A Study on the Mechanical and Tribological Properties of Carbon Fabric/PTFE Composites

Carbon fabric reinforced polytetrafluoroethylene (PTFE) composites with different PTFE content, viz. 30, 40, 50, 60, and 70 vol%, were fabricated by a dispersion impregnation technique followed by a hot-press process. The composites were evaluated for their mechanical and tribological properties. The tribological tests were conducted on a friction and wear tester with a ring-on-block arrangement. The mechanical properties were also tested and their relationship with tribological properties was analyzed. The worn surface and wear debris were analyzed by a scanning electron microscope (SEM) to study the wear mechanism. It was found that the resin content had a great influence on both the mechanical properties and the tribological properties, and the tribological properties were correlated with the mechanical properties. The composite with 50 vol% PTFE showed promising tribological behaviors under the selected test conditions.     

Evaluating the effect of different test parameters on the tensile mechanical properties of single crystal silver nanowires using molecular dynamics simulation

Nanowires show amazing mechanical properties with respect to their bulk counterpart owing to their very high specific surface and/or interface area and, thus, are widely studied among several researchers. But it is difficult to study the mechanical properties of nanowires at atomistic level, and computational tools provide the required solution. Molecular dynamics simulation studies were carried out in this work to evaluate the mechanical properties of single crystal silver nanowire subjected to tensile deformation under varying wire diameter (4–14 nm), test temperature (100–500 K), and strain velocity (1–6 Å/ps). The simulation were carried out in analogous to real experiment, and the engineering stress and strain were calculated from the simulation result of load and displacement data. The mechanical properties like yield strength and Young’s modulus were calculated from the engineering stress-strain curve. The effect of different test parameters like wire diameter, equilibration temperature, and strain velocity on the mechanical properties were also thoroughly investigated. The result shows that single crystal silver nanowire shows excellent mechanical properties and, thus, can be used as a reinforcing agent to develop ultra-high strength advanced materials for defense and aerospace applications.     

Effects of Viscosity Ratio on Morphological,Rheological and Mechanical Properties of PP/PBT Melt Spun Alloy Fibers

Phase morphology formation plays an important role in the mechanical properties of polymer alloy fibers. The development of the blend morphology depends not only on the intrinsic properties of the component polymers but also on extrinsic factors such as viscosity ratio, λ, in the melt spinning process. The effects of blend component viscosity ratio on the morphological, rheological, and mechanical properties of polypropylene/poly(butylene terephthalate) (PP/PBT) melt spun alloy fibers were investigated. Accordingly, two kinds of PP as matrix phase and two kinds of PBT as dispersed phase, with various melt viscosity, were physically mixed and then blended during the extrusion step of melt spinning. SEM micrographs and rheological and mechanical properties evaluations showed that the morphology of PP/PBT alloy fibers strongly depend on the viscosity ratio, λ. Finer diameter PBT fibrils were observed for Viscosity ratios less than 1 (λ < 1) compared to samples with λ > 1. The best mechanical properties in alloy fiber samples were obtained for the viscosity ratio closest to unity (sample with λ = 0.9). The lowest differences among measured complex viscosities at various shear rates (0.1, 10, and 100 s^?1) were also observed in samples with λ = 0.9. The results showed that the mechanical properties of alloy fiber samples are affected not only by morphological properties observed at different viscosity ratios but also by the properties of the individual polymer components.     

Powder compaction,sintering, and rolling of ultra high molecular weight polyethylene and its composites

The applicability of powder compaction and sintering techniques to the processing of ultra high molecular weight polyethylene (UHMWPE) powder is demonstrated. With proper processing procedure and type of UHMWPE powder, the mechanical properties obtained are nearly equivalent to those obtained by conventional melt processes. The properties were optimized by selection of a sintering temperature just above the melting point and by close control of particle size and distribution. The processability of UHMWPE is dependent on the morphology of the powder. Only those powders with a fibrous morphology provided good mechanical properties after sintering. The mechanical properties of powder compacts can be improved by several techniques. Liquid sintering with added normal molecular weight polyethylene, with close control of particle size and distribution and amount of the second component, yielded improved properties. Composites of UHMWPE, with short glass and graphite fiber reinforcement, processed by powder compaction and sintering resulted in increased modulus. The properties of these composites depended upon the amount of fibers, fiber length, fiber-matrix bonding, and fiber orientation. Rolling the powder-processed UHMWPE oriented the structure and improved the mechanical properties, although it decreased the mechanical properties of the glass and graphite fiber composites because of debonding between fiber and matrix. The properties of carbon black—UHMWPE mixtures were improved by rolling because of a more uniform distribution of carbon black.     

Investigation of the effects of tensile strain on optical properties of ZnO nanowire

In this paper, the effects of mechanical tensile strain on optical properties of ZnO nanowire before and after embedding ZnS nanowire were investigated by simulation. Finite element modeling (FEM) software package ABAQUS and three-dimensional (3D) finite-difference time-domain (FDTD) methods were furnished to analyze the problems numerically, including the nonlinear mechanical behavior and optical properties of the sample, respectively. The physical deformation model was imported into the FDTD to investigate optical properties of ZnO nanowire under mechanical tensile strain. Besides, the stress-strain curve via tensile experimental was compared with stress-strain curve that was obtained from finite element modeling. The results disclosed that the mechanical strain was demonstrated to play an important role in determining the optical properties of ZnO nanowire such as absorption coefficient and optical density.     

