纤维素羧酸钠基半互穿高吸水凝胶的温控溶胀效果

具有温控溶胀性的高吸水凝胶由于其独特的性能,如随环境温度微小变化,材料体积发生多种改变,在学术研究及工业应用领域都属于一种多用途、有前途的功能材料。纤维素羧酸钠(CAS)是一类通过纤维素选择性氧化反应得到的水溶性衍生物,但对其功能凝胶改性的研究鲜有报道。本工作以蔗髓为原料改性得到的CAS为线性聚合物,丙烯酰胺(AM)和二烯丙基二甲基氯化铵(DAC)为共聚单体,N,N'-亚甲基双丙烯酰胺(MBAM)为交联剂,采用序列合成法制得半互穿网络结构的CAS/聚合(AM-co-DAC)凝胶。利用红外光谱、X射线光电子能谱仪及扫描电镜对凝胶化学组成及表面形态进行表征,研究CAS、引发剂用量及介质性质对凝胶在不同温度作用下溶胀能力的影响。结果表明:制备的CAS基凝胶的溶胀度高且受温度控制;随着温度升高,溶胀度提升;溶胀能力及其温控灵敏性取决于凝胶的化学构成及溶液性质。     

温敏互穿网络水凝胶/改性膨润土复合吸水保水材料的制备及表征

以改性膨润土、2-丙烯酰胺基-2-甲基丙磺酸、丙烯酰胺和新型温敏大分子单体为主要原料,N, N′-亚甲基双丙烯酰胺为交联剂,采用水溶液互穿网络聚合技术制备了温敏互穿网络水凝胶/改性膨润土复合吸水保水材料。利用X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)、热重分析仪(TG)、扫描电子显微镜(SEM)和差示扫描量热仪(DSC)对样品进行了表征分析。考察了复合吸水保水材料的溶胀性能、温度敏感性能、去溶胀性能、振荡溶胀-去溶胀性能和拉伸性能。结果表明,20℃时复合吸水保水材料DNB5在蒸馏水和0.9%(质量分数)NaCl溶液中的最大溶胀率分别为20.59 g/g和7.92 g/g;随着改性膨润土或第二网络结构中丙烯酰胺(AM)含量的增加,复合吸水保水材料的低临界溶解温度(LCST)、溶胀率和拉伸强度增加,表现出良好的吸水、保水和温敏性;复合吸水保水材料呈现可逆溶胀-去溶胀行为和较好的机械强度。     

蛋白质凝胶的结构表征和应用研究进展

蛋白质凝胶作为一种原料来源丰富并可生物降解的高分子材料受到人们的关注.在蛋白质凝胶形成机理的基础上,介绍了力学性能表征、热分析、电泳、波谱和显微镜等方法在蛋白质凝胶结构研究方面的应用,并综述了国内外蛋白质凝胶在吸水凝胶、智能凝胶及组织工程方面的应用,指出了蛋白质凝胶研究中存在的问题及发展方向.     

高吸水性树脂溶胀理论研究

高吸水树脂是一种新型功能高分子材料,具有高吸水性能和良好的保水性能.采用溶液热力学理论对高吸水性树脂的吸水机理进行探讨;同时,对树脂的凝胶在不同环境中的溶胀性能、溶胀动力学以及水在树脂中的扩散行为进行阐述.     

EDTAD酰化改性对明胶蛋白凝胶性能的影响

用乙二胺四乙酸二酐(EDTAD)对明胶进行酰化改性,研制出一种溶胀率高的改性明胶蛋白水凝胶.确定了酰化反应预处理条件,并用正交实验对酰化反应条件进行了优化.在最优工艺条件下,所制备凝胶的平衡溶胀率可达188.0g·g-1.经扫描电镜观察断面结构发现,用EDTAD改性后明胶凝胶的内部结构更加规整有序.     

