辐照在高分子材料制备与改性研究中的新动向

扼要介绍了含氟聚合物辐射交联、聚烯烃辐照改性、辐照过程中自由基形成机理、通过辐照制备具有某些特殊结构和性能聚合物的方法、辐照效应与聚合结构和辐照条件关系等领域研究的最近进展。     

纤维素辐照改性及其应用

辐照技术利用电离辐射诱发物理化学反应(例如交联、聚合、接枝、降解等)对材料进行加工或改性,与常规加工方法相比,具有节能、无环境污染等特点。将辐照技术应用于纤维素改性过程近年已成为非动力核技术应用领域研究的热点之一。本工作对目前纤维素的辐照技术及其基本反应机理进行了概述,其中包括纤维素膜材料、纤维素水凝胶、纤维素微晶/纳米材料,并对纤维素辐照改性过程的辐照环境,包括溶剂、敏化剂、温度、辐照剂量、环境氛围、结晶度等进行了总结。     

Role of lateral and radial irradiations on efficient microwave processing of food cylinders

A detailed theoretical analysis has been carried out to assess the role of lateral and radial irradiations on microwave heating of 2D cylinders for beef and oil samples. The lateral irradiation may represent the sample incident at one direction and the radial irradiation refers to sample exposed to uniform microwave intensities at all directions. For both lateral and radial irradiations, the effective microwave incidence from the source is assumed to be identical. A preliminary analysis on microwave heating of samples has been shown via average power within a sample vs sample radius for beef and oil samples. The samples with smaller radius are found to have larger average power with radial irradiation for both beef and oil samples. The hot spot formation within a sample is found to be a strong function of lateral/radial irradiation for various food dielectrics. The radial irradiation is found to be not favorable especially for large oil samples where the hot spot occurs at the center resulting in larger thermal gradient that contrasts earlier works which established that the radial irradiation minimizes the thermal gradient irrespective of sample size. The present work provides guideline on heating policy based on either lateral or radial irradiation depending on sample size and food dielectric properties.     

掺铈锂铝硅系统玻璃耐辐照性能的研究

采用LiO-Al2O3-SiO2系统为基础玻璃,CeO2为稳定剂,制备出耐辐照玻璃。研究了CeO2含量、熔制气氛及辐照剂量对玻璃耐辐照性能的影响。本文首次提出用耐辐照损伤因子Z表征玻璃的耐辐照稳定性。     

微波辐射合成苯甲酸和苯甲醇的研究

采用微波密闭合成反应技术,对Cannizzaro反应进行了研究,研究了碱(NaOH)的质量分数、微波功率、辐射时间、反应温度对该反应的影响,通过测定苯甲酸熔点、苯甲醇的折光率检测产品纯度。结果表明:在微波辐射条件下,该反应速度快,比传统合成方法缩短反应时间数十倍,产率最高达85%,同常规方法相比有不同程度的提高。     

Irradiation effects on polycaprolactone

The structure and some physical properties of γ-irradiated polycaprolactone (PCL), a semi-crystalline linear saturated polyester, were studied as function of the irradiation dose level. The critical dose level for gel formation is 26 Mrad and above this irradiation dose the number of scission events is similar to the number of crosslinking events. G.p.c. results show that the initial rather narrow molecular weight distribution gradually widens with increasing dose in the pre-gelation region. A significant difference between first and second d.s.c. scans of irradiated PCL is shown and explained. Scission and crosslinking reactions associated with the irradiation process occur preferentially in the non-ordered regions. Small irradiation doses, 2–5 Mrad, are shown to have a dramatic effect on the tensile elongation at break by converting ductile PCL samples into brittle materials.     

The effect of some fluoropolymers' structures on their response to UV irradiation

The response of three commercial fluoropolymer films, untreated and γ-irradiated poly(vinyl fluoride) (PVF), poly(vinylidene fluoride) (PVDF), and poly(ethylene-co-tetrafluoroethylene) (ETFE), to ultraviolet (UV) irradiation was studied. The changes in tensile properties, thermal behavior, and chemical structure were investigated. The UV resistance of the PVF film is the lowest, and that of ETFE is the highest among the studied films. The biaxially oriented PVF films undergo massive chain scission under the UV irradiation. The chain scission process in both oriented PVF and PVDF films, although at different levels, is accompanied by increased solubility, increased upper glass transition temperatures, and decreased elevated temperature shrinkage. The UV exposure at 50°C, above the polymers' T_g has annealing effects, mainly reflected by a shift to higher temperatures of their upper glass transition. PVF films are unaffected by a low-dose ionizing radiation. However, the γ-irradiated films show reduction of their UV resistance. PVDF films undergo both chain scission and crosslinking by γ radiation, and the addition of UV exposure mainly causes further chain scission. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1471–1481, 1998     

乙烯-四氟乙烯共聚物的辐照交联及辐照敏化剂研究

简述了高分子辐照加工及其影响因素,详细综述了乙烯-四氟乙烯共聚物(F40)辐照交联研究,同时归类分析了F40辐照交联的辐照敏化剂合成及开发研究,并对F40的辐照交联开发做了相应的展望.     

