Pu在膨润土层中的反应性迁移模拟研究(2)——Pu的种态分布及反应性迁移分析

为评估柯尔碱膨润土工程屏障材料的安全性能,采用考虑渗流扩散、溶解-沉淀、表面配位吸附、放射性衰变等多过程动态耦合的反应性迁移模拟方法,综合运用TOUGHREACT等程序开展了Pu在柯尔碱膨润土层中反应迁移的数值模拟,结合地下水-膨润土体系演化模拟分析了Pu的种态分布特征,叠加表面配位模型预测分析了Pu的长期迁移规律。结果表明:地下水中Pu主要以难迁移的Pu(OH)_(4)(aq)形式存在;由于膨润土的低渗透性和强吸附性,正常情景下Pu的扩散范围很小而将长期滞留于1 m厚膨润土中;在忽略强吸附阻滞作用的保守情景下,Pu在渗流作用下可扩散迁移出膨润土层;考虑到长时间尺度下不可避免存在的不确定性,建议重视渗流扩散为主导的其他过程和情景研究。

南海环境中Pu、Np的清除机制和空间迁移模拟研究

海洋环境中Pu、Np两种放射性元素源自人类核活动.由于洋流、海陆交汇等多重效应导致Pu、Np被富集于边缘海区域,威胁人类的环境安全.目前国内外对海洋中Pu、Np的研究未成体系,研究方法多局限于含量分析.为研究河流输入量、地形、气候等因素对于海洋中Pu、Np清除效率的影响,本文采用扇形磁场高分辨率质谱(SF-ICP-MS)对南海水体、沉积物中的Pu、Np比活度,^(240)Pu/^(239)Pu和^(237)Np/^(239)Pu原子比进行精确分析.在模拟海洋生态环境和顺序提取实验基础上,研究Pu、Np在海洋中的扩散问题.根据得到的Pu、Np比活度和同位素原子比等在水体、颗粒物以及沉积物中的分布数据,拟合得到Pu、Np在南海传输和扩散的特征关键参数,以解释南海海水中Pu、Np的清除机制.最后利用数据构建南海Pu、Np空间迁移与清除的稳态模型(S-ADE),后续将通过模拟及现场取样分析对模型进行相互校验.研究结果可为核事故中Pu、Np等放射性污染物的溯源与迁移的快速分析与综合评估,以及放射性污染防护与治理提供方案.

热中子诱发^(239)Pu裂变气体产物核Xe产额的评价

裂变产额数据是核反应堆设计与运行、核装置设计与测试以及乏燃料处理与核废料管理等应用中的重要数据,同时也是裂变物理研究的基础数据。采用基于Zp模型的裂变产额统一评价方法,对中子诱发^(239)Pu裂变气体产物核Xe的A=131~135,138,140等7个同位素核所在质量链上的产物核产额进行了分析评价,获得了能量为0.0253 MeV(T)、裂变谱(F)和14 MeV(H)的中子诱发^(239)Pu裂变产物核Xe的7个同位素核的独立产额和累积产额评价结果,并建立了ENDF/B-VI格式数据库。与传统评价方法比较,统一评价方法考虑了同一质量链上的独立产额、累积产额的相互关联,给出的产额相互自洽,增加了产额评价数据的可靠性。其中^(131-133)Xe考虑了先驱核碘的贡献,累积产额比JEFF-3.3和ENDF/B-VIII.0有所增加。^(134)Xe的产额存在分歧,通过分析,采用了较高的实验数据,认为该数据比较合理。

Preparation and Properties of Electrospun Polyvinylidene Fluoride (PVDF)/Polyurethane (PU) Composite Nanofiber Membranes

Polyvinylidene fluoride(PVDF)/polyurethane(PU)composite nanofiber membranes were prepared by mixing PVDF and PU at different mass ratios.The microstructure and the crystal structure of the composite nanofiber membranes were analyzed by scanning electron microscopy(SEM),Fourier transform infrared(FTIR)spectroscopy and X-ray diffraction(XRD).The hydrophilicity,mechanical properties and piezoelectric properties were also tested.Results showed that when the mass ratio of PVDF to PU was 9∶1,the fiber membrane had the best microstructure,and the crystal form of PVDF changed fromαcrystal toβcrystal in the electrospinning.The addition of PU improved the hydrophilicity,mechanical properties,and piezoelectric signal of the fiber membrane.When the mass ratio of PVDF to PU was 9∶1,the tensile strength reached the peak value of(10.39±0.41)N,and the output voltage reached the maximum value of(1.98±0.12)V.