壳聚糖膜在渗透汽化中的研究进展

渗透汽化膜分离液体混合物不但能耗低,且具有明显的经济优势,因而被广泛应用于食品、医药、农业和化工等多个领域,但其分离性能、热稳定性、耐酸碱性和环保性等方面还有待提高.壳聚糖因具有强亲水性和易改性而使其分离性能优异,此外,壳聚糖稳定性好,来源广泛且具有生物可降解性,是一种极具发展潜力的渗透汽化膜材料.然而,由于单一的壳聚糖膜易吸水溶胀而分离选择性较差,限制了其在渗透汽化领域的应用.因此,对壳聚糖进行改性,使其具有良好的力学性能和选择性至关重要.常用的改性方法有交联、接枝、共混和复合等.交联可提高壳聚糖膜的力学性能,但是会消耗大量的亲水基团,并显著降低渗透通量;共混使壳聚糖膜具有更佳的渗透选择性和渗透通量,但更易吸水溶胀;复合膜中掺入少量的无机粒子可在提高材料分离性的基础上改善其力学性能和热性能,然而,复合膜受聚合物和无机离子之间的界面差异以及无机粒子团聚性影响较大.为了使壳聚糖膜具有更加优异的综合性能,研究者往往会同时采用多种改性方法.本文介绍了渗透汽化技术的研究背景和分离机理,分析了壳聚糖膜的成膜机理、制备和应用.重点从有机物/水和有机物/有机物两个方面综述了壳聚糖膜材料在渗透汽化分离中的研究进展,对其未来的发展趋势进行了展望,以期为快速制备稳定性高、分离性能优异的新型壳聚糖膜提供参考.     

明胶/聚(N-异丙基丙烯酰胺)水凝胶的制备及其在药物控释中的应用

以马来酸酐改性后的明胶(N-马来酰化明胶)(明胶-g-MA)为交联剂与N-异丙基丙烯酰胺共聚制备了一系列水凝胶。研究了交联剂用量对水凝胶溶胀性的影响,结果表明交联剂用量为45%(质量分数)时水凝胶具有最高的溶胀率,水凝胶的平衡溶胀率随温度升高逐渐降低,温敏性随缓冲液中NaCl浓度增加逐渐增强。包埋在水凝胶样品内的牛血清蛋白(BSA)具有良好的缓释效果,其累积释放率随交联剂用量增加而降低,高于相变温度时释放速度加快。     

季铵化壳聚糖/聚苯乙烯半互穿水凝胶的制备及溶胀动力学

利用高季铵化取代度的季铵化壳聚糖(QCS)和苯乙烯单体为原料,借助原位乳液聚合、交联的手段制备具有半互穿网络结构的高分子凝胶。该凝胶具有较高的力学强度和较快的溶胀速度,溶胀过程满足Schott’s二级溶胀动力学方程。随凝胶中聚苯乙烯(PS)含量增加,凝胶的拉伸强度增强,断裂伸长率降低,热稳定性增强,含水量下降,吸水溶胀速度加快。当PS质量分数为21%时,干凝胶的拉伸强度为20 MPa,吸水溶胀过程在3 min内达到平衡。扫描电镜结果表明,凝胶结构中没有明显的相分离现象。同时,热稳定性测定结果表明,该凝胶具有良好的热稳定性能,最低分解温度高于150℃。     

新型胶原/聚丙烯酸互穿网络pH敏感水凝胶的制备及性能研究

以Bis为交联剂,采用互穿网络(IPN)技术制备胶原/聚丙烯酸pH敏感水凝胶.研究了不同配比的水凝胶的溶胀动力学、pH敏感性及pH溶胀-退胀特性,并利用傅里叶变换红外光谱法(FTIR)和差示量热扫描法(DSC)对其结构进行表征.结果显示:制备的水凝胶具有较快的溶胀速率,在13min时吸水率可达93%左右;水凝胶有明显的pH敏感性且pH溶胀-退胀可逆性良好.FTIR和DSC结果表明,在保持胶原三股螺旋结构的同时,材料间形成了互穿网络,材料的热稳定性显著提高,从而扩大了材料的应用范围.     

疏水型气凝胶的制备及应用

气凝胶是一种多孔固体材料,具有高比表面积、高孔隙率、低密度、低热导率和高吸附性等特性,在隔热隔音材料、光学器件和超级电容器等方面具有广泛的应用前景。对气凝胶进行改性可进一步拓展气凝胶的应用性能。疏水改性是近年来气凝胶研究的一个热点方向,可赋予气凝胶对不同液体特殊的亲和性,疏水型气凝胶目前多用于吸附和隔热材料等。疏水改性主要方法有原位法、化学气相沉积法、表面后处理法和冷等离子改进技术等。主要针对气凝胶疏水改性方法及应用进行了介绍。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.