Gamma radiation synthesis of comb-type graft hydrogels based on poly(acrylic acid) and 4-vinylpyridine

A pH-sensitive comb-type hydrogel was obtained by gamma radiation polymerization and crosslinking of acrylic acid (AAc) in solution. The pH-sensitive 4-vinylpyridine (4VP) was then grafted to the poly acrylic acid (PAAc) hydrogel using gamma radiation from a ⁶⁰Co source. The comb type graft polymers obtained (net-PAAc)-g-4VP has been studied through determination of graft yield and swelling behavior. The critical pH value was found to be 5.6. The apparent mechanical properties appear to be qualitatively better than hydrogels of PAAc upon swelling. The new comb-type system presents faster swelling response (30 h) than the polyacrylic acid hydrogel (50 h). The increase in dose rate from 7.3 to 11.3 kGy h⁻¹, increase the radiation grafting percentage of 4VP in the system. Comb-type polymers were also characterized by DSC, TGA and FTIR-ATR.     

辐射交联制备改性CMC水凝胶的溶胀行为研究

利用丙烯酰胺 (AAm)接枝改性纤维素 ,然后进行羧甲基化反应得到高取代度的丙烯酰胺 羧甲基纤维素钠 (AAm CMC Na) .对该材料进行γ射线辐照制备出新型改性CMC水凝胶 .研究了这种水凝胶的溶胀动力学、交联动力学以及温度、pH值和无机盐浓度对水凝胶溶胀行为的影响 ,并与CMC Na水凝胶进行了比较 .结果表明 ,该水凝胶和CMC Na水凝胶相比 ,优点在于辐照交联所用的剂量下降 ,而且所需的CMC浓度减少 .AAm CMC Na水凝胶的溶胀度随温度升高而增大 ,在pH为 6～ 8范围内达到最大值 ,并随无机盐浓度与吸收剂量增加而下降 ,表现出较好的温度敏感性和pH敏感性 ,可望作为吸水材料和水保持剂     

EPR evaluation of absorbed doses in γ-irradiated animal bone tissues

The accumulation of CO ₂ ^- radicals in γ-irradiated porcine, chicken, bovine, walleye pollack, and navaga bone tissues and chicken eggshells was studied by EPR spectroscopy for the purpose of detecting irradiated food and evaluating the dose absorbed during its radiation processing. It was found that, in the dose range 0–10 kGy, the concentration of radicals is a linear function of dose, and the variation coefficient of the radiationchemical yield of radicals is no higher than 30% for bone tissues from various biological species. The applicability of the additive dose method to the EPR dosimetry of irradiated beef was examined. A linear regression model used in the additive dose method was found to give overestimated results, as compared with an exponential fitting model.     

EPR identification of irradiated Monascus purpureus red pigment

Fresh red alimentary pigment extracted from Monascus purpureus fungus exhibits an intense EPR line consisting of a single, narrow line, attributed to a quinone radical. When irradiated with 7 MeV electrons or ⁶⁰Co γ-rays, the amplitude of this line increased with the absorbed dose following a saturation exponential dependency up to 10 kGy. During annealing treatment (isothermal heating at 100°C) the irradiation centers decay exponentially with a half-life time of 2.30 min.     

Assessment of radon concentration and external gamma radiation level in the environs of Narwapahar uranium mine,India and its radiological significance

In the environs of uranium mining, milling and processing facilities and in the uranium mineralized terrain, a little higher ambient radon concentration and gamma radiation level may be expected in comparison with natural background. The present study gives a brief account of atmospheric radon concentration, gamma absorbed dose rate and radiation dose received by the members of public in the vicinity of Narwapahar uranium mine. The ambient radon concentration in the air in the study area was found to vary from 5 to 107 Bq m⁻³ with geometric mean of 24 Bq m⁻³ and geometric standard deviation of 1.74 Bq m⁻³. The measured gamma absorbed dose rate in air at 1 m above the ground ranged from 87 to 220 nGy h⁻¹ with an overall arithmetic mean of 128 ± 18.5 nGy h⁻¹. The mean annual effective dose received by the members of public from inhalation of radon and its progeny and external gamma exposure was estimated to be 0.32 mSv year⁻¹, which is comparable to other reported values elsewhere.     

