辐射引发淀粉-丙烯腈接枝共聚以制备高吸水树脂

在(60)Coγ射线引发下丙烯腈(AN)可以很容易地接枝到淀粉(S)上,这种接枝共聚物(SPAN)可以制成高吸水树脂(HS-PAN)。本文报导了有关影响接枝率的因素,如剂量、剂量率、淀粉-丙烯腈摩尔比,并测得接枝PAN的分子量级为10~5。对于HS-PAN的性质也作了初步探讨。     

偕胺肟水热碳对U(VI)-CO3/Ca-U(VI)-CO3的吸附性能研究

水热碳吸附材料具有制备工艺简单、合成条件温和、表面易改性等优点。本研究以可溶性淀粉为碳源, 在硝酸铈铵催化作用下, 将丙烯腈开环接枝到淀粉分子上, 通过水热反应和盐酸羟胺还原制备偕胺肟化水热碳(AO-HTC)。结合静态和动态吸附实验, 重点研究了溶液pH、碳酸根和钙离子浓度对AO-HTC吸附铀性能的影响, 通过Thomas和Yoon-Nelson模型探究AO-HTC吸附铀的动态过程。结果表明: 随着pH、碳酸根浓度和钙浓度的增加, AO-HTC吸附铀的容量逐渐降低; 掺杂5wt%AO-HTC土壤柱的穿透点和饱和点体积也随之减小。与纯土壤柱相比, 掺杂5wt%AO-HTC土壤柱的最大吸附容量(q_o)和吸附质穿透50%所需的时间(τ)增大了数倍。由此可见, AO-HTC是一种性能优异的可渗透性反应墙(PRB)介质, 有望用于修复铀污染土壤和地下水。     

紫外光引发淀粉接枝丙烯腈的研究(Ⅱ)

用紫外光引发玉米淀粉与丙烯腈接枝,对影响反应接枝百分率和接枝效率的诸因素进行了研究;对接枝皂化产物进行了吸水性试验;用ＩＲ对接枝产物进行了表征。     

Degradation of hexachlorobenzene by electron beam irradiation

Hexachlorobenzene removal efficiencies in different solvents by electron beam irradiation were investigated. Several factors that might affect the removal efficiencies were further examined. At 10 kGy, HCB degradation value was 85.8% in the solvent of acetone:water mixture (20:80, v/v), while at the same dose, the reduction value of 42.6% was achieved in hexane solvent. In the solvent of acetone:water mixture (20:80, v/v), Na(2)CO(3) as additive could enhance the degradation efficiency by 4.5%. However, Triton X-100, NaNO(3), NaNO(2) and H(2)O(2) as additives reduced the degradation value by 20.0%, 6.3%, 85.7% and 20.5%, respectively. Furthermore, the increase of these additives would result in the decrease of the degradation efficiencies. The pH value of the solvent of acetone:water mixture (20:80, v/v) could affect HCB removal efficiency. At pH 11.8, reduction value of 90.2% was achieved at 10 kGy, while at the same dose, at pH 2.7 and 6.8, the reduction values were only 82.4% and 86.9%, respectively. At the same time, the degradation value of pentachlorobenzene was 94.7% at 10 kGy. In the presence or absence of additives, pH value of the solvent of acetone:water mixture (20:80, v/v) became lower with increasing dose after electron beam irradiation.     

辐照处理对玉米醇溶蛋白流变性的影响

为了改善玉米醇溶蛋白在复合材料加工中的流变特性,研究了辐照剂量、温度、剪切速率对玉米醇溶蛋白流变性的影响。结果表明,玉米醇溶蛋白经辐照处理后具有假塑性流体特性,呈现"剪切变稀"现象。辐照剂量、剪切温度和剪切速率对玉米醇溶蛋白的流变性有显著影响。随着辐照剂量增加,溶液黏度呈现先增加后减小的趋势,当辐照剂量为10kGy时,黏度最高;随着剪切温度的增加,溶液黏度呈现先下降后增加的趋势,当温度为308K时,黏度最低;随剪切速率的增加,溶液的黏度降低,但当剪切速率接近100s-1时,黏度变化不明显。     

聚丙烯胺肟螯合纤维的合成及性能

采用＾６０Ｃｏ－γ射线预辐照方法合成了聚丙烯胺肟（ＰＰＡＯ）螯合纤维。研究了影响接枝率和胺肟基团含量的因素。结果表明，接枝率随预辐照剂量、单体浓度、反应时间和反应温度的增加而增加。羟胺溶液的ｐＨ＝７时，胺肟基团含量最高。胺肟化反应时间大于１．５ｈ，胺肟基团含量不再增加。该纤维对金的吸附容量为９９．１ｍｇ／ｇ干纤维，对钯和铜也有较好的吸附性能。     

