Interrelation of Scanning Electron Micrographs with Flexural Behavior of Ferrite and Nano-Barium Titanate Reinforced Poly-Ether-Ether-Ketone (PEEK) Composites

ABSTRACT

The flexural behavior of ferrite filled poly-ether-ether-ketone (PEEK) composites, with and without reinforcement of nano-barium titanate, was studied and was corroborated through scanning electron microscopy (SEM). In this study, ferrite filled PEEK, and ferrite and nano-barium titanate reinforced PEEK composites were prepared. Ferrite filled PEEK composites showed reduction in flexural strength and increase in flexural modulus with the increase in ferrite content, whereas, with the reinforcement of nano-barium titanate, flexural strength increased and flexural modulus decreased at similar ferrite content. The SEM micrographs corroborated well with flexural behavior, as ferrite particles and smooth topographic surfaces of brittle fracture were evident in the samples having higher ferrite content in ferrite filled PEEK composites, whereas, typical yield pattern of crust and trough on fractured topographic surfaces of ferrite and nano-barium titanate, reinforced PEEK composites, was visible.     

金属—橡胶硫化粘接复合体剥离破坏行为的研究

本文分析了对橡胶分子链特性、部分交联弹性聚合物材料的粘弹行为及金属──橡胶硫化粘接体剥离过程中聚合物分子链的应力分布状况和剥离破坏模型，认为粘着一滑动（Stick—slip）模型剥离破坏并非是橡胶类材料的固有特征，而是由于金属──橡胶硫化粘接过程中的分子取向交联和部分交联弹性材料多个凯尔文（Kelvin）模型粘弹行为的综合结果．同时指出单从剥离试验的结果难以表征金属——橡胶硫化粘接复合作的粘接效果．     

Scanning Electron Microscopic Evidence of Spontaneous Heteropeptide Formation in Abiotic Solutions of Selected α-Amino Acid Pairs

Spontaneous nonlinear peptidization of the monomeric and enantiomerically pure α-amino acids in abiotic aqueous and nonaqueous solutions is still regarded by some as a somewhat puzzling phenomenon, and therefore it needs additional experimental authentication. In our earlier studies, we employed several analytical techniques to prove its occurrence. In this study, we present the scanning electron microscopic (SEM) evidence of spontaneous heteropeptide formation in the binary L-Cys−L-Phe, L-Cys−L-Phg, and L-Cys−L-Pro mixtures dissolved in 70 % aqueous methanol. With each α-amino acid pair, one amino acid (L-Cys) is equipped with three functionalities (−SH, −NH₂, and −COOH), enabling formation of the spherical homopeptide microstructures, while its counterpart (L-Phe, L-Phg, or L-Pro, respectively) is equipped with the two functionalities only (−NH₂ or =NH, and −COOH). The SEM micrographs of the peptidization products originating from the three investigated α-amino acid pairs show three different, yet spherical, structures, which seem suggestive of the heteropeptide formation involving both L-Cys and its counterpart α-amino acid. Additional confirmation of heteropeptide formation is furnished by high performance liquid chromatography (HPLC), the biuret test, and mass spectrometry (MS).     

Scanning Electron Microscopy Studies on Failure of Natural Rubber

Abstract

The changes in failure mode of natural rubber reinforced with HAF black (N 330) and vulcanized by two systems (conventional and efficient vulcanization) have been studied by scanning electron microscopy (SEM). The effect of vulcanization system on the failure mode is not pronounced. However, effect of reinforcing filler is quite distinct. In the case of fracture by tension and tear, it is observed that with the addition of filler tear lines gradually start deviation resulting curved tear paths which, in many instances, are parabolic in nature. Likewise in abrasion, change in structure of the ribs with the addition of filler is observed. In flex failure, gradual addition of filler causes change from ductile failure to brittle failure for both conventional and EV systems. E V mixes show more cracks and less flow on the surface leading to poorer flexing strength.     