CPE增容TPU/PVC共混弹性体及相形态

为提高热塑性聚氨酯弹性体(TPU)与聚氯乙烯(PVC)的相容性,以氯化聚乙烯(CPE)为增容剂,经双螺杆挤出机熔融共混制备TPU/PVC共混型热塑性弹性体,测试了不同CPE用量的共混弹性体的拉伸强度、断裂伸长率和硬度等力学性能,以及动态流变性能、动态力学性能和热稳定性。通过扫描电子显微镜(SEM)对共混弹性体的相态结构进行研究。结果表明,当TPU/PVC质量比为70/30时,共混弹性体综合力学性能最佳,拉伸强度为19.92 MPa,断裂伸长率为972%。随着CPE用量的增加,TPU/PVC共混弹性体的拉伸强度、断裂伸长率、硬度等均先增大后减小;CPE用量为6份时,TPU/PVC共混弹性体拉伸强度达到最大,为23.73 MPa,相较未加CPE时提高19.1%。加入CPE的共混弹性体复数黏度和储能模量均呈下降趋势。此外,CPE的加入还能有效提升弹性体高温热稳定性,TPU和PVC两种组分的损耗因子峰内移靠近,共混弹性体液氮脆断面的SEM照片显示PVC相筹明显变小且更为均匀,以上说明CPE对共混弹性体的增塑、增容作用明显,且CPE用量为6份时增容效果最佳。

舞蹈器材用改性PU胶粘剂的耐老化性能测试分析

针对聚氨酯(PU)胶粘剂在使用与存储环节较容易出现的老化问题,研制改性剂TiO_(2)-TDI粒子,其原料为甲苯2,4-二异氰酸酯(TDI)与抗氧剂2246、纳米二氧化钛(TiO_(2),金红石型),通过对二氧化钛、TiO_(2)-TDI粒子结构的热失重分析(TGA)、傅里叶变换红外光谱(FTIR)、紫外-可见漫反射(UV-vis)等加以表征。结果显示,在二氧化钛表面,通过化学键作用与TDI成功键合,完成了该改性粒子制备。此粒子对可见光、紫外线有着更强水平的吸收能力,通过化学法成功完成抗热氧化、光氧化的改性剂,可以使得PU胶粘剂耐老化性能得到显著改善,更好地应用于舞蹈器材中。

Synthesis of a Novel UV Curable Aqueous Dispersion Polyurethane PDHA-PEDA-PU and the Properties of Cured Film

A novel ultraviolet （UV） curable aqueous dispersion polyurethane PDHA-PEDA-PU was synthesized based on isophorone diisocyanate （IPDI）, polyester dihydric alcohol （PDHA）, dimethylol propionic acid （DMPA）, pentaerythritol diacrylate （PEDA）, 2-hydroxyethyl acrylate （HEA） and triethylamine （TEA）. Acrylate groups were incorporated in the side and end of PDHA-PEDA-PU chain. The C=C content in the chain can be controlled easily through the change of IPDI/PDHA/PEDA ratio. Fourier transform infrared spectroscopy （FTIR） was used to identify the structure of prepolymer, aqueous dispersion and cured polyurethane. The curing rule of the polyurethane for different C=C content has been investigated depending on the change of C=C content during the curing process. The hardness, thermal stability and scrub resistance to MEK of UV cured PDHA-PEDA-PU were also discussed for the samples with different C=C content.

