Investigation of metal ion removal selectivity properties of the modified polyacrylamide hydrogels prepared by transamidation and Hofmann reactions

Modified crosslinked polyacrylamides having different functional groups prepared by transamidation reaction in aqueous and non-aqueous medium and by Hofmann reach. on were used as chelating agents for removal of Cu(II), Cd(II) and Pb(II) ions from aqueous solutions' at different pH values. Under non-competitive conditions, polymers adsorbed different amounts of metal ions, depending on their functional groups and swelling abilities. The metal ion adsorption capacities of polymers changed between 0.11 - 1.71 mmol/g polymer. Under competitive conditions, while the polymers having mainly secondary amine groups were highly selective for Cu(II) ions (99.4%), those having mainly secondary amide and carboxylate groups have shown high selectivity towards Pb(II) ions (99.5%). The selectivity towards Cu(II) ion decreased and Job(II) ion selectivity increased by the decrease of the pH of the solutions. The high initial adsorption rate (< 10 min) suggests that the adsorption occurs mainly on the polymer surface. A regeneration procedure by treatment with dilute HCl solution showed that the modified polymers could be used several times without loss of their adsorption capacities

A novel type of Si-containing poly(urethane-imide)s: synthesis, characterization and electrical properties

A novel type of a Si-containing poly(urethane-imide) (PUI) was prepared by two different methods. In the first method, Si-containing polyurethane (PU) prepolymer having isocyanate end groups was prepared by the reaction of diphenylsilanediol (DSiD) and toluene diisocyanate (TDI). Subsequently the PU prepolymer was reacted with pyromellitic dianhydride (PMDA) or benzophenonetetracarboxylic dianhydride (BTDA) in N-methyl pyrolidone (NMP) to form Si-containing modified polyimide directly. In the second method, PU prepolymer was reacted with diaminodiphenylether (DDE) or diaminodiphenylsulfone (DDS) in order to prepare an amine telechelic PU prepolymer. Finally, the PU prepolymer having diamine end groups was reacted with PMDA or BTDA to form a Si-containing modified polyimide. Cast films prepared by second method were thermally treated at 160 degrees C to give a series of clear, transparent PUI films. Thermogravimetric analysis indicated that the thermal degradation of PUI starts at 265 degrees C which is higher than degradation temperature of conventional PU, confirming that the introduction of imide groups improved the thermal stability of PU

Competitive removal of heavy metal ions by cellulose graft copolymers

The effect of composition of graft chains of four types cellulose graft copolymers on the competitive removal of Pb2+, Cu2+, and Cd2+ ions from aqueous solution was investigated. The copolymers used were (1) cellulose-g-polyacrylic acid (cellulose-g-pAA) with grafting percentages of 7, 18, and 30%; (2) cellulose-g-p(AA-NMBA) prepared by grafting of AA onto cellulose in the presence of crosslinking agent of NN'-methylene bisacrylamide (NMBA); (3) cellulose-g-p(AA-AASO(3)H) prepared by grafting of a monomer mixture of acrylic acid (AA) and 2-acrylamido-2-methyl propane sulphonic acid (AASO(3)H) containing 10% (in mole) AASO(3)H; and (4) cellulose-g-pAASO(3)H obtained by grafting of AASO(3)H onto cellulose. The concentrations of ions which were kept constant at 4 mmol/L in an aqueous solution of pH 4.5 were equal. Metal ion removal capacities and removal percentages of the copolymers was determined. Metal ion removal capacity of cellulose-g-pAA did not change with the increase in grafting percentages of the copolymer and determined to be 0.27 mmol metal ion/g(copolymer). Although the metal removal rate of cellulose-g-p(AA-NMBA) copolymer was lower than that of cellulose-g-pAA, removal capacities of both copolymers were the same which was equal to 0.24 mmol metal ion/g(copolymer). Cellulose did not remove any ion under the same conditions. In addition, cellulose-g-pAASO(3)H removed practically no ion from the aqueous solution (0.02 mmol metal ion/g(copolymer)). The presence of AASO(3)H in the graft chains of cellulose-g-p(AA-AASO(3)H) created a synergistic effect with respect to metal removal and led to a slight increase in metal ion adsorption capability in comparison to that of cellulose-g-pAA. All types of cellulose copolymers were found to be selective for the removal of Pb2+ over Cu2+ and Cd2+. (C) 2003 Wiley Periodicals, Inc

Preparation, characterization and dielectric properties of 4,4-diphenylmethane diisocyanate (MDI) based cross-linked polyimide films

Four different types of cross-linked polyimides based on 4,4-diphenylmethane diisocyanate (MDI) were prepared by the reaction of different types of conventional poly(amic acid) intermediates with MDI as a cross-linking agent. Subsequently, they were thermally imidized in order to obtain corresponding cross-linked polyimide structure. The results of FTIR-ATR showed that MDI can effectively react with carboxylic acid groups of PAA to form cross-linked polyimide films. TGA, FTIR-ATR and SEM analyses were carried out for characterization of cross-linked polyimide (CPI) films. Moreover, the electrical properties such as dielectric breakdown strength, dielectric constant, I-V characteristics and loss factor of MDI based cross-linked polyimides have been checked. In addition, some physical properties such as water uptake, adhesion, hardness and solubility properties of the films were investigated

Electrical properties of conventional polyimide films: Effects of chemical structure and water uptake

A series of conventional polyimide (CPI) films, based on pyromellitic dianhydride (PMDA) and benzophenonetetracarboxylicdianhydride (BTDA), were prepared by a two step process, and their dielectrical constant dielectrical loss, and DC conduction behaviors were studied at different frequencies and voltages. Their dielectrical breakdown voltage, water uptake, and solubility properties were also investigated. The effects of chemical structure and water uptake on the electrical properties of the films are discussed in detail. The dielectric constants of the CPI films vary between 2.93 and 3.72 at 1 MHz frequency and they are in the following decreasing order: BTDA-DDS > BTDA-DDE > PMDA-DDS > PMDA-DDE. The structure and thermal and oxidative stability of films were analyzed by FTIR-ATR and TGA, respectively. The results showed that all CPI films have good insulating properties, such as high dielectric breakdown voltage, low dielectric constant with stability for long period of frequency, and low leakage density. Our results concerning electrical properties also suggest that electron hopping is responsible for AC conduction and Poole-Frenkel mechanism is predominant for DC conduction of all CPI films. (c) 2006 Wiley Periodicals, Inc

Simultaneous glycolysis and hydrolysis of polyethylene terephthalate and characterization of products by differential scanning calorimetry

Simultaneous glycolysis and neutral hydrolysis of waste polyethylene terephthalate (PET) has been carried out at 170 and 190 degreesC with constant amount of ethylene glycol (EG) and increasing amounts of water, in the presence of xylene. The organic solvent made it possible to employ very low amounts of reactants as well as application of lower temperatures and pressures in contrast with previous methods, yielding intermediates suitable for PET or other polymeric materials. These intermediates were characterized by acid value (AV), hydroxyl value (HV) determinations as well as by differential scanning calorimetry (DSC). A water soluble crystallizable fraction with high purity, consisting of mono 2-hydroxy ethyl ester of terephthalic acid (monohydroxyethyl terephthalate, MHT) monomer has been obtained with significant yield and its polymerization tendency has been compared with that of bis(2-hydroxy ethyl) terephthalate (BHET) by application of multiple heating/cooling cycles in DSC. (C) 2003 Elsevier Ltd. All rights reserved

Modification of waste poly( ethylene terephthalate) (PET) by using poly(L-lactic acid) (PLA) and hydrolytic stability

The purpose of this study is the preparation of hydrolytically degradable copolymers of waste poly( ethylene terephthalate) ( PET). To achieve this, we modified PET by using biodegradable poly( lactic acid) (PLA). Modification reactions were carried out in o-nitrophenol as solvent at 140 and 170 degrees C for 8, 16, and 24 h in the presence of dibutil tin oxide (DBTO) as catalyst. The amount of the total polymers ( PLA and PET) in the reaction mixture was 30% by weight, and the weight ratios of PLA/PET were 10/90, 50/50, and 90/10. These modified products were characterized by Fourier transform infrared spectrometer ( FTIR), differential scanning calorimeter (DSC) as well as by hydrolytic degradation determinations. Hydrolytic degradations of the products were determined gravimetrically. Disc-shaped samples were placed in tubes containing phosphate buffer solution of pH 7.2 and kept in a water bath at 60 degrees C for 28 days. The weight loss of the products after hydrolytic degradation ranged from 1.25% to 48.75% after 28 days

Study on novel exfoliated polyampholyte nanocomposite hydrogels based on acrylic monomers and Mg-Al-Cl layered double hydroxide: Synthesis and characterization

Novel exfoliated polyampholyte nanocomposite hydrogels (NH-LDHs) based on acrylic acid (AA), 2(diethylamino) ethyl methacrylate (2-DEAEMA), N,N-methylenebisacrylamide (NMBA) and layered double hydroxide (Mg-Al-CI LDH) were synthesized using an in situ free radical addition polymerization method in aqueous media. First, Mg-Al-CI LDH with a highly crystalline structure was prepared and characterized using FTIR, XRD, TGA and SEM analyses. The formation of NH-LDHs was confirmed by FTIR and XRD analyses. The morphological structure and select properties, such as the thermal, swelling and mechanical properties, of the NH-LDHs were also investigated. NH-LDHs have an exfoliated structure and smooth and nonporous surface morphologies. They can also be used as thermally stable nanocomposite hydrogels. The results revealed that adding a small amount of exfoliated Mg-Al-CI LDH could effectively increase the compressive modulus of the polyampholyte gels. When the Mg-Al-CILDH was incorporated into the polyampholyte hydrogel matrix, two synergic effects, additional co-crosslinking and additional hydrophilicity, occur in the swelling behaviors of the gels. All NH-LDHs are sensitive to pH, and they have zwitterion characteristics at pH 5.5. It was concluded that the NH-LDHs synthesized in this study might be used as alternative water absorbents in solutions with different pH. The diffusion of water into the NH-LDHs gel systems in deionized water at room temperature is assumed to be a non-Fickian behavior. (C) 2013 Elsevier B.V. All rights reserved

Effects of Nanoparticles on Film Properties of Waterborne Acrylic Emulsions

Waterborne acrylic emulsion was obtained by using methyl methacrylate, ethyl and butyl acrylate monomers. Emulsions containing nanoparticles were prepared by blending the stable dispersions containing SiO2 or MMT nanoparticles. The films were prepared from emulsions and coating tests were applied. The physical properties of prepared emulsions are better than the commercial emulsions. The addition of the nanoparticles especially SiO2 have positive effect on the resistance to environmental conditions of emulsions. Waterborne acrylic emulsions containing nanoparticles prepared in this study can be used in the manufacturing of the semi-lustrous emulsion type nano paint with low cost, high performance and environmentally friendly

A novel type of Si-containing acrylic resins: Synthesis, characterization, and film properties

A novel type of Si-containing acrylic resins was prepared by two steps and investigated their usage as surface coatings materials. At first a reactive polysiloxane intermediate Z-6018 was reacted with 2-hydroxyethyl methacrylate (HEMA) in toluene at 110 degrees C under N-2 atmosphere. After the condensation reaction was stopped, reacted with different acrylic ester monomers such as ethyl acrylate (EA) and methyl methacrylate (MMA) at different mole ratio (1/3 and 1/4) by the free radical addition polymerization. Structures of Si-containing acrylic resins were characterized by Fourier Transform Infrared Spectrometer (FTIR) and thermal properties of these resins were investigated by thermogravimetric analysis and differential scanning calorimetry DSC techniques. Surface coating properties of the films prepared from these resin were also determined. The results showed that all films are flexible, glossy or semi gloss and have excellent drying and adhesion properties. All films also exhibit abrasion resistances moderately. Water resistance of the films was generally modified by cured in oven and alkaline resistance of the films prepared from resins containing ethyl acrylate units are excellent. (c) 2007 Wiley Periodicals, Inc