复合材料表面密封剂与抗静电涂料在燃油中稳定性研究

研究了复合材料表面上HM108B4密封剂和H06—1020HD抗静电涂层材料在航空煤油中的质量变化、密封剂的180°剥离强度和破坏模式。研究结果表明：随着时间的延长,HM108B4密封剂／复合材料和抗静电涂层／密封剂／复合材料在航空煤油中质量变化率均先下降后上升,最后趋于稳定,抗静电涂层／密封剂／复合材料在煤油中质量变化率小于密封剂／复合材料。未浸油老化和60±2℃浸油老化7天密封剂／抗静电涂层试样的180°剥离强度分别为10．9KN／m和11．1KN／m,试样的破坏模式为内聚破坏。     

Peel Strength of Aluminium-Aluminium Joints Bonded by Adhesive Based on Carboxylated Nitrile Rubber-Chlorobutyl Rubber Blend

The peel strength of aluminium-aluminium joints bonded by an adhesive based on carboxylated nitrile rubber and chlorobutyl rubber was found to depend on surface topography and use of a silane primer. Anodization causes a marginal increase in bond strength while the silane primer improves the adhesive joint strength remarkably.

The peel strength was also found to be dependent on test conditions (test rate and temperature). The threshold peel strength value obtained by measurements at low peel rate and high test temperature was found to depend on the type of failure during peeling (cohesive or interfacial) which, in turn, is controlled by the presence of silica filler in the adhesive. Two different threshold values of peel strength were obtained: 60 N/m for interfacial failure (in silica-filled adhesive), 140 N/m for cohesive failure (in unfilled adhesive).     

基于多种微观表征方法探究氯丁橡胶热氧老化机理

本文采用溶胀法、核磁共振(NMR)、扫描电镜(SEM)和红外光谱(FTIR)等方法,对氯丁橡胶热氧老化过程微观结构变化进行了表征。结果表明：随着老化时间的延长,交联密度增大,老化温度越高增幅越大,老化后期有所下降;氯丁橡胶微观形貌由颗粒状逐渐变成了胶着状;分子内的C=C键的峰值随老化温度的提高而降低,C-Cl键的峰值发生微小变化。     

扫描电子显微镜的结构及对样品的制备

扫描电子显微镜作为一种有效的分析工具,可对多种材料的表面形貌进行观察,使用范围广泛。本文论述了扫描电子显微镜的原理及结构,介绍了样品导电处理的常见方法,重点介绍了离子溅射法和真空蒸发法,并对二者的特点进行了简单总结。     

Confocal Scanning Laser Microscopic Study of the RDX Defect Structure in Deformed Polymer‐Bonded Explosives

The influence of an explosion‐driven deformation on the defect structure in RDX crystals embedded in a polymer‐bonded explosive was investigated by means of confocal scanning laser microscopy. The images were compared to the defect structure in the as‐received RDX grades, embedded in an epoxy resin. In this way it is possible to qualitatively analyze the changes in defect structure of the RDX crystals that were induced by the explosion‐driven deformation. For the first time, these data therefore provide experimental confirmation of how shock waves mechanically interact with energetic crystals – a topic that, up to now, was only explored by means of simulations.     

In Situ Measurements of Bridged Crack Interfaces in the Scanning Electron Microscope

A device for in situ SEM examination of crack propagation during loading of compact tension specimens is described, with a specific demonstration on an alumina ceramic. The device facilitates direct qualitative observations of the inception and subsequent frictional pullout of grain-localized bridges at the crack interface. Quantitative data on the bridging mechanism are obtained from measurements of the crack-opening displacements behind the crack tip. The crack profile is found to be closer to linear than parabolic at the bridged interface. Deconvolution of these crack-opening data allow for an evaluation of the closure tractions operative at the crack walls within the bridging zone, and thence the R -curve.     

橡胶与金属热硫化粘结剥离方向性研究

对以天然橡胶为基料，硫黄硫化的三种硫化体系的胶料进行金属样板及圆柱型金属同橡胶的粘接实验。实验表明配合胶料的硫化体系不仅影响橡胶同金属的粘结强度而且是产生其粘结剥离方向性差异的主要原因。     

Scanning Electron Microscopic Study of Microstructure of Gala Apples During Hot Air Drying

