共查询到20条相似文献,搜索用时 63 毫秒
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以端羟基聚丁二烯(HTPB)、环氧乙烷-四氢呋喃共聚醚(PET)以及聚叠氮缩水甘油醚(GAP)为粘合剂,多异氰酸酯(N100)、异佛尔酮二异氰酸酯(IPDI)为固化剂,三羟甲基丙烷(TMP)为交联剂,制备了PETS/PETL/N100、GAP/PETL/N100、GAP/PET/IPDI/TMP、GAP/HTPB/IPDI/TMP四种双模聚氨酯交联体系,研究了双模网络对聚氨酯弹性体力学性能的影响。结果表明,双模体系较之于短链单模体系,力学性能有了较大的改善。双模聚氨酯交联体系力学性能的提高主要是非仿射变形的结果,非仿射变形程度主要取决于交联点之间的氢键数。单组分固化反应速率的差异对双模体系的力学性能影响较大。 相似文献
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以羟基化碳纳米管(CNT-OH)为交联剂,环氧乙烷-四氢呋喃共聚醚(P(E-CO-T))为预聚物,甲苯二异氰酸酯(TDI)为固化剂,制备了碳纳米管(CNT)交联改性的P(E-CO-T)热固性聚氨酯弹性体,并进行了相关性能表征。当CNT-OH的质量分数为1.5%时(质量分数),弹性体拉伸强度可达12MPa,延伸率为750%;溶度参数为21.43J1/2/mL1/2,与常用硝酸酯增塑剂的溶度参数相差均小于2J1/2/mL1/2,表现出良好的相溶性;玻璃化转变温度(Tg)为-50℃;在玻璃化转变区域,弹性体的储能模量(E’)降低,损耗模量(E’)出现峰值,力学损耗(tanδ)不断增大。在-18℃~20℃之间E’出现肩峰,归属于氨基甲酸酯硬段的玻璃化转变。 相似文献
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《高分子材料科学与工程》2021,37(7)
以双端氨基的尼龙1212预聚物(OPA)为硬段、异氰酸酯封端的聚醚型聚氨酯预聚物(OPU)为软段,通过改变软、硬段的摩尔比制得了不同相对分子质量的聚(氨酯-脲-酰胺)热塑性弹性体(PUUA)。通过傅里叶变换红外光谱(FT-IR)考察了OPU合成过程中-NCO基团与C-O-C醚键的相对强度变化,进而确定了合成OPU的反应时间为60 min。通过核磁氢谱和FT-IR确定了产物结构。凝胶渗透色谱法(GPC)测试结果表明,硬、软段摩尔比在1.2~1.5范围内,产物重均分子量可在(1.82~3.59)×10~4范围内调控。差示扫描量热分析(DSC)结果表明,随着硬、软段摩尔比由1.2提高至1.5,硬段的熔点由185℃降低至174℃,结晶温度由167℃降低至138℃,但OPU软段的熔点和结晶温度基本不变。PUUA的力学性能测试结果表明,其拉伸强度为28 MPa,断裂伸长率可达417%,缺口冲击未能冲断,是一种性能优异的热塑性弹性体。 相似文献
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为改善聚叠氮缩水甘油醚(GAP)推进剂的力学性能,选用链段柔软的环氧乙烷/四氢呋喃共聚醚(PET),采用三羟甲基丙烷(TMP)为交联剂,异佛尔酮二异氰酸酯(IPDI)为固化剂,与GAP制备聚氨酯粘合剂胶片.实验结果表明:在R为1.9,GAP:PET:TMP羟基比为1:1:3条件下,粘合剂胶片拉伸强度为3.29MPa,延伸率为625.07%.粘合剂胶片经硝化甘油/一缩二乙二醇二硝酸酯增塑后,其力学性能变化较大.在增塑比为0.5~2.1范围内,增塑胶片的Tg符合方程:Y=-77.60233+36.45135exp(-x/0.055019). 相似文献
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PPG/PST交联嵌段共聚物的合成与表征 总被引:5,自引:2,他引:5
聚1,2-丙二醇(PPG)与甲苯二异氰酸酯反应得到端异氰酸酯基聚丙二醇,再与丙烯酸2-羟基乙酯(HEA)反应,制备出端乙烯基聚丙二醇预聚物。此预聚物再与苯乙烯(ST)通过自由基聚合,得到交联的嵌段共聚物。本文对得到的端异氰酸酯和端乙烯基预聚物以及交联的嵌段共聚物进行了表征。 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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Steffen Müller-Probandt 《材料科学与工程:中英文B版...》2018,(4):161-177
We associate a variety of innovations with the term "Industry 4.0". The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di... 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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Janet Lang 《Materials and Manufacturing Processes》2017,32(7-8):857-866
ABSTRACTThe production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them. 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