Gamma dose rate due to natural and manmade radiation sources from a nuclear facility in Mexico

The environmental external gamma dose rate has been determined at the Mexican Nuclear Research Centre and surrounding communities, located in a forest area. Outdoor direct measurements of external gamma exposure and absorbed dose rates in air were performed using passive integrating thermoluminescent dosimeters. Radiological measurements were also carried out with a portable high pressure ionization chamber. The gamma dose rate was evaluated from data obtained along 10 years measurements. The activity concentrations of ⁴⁰K, ²²⁶Ra, ²³²Th, ¹³⁷Cs, and ²³⁵U in surface soil samples at sampling sites are also presented. The radionuclide activity concentrations were determined by low background gamma spectrometry with hyper-pure germanium detectors. A site specific lineal model to describe the relationship between the external gamma dose rate and the ²²⁶Ra concentration values in the soil is proposed.     

A study of dosimetry characteristics of GAF DM-1260 radiochromic films

The dosimetric characteristics of gamma-ray, x-ray and electron irradiated GAF-DM-1260 radiochromic film have been studied, and the dependence of radiation-induced film absorbance on irradiation temperature and reading temperature and the changes of the absorption spectrum peaks at different reading temperatures and absorbed doses (3×10¹ to 5×10⁴ Gy) are reported. It is shown that the responses are independent of the gamma-ray dose rate in the dose rate range considered in the experiment. The film response characteristics as a function of the absorbed dose to ⁶⁰Co gamma irradiation at the spectrophotometric reading wavelengths of 400, 580, 600, 650 and 670 nm and two absorption peaks are determined as well as the response characteristics to the electron beam at the reading wavelength of 400 nm. The results demonstrate that the film responses to gamma rays, x-rays and a 3.8 MeV electron beam are equivalent, over the absorbed dose rate range of about 0.8 Gy·s⁻¹ to 5×10⁸ Gy·s⁻¹. Some advice and points of view about the dosimetric characteristics of the film and some problems in usage are provided according to the experimental results.     

ABSORPTION OF METAL IONS AND SWELLING PROPERTIES OF POLY(ACRYLIC ACID-CO-ITACONIC ACID) HYDROGELS

Hydrogels of acrylic acid and itaconic acid has been synthesized with different monomers ratios. The swelling process of the different xerogels immersed in water and salt solutions has been studied. The swelling of hydrogels loaded with metal cations (Cu²⁺, Zn²⁺) was also investigated. The swelling process was monitored by the increase in the weight of hydrogel as a function of time. The absorption properties of metal ions were studied by using the hydrogel, and different concentrations of copper and zinc solutions (prepared from sulphate salts). The influence of pH on the absorption process was studied. For the absorption of metal ions, the amount of ions absorbed within the hydrogel can be calculated from the initial and equilibrium concentrations of the metal ions in aqueous phase, the weight of the hydrogel, and the volume of solution used. Metal absorption increased when pH, salt concentration in external solution and itaconic acid content is levelled.

The swelling isotherms which consisted of an initial fast increase levelled off asymptotically to the equilibrium swelling limit. The experimental data clearly suggest that our hydrogels follow a second-order kinetics for both cases (unload and metal loaded). The kinetics rate constant and the equilibrium water content, K, have been calculated for every monomer ratio from the experimental data according to the kinetics equation. Both magnitudes decreased as the itaconic acid content decreases in the xerogels.     

Flexible,high sensitive and radiation-resistant pressure-sensing hydrogel

Excellent radiation resistance is a prerequisite for pressure-sensitive hydrogels to be used in high-energy radiation environments. In this work, tannic acid-modified boron nitride nanosheet（BNNS-TA） is first prepared as the radiation-resistant additive by a facile one-step ball milling of hexagonal boron nitride and tannic acid. Then, polyacrylamide（PAAm）-based pressure-sensitive hydrogel doped with BNNS-TA and Fe³⁺ions is fabricated. The ternary BNNS-TA/Fe³⁺/PAAm hydrogel...     

