Time filter

Source Type

El-Nemr K.F.,National Center for Radiation Research And Technology
Materials and Design | Year: 2011

In the present study, the effect of different curing systems including sulfur, dicumyl peroxide, dicumyl peroxide/coagent and radiation/coagent on the mechanical and physico-chemical properties of acrylonitrile butadiene rubber (NBR) was studied. In order to correlate, the effect of curing systems on rubber, the comparison was carried out at comparable value of volume fraction of rubber in swollen gel (Vr) for NBR vulcanizates. Mechanical properties like tensile strength, elongation at break, modulus, Young's modulus, tearing strength and abrasion loss of vulcanizates have been followed up for comparison. In addition, physico-chemical properties like swelling ratio, soluble fraction, and cross-link density were investigated. On the other hand, the effects of fuel, thermogravimetric analysis, and thermal ageing have been studied. © 2011 Elsevier Ltd. Source

Eid M.,National Center for Radiation Research And Technology
Journal of Inorganic and Organometallic Polymers and Materials | Year: 2011

Starch based polyelectrolyte hydrogels are composed of combination of starch with N-vinyl pyrrolidone (NVP), acrylamide (AAm) and acrylic acid (AAc). The Starch based polyelectrolyte hydrogels were successfully synthesized by using gamma radiation polymerization technique. Silver nanopaticles were formed by reduction of silver nitrate in the hydrogels with sodium borohydride under room temperature. The formation of silver nanoparticles in hydrogels were well characterized by using Fourier-transform infrared (FTIR), UV-Visible spectroscopy, X-ray diffraction studies transmission electron microscope (TEM) and scanning electron microscopy (SEM) studies. The X-ray diffraction analysis confirmed the formation of silver nanoparticles in the range of 38.86, 41.44 and 47.07 nm for P(Starch/NVP)-Ag, P(Starch/AAm)-Ag and P(Starch/AAc)-Ag nanoparticles hydrogels, respectively. The TEM images supported the mean size particle of 35.81, 39.29 and 40.45 nm for P(Starch/NVP)-Ag, P(Starch/AAm)-Ag and P(Starch/AAc)-Ag, respectively. The SEM images indicated clearly the formation of silver nanoparticles with spherical shape within the network of the hydrogels. © 2010 Springer Science+Business Media, LLC. Source

Raafat A.I.,National Center for Radiation Research And Technology
Journal of Applied Polymer Science | Year: 2010

Based on gelatin (Gltn) and acrylic acid (AAc), biodegradable pH-sensitive hydrogel was prepared using gamma radiation as super clean source for polymerization and crosslinking. Incorporation of PAAc in the prepared hydrogel was confirmed by Fourier transform infrared spectroscopy (FTIR). The effect of PAAc content on the morphological structure of the prepared hydrogel swollen at pH 1, 5, and 7 was examined using scanning electron microscopy (SEM). The results showed the dependence of the porous structure of the prepared hydrogels on AAc content and the pH of the swelling medium. Swelling properties of gelatin/acrylic acid copolymer hydrogels with different AAc contents were investigated at different pH values. Swelling data showed that the prepared hydrogels possessed pronounced pH sensitivity. In vitro release studies were performed to evaluate the hydrogel potential as drug carrier using ketoprofen as a model drug. Experimental data showed that the release profile depends on both hydrogel composition and pH of the releasing medium. © 2010 Wiley Periodicals. Source

Mahmoud G.A.,National Center for Radiation Research And Technology
Monatshefte fur Chemie | Year: 2013

Hydrogels based on acrylamide and 2-acrylamido-2-methyl-1-propanesulfonic acid were synthesized via a gamma irradiation technique and used for preparation of magnetic responsive hydrogels. The hydrogels obtained were investigated by means of X-ray diffraction, Fourier-transform infrared (FT-IR), magnetic properties, thermogravimetric analysis, and energy-dispersive X-ray analysis. The extent of adsorption was investigated as a function of pH of medium, initial metal ion concentration, and contact time. The adsorption process was well described by pseudo-second-order kinetics, and the best interpretation of the equilibrium data was given by the Freundlich isotherm. The results from sequential adsorption-desorption cycles showed that the hydrogel exhibited good desorption and reusability. It was revealed that such hydrogel networks with magnetic properties can be effectively utilized for removal of pollutants and adsorbed heavy-metal ions. The maximum adsorption capacities were 321, 436, and 470 mg g-1 for Pb(II), Cd(II), and Cu(II) ions, respectively. © 2013 Springer-Verlag Wien. Source

Madani M.,National Center for Radiation Research And Technology
Current Applied Physics | Year: 2011

Methyl methacrylate (MMA) monomer was grafted onto Low density Polyethylene by the direct method of radiation grafting. The effect of cohesive energy density of different organic solvents on the degree of grafting was investigated. It was found that the extent of grafting depends largely on the kind of solvent, in which the highest degree of grafting was achieved in the presence of dioxane, whereas the lowest degree of grafting occurred in the presence of methanol. This behaviour was attributed to the solubility parameters of the solvent, monomer and polymer. The change in structure of the LDPE graft copolymer films was characterized by scanning electron microscopy, X-ray diffraction, UV/vis absorption and thermogravimetric analysis. The X-ray diffraction results showed a decrease in the crystallinity of LDPE graft copolymer matrix at high degree of grafting. Studies were made on the UV-absorption edge, indirect allowed transitions with their optical energy gaps are determined. At the same time the Urbach energy was evaluated. The activation energy of the thermal decomposition was calculated according to Horowitz and Metzger method. © 2010 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations