交联聚乙烯醇纳米纤维膜的制备与性能研究

采用静电纺丝法成功制备了聚乙烯醇(PVA)纳米纤维膜,利用戊二醛气相法对纤维膜进行交联处理。运用扫描电镜显微镜(SEM)测纤维直径,红外光谱(FT-IR),热重分析(TGA)对纳米纤维膜和交联纳米纤维膜进行表征,同时,测试了交联纳米纤维膜的吸水性和拉伸性。结果表明,当PVA质量分数为12%时,纤维分布及直径大小最均匀,并且经过交联的纤维膜热性能更稳定。红外光谱分析表明,成功制备了戊二醛交联PVA纳米纤维膜。吸水性和拉伸性实验表明,在交联时间为5h时,纳米纤维膜的最高吸水倍率达到885g/g,且力学性能也达到最佳,拉伸强度和断裂应变分别为6.0MPa和228.9%。     

静电纺丝素/聚左旋乳酸复合纳米纤维膜的制备及性能研究

采用静电纺丝技术成功制备丝素(SF)/聚左旋乳酸(PLLA)复合纳米纤维膜,对其理化性能进行研究。本实验以六氟异丙醇(HFIP)为溶剂,将SF与PLLA按100∶0、70∶30、50∶50、30∶70、0∶100的质量比共混进行电纺,制备的5种材料用戊二醛(GTA)蒸汽交联48h。通过扫描电镜(SEM)、拉伸性能测试、X射线衍射(XRD)、热重分析(TG)和亲水角等方法对其理化性能进行表征。结果显示制备的SF/PLLA复合纳米纤维平均直径在162~680nm之间,并随着PLLA含量的增加而增加;交联后纤维虽有溶胀,但仍然保持了纤维形貌;SF/PLLA复合纳米纤维膜的力学性能、结晶度、热稳定性和疏水性较纯SF明显提高,且随着PLLA含量的增加而增加,有望成为一种新型的组织工程支架材料。     

静电纺丝羽毛角蛋白纳米纤维膜的交联改性研究

将羽毛角蛋白(FK)、聚乙烯醇(PVA)及聚氧化乙烯(PEO)共混,利用静电纺丝加工技术制备FK纳米纤维膜,并使用戊二醛对其进行交联改性。利用扫描电子显微镜、傅里叶变换红外光谱仪、X射线衍射光谱仪、热重分析仪、差示扫描量热仪、接触角测量仪及电子万能试验机对交联前后纤维膜的形貌、结构、热稳定性、抗水性以及力学性能进行了测试和表征。结果表明:交联前纳米纤维膜的纤维结构均匀且光滑;随着交联剂戊二醛含量的增加,纤维膜形貌变化不大,热稳定性有所提高,接触角及力学性能增加较明显。当戊二醛质量占纺丝液溶质质量的15%时,纳米纤维膜的接触角大约是交联前的4倍,抗拉强度增至交联前的2.8倍。     

不同交联方式的明胶及明胶/蒙脱土纳米复合材料的力学性能

研究了戊二醛(GLA)蒸汽交联、溶液交联以及葡糖二醛溶液交联对明胶及明胶／蒙脱土(MMT)纳米复合材料力学性能的影响，并利用扫描电子显微镜(SEM)对材料的拉伸断口进行了观察。结果表明，与溶液交联相比，明胶蒸汽交联样品的交联度较大。溶液交联时，戊二醛比葡糖二醛交联效率高，相同浓度下试样的力学性能较好。明胶／MMT纳米复合材料无法通过GLA溶液交联方式制样，由于MMT片层的阻隔性，使蒸汽交联需要更长的时间才可达到一定的交联度。与MMT插层复合可大幅度提高明胶材料的力学性能，SEM表明韧性同时得到改善。     

交联改性对静电纺乌拉草提取液/聚乙烯醇纳米纤维膜性能的影响

为了优化用于医用敷料的乌拉草提取液/聚乙烯醇纳米纤维膜的耐水性,对制备好的纤维膜进行气相交联改性。选用戊二醛和浓盐酸作为交联剂和催化剂,在满足医用敷料性能的基础上提高膜的耐水性,进而提高抗菌性,并研究交联时间对膜的影响,确定最优交联时间。采用扫描电子显微镜、电子单纤强力仪及红外光谱仪对改性前后膜的微观形貌、力学性能及分子结构进行表征,并对膜的透气性和孔隙率、接触角和吸水性以及抗菌性进行测试。结果表明,经戊二醛交联改性后,纳米纤维膜的接触角从16°逐渐增大到78°,耐水性显著提高;其形貌、水蒸气透过率及孔隙率均能满足医用敷料的要求。随着交联时间的延长,其力学性能和吸水倍率先增强后减弱,在交联4 h时分别达到最大值(7.34±0.80) MPa和857%;其抗菌性在交联2 h时达到最优,此时大肠杆菌和金黄色葡萄球菌的抑菌圈直径分别为3.0 mm和1.1 mm。由以上结论得出,交联2 h和4 h的纳米纤维膜的综合性能最好。     