Sequential ion-electron irradiation of zirconium carbide ceramics: Microstructural analysis

Zirconium Carbide (ZrC_x) was irradiated with 10 MeV Au³⁺ ions to a dose of 10 displacements per atoms (dpa) and subsequently with 100 and 300 keV electrons in a transmission electron microscope (TEM). After ion irradiation, dislocation loops were observed in the microstructure and an increase in the number of carbon vacancies was revealed by Raman spectroscopy. Grazing incidence X-ray diffraction (GIXRD) analysis showed that neither amorphization nor oxidation occurred during ion irradiation of the specimen. Subsequent electron irradiation of the pre-implanted ZrC_x foil led to formation of nanosized tetragonal ZrO₂ precipitates (5−10 nm diameter) on the surface of the TEM lamella. The formation of the new oxide phase was not related to the electron beam-induced heating of the specimen, but to electron stimulated oxidation caused by the residual oxygen inside the transmission electron microscope. Changes in size and density of ZrO₂ crystallites were observed between the pristine and ion irradiated ZrC_x regions following electron irradiation, suggesting that the initial microstructure of the ZrC_x substrate played a key role in the nucleation and growth of the oxide islands. The obtained results provide insights into the microstructural response of ZrC_x to different types of radiation and the inadvertent effects of the electron beam during TEM analysis of in-situ and ex-situ ion irradiated ZrC_x. Additionally, the findings of this work suggest a method to prepare local ZrO₂ nanoprecipitates within ZrC_x grains by selective electron beam irradiation.     

不同方法制备高吸水性树脂性能的研究

以玉米秸秆为主要原料,除杂改性得羧甲基纤维素。然后以N,N’-亚甲基双丙烯酰胺为交联剂,分别采用传统加热聚合、微波辐照聚合和超声辐照法合成高吸水性树脂,并对吸水树脂的吸水倍率、吸盐水(质量分数为0.9%NaC l水溶液)倍率及保水能力进行测试。结果表明,同一比例下,超声辐照法制得的吸水性树脂的吸水倍率及保水能力均高于其它两种方法;超声功率为60%的条件下,吸水倍率可达635 g/g。微波辐照法制得的吸水性树脂的吸盐水倍率较高,微波功率为320 W时制得的吸水树脂吸盐水倍率可达65 g/g。     

茶螺烷的合成

以β-紫罗兰酮为起始原料,经环氧化、开环、超声辐射还原碳碳双键、羰基还原及硫酸氢钠脱水环化等5步反应合成了标题化合物.通过改进生产工艺,总收率可达57.8%.产物的结构经IR、~1HNMR、MS和元素分析确证.     

透明玻璃内部金纳米颗粒的空间选择性析出控制

使用飞秒激光或X射线辐照和热处理相结合 ,在掺杂金离子的玻璃中成功诱导出金纳米颗粒。样品经飞秒激光或X射线辐照后产生暗化 ,高温热处理后显示不同深浅的红色。通过吸收光谱和透射电镜测试研究了激光和X射线辐照对诱导金纳米颗粒析出的影响。实验结果表明 :飞秒激光或X射线辐照可以使玻璃内部金纳米颗粒析出的热处理温度降低 3 0℃和减小显色尺寸近 10nm。通过激光和X射线辐照 ,结合热处理可以在一块玻璃样品上实现多色显示。     

微波辐射制备聚维酮碘的研究

报道了用微波辐射制备聚维酮碘的研究，对混合加热法及溶剂法进行了比较，大大缩短了反应时间。具有时间短、产率高、操作简便等优点。     

Effect of irradiation modification above melting point on the wear resistance of polytetrafluoroethylene

The cross-linked polytetrafluoroethylene (PTFE) and PTFE/carbon fiber (CF) composites were synthesized through electron beam irradiation in the molten state of PTFE at a controlled temperature of 340 ± 3°C under an inert gas atmosphere for this study. The wear resistance of raw (raw-PTFE), irradiated modified PTFE (RM-PTFE), and CF-reinforced PTFE composites were evaluated using a friction and wear testing machine. The testing was conducted under varying ambient temperatures and dynamic loads. After irradiation, the samples were sectioned into specific sizes for subsequent testing purposes. Under the test conditions of 4.64 MPa positive pressure, 800 rpm speed, and a duration of 300 s at 20°C, the wear amount of PTFE after irradiation modification is significantly reduced from 1.4103 mm to only 0.0233 mm, representing a remarkable reduction by a factor of 60. Similarly, under the test conditions of 4.64 MPa positive pressure, 200 rpm speed, and a duration of 300 s at 20°C, the friction coefficient of PTFE after irradiation modification is substantially decreased from an initial value of 0.13 to just 0.03. The observed improvement can be attributed to the transformation of PTFE's crystalline form into spherulite, accompanied by a significant enhancement in the degree of cross-linking within its molecular chain. The PTFE was supplemented with 10% CF prior to irradiation. Under the test conditions of a positive pressure of 4.64 MPa, rotation speed of 800 rpm, and a duration time of 300 s at 20°C, the wear amount of the composite material measured only 0.0007 mm, representing a reduction by a factor of 2000 compared to that observed for pure PTFE. This improvement can be attributed to the CF filler's high wear resistance properties and the composite's enhanced thermal conductivity.     

