低熔点固化剂对环氧树脂性能的影响

研究低熔点固化剂(MOEA)对环氧树脂性能的影响,并和以4,4′-二氨基二苯甲烷(DDM)为固化剂的环氧树脂的性能进行对比。通过流变仪研究固化剂对环氧树脂体系的黏度-温度特性的影响;采用差示扫描量热法(DSC)研究固化剂对环氧树脂固化行为的影响;并通过万能材料试验机、动态热机械分析仪(DMA)和热失重分析仪(TGA)研究环氧树脂固化物的力学性能和热性能。结果表明,以MOEA为固化剂的环氧树脂(MOEA40)比以DDM为固化剂的环氧树脂(DDM30)具有更好的黏度-温度特性,在宽的温度区间(60~140℃)表现出低的黏度(0.2~3.5Pa·s)。固化工艺处理后,MOEA40的固化物表现出了优异的力学性能,其弯曲强度为147MPa,拉伸强度为89MPa,比DDM30的固化物的弯曲强度(134MPa)和拉伸强度(80MPa)分别提高了9.7%和11.2%。此外,MOEA40的固化物还具有高的玻璃化转变温度(168℃)和初始分解温度,在氮气条件下,其失重5%的温度为367℃。     

新型环氧树脂体系固化动力学及其碳纤维复合材料性能研究

以多官能环氧树脂TDE-85、E-51环氧树脂、活性稀释剂和固化剂为主要原材料，制备了一种中高温固化的环氧树脂。采用非等温差示扫描量热(DSC)法研究树脂固化行为，利用Kissinger和Crane方程求得该树脂的固化反应动力学参数，并使用T-β外推法得到该树脂的最佳固化温度，从而建立了该环氧树脂体系的固化动力学模型。在此基础上，以该树脂为基体，T800碳纤维为增强相，采用缠绕模压工艺制得复合材料单向板及NOL环。利用扫描电镜(SEM)观察复合材料的微观形貌，通过动态机械热分析仪发现T800碳纤维/EP复合材料的储能模量随温度的升高而降低，损耗因子峰值对应的玻璃化转变温度为137℃。复合材料单向板在室温下的拉伸强度为2784MPa, NOL环在350℃下的拉伸强度为1349MPa,其拉伸强度随温度的增加而减小。     

风电叶片用环氧树脂的研究

以BPA环氧树脂、BPF环氧树脂为基体树脂,1,4-丁二醇二缩水甘油醚为稀释剂,配制出可用于风电叶片的复合型环氧树脂.考察了不同的原料配比与力学性能的关系,并采用Statistica6.0统计软件对配方进行优化.研究结果表明:当BPA树脂:稀释剂=13.5(质量比),BPA树脂:BPF树脂=1.6(质量比),树脂固化物冲击强度为88.00KJ·m-2,拉伸强度为68.52MPa,弯曲强度为88.20MPa,其性能接近进口树脂.     

海因环氧树脂/DDS体系的制备与性能

合成了海因环氧树脂,采用红外光谱和核磁共振进行了表征,制备了海因环氧树脂/二氨基二苯砜(DDS)体系,研究了海因环氧树脂/DDS体系的固化反应特性及固化物的性能。结果表明,树脂体系在100℃~296℃有一放热峰,峰值温度为197℃,140℃的凝胶时间长于42 min,在180℃下仅8 min;树脂浇铸体的氧指数为26.6,弯曲强度为111MPa,弯曲模量为4.14 GPa,冲击强度为14.8 kJ/m2。     

短切玻纤增强PEKK与BDM/DABPA共混体系固化反应动力学及断裂韧性

利用二烯丙基双酚A(DABPA)对二苯甲烷型双马来酰亚胺(BDM)树脂进行扩链,采用短切玻纤增强聚醚酮酮(PEKK-GF)对BDM/DABPA树脂进行改性。利用差示扫描量热法(DSC)研究了PEKK-GF改性BDM/DABPA树脂固化动力学,确定了改性树脂的固化工艺,并计算出了改性树脂的部分动力学参数。改性树脂的力学性能通过万能拉力机进行测试,结果表明当BDM/DABPA体系中加入10%(质量分数)的PEKK-GF时,改性树脂固化物的冲击强度比原来体系提高了69%,临界应力强度因子(KIC)和临界应变能释放率(GIC)值分别为1.22 MPa·m0.5和295J/m~2,分别提高了21%和59%;拉伸强度从85.21 MPa增加到96.39 MPa,拉伸模量从4.198GPa增加到4.531GPa;弯曲强度从133.0 MPa增加到140.4 MPa,弯曲模量从4.080GPa增加到4.251GPa。采用动态热机械分析法(DMA)对改性树脂体系耐热性进行研究,结果表明,当BDM/DABPA树脂中加入10%(质量分数)的PEKK-GF时,改性树脂固化物的玻璃化温度提高了16.5℃,达到263.5℃。该改性树脂综合性能优异,在耐高温预浸料基体树脂及胶黏剂等领域具有很好的应用前景。     

