Gamma Radiation Induced Biodegradable Shellac Films Treated by Acrylic Monomer and Ethylene Glycol

In this study the mechanical properties of shellac films, prepared by solution casting, were evaluated with varying amounts of Ethylene Glycol (EG) and 2-Ethyl-2-(hydroxymethyl)-1,3-propandiol-trimethacrylate (EHMPTMA). Mechanical properties such as tensile strength (TS) and elongation at break (Eb) of the raw shellac film were found to be 1.86 MPa and 4%, respectively. A series of formulations was prepared using shellac and varying percentages of EG and EHMPTMA in methanol. The films were prepared and irradiated under gamma (Co-60) radiation at different doses (50–500 krad). Grafting of EHMPTMA showed better results compared to raw shellac and EG treated films. Thermal properties, degradation tests in water and soil of the films were also evaluated.     

Influence of Gamma Radiation on Electrical Conduction of Polyethylene Terephthalate (PET) at Ambient Temperature

The electrical conduction in polyethylene terephthalate (PET) exposed to a gamma radiation dose of 150 kGy was investigated in the applied field range from 4 to 36 kV/mm. Samples were irradiated in air at room temperature by means of a ⁶⁰Co gamma source at a dose rate of approximately 42 Gy/min. The electrical properties of virgin and irradiated materials were examined by charging and discharging current measurements. The current decays with time can be represented according to an inverse power law. The changes of dielectric behavior after irradiation were attributed to scission effects.     

Effect of Gamma Radiation-grafted Aramid Chopped Fibers as the Reinforcing Filler in Styrene–Butadiene Rubber Mixtures

Poly(p-phenylene-terephthalamide) PPTA chopped fibers, known as Kevlar 49 and related to aramid fibers, were subjected to graft copolymerization with styrene under the effect of gamma radiation. The effects of different parameters including irradiation dose, type of solvent and monomer concentration on the graft yield were studied. The surface-modified chopped fibers were introduced in styrene–butadiene rubber (SBR) mixtures. The properties of rubber mixtures and their corresponding vulcanizates were markedly affected depending on the fiber concentration. Grafting of styrene on to chopped PPTA fibers improves the mechanical properties of SBR–PPTA composites, especially in the presence of additional crosslining systems based on benzoyl peroxide EDMA (ethylene dimethacrylate) system. © 1997 John Wiley & Sons, Ltd.     

Radiation Vulcanization of Nitrile Butadiene Rubber/Butadiene Rubber Blends

Blends of nitrile butadiene rubber (NBR) with butadiene rubber (BR) with varying ratios have been prepared. Vulcanization of prepared blends has been induced by ionizing radiation of gamma rays with varying dose up to 250 kGy. Physical properties, namely soluble fraction and swelling number have been followed up using toluene as a solvent. Mechanical properties, namely tensile strength, tensile modulus at 100% elongation and elongation at break have been followed up as a function of irradiation dose, as well as blend composition. Thermal stability of blends was studied by TGA. The result indicated that the addition of NBR has improved the properties of NBR/BR blends. Also, NBR/BR blend is thermally stable than BR alone.     

TBP-DPPP两元体系辐射保护效应研究

本文报道磷酸三丁酯(TBP)-苯基膦酸二苯酯(DPPP)两元体系在γ-辐射作用下 DPPP 的辐射保护效应(a值),测定了该体系各类主要辐解产物的 G 值与 X_(DPPP)(DPPP mole 分数)的关系,并按 WAS 方程计算了 DPPP在两元体系中的辐射保护效应α值,还与其他辐射保护剂(苯、TOA、DBPP、DBBP)**的α值作了对比,表明DPPP 具有最大辐射保护能力。     

Effect of gamma radiation on microbial population of natural casings

The high microbial load of fresh and dry natural casings increases the risk of meat product contamination with pathogenic microorganisms, agents of foodborn diseases.

The aim of this work is to evaluate the killing effect of gamma radiation of the resident microbial population of pork and beef casings, to improve their hygiene and safety.

Portions of fresh pork (small intestines and colon) and dry beef casings were irradiated in a Cobalt 60 source with with absorbed doses of 1,2,5 and 10 kGy.