水泥中放射性物质与比活度

放射性污染是建筑材料主要的环境污染方式之一,水泥以及水泥制品是建筑材料中重要的放射性污染源之一。建筑材料的放射性污染会在日常的工作和生活中严重危害人体的健康,故而水泥以及水泥相关制品中的放射性污染需要重点关注和讨论。本文主要讨论水泥中放射性污染物质的种类以及其对人体的危害,同时对我国水泥产品中主要放射性物质的含量进行分析,对比国家相关标准,了解现有水泥产品中放射性物质对人体的影响程度。     

Photocatalytic behavior of TiO_2 and ZnO prepared with different methods under ultraviolet and visible light irradiation

IntroductionIn recent years photocatalytic oxidation hasreceived considerable attention as an alternativeremediation technology since the method offers anumber of advantages over conventionaltechnologies [1,2] Elimination o…     

紫外红外共同固化环氧树脂的固化行为

采取先用紫外辐照引发,后改用红外辐照的方法固化添加了不同用量稀释剂的环氧树脂体系,通过凝胶转化率表征体系固化度,对不同体系的固化行为进行研究,并用Avrami方程分析体系的固化反应行为。结果表明,紫外辐照时间延长可以提高固化反应速率,而稀释剂用量的增加则会降低固化反应速率。用Avrami方程可以较好地描述终止紫外辐照后体系的固化反应行为,Avrami方程中的Avrami指数值和体系中活性反应中心有关。非平衡态热力学涨落理论分析表明,固化体系的松弛时间随着紫外辐照时间的增加而减小。     

Non‐Fickian vapor sorption kinetics in rubbery poly(dimethyl silamethylene) and the effect of radiation‐induced crosslinking

Successive sorption runs of n‐hexane vapor in supported amorphous poly(dimethyl silamethylene) films at 25°C are presented and discussed. Deviations from Fickian sorption kinetics were observed, and they were more distinct in the as‐prepared films and in the lower n‐hexane vapor pressure runs. Polymer films, γ‐irradiated to produce various degrees of crosslinking, exhibited closer conformity to Fickian sorption kinetics and enhanced diffusivity of n‐hexane vapor. These results were consistent with the presence in the as‐prepared polymer of some labile structural order (undetectable by differential scanning calorimetry or X‐ray diffraction), which tended to be eliminated by radiation‐induced crosslinking or strong swelling. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 226–230, 2005     

Dispersion control of immiscible polymer blend using selective heating by infrared laser irradiation

In this study, a selective heating technique by irradiating an infrared laser to an immiscible polymer blend was proposed to actively control the distribution of the dispersed phase in the blend. In the technique, the viscosity ratio between the matrix and dispersed phases was not changed by the molecular weight or shear rate but was changed by the controlled temperature distribution due to selective heating. The feasibility of the proposed technique was investigated through a numerical simulation of the temperature field and an experimental study using a test blend. The results showed that the technique successfully caused the deformation of relatively large droplets and enhanced the micro‐scale dispersion. It was also confirmed that the droplet size of the dispersed phase could be estimated by a simple method similar to the conventional technique: the chart of capillary number change with respect to the viscosity ratio. From the obtained results, it was concluded that the technique proposed in this study is a promising candidate for the development of a new blend process. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Microwave preparation and copper ions adsorption properties of crosslinked chitosan/ZSM molecular sieve composites

A novel chitosan‐based composite (CTS/ZSM) made of chitosan and ZSM molecular sieve was prepared under microwave irradiation and was used for the removal of Cu (II) ions from aqueous solution. The composites were characterized by FTIR spectra, XRD spectra, and thermogravimetric analysis. The effects of the ZSM content, amount of glutaraldehyde and pH value on adsorption properties of Cu (II) ions by CTS/ZSM were discussed in detail. Contrast with crosslinked chitosan (CCTS), the CTS/ZSM had higher adsorption capacity for Cu (II). Kinetic studies showed that the adsorption of Cu (II) onto CTS/ZSM composite had low correlation coefficients for the pseudo‐first and ‐second order model and intraparticle diffusion model. The equilibrium process was better described by the Langmuir than Freundlich isotherm model. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013