Reactivity of poly(vinyl chloride) containing N-methyl-N-carboxymethyl dithiocarbamate toward metal ions in heterogeneous system and effect of γ-irradiation on the reactivity

The reaction of poly(vinyl chloride) containing N-methyl-N-carboxymethyl dithiocarbamate (PSDC) with metal ions in a heterogeneous system and the effects of γ-irradiation on the reactivity were studied. Slurried PSDC has an affinity for a number of metal ions in aqueous solutions. On the basis of analyses for nitrogen and sulfur and on infrared spectra, a possible chelating structure for PSDC was deduced. The gaseous products evolved during the gamma radiolysis of PSDC under vacuum were measured. Although the dithiocarbamate group bonded to the main chain gave some protection against the dehydrochlorination of poly(vinyl chloride) component, a small amount of the carboxymethyl group was decomposed. It was found that with γ-irradiation doses up to 30 Mrad, only about 1 mole-% out of 17.6 mole-% of N-methyl-N-carboxymethyl dithiocarbamate in the polymer was decomposed. It was shown that the reactivity of the irradiated PSDC in water toward metal ions was almost the same as that before irradiation.     

Preparation of modified poly(vinyl chloride) containing N,N-di(β-hydroxyethyl)dithiocarbamate and its reaction with metal ions

Reaction of N,N-di(β-hydroxyethyl)dithiocarbamate ion with poly(vinyl chloride) (PVC) was undertaken, and the reaction with metal ions of the polymer obtained was investigated. The effect of γ-irradiation on the reaction with metal ion was also studied. The modified PVC (PHDC) obtained from the reaction with N,N-di(β-hydroxyethyl)dithiocarbamate ion is pale yellow even after reaction at 100°C for 5 hr in dimethylformamide (DMF); it is soluble in dipolar solvents and its chlorine content is decreased considerably. This polymer reacted well with acetate salts of copper(II), nickel(II), zinc(II), and silver(I) heterogeneously in aqueous solution because of the introduction of hydrophilic groups (two hydroxy groups). The reactivity of the metal ions toward the polymer was of the order Ag(I) ? Cu(II) > Ni(II) > Zn(II). From the result of the reaction of γ-irradiated polymer with cupric ion, the polymer was judged to have fairly good antiradiation property.     

Effect of γ-Radiation on the Electronic Spectra of Poly(Methyl Methacrylate) Doped with Some Divalent Nd10 Cation Dithizones

The electronic absorption spectra of dithizone (H₂DZ) and its metal complexes of Hg. Cd, and Zn doped in poly(methyl methacrylate), PMMA has been investigated before and after γ-irradiation. It is found that the complex formation resulted in significant changes in both the position and the intensity of the electronic bands of H₂DZ. γ-Radiation causes remarkable decrease in the intensity of the most absorption bands of the metal complexes. The rate of decrease depends on the nature of the metal ions.     

Comparison of the effect of ethylene oxide and γ-irradiation on selected tyrosine-derived polycarbonates and poly(L-lactic acid)

Tyrosine-derived polycarbonates are a new class of degradable polymers that have possible biomedical applications. In this study, the effect of the two most common sterilization techniques, ethylene oxide and γ-irradiation (0.3, 1.1, 3.9, 6.4, 10.6 Mrad), was evaluated for a family of four structurally related tyrosine-derived polycarbonates and for poly(L-lactic acid) (PLLA). The four polycarbonates were poly(DTE carbonate), poly(DTB carbonate), poly(DTH carbonate), and poly(DTO carbonate) and differed only in the length of the pendent chain. Ethylene oxide exposure had little effect on molecular weight, surface composition, mechanical properties, or degradation rate of all test polymers except for poly(DTO carbonate). Poly(DTO carbonate) was unique since following ethylene oxide exposure it degraded faster than did the nonsterilized control. γ-Irradiated tyrosine-derived polycarbonates retained over 81% of their initial molecular weight when exposed to a clinically relevant dose of 3.9 Mrad and retained still 58% of the initial molecular weight when exposed to the highest test dose of 10.6 Mrad. No changes in surface composition and only slight changes in yield strength and the Young's modulus were detected for any of the tyrosine-derived polycarbonates following γ-irradiation. In vitro, irradiated films of poly(DTE carbonate), poly(DTB carbonate), and poly(DTH carbonate) degraded at approximately the same rate as did the nonsterilized films regardless of irradiation dose. Only poly(DTO carbonate), irradiated at high doses, degraded faster than did the control. Medical-grade PLLA was tested under identical conditions. Ethylene oxide exposure of PLLA did not affect the molecular weight, surface composition, mechanical properties, or in vitro degradation rate. However, upon irradiation at 10.6 Mrad, PLLA retained only 29% of its initial molecular weight; a dose of 3.9 Mrad resulted in retention of 49% of the initial molecular weight. In correspondence with earlier publications, irradiation of PLLA induced significant losses in the Young's modulus, % strain at break, and changes in the postirradiation rate of degradation in some specimens. Compared to PLLA, tyrosine-derived polycarbonates are significantly more stable to γ-irradiation and can be sterilized by conventional γ-sterilization techniques. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1499–1510, 1997     