The D₁₀ values of total aerobic microorganisms in the pork casings were 1.65 kGy for colon and 1.54 kGy for small intestine. The D₁₀ value found in beef dry casings (small intestine) was 10.17 kGy. Radurization with 5 kGy was able to reduce, at least, 6 logs the coliform bacteria in pork casings. The killing effect over faecal Streptococci was 4 logs for pork fresh casings and 2 logs for beef dry casings. Gamma radiation with 5 kGy proved to be a convenient method to reduce substantially the microbial population of pork fresh casings. Otherwise, the microbial population of beef dry casings still resisted to 10 kGy.     

Effect of IR Radiation on the Properties of Polyacrylonitrile and Membranes on Its Basis

The effect of processing of polyacrylonitrile membranes by IR radiation at a temperature of 100–150°С is studied. The influence of the processing temperature on the film structure is ascertained. In a film heated at 100°С, a small amount of the double C=N bonds is found. Its further heating to 120°С is accompanied by a change in the chain conformation and an increase in the content of C=N bonds. It is shown that, upon IR processing at 120°С, polyacrylonitrile ceases to dissolve in N-methylpyrrolidone, dimethylacetamide, dimethylformamide, and dimethyl sulfoxide. Heating at 150°С gives rise to the appearance of conjugated С=N–C=N bonds. The analysis of AFM micrographs demonstrates that the processing of the membranes by IR radiation makes their surface rougher, while the size of pores changes slightly. The permeability of the membranes in various media is measured.     

Radiation synthesis of acrylic acid onto poly(tetraflouroethylene-perflourovinyl ether) film: Chemical modifications and electrical conductivity

Graft-polymerization of acrylic acid (AAc) monomer onto poly(tetraflouroethylene-perflouro vinyl ether) (PFA) copolymer film was carried out using gamma irradiation technique to synthesize grafted copolymer film PFA-g-PAAc (PFA-COOH). The effect of the dose on the degree of grafting of AAc onto PFA film was investigated. The results showed that the degree of grafting increases with increasing the irradiation dose. The grafted [PFA-COOH] film was chemically modified by reaction with aniline to produce modified [PFA-CO-NH-ph] film, followed by sulphonation reaction to introduce sulfonic acid (SO₃H) groups to get other modified [PFA-CO-NH-ph-SO₃H] film. The chemical structures of the grafted and modified films were identified by FT-IR, XRD, and SEM. It is of particular interest to measure the electrical conductivity of grafted and modified membranes as a function of degree of grafting. It was found that the conductivity of the grafted films increases with increasing the degree of grafting, however a slightly increase in conductivity was observed in [PFA-CO-NH-ph-SO₃H] sample. The electrical conductivity property of the modified PFA membranes suggests their possible use for fuel cell applications.     

Effect of Low-Dose Gamma Radiation on HIV Replication in Human Peripheral Blood Mononuclear Cells

Recent studies have demonstrated that UV light and x-irradiation enhance human immunodeficiency virus (HIV) gene expression. There are few published data on related effects of γ-radiation. This may be of clinical relevance, as radiotherapy has been used extensively for the treatment of acquired immunodeficiency syndrome associated conditions. With this in mind, we have studied the effects of γ-radiation on HIV replication in mononuclear cells (MC). These cells were obtained from five seronegative healthy donors, exposed to0–200 cGy γ-radiation, stimulated with phytohemagglutinin-P (PHA-P) for 24 h, infected with a laboratory strain of HIV (HTLV-IIIB, multiplicity of infection = 0.001), then carried in culture for 14 days. Overall, when considering p24 antigen levels on days 7 and 11 in cultures established from cells exposed to 50 cGy, the maximal levels were significantly higher than those measured in the parallel control cultures taken as a whole (P < 0.05), with viral replication enhanced as much as 1000-fold in one case. No significant cytotoxicity was observed following exposure to doses up to 50 cGy. The mechanism of the observed effect remains unknown but may relate to direct gene activation and/or free radical generation, leading to such activation. To date, there is no evidence that viral stimulation occurs following therapeutic radiation in a clinical setting.     