Free volume changes in gamma-irradiated polyethylene and polytetraflourethylene

Positron lifetime spectrum was measured and the change of the free volume was studied for commercial polyethylene (PE) and polytetrafluoroethylene (PTFE) during gamma-irradiation processing up to 265 kGy. The free volume size increases but the crystallinity decreases as irradiation dose increases in PE. Both qualities (free volume size and crystallinity) in PTFE display an opposite behavior. The fractional free volume reduces monotonically with increasing irradiation dose in both PE and PTFE. The competition between the crosslinking and the splitting decomposition in polymers can be used to understand the free volume changes with irradiation dose.     

淀粉-丙烯酸-丙烯酰胺三元接枝物的制备及性质研究

在60 Co间歇式共辐射条件下探讨了淀粉与丙烯酸和丙烯酰胺流变相态的接枝共聚反应;采用FTIR和SEM对接枝产物共聚物进行了结构表征;考察了丙烯酰胺和丙烯酸盐单体的配比、原料配比、辐射剂量等因素对聚合物吸水率、耐盐性等的影响。结果表明,在没有添加任何化学引发剂的情况下可以得到较高耐盐性和高吸水速率的淀粉-丙烯酸-丙烯酰胺共聚物,克服了传统生产方法中耐盐性低、吸水速度慢、高污染、高耗能等问题。     

Radiation enhanced modification of HDPE for medical applications

Comparison of gamma irradiation induced change in properties in terms of thermal and mechanical properties between two grades of HDPE and UHMWPE was carried out. It was found that the responses to irradiation of two grades of HDPE investigated were close whereas a difference in response was found between HDPE and UHMWPE. The irradiation dose that caused the lowest wear and highest hardness for UHMWPE was 500 kGy. When irradiation dose was above 500 kGy, no significant changes in wear and hardness properties were observed. The irradiation dose for HDPE, both 2208J and 7000F, that caused the wear resistance and hardness comparable to irradiated UHMWPE at 500 kGy was 1000 kGy. In addition, the dose of 750 kGy was needed for HDPE to achieve the similar level of wear resistance as non-irradiated UHMWPE. ©2003 Kluwer Acadamic Publishers     

Free Volume Changes in γ-Irradiated Polyethylene and Polytetraflourethylene

1. IntroductionPolymers, though very useful in daily life, arestructurally complicated materials. Their chemical nature and structural specificity are not clearlyunderstood yet. As a structural sensitive probe,positrons have been applied to detect the microscopic free-volume in polymer solids and films[1'2].In polymers, several mechanisms of positron annihilation are possible, e.g. pick--off annihilation ofortho-positronium (o--Ps), self~annihilation of parapositronium (p-Ps), annihilation of…     

Gamma irradiation effect on optical and dielectric properties of potassium dihydrogen phosphate crystals

The effect of Co⁶⁰ gamma-ray irradiation on potassium dihydrogen phosphate crystals is investigated at doses ranging from 1 kGy to 100 kGy with different diagnostics, including UV–Vis absorption spectroscopy, fluorescence spectroscopy, DC electrical conductivity, positron annihilation lifetime spectroscopy and Doppler-broadening spectroscopy. The optical absorption spectra show a wide absorption band between 250 and 400 nm after γ-irradiation and its intensity increases with the increasing irradiation dose. The simulation of radiation defects show that this absorption is assigned to the formation of substitutional impurity defects due to Al, Mg ions substituting for K ions. The fluorescence peak at 355 nm blue shifts after irradiation. The fluorescence intensity is observed to increase with the increasing irradiation dose. The positron annihilation lifetime spectroscopy is used to probe the evolution of vacancy-type defects in potassium dihydrogen phosphate crystal. The variation of size and concentration of vacancy-type defects with the different irradiation dose is investigated. The Doppler-broadening spectroscopy gives direct evidence of the formation of irradiation-induced defects. The dc electrical conductivity of γ-irradiated potassium dihydrogen phosphate crystals increases with the increasing irradiation dose when the dose is less than 10 kGy, whereas keeps constant at high irradiation dose of 100 kGy. The increase of electrical conductivity is associated with the increase of the proton defect concentration in the crystal. A possible explanation about the change of proton defect concentration with irradiation dose is presented.     