钢-PPUC组合正交异性钢桥面板疲劳性能

为有效解决传统钢桥面病害,提出了钢-聚酯型聚氨酯(钢-PPUC)混凝土组合桥面板结构,开展了正交异性钢桥面板的疲劳性能研究。以马鞍山公铁两用大桥为工程背景,建立局部有限元模型,采用热点应力法获得车轮荷载作用下钢桥面易疲劳开裂部位的应力响应,基于疲劳应力幅进行疲劳强度评估。考虑不同温度、不同铺装层厚度和不同结构形式条件下PPUC铺装层对正交异性钢桥面板疲劳性能的影响。结果表明:高弹性模量的PPUC铺装层对正交异性钢桥面板典型疲劳细节处的应力具有明显的改善作用;顶板与纵肋连接部位疲劳细节应力幅降幅最大,顶板与纵肋连接处桥面板细节、纵肋与横隔板连接处纵肋细节和纵肋对接焊缝细节均满足抗疲劳开裂要求;不同温度作用下的弹性模量变化对典型疲劳细节等效应力幅的影响是非线性的,铺装层厚度变化对典型疲劳细节等效应力幅的影响是近似线性的;为兼顾正交异性钢桥面板受力性能和行车舒适性两方面要求,提出了单层和双层复合型PPUC结构形式,计算得到2种结构形式对各疲劳细节应力幅最大降幅为21%~56%,最小降幅为8%~36%,为钢-PPUC组合桥面板抗疲劳设计提供理论依据。

Synthesis of Waterborne Polyurethane Modified by Nano-SiO_2 Silicone and Properties of the WPU Coated RDX

A series of nano silica/silicone modified waterborne polyurethane(WPU) have been synthesized from polytetramethylene glycol and isophorone diisocyanate, dihydroxymethyl propionic acid and triethylamine, ethylenediamine, trimethylolpropane, nano-SiO2 and the silane coupling agent KH550. The effect of the dosage of nano-SiO2 on the WPU-Si membrane and the coated RDX(cyclotrimethylenetrinitramine) particles have been studied in terms of their surface properties, mechanical properties, and thermal stability. The results showed that with the increase of Si content, the stability of the emulsion reduced gradually. The material with more Si content displayed an increased thermodynamic stability, an increased high temperature resistance, an increased tensile strength and a decreased elongation at break. With the increase of Si content, the surface tension of the material decreased, the bibulous rate reduced, and the contact angle increased gradually, so that the surface tension of the polyurethane and RDX are close to each other which could improve the performance of coating.

基于Bootstrap-C_(pu)的机床进给机构装配过程能力评估方法

机床进给机构装配过程是其装配质量形成的过程,由于受5M1E因素影响,进给机构装配过程能力可能不足,会导致进给机构装配质量出现较大波动,甚至出现不合格产品。为此,基于C_(pu)和Bootstrap理论,构建了基于Bootstrap-C_(pu)的进给机构装配过程能力评估方法,并进行了实际应用。结果表明:在95%置信度条件下,该批机床进给机构装配过程能力是足够的,其装配质量波动较小。

Soy Protein Isolate Non-Isocyanates Polyurethanes(NIPU)Wood Adhesives

Soy-protein isolate(SPI)was used to prepare non-isocyanate polyurethane(NIPU)thermosetting adhesives for wood panels by reacting it with dimethyl carbonate(DMC)and hexamethylene diamine.Both linear as well as branched oligomers were obtained and identified,indicating how such oligomer structures could further cross-link to form a hardened network.Unusual structures were observed,namely carbamic acid-derived urethane linkages coupled with lactam structures.The curing of the adhesive was followed by thermomechanical analysis(TMA).It appeared to follow a two stages process:First,at a lower temperature(maximum 130℃),the growth of linear oligomers occurred,finally forming a physically entangled network.This appeared to collapse and disentangle,causing a decrease of MOE,as the temperature increases.This appears to be due to the ever more marked Brownian movements of the linear oligomer chains with the increase of the temperature.Second,chemical cross-linking of the chains appeared to ensue,forming a hardened network.This was shown by the thermomechanical analysis(TMA)showing two distinct MOE maxima peaks,one around 130℃ and the other around 220℃,with a very marked MOE decrease between the two.Plywood panels were prepared and bonded with the SPI-NIPU wood adhesive and the results obtained are presented.The adhesive appeared to pass comfortably the requirements for dry strength of relevant standards,showing to be suitable for interior grade plywood panels.It did not pass the requirements for wet tests.However,addition of 15%of glycerol diglycidyl ether improved the wet tests results but still not enough to satisfy the standards requirements.