Microscopic changes that occur in plant food materials during drying significantly influence the macroscopic properties and quality factors of the dried food materials. It is critical to study the microstructure to understand the underlying cellular mechanisms to improve the performance of food drying techniques. However, there is limited research on such microstructural changes of plant food material during drying. In this work, Gala apple parenchyma tissue samples were studied using a scanning electron microscope for gradual microstructural changes as affected by temperature, time, and moisture content during hot air drying at two drying temperatures: 57 and 70°C. For fresh samples, the average cellular parameter values were as follows: cell area, 20,000 µm²; ferret diameter, 160 µm; perimeter, 600 µm; roundness, 0.76; elongation, 1.45; and compactness, 0.84. During drying, a higher degree of cell shrinkage was observed with cell wall warping and an increase in intercellular space. However, no significant cell wall breakage was observed. The overall reductions in cell area, ferret diameter, and perimeter were about 60, 40, and 30%. The cell roundness and elongation showed overall increments of about 5% and the compactness remained unchanged. Throughout the drying cycle, cellular deformations were mainly influenced by the moisture content. During the initial and intermediate stages of drying, cellular deformations were also positively influenced by the drying temperature and the effect was reversed at the final stages of drying, which provides clues regarding case hardening of the material.     

Studies on the Tensile Properties of Rubberwood Fibre-Natural Rubber Composites

Abstract

Natural rubber (NR) composites were prepared by incorporating rubberwood fibres at different loadings into the NR matrix in a mixing mill according to a base formulation. Tensile properties, swelling measurement and tensile fracture surfaces of gum and composites with 0, 10, 20, 30 and 50 phr of rubberwood fibres were studied. Incorporation of rubberwood fibres in the composites increases the tensile modulus but reduces the tensile strength and elongation at break. Scanning electron microscopy (SEM) studies and swelling measurement indicate that the increasing rubberwood loading has weakened the rubber-filler interactions.     

Adhesion and Failure Mechanisms of a Model Hot Melt Adhesive Bonded to Polypropylene

A model hot melt adhesive (HMA) based on an ethylene/vinyl acetate copolymer (EVA), an Escorez® hydrocarbon tackifier, and a wax has been used to bond together polypropylene (PP) films to give equilibrium bonding. Peel strengths were determined over a broad range of peel rates and test temperatures. Contrary to the peel behavior of joints with simple rubbery adhesives [1], peel strengths with this semi-crystalline adhesive are not rate-temperature superposable, and multiple transitions in failure locus occur. The semi-crystalline structure of the HMA also prevents rate-temperature superposition of its dynamic moduli.

At different test temperatures, the dependence of peel strength on peel rate shows some resemblance to the dependence of the loss tangent of the bulk adhesive on frequency. This is consistent with a previous result [2] that the HMA debonding term. D, varies with the loss tangent of a HMA at the T-peel debonding frequency.

This model HMA, similar to block copolymer/tackifier blends [3], consists of two phases: an EVA-rich and a tackifier-rich phase, in its amorphous region. At a low peel rate of 8.33 × 10^-5 m/s, the peel strength shows a maximum at a temperature that corresponds to the transition temperature of the tackifier-rich phase (T₁). At a higher peel rate of 8.33 × 10^-3 m/s, the peel strength rises with increasing test temperature, but becomes essentially constant at temperature T₁'. It is believed that, to optimize the peel strength of a HMA at ambient temperature, it is advantageous to formulate the EVA polymer (or other semi-crystalline polyolefins) with a compatible tackifier that yields a tackifier-rich phase with a transition temperature (T₁') in the vicinity of room temperature.     

In Situ Tensile Measurements of Single Fibers by Scanning Electron Microscopy

A newly developed tensile module allows tensile experiments of single fibers to be carried out under visual observation in the scanning electron microscope. This allows correlation of measured data with observed changes in the microstructure, such as surface irregularities and crack formation. With point heating, the thermal behavior of the fibers may be studied up to 2500°C. The results are presented with tensile elongation recordings and micrograph sequences of the structural changes. Carbon fibers with and without an aluminum coating were selected as testing specimens.     

Real Space and Wave‐Number Space Studies of the Phase Structure and Morphology of iPP/PEOc Blends Using Scanning Electron Microscopy

The influence of blend composition on the phase structure and morphology of poly(propylene)/poly(ethylene‐co‐octene) blends was studied using SEM. A diameter d_g was defined and calculated in real space to discuss the phase structure and morphology of iPP/PEOc blends. The figure‐estimation method was introduced to determine the distribution width of d_g. It was shown that the distribution of d_g obeys a log‐normal distribution and the distribution width σ of d_g was calculated. In wave‐number (h) space, the correlation distance, a_c, was defined by applying light scattering theory to power spectrum images obtained by 2D Fourier transformation. Moreover, a fractal dimension, D_c, was introduced to describe the uniformity of the spatial distribution.