Gamma radiation induced effects on silica and on silica-polymer interfacial interactions in filled polysiloxane rubber

We report in our studies to assess the impact of gamma radiation on silica and on the silica-polymer interface in filled polysiloxane rubber. Electron spin resonance (ESR) and solid-state nuclear magnetic resonance (NMR) studies have been performed on samples exposed to gamma radiation. In an effort to probe directly the effect of gamma radiation on the silica surface, we employed ¹H and ²⁹Si NMR. Our ESR studies show trapped paramagnetic species (positive holes and/or trapped electrons) within the host silica matrix for all samples exposed to gamma radiation. A sample of pure cab-o-sil irradiated to a dose of 50 kGy also shows an ESR signal. Our studies on real-time aged samples (derived from field trials) also show ESR signatures indicative of silica based trapped paramagnetic species. The growth of trapped paramagnetic species as a function of gamma dose was investigated. This shows that the build up of trapped species occurs rapidly at low gamma dose before reaching saturation at about 20-30 kGy. Radiation induced band gap excitation is the likely process leading to the creation of these paramagnetic species which may be trapped in regions of local charge deficit within the silica matrix. Species that are not trapped may take part in silica surface reactions leading to changes in filler-polymer interfacial interactions. NMR studies combined with ammonia modified swell studies have shown increased polymer segmental chain mobility (softening) at low gamma dose indicative of a possible reduction in filler-polymer interfacial interactions. For those samples exposed to high gamma dose, our ammonia modified swell studies suggest increased polymer-filler interactions presumably through silica-polymer crosslinking effects. Our ¹H and ²⁹Si NMR studies on irradiated silica suggest that the silica surface is sensitive to gamma radiation. Our observations are important as they highlight the need to better control the quality (size, purity, etc.) of the silica constituent in filled polymer components used in gamma radiation environments.     

Radiation Synthesis of Superabsorbent Hydrogels Based on Chitosan and Acrylic Acid for Controlled Drug Release

Superabsorbent hydrogels based on the natural polymer chitosan and acrylic acid (CS/AAc) was prepared using ⁶⁰Co gamma radiation as a source of initiation and crosslinking. The factors, which affect the preparation of CS/AAc hydrogels such as irradiation dose, CS/AAc ratios, and acrylic acid monomer concentrations, to get the best optimum conditions, were investigated. The kinetic studies of the swelling of CS/AAc hydrogel showed that it follows a Fickian type of water diffusion. The Fickian constant value ‘n’ was more than 0.5 with a high swelling capacity of 300 g/g as superabsorbent hydrogel. In addition, the suitability of CS/AAc hydrogel as carrier material for the drug Chlortetracycline-HCl has been investigated by adsorption isotherm studies. The performance of drug release from hydrogel systems, influenced by acrylic acid ratio and the effect of pH of the medium was studied.     

Catalytic poly(vinyl alcohol) functionalized membranes obtained by gamma irradiation

Polymeric catalytic membranes bearing sulfonic acid functions have been prepared by mutual gamma irradiation at a ⁶⁰Co source, of poly(vinyl alcohol) (PVA) membranes and methanesulfonic acid. The effect of various synthesis conditions on membranes' physical–chemical properties and catalytic activity in the esterification reaction between acetic acid and isoamyl alcohol to obtain isoamyl acetate (banana flavor), was evaluated. The membranes were characterized by ATR-FTIR, TPP, AFM and SEM. Water contact angle determinations were also performed. The obtained results showed that within the range of conditions studied the increase in sulfonic acid groups' content is accompanied by an enhancement in the membranes catalytic activity, while the increase in absorbed dose leads to a decrease in catalytic activity.     