Effect of γ-irradiation and temperature on the structure of metal chloride treated poly(acrylamide)

The gamma-induced changes in the structure of Poly(Acrylamide) (PAAm) treated with metal chlorides were investigated by following the corresponding variations in their ultra-violet spectra. Careful examination of UV spectra revealed that irradiation of the specimens results in the appearance of an absorption peak at 275 nm whose intensity depends on the applied dose and the nature of the metal ions. This band is ascribed to the formation of the carbonyl group. The results indicate that the dependence of the intensities of the band at 275 nm on the nature of the metal used provides strong evidence for the formation of metal polymer complexes. It was found that the pretreatment of PAAm with the appropriate concentration of ZnCl₂, CoCl₂, or NiCl₂ reduces the effects of heating and the oxidation effects of γ-irradiation. These results show that these metal ions can be used as stabilizers against thermal degradation of PAAm in the temperature range up to 160°C. © 1993 John Wiley & Sons, Inc.     

The effect of γ-irradiation on optical and electrical properties of polycarbonate

Poly-(bisphenol A carbonate) (PC) samples were exposed to different doses of γ-rays from a ⁶⁰Co source (from 0.05 to 0.3 M rad) at room temperature. Conductivity and dielectric constant as well as optical measurements were carried out. It was noticed that almost no work has been reported on the electrical conductivity of polycarbonate at high temperatures. γ-irradiation of polycarbonate is believed to create free radicals which increases the state of disorder and perturb the orientation of dipoles inside the polymer. At about 95°C, the electrical conductivities of irradiated samples were found to increase by nearly one order of magnitude with respect to the unirradiated one. The dielectric constant, ?, of fresh polycarbonate was nearly temperature independent over a range of ～ 70°C, then it increased with temperature, but for γ-irradiated samples (from 0.05 to 0.3 M rad) the dielectric constant increased continuously with temperature and also with respect to the fresh sample what confirms the effect of γ-irradiation in perturbing the orientation of the dipoles in the polymer. It was found that the UV absorption spectrum has a broad band at 0.280 μm and the absorption intensity was strongly dependent on the dose of γ-irradiation.     

Electron spin resonance studies of γ-irradiated cellulose. I. Free radicals in decrystallized cellulose

The types of free radicals formed in decrystallized cellulose prepared from cellulose I and II after γ-irradiation in nitrogen atmosphere at room temperature were studied by ESR spectroscopy. X-Ray diffraction revealed that decrystallized cellulose I and II have the same microstructure. The ESR spectra obtained with the γ-irradiated decrystallized samples are simple. By contacting the irradiated sample with moisture in nitrogen atmosphere, the ESR spectrum changed to a narrow singlet, which gradually decreased in intensity until the spectrum completely disappeared. It was found that the types of free radicals generated in the decrystallized cellulose by γ-irradiation consist of the overlap of singlet and doublet. The singlet spectrum is mainly attributed to alkoxyl radical formed by the rupture of glycosidic linkage at the C 1 or C 4 position, and the doublet spectrum is ascribed to radical formed by hydrogen abstraction from the C 1 position in cellulose molecule.     

Electrical conductivity of γ-irradiated native and mercerized cotton celluloses

In the present study the electrical conductivity (σ) of ball-milled and NaOH-treated cotton fibers were measured in vacuum. The induced electrical conductivity and the activation energy ΔE of γ-irradiated samples were measured as a function of radiation doses and at various temperatures. It was found that γ-irradiation of cotton fibers either decreases or increases its electrical conductivity. Thus, it was found that γ-irradiation of cotton reduces the conductivity of the samples having particle sizes ranging from 0.07 to 0.11 mm and the magnitude of the reduction diminishes as the particle size increases. The results have also shown that, for any given concentration, γ-irradiation of NaOH-treated samples causes an increase of the measured electrical conductivity.     