Polyurethane grouting materials with different compositions for the treatment of mud pumping in ballastless track subgrade beds:properties and application effect

Mud pumping in subgrade beds under ballastless tracks will deteriorate the dynamic performance of infrastructure under railway lines,reduce the smoothness of the railway lines,and seriously affect the comfort and safety of the trains.Due to their good mechanical properties,twocomponent polyurethane materials can be used for grouting to treat the fouling problems caused by ballastless track mud pumping.To develop a polyurethane formula suitable for the treatment of ballastless track mud pumping,we first performed indoor experiments to investigate the mechanical properties and gelation time of polyurethane elastomers synthesized with different raw material composition ratios,to determine an optimal composition ratio of the raw materials.Then,we conducted a dynamic field test to verify the remediation effect of the polyurethane material fabricated according to the design ratio.The results showed that polyurethane grouting material with the selected design ratios improved the contact characteristics between the surface layer of the subgrade bed and the base plate in the area,coordinating the dynamic response between the track structure and the subgrade bed.Thus,the obtained polyurethane grouting material could be used to renovate mud pumping areas of ballastless tracks with a good treatment effect.

Effect of Amine Type on Lignin Modification to Evaluate Its Reactivity in Polyol Construction for Non-Isocyanate Polyurethanes(NIPU)

Polyols are groups of organic compounds which contain carbon and are randomly linked to other atoms,especially carbon-carbon and carbon-hydrogen.These compounds are mainly used as reactants to make other polymers.Among biopolymers,lignin is regarded as the base of a new polymer in polyol construction.The present study aimed to investigate the effects of amine type(diethylenetriamine and ethylenediamine)on the modification of lignin-based polyols,so as to provide an alternative to petroleum polyols and,in turn,increase functional groups and reduce their harm to humans’health and the environment.To this aim,first,lignin was extracted from raw liquor.Next,the extracted lignin was reacted with diethylenetriamine(DETA)and ethylenediamine(EDA).Finally,the Mannich method was used for the reaction between amine lignin and propylene carbonate.The results of the Fourier Transform Infrared(FTIR)spectroscopy analysis showed that modification with DETA led to more structural change in lignin and peak 1100 indicates the presence of C–O bond related to urethane bonds in modified lignin.Moreover,adding propylene carbonate to aminated lignin did not result in much change in the results of the FTIR analysis.Additionally,urethane bonds can be seen in the results of GPC at 400℃–500℃.Furthermore,a slight decrease in thermal stability was observed in lignin modified with amine and propylene carbonate,compared to the raw lignin sample.

Hydrolysable Chestnut Tannin Extract Chemical Complexity in Its Reactions for Non-Isocyanate Polyurethanes(NIPU)Foams

Non-isocyanate polyurethane(NIPU)foams from a commercial hydrolysable tannin extract,chestnut wood tannin extract,have been prepared to determine what chemical species and products are taking part in the reactions involved.This method is based on two main steps:the reaction with dimethyl carbonate and the formation of urethane bonds by further reaction of the carbonated tannin with a diamine-like hexamethylene diamine.The hydroxyl groups on the tannin polyphenols and on the carbohydrates intimately linked with it and part of a hydrolysable tannin are the groups involved in these reactions.The carbohydrate skeleton of the hydrolysable tannin is also able to participate through its hydroxyl groups to the same two reactions rendering the whole molecular complex able to react to form NIPUs.The analysis by Matrix-Assisted Laser Desorption Ionization(MALDI-TOF)mass spectrometry and 13C Nuclear Magnetic Resonance(13C NMR)to further investigate the reaction mechanisms involved revealed the unsuspected complexity of chestnut hydrolysable tannin,with different fragments reacting in different manners forming a hardened network of considerable complexity.As the morphology and performance of these types of foams changes slightly with the change in the amount of glutaraldehyde and hexamine hardeners,the best performing foam formulation previously determined was scanned by SEM and analysed chemically for the structures formed.