Conducting hydrogels based on semi‐interpenetrating networks of polyaniline in poly(acrylamide‐co‐itaconic acid) matrix: synthesis and characterization

In this work, acrylamide/itaconic acid copolymeric hydrogels are prepared by free radical polymerization initiated by redox initiators of potassium persulfate and N ,N ,N ′,N ′‐tetramethyl ethylene diamine; N ,N ′methylene bisacrylamide was employed as a crosslinking agent. Aniline monomer was absorbed in the network of poly(acrylamide‐co‐itaconic acid) P(AAm‐co‐IA) hydrogel and followed by gamma radiation induced polymerization at room temperature. The novel semi‐interpenetrating network was comprised of linear polyaniline immersed in P(AAm‐co‐IA) matrix. Electrical conductivity of the hydrogels was measured using four‐probe technique. The conductivities for the prepared hydrogels are found to increase from 5.5 × 10^?7 S cm^?1 for P(AAm‐co‐IA) alone to 4.4 × 10^?3 S cm^?1 for semi‐interpenetrating polymer network P(AAm‐co‐IA)/polyaniline. Thus, a new composite hydrogel with good conductive properties also displaying enhanced mechanical strength and pH sensitivity was prepared. Copyright © 2017 John Wiley & Sons, Ltd.     

Evaluation of radiation stability of N,N-didodecyl N′,N′-di-octyl diglycolamide: a promising reagent for actinide partitioning

The radiation stability of N,N-di-dodecyl-N′,N′-di-octyl-3-oxapentane-1,5-diamide (D³DODGA) was studied by γ-irradiation of the solvent up to a absorbed dose of 1,000 kGy. The effect of γ-irradiation on the radiolytic degradation of D³DODGA was assessed by measuring the distribution ratio of Am(III) (D _Am(III)) as well as the third phase formation in the irradiated D³DODGA-n-dodecane solution. The D _Am(III) in the irradiated solution decreased with increase of absorbed dose. The critical aqueous concentration of Nd(III) above which the third phase forms, increased with increase of absorbed dose. However, the limiting organic concentration of Nd(III) remained at ~25 mM irrespective of the absorbed dose. Recovery of Am(III) from the radiolytically degraded organic phase showed that back extraction of Am(III) was quantitative in a few contacts using dilute nitric acid. Our studies clearly indicated that radiolytic degradation of D³DODGA in n-dodecane is marginal even at the absorbed dose of 1,000 kGy, and therefore D³DODGA is a potential candidate for minor actinide partitioning.     

The daily radon dose in body organs caused by drinking milk and water

Milk is considered as the richest nutrition, being used by people. When drinking milk or water the radon gas will transfer from air to them rapidly. Since milk is majorly composed of water, probably radon existence in livestock consumable water could be the main cause of its presence in milk. Different portion of milk changed by radon gamma ray and consumption of radon included water or milk has its effects on the human body. For investigation the effect of radon in water or milk on human organs, this study has been done in two phases with MCNPX software. In the first phase, the dose rate of absorbed gamma ray by different portion of milk which is indoctrinated by 1 Bq/m³ of radon during a day is calculated. Moreover, the effects shown by milk and its components in radon gamma spectrum, which is demonstrator of milk absorption spectrum, are also surveyed. In the second phase as well, according to the human body phantom, the absorbed gamma dose caused by daily consumption of indoctrinated water or milk with 1 Bq/m³ radon is calculated. The production rate of free radicals in milk and its different components are derived according to escape data of MCNPX code.     

Radiation-induced grafting of styrene onto ultra-high molecular weight polyethylene powder and subsequent film fabrication for application as polymer electrolyte membranes: I. Influence of grafting conditions

