ammonium persulfate as an initiator. The effect of variables on the swelling capacity such as: acrylamide/AMPS weight ratio, reaction temperature, and concentration of the initiator and crosslinker were systematically optimized. The results indicated that with increasing the amount of AMPS, the swelling capacity is increased. FT-IR spectroscopy and scanning electron microscope analysis were used to confirm...