Effect of γ-Irradiation on the Electrical Properties of Poly (Methyl Methacrylate) Doped with Some Transition Metal Complexes

Abstract

The electrical resistivity (p) of pure and doped poly(methyl methacrylate), PMMA, with dithizone (HDZ) and its metal complexes, Zn(HDZ)₂, Cd(HDZ)₂ and Hg(HDZ)₂ has been investigated before and after γ-irradiation. The results show a phase transition at nearly 323°K. The activation energy of the conduction process has been calculated below and above the transition temperature. Further information concerning the electrical behaviour is obtained by considering the type and mechanism of the conduction process. This has been achieved by studying the effect of temperature and γ-irradiation on the mobility and the number of charge carriers which take part in the conduction process.     

Effect of γ-Irradiation on Electrical Conductivity of Metal-Chloride-Treated Polyacrylamide

The electrical conductivity of polyacrylamide (PAAm) before and after treatment with low concentrations of ZnCl₂, NiCl₂, and CoCl₂ was determined at different temperatures. The effects of γ-irradiation on the electrical conductivity and activation energy of the original and the metal-chloride-treated specimens were investigated. The experimentally obtained data revealed that the conduction in PAAm is ionic in nature. The treatment of the polymer with 2% or 4% (w/w) of ZnCl₂, NiCl₂, or CoCl₂, as determined from its weight, either increases or decreases its conductivity according to the nature of the metal ions, concentration of metal chloride, ratio of KOH/metal chloride, and temperature and cycle of measurement. The exposure of PAAm to 2 to 10 Mrad of γ-radiation produces no significant changes in its conductivity. On the other hand, the exposure of the PAAm pretreated with a metal chloride produces considerable changes in its conductivity. Also, the γ-irradiation of PAAm increases its activation energy. The extent of the γ-induced changes in activation energy was influenced by the pretreatment of PAAm with metal chlorides.     

Chelating polymers derived from polyvinyl alcohol and cellulose

Hydrophilic chelating polymers have been prepared by the reaction of organic compounds containing both a reactive halogen and a chelating function, with cellulose and, more especially, polyvinyl alcohol or their alkali metal derivatives. Suitable organic compounds used to illustrate the general reaction included: 5-chloromethyl-8-hydroxyquinoline, 5-chloro-8-hydroxyquinoline, ethyl γ-chloroacetoacetate and chloromethyl-kojic acid. Subsequent reaction of the kojic acid-polyvinyl alcohol polymer with diazotised o-arsanilic acid to give a polymer containing the azo-phenylarsonic acid group indicates further scope for these materials. Preliminary tests have shown that the polymers remove metal ions from aqueous solutions. Degradation occurred, however, when the polymers were regenerated with acids to elute adsorbed metal ions.     

Adsorptions of Some Heavy Metal Ions in Aqueous Solutions by Acrylamide/Maleic Acid Hydrogels

Abstract

In this study, acrylamide—maleic acid (AAm/MA) hydrogels in the form of rod have been prepared by γ-radiation. They have been used for adsorption of some heavy metal ions such as uranium, iron, and copper. For the hydrogel containing 40 mg of maleic acid and irradiated at 3.73 kGy, maximum and minimum swellings in the aqueous solutions of the heavy metal ions have been observed with water (1480%) and the aqueous solution of iron(III) nitrate (410%), respectively. Diffusions of water and heavy metal ions onto hydrogels have been found to be of the non-Fickian type of diffusion. In experiments of uranyl ions adsorption, Type II adsorption has been found. One gram of AAm/MA hydrogels sorbed 14–86 mg uranyl ions from solutions of uranyl acetate, 14–90 mg uranyl ions from solutions of uranyl nitrate, 16–39 mg iron ions from solutions of iron(IV) nitrate, and 28–81 mg copper ions from solutions of copper acetate, while acrylamide hydrogel did not sorb any heavy metals ions.     