     

Effect of silica filler on aluminum-aluminum bonding by a self-vulcanizable blend based on chlorobutyl rubber and carboxylated nitrile rubber

Silica filler improves the aluminum-aluminum bonding by a self-vulcanizable rubber blend based on chlorobutyl rubber and carboxylated nitrile rubber. The joint peel strength depends on the filler loading, the state of cure, the molding temperature, and the adhesive film thickness. The higher peel strength in the filled adhesive system is due to filler reinforcement resulting in tear path deviation and the formation of Si—O—Al linkage at the aluminum-adhesive interface. Maximum peel strength was obtained at 10 phr filler loading, when the molding temperature was 180°C and the molding pressure was 0.35 MPa.     

Imaging the Kidney with an Unconventional Scanning Electron Microscopy Technique: Analysis of the Subpodocyte Space in Diabetic Mice

Transmission electron microscopy (TEM) remains the gold standard for renal histopathological diagnoses, given its higher resolving power, compared with light microscopy. However, it imposes several limitations on pathologists, including longer sample preparation time and a small observation area. To overcome these, we introduced a scanning electron microscopy (SEM) technique for imaging resin-embedded semi-thin sections of renal tissue. We developed a rapid tissue preparation protocol for experimental models and human biopsies which, alongside SEM digital imaging acquisition of secondary electrons (SE–SEM), enables fast electron microscopy examination, with a resolution similar to that achieved by TEM. We used this unconventional SEM imaging approach to investigate the subpodocyte space (SPS) in BTBR ob/ob mice with type 2 diabetes. Analysis of semi-thin sections with secondary electrons revealed that the SPS had expanded in volume and covered large areas of the glomerular basement membrane, forming wide spaces between the podocyte body and the underlying filtering membrane. Our results show that SE–SEM is a valuable tool for imaging the kidney at the ultrastructural level, filling the magnification gap between light microscopy and TEM, and reveal that in diabetic mice, the SPS is larger than in normal controls, which is associated with podocyte damage and impaired kidney function.     

基于场发射扫描电镜和Image J的锂电池隔膜孔隙率研究

通过对场发射扫描电镜(FESEM)条件的优化得到超高分子量聚乙烯(UHMWPE)锂电池隔膜表面清晰电镜图,然后用Image J软件处理得到孔隙分布图,运用膜孔隙率计算公式,成功获取锂电池隔膜表面膜孔的孔隙率。结果表明:通过FESEM和Image J软件相结合的方法可以形象地对锂电池隔膜的孔隙率进行表征,得到的孔隙率变异系数为6.36%,平均孔隙率为41.07%。     

Gauge length effect on the tensile properties of leather

Tensile properties are important basic characteristics of materials and influence their end‐use and performance. More importantly, in the case of leather due to end‐use applications such as shoe uppers, automotive and furniture upholstery, mechanical properties such as tenacity are of extreme importance. Therefore, fundamental studies on the tensile properties of leather are needed. In this study, an attempt has been made to examine the effect of gauge length (GL) on the tensile properties of shoe upper leather. Two different specimens in the form of rectangular and dumbbell shapes have been cut from parallel and perpendicular directions to the body axis of the leather and have been tested. Results showed that the maximum breaking load and the percentage extension at break decreased with the increase in GL. Rectangular specimens showed a 30% decrease in maximum breaking load and a 13% decrease in percentage extension at break, while dumbbell specimens showed reductions in the order of 28 and 6%, respectively, as the GL increased from 9.53 cm to 23.5 cm. Highly varying supramolecular architecture of the collagen matrix and the frictional slippage caused by the free ends present in the collagen fibrils, which induce a weak‐link effect similar to the one found in cotton fibers and yarns, are considered to be the probable reasons for this behavior. A limited scanning electron microscopic study has been undertaken to pictorially represent the breakage of leather at different GLs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1202–1209, 2006