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《功能材料》2017,(2)
利用单向热牵伸法,在PETG收缩薄膜中添加25%(质量分数)COC,在一定的温度和牵伸比例下制备了内部含有微孔结构的高收缩率薄膜。利用SEM、紫外-分光光度计、收缩率测试仪、电子拉伸机等研究了热牵伸行为对薄膜内部结构、力学性能、收缩应力、收缩曲线以及紫外线透过性能的影响。结果发现,COC/PETG属于共混不相容体系,一定温度下的热牵伸行为造成了COC与PETG的相分离,在COC周围产生2~10μm的微孔结构;随着热牵伸温度的提高,95℃下的横向收缩率逐步降低,收缩应力逐步降低,紫外线透过率变化不大;随着热牵伸比例的增加,95℃下的横向收缩率逐步增大,收缩应力逐步降低,紫外线透过率变化不大;当m(COC)/m(PETG)=25∶75时,在拉伸温度80℃、拉伸比例5.0倍的条件下,可获得50μm厚度、0.95g/cm3超低密度、72%超高横向收缩率、99%以上紫外线阻隔效果的稳定的热收缩微孔薄膜。 相似文献
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吴鹏李忠伦余智刘鹏波 《高分子材料科学与工程》2018,(3):132-137
利用非溶剂诱导相分离法,制备了一种低介电常数聚酰亚胺(PI)微孔薄膜。扫描电镜观察表明,聚酰亚胺微孔薄膜中泡孔均匀,其平均孔径在6~28μm之间。随着聚酰胺酸(PAA)浓度的增大及凝固浴温度的升高,所制得的聚酰亚胺微孔薄膜的孔隙率和平均孔径均增大。介电性能分析表明,聚酰亚胺微孔薄膜的介电常数明显下降,当孔隙率为80%时,聚酰亚胺微孔膜的介电常数(1 MHz)为1.81。拉伸性能测试表明,随着孔隙率增加,聚酰亚胺微孔膜的拉伸强度和拉伸模量均逐渐下降,但断裂伸长率增大。 相似文献
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利用非溶剂诱导相分离法,制备了一种低介电常数聚酰亚胺(PI)微孔薄膜。扫描电镜观察表明,聚酰亚胺微孔薄膜中泡孔均匀,其平均孔径在6~28μm之间。随着聚酰胺酸(PAA)浓度的增大及凝固浴温度的升高,所制得的聚酰亚胺微孔薄膜的孔隙率和平均孔径均增大。介电性能分析表明,聚酰亚胺微孔薄膜的介电常数明显下降,当孔隙率为80%时,聚酰亚胺微孔膜的介电常数(1 MHz)为1.81。拉伸性能测试表明,随着孔隙率增加,聚酰亚胺微孔膜的拉伸强度和拉伸模量均逐渐下降,但断裂伸长率增大。 相似文献
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采用不同的条件研究了PETG热收缩薄膜挺度的主要影响因素,选取了原料配比、厚度、添加剂、拉伸倍率、拉伸速率、拉伸温度、定型温度及环境温湿度等条件对PETG热收缩薄膜进行研究,通过结果的对比分析发现:薄膜厚度基本与薄膜挺度成正比关系;在一定范围内薄膜配比中PET含量升高有助于提升薄膜挺度;在保证薄膜正常生产的前提下,拉伸倍率越大,薄膜挺度越高,拉伸速率对挺度影响不大;在一定范围内,定型温度与薄膜挺度成正比关系,拉伸温度与薄膜挺度成反比关系;环境的温湿度高也会提升薄膜的挺度,同时会使得薄膜其他性能如拉伸性能等发生下降。 相似文献
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利用超临界CO2发泡技术,制备了一种低介电常数的聚酰亚胺微孔薄膜。扫描电子显微镜观察表明,微孔薄膜具有实心表层及中心微孔层结构,中心微孔层内泡孔孔径约2μm,泡孔分布均匀。在相同的发泡温度下,发泡时间在10 s内,随着发泡时间增长,孔径较小(<1μm)的泡孔数目明显减小,泡孔尺寸增大。发泡约10 s后,泡孔尺寸变化略微增加。在230℃~270℃范围内,发泡温度越高,微孔薄膜中心微孔层内的泡孔孔径越小,孔径分布越均匀,泡孔密度越大,薄膜密度也越小。拉伸性能测试表明,随着密度减小,聚酰亚胺微孔薄膜的拉伸强度和拉伸模量下降。介电性能分析表明,聚酰亚胺微孔薄膜的介电常数明显下降,当密度为0.75 g/cm3时,聚酰亚胺微孔薄膜的介电常数降至2.21;在102Hz~107Hz频率范围内,微孔薄膜的介电常数具有较高的频率稳定性。 相似文献
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对TC4预合金粉末进行模壳热等静压成型,并对成型构件的尺寸收缩、合金的微观组织、室温拉伸性能,以及合金/模壳界面微观结构进行了分析。结果表明:采用TC4预合金粉末模壳热等静压技术实现了构件的完整成形,合金致密度达到98%,粉末在致密化过程中,沿构件的长度及宽度方向收缩较少,沿厚度方向收缩较大,中心部位收缩率达到30%;成型得到的合金为细小均匀的网篮组织,片层周围分布少量等轴α相;合金塑性为铸造TC4合金的1.5倍以上,拉伸性能完全达到甚至超过锻件水平;粉末模壳热等静压工艺中,TC4合金与模壳之间无明显的界面反应,在构件表面存在10μm左右的疏松层。 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
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. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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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. 相似文献
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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.…… 相似文献
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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. 相似文献
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C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
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. 相似文献
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Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
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 ... 相似文献
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《中国标准化(英文版)》2014,(4)
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 相似文献
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《中国标准化(英文版)》2014,(5)
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. 相似文献