Model Study of Different Antioxidant Properties of α- and γ-Tocopherol in Fats

A model study using 2,2,5,7,8-pentamethyl-6-hydroxychroman (α-COH) and 2,2,7,8-tetramethyl-6-hydroxychroman (γ-COH) as antioxidants, and linoleic acid and its methyl ester (both in bulk phase) as the lipids was performed. After having demonstrated that the antioxidative activities of the model substances did agree with those of the corresponding tocopherols (α-T, γ-T), the stability of α-COH and γ-COH was determined, and the products arising from α-COH, γ-COH, linoleic acid and its methyl ester were identified. α-COH did oxidize to different major products (quinone, trimer) depending on the reaction temperature (37°C and 47°C) and the antioxidant concentration, whereas the products obtained by oxidation of γ-COH (diphenyl ether dimer, biphenyl dimer) did not seem to be affected by differences in the reaction conditions. It was concluded that γ-T was superior to α-T as antioxidant because it appears more stable and, also, being oxidized to compounds which are still effective as antioxidants.     

Radiation protection of poly(vinyl chloride) by N-methyl dithiocarbamate substitution

The effect of N-methyl dithiocarbamate substitution on the radiation stability of poly-(vinyl chloride) (PVC) films was studied. PVC containing between 2 and 11 mole-% N-methyl dithiocarbamate (PMD) was irradiated with γ-rays from a ⁶⁰Co source at 40°C and the evolved gaseous products were measured and analyzed with a mass spectrometer. The apparent G values for gas evolution for PMD decreased remarkably. For example, a G value of 0.28 was obtained for a PMD which contains 11 mole-% dithiocarbamate group compared with a G value of 10.8 for unmodified poly(vinyl chloride). Furthermore, the mass spectrum of the evolved gas from the same PMD sample (PMD-44) with 10 Mrad irradiation showed no hydrogen chloride to be present. The external protection was studied using polymer-blended films of PVC and PMD-44. The stabilization coefficients for internal protection and external protection in polymer blends were calculated. The ESR spectrum of the irradiated PMD-44 showed a strong anisotropy with high g values which differed significantly from the spectrum of the irradiated PVC. A suggested mechanism for radiation protection of PVC against γ-rays irradiation by the N-methyl dithiocarbamate group is discussed.     

Effects of enzymes and gamma irradiation on the tensile strength and morphology of poly(p-dioxanone) fibers

The objective of this study was to examine how and to what extent a new degradable polymeric fiber, poly(p-dioxanone), used as a surgical suture material, degrades in the presence of enzymes and after γ-irradiation. The degradation of the fiber was studied mechanically using an Instron and morphologically by SEM. Both esterase and trypsin enzymes and their corresponding buffer controls were used. The fibers were γ-irradiated at the dosages ranging from 0 to 20 Mrad, immersed in the solution for up to 70 days, and then removed for tensile strength and morphological examinations. It was found that γ-irradiation alone lowered the tensile strength of PDS fibers and made them more susceptible to hydrolysis. Esterase and trypsin did not accelerate the hydrolytic degradtion of this fiber to any significant level. Both γ-irradiation and enzymes influenced the gross morphological characteristic of PDS fibers when they were subjected to hydrolysis. The most important morphological observations were the formation of surface cracks and chips on the fibers and the subsequent peeling of the chips. Enzyme-treated PDS fibers exhibited similar morphological findings but the size of the chips was smaller. The morphological observations of PDS fibers were consistent with the tensile strength data.     

Functionalization of polymer supports for polymerization catalysts by graft polymerization method

The specific features of the gas-phase radiation-induced and plasma-initiated graft polymerization of certain monomers possessing the functionality needed for immobilization of transition metal compounds were studied. The radiation yields of allyl monomers grafted to polyethylene, polypropylene, and poly(vinyl chloride) (5–25 molecules/100 eV) were found to be close to the radiation yields of the polymerization of these monomers in a liquid state. The kinetics of methyl methacrylate and acrylic acid postgrafting to polyethylene pretreated with helium discharge plasma were also studied. The graft-initiating effect of PE powder treated with plasma for 5–10 min was found to be comparable with that of γ-irradiation in a dose 0.5–4 Mrad. The results of immobilization of transition metal compounds [TiCl₄, VCI₄, VO(OC₂H₅)₃, Ti(OC₄H₉)₄, etc.] on carriers prepared by the method of polymer support functionalization by grafting are described. The extent of completion of the immobilization reaction is found to vary from 0.1 to 0.96 and to depend both on the nature of the transition metal and on the specificity of the grafted fragments.     