Improving the Sound Absorption Properties of Flexible Polyurethane (PU) Foam using Nanofibers and Nanoparticles

Polyurethane foam as the most well-known absorbent materials has a suitable absorption coefficient only within a limited frequency range.The aim of this study was to improve the sound absorption coefficient of flexible polyurethane(PU)foam within the range of various frequencies using clay nanoparticles,polyacrylonitrile nanofibers,and polyvinylidene fluoride nanofibers.The response surface method was used to determine the effect of addition of nanofibers of PAN and PVDF,addition of clay nanoparticles,absorbent thickness,and air gap on the sound absorption coefficient of flexible polyurethane foam(PU)across different frequency ranges.The absorption coefficient of the samples was measured using Impedance Tubes device.Nano clay at low thicknesses as well as polyacrylonitrile nanofibers and polyvinyl fluoride nanofibers at higher thicknesses had a greater positive effect on absorption coefficient.The mean sound absorption coefficient in the composite with the highest absorption coefficient at middle and high frequencies was 0.798 and 0.75,respectively.In comparison with pure polyurethane foam with the same thickness and air gap,these values were 2.22 times at the middle frequencies and 1.47 times at high frequencies,respectively.Surface porosity rose with increasing nano clay,but decreased with increasing polyacrylonitrile nanofibers and polyvinyl fluoride nanofibers.The results indicated that the absorption coefficient was elevated with increasing the thickness and air gap.This study suggests that the use of a combination of nanoparticles and nanofibers can enhance the acoustic properties of flexible polyurethane foam.

Improving the Compatibility of Biodegradable Poly (Lactic Acid) Toughening with Thermoplastic Polyurethane (TPU) and Compatibilized Meltblown Nonwoven

Poly (Lactic Acid) (PLA) is a biodegradable polymer which originates from natural resources such as corn and starch, offering excellent strength, biodegradability, nevertheless its inherent brittleness and low impact resistance properties have limited its application. On the other hand, Thermoplastic Polyurethane (TPU) has high toughness, durability and flexibility, which is one of the most potential alternatives for enhancing the flexibility and mechanical strength of Poly (Lactic Acid) (PLA) by blending it with a compatibilizer. With the aim to improve the mechanical and thermal properties of Poly (Lactic Acid) (PLA) meltblown nonwovens, The Thermoplastic Polyurethane (TPU) was melt blended with Poly (Lactic Acid) (PLA) at the different corresponding proportions for toughening the Poly (Lactic Acid) and the corresponding PLA/TPU MBs (meltblown nonwovens) were also manufactured. Joncryl ADR 4400 is mixed into the PLA matrix during processing. It was found that Joncryl had a much higher chain extension that substantially increased the molecular weight of the PLA matrix. SEM study revealed that Joncryl ADR 4400 is a good compatibilizer. Moreover, in this study, the crystallization, thermal and rheological behaviors of the corresponding PLA and TPU blends were also investigated. PLA/TPU MBs were also characterized by morphology and mechanical properties. The rheological property of the PLA/TPU meltblown nonwoven revealed that the viscosity is increasing as the amount of TPU is increasing in the blend, PLA/TPU meltblown nonwovens exhibited excellent mechanical properties;they are soft, elastic, and have certain tensile strength. New materials have potential applications in the medical and agricultural fields. Joncryl ADR 4400 compatibilized blends showed higher strength than simple PLA/TPU blends at the same PLA/TPU ratio.

