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Abstract  

The temperature influence on the adsorption mechanism of anionic polyacrylic acid (PAA) macromolecules on the silica surface was studied. For this purpose, the following techniques were applied: spectrophotometry, thermogravimetry, potentiometric titration and microelectrophoresis. This method allowed to determine the adsorbed amounts of polymer, changes in thermal characteristic of silica surface with adsorbed PAA, surface charge density of the solid as well as zeta potential of SiO2 particles in the presence and absence of polyacrylic acid. All measurements were carried out in the temperature range 15-35 °C. The free energies of adsorption were calculated from the adsorption data fitted by the Langmuir model. The obtained results of increase of PAA adsorption and its adsorption free energies with the rising temperature suggest that adsorbed polymer conformation changes from the coiled structure to more stretched one. Moreover, the polymer adsorption on the silica surface at 25 °C leads to changes in the course of thermogravimetric curves as a result of surface properties modification of the solid by bonded macromolecules.

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The processes of thermal and thermal-oxidative degradation taking place in polyethylene (PE) films modified by graft polyacrylic acid (PAA) have been studied by TG and DTA. The mutual influence of the components on the degradation of the macromolecules present in the graft copolymer has been revealed. The increase in thermal stability of PE in the graft copolymers is explained by the decrease in the molecular mobility in PE amorphous regions containing microphase particles of graft PAA.

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Abstract  

The inhibitory action of cupric ions in the process of radiation polymerization of acrylic acid (AA) in aqueous solution was investigated as well as the reaction of the products of gamma radiolysis of water with polyacrylic acid (PAA) in the presence of cupric ions. In the case of AA-CuSO4 and PAA-CuSO4 systems irradiated at 77 K an external protective effect caused by copper ions was observed. This effect was connected with the electron transfer between a radical and the Cu2+ ion. During radiolysis of copper arcylate (A2Cu) and a system AA-A2Cu in aqueous solutions a protective effect exerted by copper ions was observed which seemed to be connected with the dispersion of the absorbed radiation energy by the groups: copper-ligands.

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Abstract  

Polyacrylic hydrogels were14C- and3H-labeled in three main steps. In the first one, the monomer as sodium salt was14C-labeled at the carboxyl group via the carbonation of vinylmagnesium bromide and [1-14C]acrylic acid was obtained, followed by labeling with tritium via isotopic exchange in heterogeneous catalysis. The monomer was purified and its radiochemical purity was analyzed using TLC. In the last step, the hydrogel was obtained through radiopolymerization of the doubly labeled monomer using a60Co source. The oligomers and unpolymerized monomers were eliminated from the hydrogel by swelling in water followed by dehydration with methanol.

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Journal of Thermal Analysis and Calorimetry
Authors: Mayté Paredes Zaldivar, Norma Galego Fernández, Cristina Gastón Peña, Manuel Rapado Paneque, and Sonia Altanés Valentín

advantage of having a greater mechanical strength [ 1 , 2 ]. IPNs based on polyacrylic acid (PAA) with different polymers are reported in the literature [ 6 – 8 ]. Polyhydroxybutyrate (PHB) is a semicrystalline thermoplastic polymer with

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De Clercq, E., De Somer, P.: Protective effect of interferon and polyacrylic acid in newborn mice infected with a lethal dose of vesicular stomatitis virus. Life Sci 7 , 925-933 (1968). Protective effect of interferon and

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Concetta De Stefano, Antonio Gianguzza, Alberto Pettignano, Daniela Piazzese, and Silvio Sammartano

Abstract  

Stability data on the formation of dioxouranium(VI) species with polyacrylic (PAA) and fulvic acids (FA) are reported with the aim to define quantitatively the sequestering capacity of these high molecular weight synthetic and naturally occurring ligands toward uranium(VI), in aqueous solution. Investigations were carried out at t = 25 °C in NaCl medium at different ionic strengths and in absence of supporting electrolyte for uranyl–fulvate (
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–FA) and uranyl–polyacrylate (
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–PAA, PAA MW 2 kDa) systems, respectively. The experimental data are consistent with the following speciation models for the two systems investigated: (i) UO2(FA1), UO2(FA1)(FA2), UO2(FA1)(FA2)(H) for
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–fulvate (where FA1 and FA2 represent the carboxylic and phenolic fractions, respectively, both present in the structure of FA), and (ii) UO2(PAA), UO2(PAA)(OH), (UO2)2(PAA)(OH)2 for
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–polyacrylate. By using the stability data obtained for all the complex species formed, the uranium(VI) sequestration by PAA and FA was expressed by the pL50 parameter [i.e. the −log(total ligand concentration) necessary to bind 50% of uranyl ion] at different pH values. A comparison between pL50 values of FA and PAA and some low molecular weight carboxylic ligands toward uranyl ion is also given.
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Abstract  

Waste rubber powder was grafted with different vinyl monomers by using gamma-radiation. The monomers used for grafting were acrylic acid, acrylamide and acrylonitrile. The sodium salt of grafted polyacrylic acid as well as the amidoxime derivative of grafted polycacrylonitrile were also obtained. Evaluation of the efficiency of the products obtained to the recovery of some metal ions such as cobalt and nickel as well as to phenol was carried out. It was found that the grafted waste rubber powder is able to recover cobalt and nickel ions from their corresponding salts depending on the type of monomers used. It was also found that phenol can be reasonably recovered by using rubber powder grafted with acrylamide and amidoxime derivative.

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Abstract  

Aqueous solution of polyacrylic acid (PAA), poly-N-isopropylacrylamide (PNIPAAm), bovine serum albumin (BSA), superoxide dismutase (SOD) and their mixtures (PAA-BSA, PAA-Cu-BSA, PNIPAAm-BSA, PAA-SOD) were irradiated in the presence of oxygen in neutral media (pH 7.0) with 60Co γ-rays. In addition, aliquots of aqueous solutions of PAA, PAA-Cu2+, BSA and PAA-Cu2+-BSA saturated with N2 and N2O were also irradiated. The decomposition rate of irradiated solutions were measured by UV-visible spectrophotometry, fluorescence spectroscopy, and high performance liquid chromatography (HPLC). Protective effect of copper ions on radiolysis of aqueous solution of PAA-Cu-BSA and conversion of Cu(II) to Cu(I) was observed. The possible mechanism of this phenomenon is discussed.

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Abstract  

Thermodynamic investigation of the extraction of both uranium(VI) and uranium(IV) from nitric acid solutions using tri-n-butyl phosphate (TBP) loaded on polyacrylic acid polymer (SM-7) as an inert supporting material has been done using batch technique. The effect of temperature on the equilibrium extraction values has been utilized to evaluate the change in standard thermodynamic quantities (viz. DH, DS, and DG). The Freundlich isotherm was successfully applied to the extraction data of both metal ions. The Dubinin-Radushkevich (D-R) isotherm was found to be valid only in case of U(IV) extraction. Based on the D-R expression, the maximum extraction capacity of loaded TBP and the mean free energy of U(IV) extraction have been determined.

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