改性二氧化钛/DPPA阻燃环氧树脂的制备及性能

采用3-氨丙基三乙氧基硅烷(APTS)对亲水性纳米二氧化钛(TiO_2)进行表面改性,用FT-IR和TG对改性TiO_2结构进行表征。然后将不同量的改性二氧化钛与固定量的5,10-二氢-磷杂吖嗪-10-氧化物(DPPA)进行复配,添加到环氧预聚物中制备阻燃环氧树脂,对环氧树脂的阻燃、力学和热性能进行研究。结果表明,APTS对TiO_2改性成功。2.5%(质量分数)DPPA与0.05%(质量分数)改性TiO_2构成的复配阻燃剂,能使环氧树脂的阻燃级别达到UL-94 V-0级,LOI值由24.2%提高至28.8%。该阻燃环氧树脂的拉伸强度和弯曲强度分别为86.52和116.75 MPa,与未加阻燃剂的环氧树脂相比,拉伸强度和弯曲强度分别提高了6.66和8.25 MPa。且其初始降解温度(T_(5%))和玻璃化转变温度(T_g)分别高达364.3和162.0℃,所制备阻燃环氧树脂材料具有较好的综合性能。     

紫外光辐射固化共混改性环氧树脂复合材料的力学和热老化性能

利用湿法手工铺叠工艺和紫外光固化技术,制备以双酚A环氧树脂E-44与有机硅环氧树脂ES-06共混改性光敏树脂体系为基体的玻璃布增强复合材料,测试并分析比较了复合材料的力学和热老化性能.结果表明,在光敏树脂基体中加入链转移剂以及对光固化后的复合材料进行加压后固化处理,均能显著提高复合材料的性能.采用E-44与ES-06质量比为2:1的共混改性树脂体系制备的复合材料的力学性能和耐热老化性能最佳,其拉伸强度达到146.6 MPa,拉伸模量为19.4GPa,弯曲强度为152.5MPa,层间剪切强度达到16.2 MPa.     

碱性EP_b-POSS增韧E-51/DDS环氧树脂的研究

以KH560在碱性条件下水解缩合制备的环氧基倍半硅氧烷(EPb-POSS)为改性剂,对双酚A型环氧树脂(E-51)/4,4′-二氨基二苯砜(DDS)进行改性,制备EPb-POSS/E-51/DDS改性树脂体系,研究该树脂体系的固化工艺和不同含量的EPb-POSS对改性树脂体系力学性能和热稳定性的影响。结果表明,EPb-POSS对改性树脂的固化工艺及其刚性影响不大,但是能显著提高其韧性。POSS含量为1.0%(质量分数)时,改性树脂的冲击强度达到49.2kJ·m2,提高了90.0%,并表现为明显的韧性断裂;弯曲强度132.8MPa,略有提高;初始分解温度378.0℃,提高了26.0℃。     

树脂膜熔渗(RFI)工艺用环氧树脂/DDS体系的研究

树脂膜熔渗(Resin Film Infusion,RFI)工艺以其低成本,适合制造大型、复杂型面、带加强筋的结构件等优点受到越来越多的关注.本文对适合RFI工艺要求用树脂膜的制备及性能进行了研究.实验证明在室温下,体系配方为:双酚F型环氧树脂(BPFEP):DDS:PES=95:34.3:5时树脂的成膜性和韧性非常好.DSC方法和凝胶时间确定熔渗温度为120℃,固化工艺为150℃/2h 180℃/2h.采用RFI方法制备了GF/EP和CF/EP复合材料层合板,并对力学性能和Tg(DMA方法)进行了测试.前者层间剪切强度、弯曲强度分别达到52.1MPa和432MPa,树脂含量达到39.6%,Tg为166·1℃.后者的层间剪切强度、弯曲强度分别为66.1MPa和862MPa,树脂含量达到30.7%,Tg为164.0℃.     

粗酚基苯并噁嗪树脂预聚体的制备、固化及性质分析研究

以工业粗酚、多聚甲醛及聚醚胺作为起始原料,通过无催化的Mannich反应,在温和条件下合成出一种新型的苯并噁嗪树脂预聚体。通过红外光谱(FT-IR)、核磁共振氢谱(~1 H-NMR)和示差扫描量热法(DSC)对上述苯并噁嗪树脂预聚体的化学结构和固化过程进行了研究。对固化后树脂的弯曲及拉伸等机械性能进行了检测。结果表明:树脂预聚体在185℃开始固化,固化后树脂具有近乎为零的体积收缩率、良好的抗溶蚀性及低吸水率,弯曲强度达92.71MPa,拉伸强度达25.79MPa。     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

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...     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Roman iron and steel: A review

ABSTRACT

The 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.     

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.……     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.