Ultra-high molecular weight polyethylene (UHMWPE) powder was irradiated by gamma rays using a ⁶⁰Co source. Simultaneous and pre-irradiation grafting was performed in air and in inert atmosphere at room temperature. The monomer selected for grafting was styrene, since the styrene-grafted UHMWPE could be readily post-sulfonated to afford proton exchange membranes (PEMs). The effect of absorbed radiation dose and monomer concentration in methanol on the degree of grafting (DG) is discussed. It was found that the DG increases linearly with increase in the absorbed dose, grafting time and monomer concentration, reaching a maximum at a certain level. The order of rate dependence of grafting on monomer concentration was found to be 2.32. Furthermore, the apparent activation energy, calculated by plotting the Arrhenius curve, was 11.5 kJ/mole. Lower activation energy and high rate dependence on monomer concentration shows the facilitation of grafting onto powder substrate compared with film. The particle size of UHMWPE powder was measured before and after grafting and found to increase linearly with increase in level of grafting. FTIR-ATR analysis confirmed the styrene grafting. The grafted UHMWPE powder was then fabricated into film and post-sulfonated using chlorosulfonic acid for the purposes of evaluating the products as inexpensive PEM materials for fuel cells. The relationship of DG with degree of substitution (DS) of styrene per UHMWPE repeat unit and ion exchange capacity (IEC) is also presented.     

Radioactivity level of soil around Baqiao coal-fired power plant in China

Natural radioactivity level of soil around Baqiao coal-fired power plant in China was determined using gamma ray spectrometry. The concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied soil samples range from 27.6 to 48.8, 44.4 to 61.4 and 640.2 to 992.2 Bq kg^?1 with an average of 36.1, 51.1 and 733.9 Bq kg^?1, respectively, which are slightly higher than the average values of Shaanxi soil. The radium equivalent activity, the air absorbed dose rate and the annual effective dose rate were calculated and compared with the internationally reported or reference values. The radium equivalent activities of the studied samples are below the internationally accepted values. The air absorbed dose rate and the annual effective dose rate received by the local residents due to the natural radionuclides in soil are slightly higher than the mean value of Xi'an and worldwide.     

RADIATION INDUCED ACRYLAMIDE/CITRIC ACID HYDROGELS AND THEIR SWELLING BEHAVIORS

Citric acid (CAc) moieties containing acrylamide (AAm) hydrogels were prepared by gamma irradiation of their aqueous solutions. A possible polymerization and crosslinking mechanism for acrylamide/citric acid (AAm/CAc) hydrogels is proposed. The effects of irradiation dose and citric acid content on swelling behavior were investigated. Swelling took place in water at 25°C and was followed gravimetrically. Incorporation of a relatively low amount of citric acid to acrylamide hydrogel increased its swelling up to 950% from 700%. The diffusion of water into AAm/CAc hydrogels was found to be a non-Fickian type. Diffusion coefficients of AAm/CAc hydrogels found as 5 × 10^?7? 10 × 10^?7 cm² sec^?1. It has also been found that the number average molar mass between crosslinks is increased with the CAc content and decreased with irradiation dose.     

Oxidation of benzalkonium chloride by gamma irradiation: kinetics and decrease in toxicity

The gamma degradation of toxic non-oxidizing biocide dodecyl dimethyl benzyl ammonium chloride (DDBAC) was investigated. The degradation of DDBAC achieved 70–100% depending on the initial concentration and the absorbed dose, but only 10–33% dissolved organic carbon was removed. The presence of NO₃ ^?, HCO₃ ^?, 2-propanol and tert-butanol inhibited the degradation of DDBAC. The DDBAC degradation rate constant ratios of ·OH, ·H and e _aq ^? was calculated as 7.4:1.4:1. The acute toxicity of 10 mg L^?1 DDBAC was removed by 60% at absorbed doses of 0.5–3.0 kGy. The results showed that gamma irradiation was effective to remove DDBAC and its toxicity.     

Investigations of microstructural changes and spectral characteristics of tantala stabilized zirconia refractories

Several samples of zirconia doped tantala have been prepared and well sintered. Measurements of X-ray diffraction, infrared absorption spectra and bulk density were carried out before and after an absorbed energetic gamma radiation dose (5·26 × 10⁶ rd.). Results obtained were consistent and explained on the basis of the interactions of tantala dopant (at high temperature) and energetic gamma radiation with zirconia and stabilized zirconia lattices.