聚丙撑碳酸酯的辐射效应

研究了室温条件下聚丙撑碳酸酯(PPC)在钴-60和电子加速器辐照过程中的响应行为。结果表明,聚丙撑碳酸酯是一种辐射裂解型聚合物,其分子量随着辐射剂量的增加而减小。1mm厚PPC片材在室温和N2气保护条件下,其裂解G值为Gs,γ-ray=10.81;Gs,EB=4.9。不同的裂解G值表明,O2气在聚丙撑碳酸酯的辐射裂解过程中有重要影响。红外光谱研究表明,辐射后聚丙撑碳酸酯在3474cm-1处的峰宽峰高增加,表明其裂解后端—OH基增加。由于裂解作用,辐射后聚丙撑碳酸酯的抗张强度和断裂伸长率均下降。在通常的辐射消毒剂量范围内(25~50kGy),PPC的保留抗张强度大于23MPa,断裂伸长率大于4%,裂解后试样的力学性能依然能够满足实际应用需要,因此PPC可以经受辐射消毒。     

Gamma Radiation-Induced Graft Copolymerization of Styrene Onto Polyethyleneterephthalate Films: Application in Fuel Cell Technology as a Proton Exchange Membrane

Polyethyleneterephthalate (PET) based proton exchange membrane for using in fuel cells was successfully prepared by gamma radiation-induced graft copolymerization of styrene monomer onto PET film and the consequent selective sulfonation of the grafting chain in the film state using chlorosulfonic acid (ClSO₃H). The effects of grafting conditions (e.g., monomer concentration, irradiation dose) on the degree of grafting and sulfonation condition (e.g., optimum concentration of ClSO₃H) on the degree of sulfonation were studied. The degree of grafting, the degree of sulfonation and the physico-chemical properties (such as, water uptake, mechanical strength, thermal durability, hydrolytic stability, oxidative stability) of the gamma radiation-induced grafted membrane were found to be better when compared to those of the UV-radiation grafted membrane. The membrane shows higher ion exchange capacity (0.9 mmol g^?1) and higher proton conductivity (0.075 S cm^?1), similar to those of Nafion membrane.     

重组人干扰素—γ的凝胶色谱分离及其变性剂对分离结果的影响

使用十二烷基硫酸钠，盐酸胍和尿素三种不同的变性剂溶解基因重组人干扰素－Ｇａｍｍａ（ｒ－ＩＦＮ－γ）包含体，然后进行凝胶色谱分离。使用活性，电泳和高效疏水作用色谱三种方法，比较了三种变性剂对分离结果的影响，结果为：尿素溶解包含体后ｒ－ＩＦＮ－γ的分子量与杂质相差较大，盐酸胍溶解液经分离后ｒ－ＩＦＮ－γ比活最高，ＳＤＳ对ｒ－ＩＦＮ－γ的构象影响较大。     

昆虫几丁质抑制剂苯甲酰基苯脲类中苯甲酰基邻位取代基团对杀虫活性的影响

采用分子力学方法对苯甲酰基脲类昆虫几丁质抑制剂进行计算，发现苯甲酰基中的苯环与相连酰胺平面的夹角影响该类药物的杀虫活性，其中夹角在４０°左右杀虫活性最高。说明了分子中的构象影响杀虫活性。而这方面结果用传统的ＱＳＡＲ法难以得到，本计算结果较好的说明了苯甲酰基部分邻位取代基中２，６－二氟＞２－氯＞２，６－二氯＞２－氟的杀虫活性次序。     

Effect of chemical structure on the properties of some hydrogels prepared by using gamma radiation polymerization

Several hydrogels were prepared using radiolytic polymerization of aqueous solutions of acrylamide or acrylamide containing appropriate comonomer such as acrylic acid, maleic acid, itaconic acid, and maleic anhydride. The hydrogels have been prepared at an irradiation dose of 30 kGy. The effects of the chemical structure of the monomer(s) and crosslinking agents on the yield of homopolymer(s) or copolymers have been studied. These crosslinking agents include N, N′‐methylene dimethacrylate (MDA) and N, N′‐methylene bisallyamide (MBA). The hydrogels obtained were characterized using swelling technique, thermal and spectroscopic analysis. The results obtained showed that the prepared samples are able to reject sodium ions and are not able to recover the Basic Blue Dye from their aqueous solution. © 2005 John Wiley & Sons, Ltd.     