High radiation tolerance of electrocaloric (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3

High radiation tolerance of functional materials in harsh environments is the key requirement for the operation of particle accelerators, medical devices, nuclear power plants, satellites, and spacecraft. Neutron and gamma (γ) radiation can seriously affect the functional properties of the irradiated materials and thus the performance of the entire device. In this work, the feasibility of using (1-x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃ (PMN–100xPT) electrocaloric materials in applications where the material is exposed to high neutron and γ-radiation is investigated. For this purpose, three different compositions of PMN–100xPT ceramics (x = 0, 0.1, and 0.35) were prepared and their dielectric, ferroelectric and electrocaloric properties were investigated before and after neutron and γ-irradiation. The samples were irradiated with a neutron fluence of 10¹⁵ to 10¹⁷ neutrons cm^?2 with an energy of 1 MeV, which exceeds the largest expected neutron irradiation in the European Council for nuclear Research (CERN) and simultaneously exposed to γ-irradiation. The neutron and γ-radiation partially affect the functional properties of the PMN–35PT, the ceramic with distinct ferroelectric and weakened relaxor features, with some differences observed in the domain switching behavior, measured by conventional polarization versus electric field (P–E) hysteresis, at the highest radiation dose of 10¹⁷ neutrons cm^?2. In contrast, the functional properties of the irradiated PMN and PMN–10PT samples with relaxor behavior are quite similar to those of the pristine samples, therefore, we conclude that these materials can be used as working materials in EC coolers exposed to such harsh environments.     

EPDM recycling assisted by γ-processing

The integration of waste ethylene–propylene–diene terpolymer (EPDM), containing carbon black into pristine EPDM can be achieved by γ-irradiation as a versatile procedure to process ethylene–propylene elastomers. The presence of acrylic acid in the material formulation allows the formation of intermolecular bridges by threefold increase in gel content. The possibility of achieving greater stability by the addition of acrylic acid in EPDM systems was analyzed. The start materials were EPDM containing 30 and 50 phr of EPDM powder loaded with 40 phr of carbon black aged by pre-exposure to electron beam irradiation. The advanced γ-irradiation exceeding 100 kGy represented the optimal radiation processing condition. Two procedures of chemiluminescence under isothermal and non-isothermal regimes for the evaluation of radiation stability were applied on γ-irradiated samples. The thermal strength of irradiated samples was characterized based on the radiolysis mechanism of EPDM. The variation in the activation energy required for the thermal oxidation of these samples and the modification in gel contents due to the gelation action of acrylic acid were presented for the validation of proposed recycling radiochemical technique. Charlesby–Pinner representation provided different values for the ratios between radiochemical yields of cross-linking and scission, proving that the presence of acrylic acid promoted the conversion of EPDM wastes into valuable materials.     

Effect of γ-Irradiation on the Dielectric Properties of Poly(methyl methacrylate) Doped with Some Luminescent Materials

A systematic dielectric study over the frequency range from 0.1 to 10 MHz has been carried out on pure and doped poly(methyl methacrylate) (PMMA) with tetracyanoquinodimethane (TCNQ) as an acceptor and rhodamine-6G (Rh-6G) and rhodamine-B (Rh-B) as donors before and after being exposed to γ-irradiation. The results indicate that the addition of TCNQ to PMMA increases its ability to withstand γ-irradiation and improves its insulation properties.     

Reaction with metal ions of chloromethylated polystyrene resin containing dithiocarbamate group

The derivatives of poly(chloromethylstyrene) resin (PCMS) with N-methyl-N-carboxylmethyl-dithiocarbamate (1), N,N-di(β-hydroxyethyl)dithiocarbamate (2), N-methyl-N-carboxylmethylamino (3), and di(β-hydroxyethyl)amino (4) groups were prepared, and the metal ion reactivity of the polymer resins with these functional groups were investigated. Additionally, the effect of γ irradiation on the reaction with metal ion was also investigated. In the reaction of PCMS under the same conditions, the substitution ratio order is as follows: (2) > (1) > (4) > (3). In the reaction of the resins with cupric ion, the reaction amount reached a maximum of 4.17 mequiv/g for resin (1) and 4.75 mequiv/g for (2). The polymers containing sulfur atom have a large reactivity toward metal ion in comparison to the polymers without sulfur atom. The reactivity of polymer (1) toward metal ions decreased in the following order: Ag(I) ? Cu(II)> Zn(II) ? Ni(II) ? Co(II). The other metal ions, except Ag(I) and Cu(II), hardly reacted with polymer (2). Thus, polymer (2) has a remarkable selectivity. It was also found that the reaction amount of polymers containing sulfur after γ irradiation is almost the same as that before γ irradiation.