可见光激发下具有增强抑菌作用的聚乙烯醇/石墨氮化碳复合纳米纤维膜

将聚乙烯醇(PVA)溶液与分散在其中的石墨氮化碳(g-C₃N₄)纳米片通过静电纺丝技术和交联反应成功地制备了具有增强抑菌性能的可生物降解复合纳米纤维膜。对PVA/g-C₃N₄(P-CN)复合纳米纤维膜的微观形貌、物理性能及抗菌性能进行了研究,分析了g-C₃N₄含量对复合纳米纤维膜的形貌及性能的影响。扫描电镜分析结果表明,P-CN纤维直径为200～300 nm,交联后纤维直径变为1μm左右,g-C₃N₄质量分数小于3%时,纳米片均匀地分布在纳米纤维的表面,通过拉伸和溶胀测试发现,交联复合纳米纤维膜具有良好的力学性能和优良的抗溶胀性能。抑菌测试结果表明,复合纳米纤维对大肠杆菌和金黄色葡萄球菌的抗菌效果随着g-C₃N₄含量的增加明显提高,在4×10⁴ Lux的LED光激发10min后培养24 h的P-CN-5的最大抗菌环直径可以达到20 mm。研究结果表...     

静电纺丝制备PEI/PVA纳米纤维膜负载甘草酸的研究

通过静电纺丝技术制备了聚乙烯亚胺/聚乙烯醇(PEI/PVA)复合纳米纤维,并用戊二醛作为交联剂使其疏水化,然后在交联后的PEI/PVA复合纤维膜上修饰了甘草酸。利用傅里叶红外光谱仪(FT-IR)、扫描电子显微镜(SEM)对PEI/PVA交联前后的复合纤维膜以及甘草酸修饰的PEI/PVA复合纳米纤维膜分别进行了表征。SEM结果表明,交联后的纳米纤维形貌均匀且有明显的结节,而交联前和甘草酸修饰后的纳米纤维,表面光滑均匀,形貌没有发生明显的变化,且甘草酸修饰后的纤维直径在400~600nm之间。FT-IR表明利用静电纺丝技术可以制备甘草酸修饰的PEI/PVA复合纳米材料,利用此纤维材料,可以进一步的应用于肝癌的早期诊断和检测。     

SF/COL/PLLA静电纺丝三维纳米纤维支架材料的性能研究

基于PLLA(左旋聚乳酸)的优异性能,以六氟异丙醇(HFIP)为溶剂采用静电纺丝法制备质量比为0∶100,30∶70,50∶50,70∶30和100∶0的8%SF/COL/PLLA共混纳米纤维支架,并用浓度为25%戊二醛蒸汽交联48h,通过扫描电镜、X射线衍射、热重分析仪、接触角检测仪对共混材料交联前后的理化性能进行表征。结果表明纳米纤维直径均一,分布均匀;交联后SilkI形成稳定的β折叠,结晶度增强,且交联后材料结晶度明显较交联前增强;热稳定性也随着PLLA浓度的增加愈加稳定。交联后的材料接触角均大于90°表明材料为疏水性,PLLA的加入降低了材料的亲水性能。复合人牙周膜干细胞和材料培养,分析材料的生物学性能,结果证明细胞培养5,7和9d时,细胞在不同比例的支架上粘附、铺展和增殖均良好,但细胞与质量比为30∶70的SF/COL/PLCL纤维膜复合生长最好。     

戊二醛交联聚谷氨酸-普鲁兰多糖纳米纤维膜的条件优化

聚谷氨酸-普鲁兰多糖纳米纤维膜具有极强的吸水性,限制了其作为敷料材料的应用。为提高其耐水性,本实验采用戊二醛对纳米纤维膜进行交联,优化戊二醛与乙醇比例、戊二醛交联时间和浓硫酸添加量等实验条件对其进行改性,并采用SEM观察交联后的表面形态,接触角测定表征纤维膜表面亲水性;结果为:戊二醛与乙醇比例为1∶86,纤维平均直径为190nm,接触角由原来的36.21°提高到68.94°;戊二醛交联时间为15h,纤维平均直径为223nm接触角由原来的36.21°提高到64.54°;浓硫酸添加量为0.15mL,纤维平均直径为178nm接触角由原来的36.21°提高到64.32°。根据最优条件进行戊二醛交联,纤维直径由164nm提高到195nm,接触角由38.55°提高到67.36°,提高了46.23%,并且在5s后接触角由21.35°提高到50.27°,提高了57.53%。说明经过戊二醛交联的纳米纤维膜对水的亲和性有所降低,能够抵御一定时间的水分环境,从而可扩大其在创伤敷料中的应用。     

Genipin交联丝素蛋白纳米纤维膜的制备与性能

利用Genipin对再生丝素蛋白进行交联改性, 并通过静电纺丝法制备交联的丝素蛋白纳米纤维膜。利用场发射扫描电镜、 红外光谱仪、 X射线衍射仪、 热重分析仪以及拉力机等对其结构与性能进行表征与测试。结果表明, 随着交联剂Genipin质量比的增加, 交联度增加, 静电纺丝素蛋白纳米纤维平均直径增大, 标准偏差增大;Genipin交联对丝素蛋白纳米纤维结晶结构影响不大, 但热性能提高;常温条件下, 随着Genipin质量比从2%提高至15%, 丝素蛋白纳米纤维膜的力学性能逐渐增强, 质量比为10%时, 其力学性能较好, 拉伸强度和断裂应变分别为19.6 MPa和5.9%;随着试验温度从40 ℃升高到200 ℃, 丝素蛋白纳米纤维膜的拉伸强度和断裂应变先增大然后减小, 当试验温度为80 ℃时, 其力学性能较好, 拉伸强度和断裂应变分别为41.6 MPa和8.6%。     

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.