Cavitation erosion behavior of nitinol coating sealed by epoxy resin

The nitinol coating against cavitation erosion was prepared by air plasma spraying and sealed with epoxy resin successfully. After the coating sealed with epoxy resin, the pores and cracks of the coating were filled with the epoxy resin and then the cohesiveness between the lamellae was improved, the hardness increased from 3.68 GPa to 7.49 GPa, the energy recovery ratio (superelasticity) was improved from 41.9 % to 49.0 % and the toughness was enhanced from 0.011 GPa to 0.045 GPa. During the cavitation erosion test, the epoxy resin reduced the cavitation resources and absorbed the impact energy from the micro-jet or shock waves. Meanwhile, the high hardness and superelasticity can help the coating to resist cavitation erosion and the high toughness can delay the expansion of cracks during the cavitation erosion test. As a result, after cavitation erosion for 300 min the cumulative mass loss of the coating sealed by epoxy resin was 1/5 times as much as that of the nitinol coating without sealing. Therefore, the cavitation erosion resistance of the nitinol coating can be improved by sealed with epoxy resin.     

Graphene-induced enhanced anticorrosion performance of waterborne epoxy resin coating

In this work, waterborne epoxy resin E44 and graphene were employed as the matrix and nanofiller, respectively, to construct composite coatings with enhanced anticorrosion performance. XRD pattern and TEM observation indicated that the obtained graphene had a stacked structure of few-layer graphitic sheets with numbers of wrinkles. SEM observations revealed that no defects or microcracks existed on the surface of graphene/epoxy coatings and the internal micropores and microcracks were filled by graphene. FTIR spectra displayed that all the characteristic absorption peaks were attributed to the epoxy resin cured with polyamide. The Tafel polarization curves showed that, as the graphene addition amount increased, the corrosive potential increased and the corrosive current decreased. ESI results proved that the addition of graphene into epoxy coatings could not only increase the impedance arc in Nyquist plots, but also increase the impedance modulus at low frequency. Finally, the enhanced anticorrosion mechanism was proposed and discussed.     

Investigation on sol–gel boehmite-AlOOH films on Kapton and their erosion resistance to atomic oxygen

To improve the atomic oxygen (AO) erosion resistance of Kapton, boehmite-AlOOH films were deposited on it by sol–gel method and AO exposure experiments were performed in a ground-based AO simulator. The results indicate that the AlOOH-coated samples show an improved AO resistance and their erosion yield is one order of magnitude less than that of pristine Kapton. Furthermore, the AlOOH-coated Kapton remained optically stable under AO exposure. The AlOOH film structure before and after AO exposure was analyzed by scanning electronic microscope, atomic force microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. It was found that after AO exposure, the film structure tends to transfer from an octahedral coordination for AlOOH to an octahedral and tetrahedral mixed-coordination for γ-Al₂O₃. This implies that a more stable γ-Al₂O₃ structure could be formed in AlOOH film during AO exposure. The AO erosion mechanism of the coated Kapton was discussed.     

Chemorheology of epoxy resin Part I epoxy resin cured with tertiary amine

Epoxy resin was cured with a tertiary amine. The viscosity and dynamic mechanical properties during the curing reaction were measured by a cone-and-plate rheometer. A dual Arrhenius viscosity model was modified to predict the viscosity profile before gelation during the non-isothermal curing. The viscosity profile coincided with the experimental data. The activation energy of this system calculated using the modified model was 19.8 kcal mol^–1 for the first region, and 17.3 kcal mol^–1 for the second region. After gelation, the dynamic complex modulus was related to the reaction kinetics according to the rubber elasticity theory, and the activation energy was 15.3 kcal mol^–1. Furthermore, the gelling point can be estimated from the rheological measurements.     