Preparation and Characterization of Poly Vinyl Alcohol/Poly Vinyl Pyrrolidone/Clay Based Nanocomposite by Gamma Irradiation

A series of PVA/PVP/clay nanocomposite were prepared by gamma irradiation with different clay contents of (0.15, 0.3, 1, 1.5, 3 and 5 wt%). The gelation content and swelling behavior were investigated. The morphology and structure of PVA/PVP/clay nanocomposite and dispersion of the clay nanoparticles in the polymeric matrix were examined by infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The introduction of clay into polymeric matrix was investigated by X-ray diffraction pattern (XRD) and Transmission electron microscope (TEM). It is observed that, the increase of the clay content causes a decrease in the swelling percent. The thermal stability studies confirmed that the introduction of clay lead to an increase in the thermal stability. The TEM results showed that the clay nanoparticles are interchelated or exfoliated in the polymeric matrix. Some desirable characteristics such as relatively good swelling and excellent barrier capability against microbe penetration suggested that PVA/PVP/clay nanocomposite can be a good candidate as a wound dressing.     

聚硅氧烷辐射效应研究进展

综述了聚硅氧烷在不同类型辐射下的辐射效应及其各种影响因素,并展望了提高聚硅氧烷耐辐射性能的途径。     

Removal of Some Pesticides from Aqueous Solutions using PVP/(AAc-co-Sty) Hydrogels Prepared by Gamma Radiation

Poly(N-vinyl-2-pyrrolidone)/(acrylic acid-co-styrene) [PVP/(AAc-co-Sty)] hydrogels were prepared by γ-irradiation to design as adsorptive systems. The adsorption of agricultural pesticides Fluometuron (FH), Thiophanate Methyl (TF) and Trifluralin (TI) on radiation-induced graft copolymeric adsorbents has been studied. The prepared hydrogels were characterized by FT-IR spectroscopy, scanning electron microscopy (SEM), and the thermal properties were studied by using thermal gravimetric analysis (TGA) and Differential scanning calorimetry (DSC). The ionic character of the prepared hydrogel was improved by treatment with alkaline (NaOH), sulfonation (Sf) and alkaline/sulfonation (NaOH/Sf). The swelling as a function of PVP concentration, AAc/Sty composition, irradiation dose, temperature and pH were studies. The adsorption of pesticides on the hydrogel matrix under different conditions was studied to determine which factors have the most affect and control the adsorption capacity of hydrogel. AAc/Sty composition, type of pesticide, temperature, concentration and pH of pesticide feed solution are greatly affect the pesticide uptake. It was found that the prepared hydrogels have a great efficiency to recover the pesticides from their solutions, the maximum pesticide uptake was found to be in the sequence: TI > TF > FH. The results concluded that the alkaline/sulfonation- treated PVP/(AAc-co-Sty) hydrogels possess high efficiency for removal of pesticides.     

Preparation of antimicrobial polycaprolactone‐silica composite films with nanosilver rods and triclosan using roll‐milling method

In this study, antimicrobial polycaprolactone composite films containing 12.5% silica and 0.15% silver nanorods were prepared using the roll‐milling method. The destruction of E. coli and S. aureus on the surface of the composite films was evaluated after 6 hr of incubation at 37°C. For the E. Coli, no bacterial contamination was detected after 6 hr and the film surface was completely disinfected with 100% reduction of the microbial contamination. For the S. aureus, 94% reduction of the bacterial contamination was observed after 6 hr. The results were compared with the composite films containing triclosan, a broad‐spectrum antimicrobial agent. The antimicrobial activity tests with 0.25% triclosan incorporated polycaprolactone‐silica composite films showed only 70% reduction of E. coli and 95% reduction of S. aureus after 6 hr. The results demonstrated that the use of silver nanoparticles in the biopolymer industry has huge potential for the self‐cleaning applications. Copyright © 2009 John Wiley & Sons, Ltd.