Adsorption of Some 1. 4-Benzodiazepines on Insoluble Tablet Excipients and Charcoal

Abstract

The adsorption of five widely used 1. 4-benzodiazepines on talc, calcium phosphate, magnesium stearate, microcrystalline celluloses, ethyl cellulose and starch was studied. Adsorption of these compounds on charcoal was also investigated for comparison. Diazepam was found not to be adsorbed on talc, calcium phosphate and magnesium stearate. A relatively low adsorption of the drug by cellulose and starch was measured. The amount of diazepam adsorbed per unit weight of ethyl cellulose was high in water and in phosphate buffer, while no adsorption could be measured in 0.1 N HCL. The drug interact with ethyl cellulose at higher concentrations (100-180 mcg/ml). The UV and IR of the reactants and products were studied.

The adsorption of nordiazepam, nitrazepam, flunitrazepam and chlordiazepoxide onto ethyl cellulose and charcoal from their aqueous solutions was also studied. Diazepam and nordiazepam showed the highest adsorption on ethyl cellulose. The desorption of benzodiazepines from ethyl cellulose in 0.1 N HC1 was at the following decreasing rate: flunitrazepam, chlordiazepoxide, nitrazepam, diazepam, nordiazepam.     

Electron paramagnetic resonance of human tooth enamel at high gamma ray doses

Powdered human tooth enamel was exposed to 60Co gamma rays up to a dose of 100 kGy. The electron paramagnetic resonance (EPR) signal intensity (1) of the radiation-generated carbon dioxide radicals was measured for dependence on absorbed dose (D). The EPR dose response can be fitted with an exponential saturation function I = I(M)[1 - exp(-D/D37)] with the saturated signal intensity (I(M)) and the dose saturation value (D37). The obtained value D37 = 9.64 (+/- 0.96) kGy (measured at least one month after irradiation) exceeds those given in the literature. The saturated concentration of orthorhombic CO2- radicals was estimated at 6.5 x 10(17) per gram of enamel by comparing the integrated EPR spectra of enamel and a standard MgO:Cr probe. For enamel samples, which were heated before irradiation for one hour at +405 degrees C, the value of D37T = 3.89 (+/- 0.44) kGy and the saturated value of CO2- radicals 3.4 x 10(17) per gram of enamel were lower than for unheated samples. The initial rise of the signal with the dose was slightly higher (8.8 x 10(13) radicals/g x Gy) for heated compared with unheated samples (6.8 x 10(13) radicals/g x Gy).     

电子束辐照对高密度聚乙烯/炭黑导电复合材料电阻率的影响

研究了电子束辐照固态和熔融态高密度聚乙烯／炭黑（ＨＤＰＥ／ＣＢ）导电复合材料的电性能随辐照温度和辐照剂量的变化。结果表明,对固态或熔融态辐照材料而言,其电阻率均随温度的升而而增大。等剂量下,固态辐照材料的ＰＴＣ强度比熔嘈态辐照的要高,两各状态经高剂量辐后其材料ＮＴＣ效应消失,,ＤＳＣ测试证明电阻率的２与基体的结晶行为以及交联链的形成密切相关。     

Electron beam irradiation of denture base materials

Electron beam irradiation can be used to influence the properties of polymers. It was the aim of this study to investigate whether PMMA denture base materials can benefit from irradiation in order to have increased fracture toughness, work of fracture or hardness. Rectangular specimens of heat-and auto-curing denture base materials were electron beam irradiated (post-cured) with 25, 100 and 200 kGy using an electron acceleration of 10 MeV or 4.5 MeV respectively. Fracture toughness, work of fracture, Vickers hardness and colour changes were measured and compared with not-irradiated specimens.The toughness, work of fracture and hardness increased using 10 MeV with a dose of 25 kGy and with 100 kGy using 4.5 MeV. However, the clinical use may not benefit from the observed small changes. Higher dosage (200 kGy) decreased the values significantly. The colour changes reached a level which was found to be not clinically acceptable. Conclusion: PMMA denture base materials do not benefit from post-curing with electron beam irradiation.     

Effects of electron beam irradiation on antioxidants in commercial polyolefins: Determination and quantification of products formed

The influence of electron beam irradiation on antioxidants present in food packaging materials (OPP and LDPE) was studied. After irradiating the materials at dose levels of 2, 5,10 and 25 kGy, we have shown a partial disappearance of the antioxidant (Irganox 1010, Irganox 1076 and Irgafos 168) and a release of three compounds resulting from the antioxidants degradation related to the irradiation dose. Two of these degradation compounds have been analysed quantitatively: the 2,4-di-tert.-butyl-phenol and the 2,6-di-tert -butyl-p-benzoquinone. The third compound is a phosphate resulting from a phosphite stabilizer (Irgafos 168).     