有机硅微胶囊-有机硅树脂复合涂层对空间Kapton的原子氧防护

将采用水相分离法制备的以明胶为囊壁、有机硅为囊芯的微胶囊与有机硅树脂乳液在一定条件下混合,在聚酰亚胺薄膜(Kapton)基材表面制备出含有机硅树脂的微胶囊-有机硅复合涂层,并将所制备的涂层分别进行原子氧暴露试验。结果表明,原子氧对Kapton侵蚀严重,质量损失严重,由原来光滑平整的表面变为凹凸不平的地毯状,太阳光吸收率变化值Δα为0. 272。微胶囊2有机硅复合涂层对Kapton基体优良的保护作用,使试样的质量损失和剥蚀率明显下降,且Δα仅为 0.071。尤其是微胶囊与有机硅质量比为1∶5的涂层,质量损失为Kapton试样的2.3%。     

连续玄武岩纤维增强环氧树脂基复合材料抗冲击性能研究

制备了连续玄武岩纤维增强的环氧树脂基复合材料靶板,并进行了抗冲击性能测试,研究了影响其抗冲击性能的主要因素及抗冲击机理.结果表明,表面处理会使复合材料抗冲击性能下降;而降低织物面密度、提高纤维体积含量可以使复合材料抗冲击性能得到提高.复合材料靶板的主要能量吸收形式为靶板局部变形、分层和纤维拉伸、剪切断裂及纤维拔脱.     

氨丙基倍半硅氧烷/有机硅杂化涂层抗原子氧侵蚀

为了提高航天器用有机硅涂层的抗原子氧侵蚀性能, 用氨丙基倍半硅氧烷交联固化环氧有机硅树脂, 在聚酰亚胺基材上制备出杂化涂层, 并对杂化涂层进行了地面原子氧暴露试验, 分析了试验前后杂化涂层表面形貌、 化学成分和化学结构的变化。结果表明, 氨丙基倍半硅氧烷阻止了有机硅涂层中微裂纹的产生, 避免了“淘蚀”现象, 材料质量损失明显下降。在原子氧暴露过程中, APOSS分子中的O和Si从低的结合能态慢慢向高的结合能态(氧化态)转变, 在表面生成了SiO₂保护层, 阻止了原子氧对底层材料的进一步侵蚀。      

Impact-modified epoxy resin with glassy second component

A resorcinol-based epoxy resin was modified by incorporating a glassy second component. The mixture showed a heterogeneous morphology with two clearly defined phases, one phase rich in oligomer, the other phase composed mainly of resorcinol epoxy resin. The fracture toughness measured asG _1c andK _1c values showed an increase from 174J m^–2 and 0.89 MN m^–1.5 S in pure epoxy resin to 431 J m^–2 and 1.36 MN m^–1.5 in 30% oligomer modified resins. The scanning electron micrographs showed that the oligomer-rich phase exhibited ductile failure behaviour and formed the dispersed phase at low concentrations while it was the continuous matrix when the concentration was 30%. Optical observations on the failure mode of thin films of the oligomer-modified epoxy resin showed the existence of both inter face failure and considerable distortion in both phase.     

An epoxy resin copolymer with zero shrinkage

Epoxy resin copolymer with zero shrinkage can be obtained by copolymerizing epoxy resin E51 with the expanding monomer of 3,9-di(5-norbornene-2,2)-1,5,7,11 -tetraoxaspiro[5,5]undecane (NSOC). The volume changes of an epoxy resin copolymerized with various amounts of NSOC during cure was measured with a dilatometer. The epoxy copolymer giving zero shrinkage was an epoxy resin with a E51:NSOC ratio equivalent to 5.881. This epoxy resin copolymer with zero shrinkage has been used as an adhesive to join the optical parts of a large optical telescope.     

原子氧环境中聚酰亚胺的质量变化和侵蚀机制

用石英晶体微天平(QCM)原位监测并研究了聚酰亚胺薄膜在地面原子氧模拟装置中暴露时的质量变化.结果表明,聚酰亚胺薄膜在较低的原子氧束流通量暴露的初期,试样的质量先增加后降低,质量的降低与暴露的时间成正比.在高原子氧束流通量暴露的初期,试样质量的增加不明显,甚至一开始就发生稳态氧化失重.实验数据拟合的结果表明,原子氧对聚合物造成的侵蚀主要发生在有氧原子吸附的表面.质量的增加是由于较低的原子氧通量没有能完全氧化聚合物的表面.原子氧对聚合物材料的侵蚀机制服从Langmuir吸附理论.     

阻燃剂对双酚F型环氧树脂液氧相容性影响

为研究环氧树脂阻燃改性对其液氧相容性的影响,本文通过添加六溴环十二烷和三氧化二锑对双酚F型环氧树脂进行阻燃改性,并通过对阻燃改性树脂进行液氧相容性测试来研究其液氧相容性.实验结果表明:添加质量分数4.8%的三氧化二锑可改善树脂的液氧相容性;添加质量分数6.8%六溴环十二烷和2.2%三氧化二锑的双酚F型环氧树脂表现出更好的液氧相容性.仅添加质量分数9.0%六溴环十二烷的双酚F型环氧树脂表现出非常好的液氧相容性,在20次液氧冲击实验中未表现出敏感性反应.为了更清楚地分析液氧相容性机理,对冲击前后的试样表面进行扫描电镜(SEM)和X射线光电子能谱(XPS)分析.结果表明:六溴环十二烷和三氧化二锑在冲击过程中抑制环氧树脂与液氧反应,提高了环氧树脂与液氧的相容性.     

Chemorheology of epoxy resin

A secondary hydroxyl group containing epoxy resin was reacted and cross-linked with polyurethane (PU). This PU-cross-linked epoxy resin was cured with a tertiary amine and the viscosity and dynamic mechanical properties were determined by a cone-and-plate rheometer. A dual Arrhenius viscosity model was modified to predict the viscosity profile with time before gelation during non-isothermal curing, and the calculated values coincided with the experimental data. The activation energy of this system (NCO/OH ratio=30 mol%) calculated by the modified model was 13kcal mol^–1 for the initial region, and 16.8 kcal mol^–1 for the final region. After gelation, the dynamic complex modulus was correlated to the reaction kinetics according to the rubber elasticity theory, and the activation energy calculated was 5.2 kcal mol^–1. These activation energies are all lower than those of the unmodified epoxy resin system. Consequently, the reaction rate of the PU-cross-linked epoxide system was less affected by temperature than that of the unmodified epoxide system. It was also found that the rate of increase of viscosity and dynamic moduli decreased with increasing PU content. The gelling point was estimated by rheological measurements.     

Hydrophobic epoxy resin coating with ionic liquid conversion pretreatment on magnesium alloy for promoting corrosion resistance

A hydrophobic epoxy resin coating with an environmental-friendly deep eutectic solvent(DES)-based conversion pretreatment was proposed to enhance the corrosion resistance of magnesium alloys. The hydrophobic epoxy resin coatings on the AZ31B magnesium alloy with and without the DES-based conversion pretreatment were thoroughly compared. It is found that the DES-based conversion film on the AZ31B magnesium alloy is mainly composed of MgH_2, MgO and MgCO_3. Furthermore, the conversion film possesses porous structure, which provides more anchor points for the following epoxy resin coating.However, without the DES-conversion pretreatment, the epoxy resin is difficult to be attached on the substrate during the dip-coating process. The double layered hybrid coating system promotes the corrosion resistance of the magnesium alloys significantly, which can be ascribed to the unique architecture and component including the hydrophobicity of the surface layer, the dense and interlocked epoxy resin,and the corrosion resistant DES-based conversion pretreatment.     

Thermally mendable epoxy resin strengthened with carbon nanofibres

This paper investigates the strengthening and toughening effects of carbon nanofibres (CNFs) on a self-healing thermoset/thermoplastic blend, i.e. an epoxy/poly (ε-caprolactone) (PCL) blend. The self-healing material system was prepared by polymer blending that produced a co-continuous phase-separated structure. The addition of CNFs altered the phase structures, leading to smaller domain sizes or even completely altering the phase separation mechanism, e.g. conversion from a co-continuous phase-separated structure to a particulate phase structure when the CNF content reached a certain level (0.3 wt% in this work). As the content of CNFs increased, the resulting nanocomposite became stronger and tougher, but the self-healing efficiency diminished; the optimal CNF content was found to be 0.2 wt%, which produced the highest strength, toughness and hardness, while achieving around 70% of healing efficiency.     