PRIMARY APPLICATION OF THE WATER SOLUBLE POLYURETHANE (WPU) TO PROTEIN FABRICS

The primary application of the water soluble polyurethane (WPU) in protein fabrics was investigated. Both WCRA (wet crease recovery angle ) and DCRA ( dry crease recovery angle ) of silk fabrics finished with WPU were increased, and the other properties were only slightly influenced. As a formaldehyde - free silk finishing agent, WPU was proved to have a great future. The felting shrinkage ratio of wool fabrics treated by only WPU was reduced to 12.5% from 36.7%. On the basis of Oxidation/ Resin process, the felting shrinkage ratio of treated wool was 8.7%, and almost reached "Machine washable" level.

Polyurethane Grafted Attapulgite as Novel Fillers for Nylon 6 Nanocomposites

Attapulgite fibers were modified by polyurethane, forming polyurethane grafted attapulgite （AT-PU）, which was confirmed by Fourier transform infrared spectroscopy （FTIR）, X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）. Nylon 6/AT-PU nanocomposites of different modified attapulgite loadings were prepared by melt blending in a twin screw extruder. Scanning electron microscopy （SEM） observation on the fracture surfaces of the nanocomposites showed not only a uniform dispersion of AT-PU but also a strong interfacial adhesion with the matrix. Differential scanning calorimeter （DSC） and Thermogravimetric analyzer （TGA） were used to illustrate the infiuence of AT-PU particles on the thermal properties of the nylon 6/AT-PU nanocomposites. The results indicated that the addition of attapulgite probably induced the heterogeneous nucleation and was favorable for the formation of γ -crystalline form, and that the higher thermal stability was obtained for the composites.

Pu或Am含量对铀基混合氧化物的结构和能量及力学性质的影响

U-Pu和U-Am混合氧化物中的Pu或Am含量对核反应堆燃料的高效循环利用至关重要.研究铀基混合氧化物中不同Pu或Am的含量对其结构、力学性质和能量的影响有助于理解和预测提高反应堆中燃料的行为以及与包层的化学或力学相互作用.本文通过DFT+U方法首先探索UO_(2)、PuO_(2)和AmO_(2)的结构和能量随U的变化关系,然后研究UO_(2)结构中不同Pu或Am含量对其结构和力学性质以及能量的影响.结果表明在UO_(2)结构中掺入不同Pu或Am的含量均使得体系晶格参数收缩,且与实验观测(U,Pu)O_(2)中Pu的含量结论是一致的.从能量角度观察,UO_(2)结构中掺入不同Pu或Am的含量使得体系形成能随掺入量的变化趋势明显不同.结果显示当UO_(2)结构中掺入Pu为25%时,U-Pu混合氧化物体系的形成能最低,而当UO_(2)结构中掺入Am为75%时,U-Am混合氧化物体系的形成能最低.此外,我们也探讨和分析了在UO_(2)结构中掺入不同Pu或Am含量的弹性参量的变化和差异.

High-resolution neutronics model for ^(238)Pu production in high-flux reactors

We proposed and compared three methods(filter burnup,single energy burnup,and burnup extremum analysis)to build a high-resolution neutronics model for 238Pu production in high-flux reactors.The filter burnup and single energy burnup methods have no theoretical approximation and can achieve a spectrum resolution of up to~1 eV,thereby constructing the importance curve and yield curve of the full energy range.The burnup extreme analysis method combines the importance and yield curves to consider the influence of irradiation time on production efficiency,thereby constructing extreme curves.The three curves,which quantify the transmutation rate of the nuclei in each energy region,are of physical significance because they have similar distributions.A high-resolution neutronics model for ^(238)Pu production was established based on these three curves,and its universality and feasibility were proven.The neutronics model can guide the neutron spectrum optimization and improve the yield of ^(238)Pu by up to 18.81%.The neutronics model revealed the law of nuclei transmutation in all energy regions with high spectrum resolution,thus providing theoretical support for high-flux reactor design and irradiation production of ^(238)Pu.