Effect of Silane Coupling Agents on Rice Straw Fiber/Polymer Composites

The effect of coupling agents and electron beam (EB) irradiation dose on the mechanical properties of composites made from rice straw fibers and polymers have been studied. Samples were made by hot pressing of mix composition at 130°C. The pressed samples were subjected to electron beam irradiation dose ranged from 10 to 50?kGy. Increasing the electron beam irradiation dose increased the value of flexural strength, modulus of elasticity and impact strength. It was also observed that, the properties of composites containing γ-aminopropyltrimethoxy silane (A-1100) are lower than those of composites containing N-(2aminoethyl)-3-amino propyltrimethoxy silane (A-700) coupling agents. These are attributed to a hydrogen bonding formation between the amine or protonated amine and the hydroxyl groups of rice straw fibers. The presence of coupling agents in the composites during the EB irradiation process produce a more free radicals which are enough to form a chemical bonding between the rice straw fiber and polymer. The thickness swelling and water absorption values decrease with increasing the EB irradiation dose with presence of coupling agents in the composite.     

The effect of ionizing radiation on metoprolol

The influence of ionising radiation on physico-chemical properties of metoprolol tartrate (MT) in solid phase was studied. The compound was irradiated by radiation produced by a beam of high-energy electrons in an accelerator, in doses from 25 to 400 kGy, and the possible changes in the samples were detected by organoleptic analysis (colour, forms, clarity), chromatographic and spectrometric methods. Already at the standard sterilisation dose of 25 kGy, the presence of free radicals (0.3764 × 10¹⁶ spin/g) and a decrease in the melting point by 1°C were noted. At higher doses of irradiation products of radiolysis appeared (100 kGy) and the colour was changed from white to pale cream (200 kGy). Our observation was that with increasing mass loss of MT after irradiation with 100, 200 and 400 kGy, the concentration of free radicals increased from 1.0330 to 1.6869 × 10¹⁶ spin/g. The radiolytic yield of total radiolysis was 4.54 × 10⁷ mol/J for 100 kGy, 7.42 × 10⁷ mol/J for 200 kGy and 4.74 × 10⁷ mol/J for 400 kGy. No significant changes were observed in the character of FT–IR spectra, but in UV an increase in intensity of the band at the analytical wavelength was noted. As follows from the results MT shows high radiochemical stability for the typical sterilisation doses 25–50 kGy, and will probably be able to be sterilised by radiation in the dose of 25 kGy.     

交联型偕胺肟型凝胶的制备及对镓离子的吸附性能

以水合联胺为交联剂,利用"热致相分离"原理制备了聚丙烯腈/二甲亚砜(PAN/DMSO)交联(C-PAN)凝胶,将其进一步与羟胺(NH2OH)反应后得到交联型偕胺肟(C-PAO)凝胶,交联型偕胺肟凝胶可用于吸附强碱性模拟拜耳溶液中的镓离子(Ga~(3+))。文中采用了超临界CO_2萃取干燥法取代真空干燥,并探讨了不同溶度参数的交换溶剂对凝胶孔径的影响。红外测试结果表明,凝胶成功偕胺肟化且偕胺肟基团与镓离子发生了螯合作用;扫描电镜照片显示,当交换溶剂的溶度参数与PAN基体的差值(Δδ)增加,得到的凝胶孔径减小;吸附测试结果显示,偕胺肟凝胶对模拟拜耳溶液中镓离子的饱和吸附量为15.8 mg/g,平衡时间为140 min。     

Thermal and optical properties of electron beam irradiated cellulose triacetate

Cellulose triacetate (CTA) is a polymer which is widely used in a variety of applications in the field of radiation dosimetry. In the present work, CTA samples were irradiated by electron beam in the dose range 10–200 kGy. The modifications in the electron irradiated CTA samples as a function of dose have been studied through different characterization techniques such as thermogravimetric analysis, differential thermal analysis and color-difference studies. The electron irradiation in the dose range 80–200 kGy led to a more compact structure of CTA polymer, which resulted in an improvement in its thermal stability with an increase in activation energy of thermal decomposition.

Also, the variation of melting temperatures with the electron dose has been determined using differential thermal analysis (DTA). The CTA polymer is characterized by the appearance of one endothermic peak due to melting. The results showed that the irradiation in the dose range 10–80 kGy causes defects generation that splits the crystals depressing the melting temperature, while at higher doses (80–200 kGy), the thickness of crystalline structures (lamellae) is increased, thus the melting temperature increased.

In addition, the transmission of these samples in the wavelength range 200–2500 nm, as well as any color changes, was studied. The color intensity ΔE^* was greatly increased with increasing the electron beam dose, and accompanied with a significant increase in the blue color component.