氰酸酯／双马来酰亚胺／环氧树脂三元共聚物及性能研究

采用双马来酰亚胺和环氧树脂与氰酸酯共聚对氰酸酯树脂进行改性，用FTIR跟踪了其固化过程。性能测试表明，当BCE：BMI：EP为5：2：3时，其固化物的冲击强度达到了12．2kJ·cm^-2，韧性有较大的提高；改性树脂的耐热性随着EP含量的增加而下降，当EP含量为30％时，Tg为233．7℃；改性后的氰酸酯树脂在1MHz频率下的介电常数和介电损耗角正切都比纯CE的有所增加，但上涨的幅度较小，仍具有优异的介电性能；DMA分析表明，在瓦温度时，损耗因子和损耗模量达到最大值，其中，tanδmax为0．359。     

Chemical recycling of carbon fibers reinforced epoxy resin composites in oxygen in supercritical water

The carbon fibers in carbon fibers reinforced epoxy resin composites were recovered in oxygen in supercritical water at 30 ± 1 MPa and 440 ± 10 °C. The microstructure of the recovered carbon fibers was observed using scanning electron microscopy (SEM) and atom force microscopy (AFM). The results revealed that the clean carbon fibers were recovered and had higher tensile strength relative to the virgin carbon fibers when the decomposition rate was above 85 wt.%, although the recovered carbon fibers have clean surface, the epoxy resin on the surface of the recovered carbon fibers was readily observed. As the decomposition rate increased to above 96 wt.%, no epoxy resin was observed on the surface of the carbon fibers and the oxidation of the recovered carbon fibers was readily measured by X-ray photoelectron spectroscopy (XPS) analysis. The carbon fibers were ideally recovered and have original strength when the decomposition rates were between 94 and 97 wt.%. This study clearly showed the oxygen in supercritical water is a promising way for recycling the carbon fibers in carbon fibers reinforced resin composites.     

Mechanical fatigue of epoxy resin

In static bending fatigue tests, epoxy resins show practically no fatigue if the stress given to specimen is lower than a critical value, which is close to the bending strength of the specimen. In cyclic bending fatigue tests, on the other hand, the resins are easily fractured even though the stresses are far below the critical values. Some strain may be accumulated on the surface of specimen through cyclic deformations. However, the strain accumulated is reversible. If the specimen is allowed to rest, the strain disappears. If the strain reaches a critical value, an irreversible transition may be induced, probably in the arrangement of segments on the surface. A crack nucleus thus created may propagate and cause the final fracture of the specimen, following the fracture mechanics of elastic materials. The lifetime of epoxy resins under cyclic bending load is determined by the time required for creating a crack nucleus on surface.     

聚氨酯对环氧树脂涂料力学性能和微观结构的影响

通过聚氨酯增韧环氧树脂制备一种强度高、附着力大、耐水性好、耐化学稳定性强的涂料.通过正交实验法,确定了涂料的最佳工艺条件,进行了拉伸强度、冲击强度、吸水率、附着力、红外光谱和扫描电镜等测试.实验结果表明:聚氨酯含量15％(质量分数,下同),固化剂含量15％,反应温度70℃,反应时间60min时,涂料的力学性能最佳;制备...     

碳质材料增强环氧树脂复合材料力学性能研究进展

综述了炭黑、碳纤维、碳纳米管等碳质材料增强环氧树脂复合材料的力学性能特征、论述了碳质材料的类型、用量,改性方法对复合材料抗张强度、抗拉强度、断裂伸长率、抗冲击强度以及韧性等力学性能的影响.讨论了表面化学修饰碳质材料、改进共混技术以及材料微观结构对复合材料力学性能的影响,碳质材料的分散性是影响复合材料力学性能和微观结构的...