Mechanical Properties and Corrosion Resistance of Vulcanized Silicone Rubber after Exposure to Artificial Urine

Medical devices, such as Foley catheters, which are commonly fabricated from silicone rubber, need to have excellent mechanical properties and physiological inertness. This study reports the development of a facile method to prepare silicone rubber with excellent long-term performance by controlling the vulcanization procedure parameters only. Mechanical, viscoelastic, and chemical properties of vulcanized silicone rubber were investigated. The corrosion resistance of vulcanized silicone rubber was assessed by exposure to artificial body urine for a period of up to 14 days. The mechanical properties of silicone rubber were changed via adjusting the vulcanization procedure parameters. The improved mechanical properties of silicone rubber are attributed to an increase in crosslink density resulting from the proposed vulcanization technology. After 14 days of immersion in urine, no significant changes in mechanical properties and internal structure were observed. This indicated that the as-prepared rubber samples had high tear resistance and physiological inertness. These long-term properties are important for their applications as semi-permanent implant materials, such as Foley catheter balloons in clinics. Our process of vulcanization of silicone rubber may have potential for fabrication of such medical devices.     

Correlation of the Morphological and Mechanical Properties of a Biodegradable Blend Based on Polylactic Acid

A series of binary and ternary blends composed of polylactic acid (PLA), low-density polyethylene (LDPE), and chitosan (CS) were prepared and characterized in terms of their morphological and mechanical properties. The mechanical properties of the prepared blends, including tensile properties and impact strength, were compared with neat PLA. In addition, the effect of incorporation of maleic anhydride-grafted linear low-density polyethylene (LLDPE-g-MA) as a compatibilizing agent, and the order of mixing on the mechanical and morphological properties of the ternary blends were also studied. It was observed that addition of CS enhanced the stiffness of PLA/LDPE blends while it decreased the toughness and tensile strength. It was demonstrated that addition of LLDPE-g-MA, up to 10 wt%, had no significant compatibilizing effect. However, the mechanical results indicated that when 15 wt% of LLDPE-g-MA was loaded, it started to play a compatibilizing role and caused an improvement in the toughness properties of ternary blend.     

Pithecellobium Clypearia Benth Fiber/Recycled Acrylonitrile-Butadiene-Styrene (ABS) Composites Prepared in a Vane Extruder: Analysis of Mechanical Properties and Morphology

The effect of compatibilizer types and concentrations on the mechanical properties and morphology of Pithecellobium Clypearia Benth Fiber (PCBF)/recycled ABS composites prepared by a vane extruder were characterized. In addition, the percentage of compatibilizer was fixed at 8%, and the effect of lubricant concentrations on the mechanical properties and torque behaviors of the composites was also studied. Maleic anhydride grafted ABS (ABS-g-MAH) and maleic anhydride grafted PS (PS-g-MAH) were used as compatibilizers; the lubricant used was Struktol TPW 604 (blend of aliphatic carboxylic acid salts and mono diamides). The composite with 8% ABS-g-MAH showed superior mechanical properties compared to the composite without compatibilizer and the 8% PS-g-MAH compatibilized composites. Compared with PS-g-MAH, ABS-g-MAH was more effective for the composites to improve the interfacial interaction and mechanical properties. The comprehensive mechanical properties of PCBF/recycled ABS composite filled with 4% lubricant were better than the composites without lubricant and the composites with any other content of TPW 604. Moreover, the torque of the composites in an internal mixer decreased with an increasing lubricant content.     

Mechanical and Thermal Properties of Poly(Tetrahydrofurfuryl Methacrylate) Nano-Composites

To obviate the brittleness and improve the mechanical properties of poly(tetrahydrofurfuryl methacrylate) (PTHFMA), clay mineral nano-composites of PTHFMA with two different montmorillonites (MMT), Cloisite® 20A and Cloisite® 30B, were prepared. The mechanical properties were investigated by dynamic mechanical analysis (DMA) and nanoindentation. The thermal properties of the nano-composites were studied using thermogravimetric analysis (TGA). According to the DMA results, tanδ was increased by addition of the clay, leading to the improvement in the mechanical properties which was also confirmed by the nanoindentation results. TGA thermograms showed better thermal stability for the nano-composites compared to that of the homopolymer. Considering all results, the clay mineral polymer nano-composites (CPN) with Cloisite® 20A exhibited better properties compared to those with Cloisite® 30B. Transmission electron microscopy (TEM) micrographs, and X-ray diffraction (XRD) patterns validated intercalation-exfoliation of the clay mineral layers for the Cloisite 20A and intercalation of the Cloisite 30B in the polymer matrix.     

Banana fiber strands–reinforced polymer matrix composites

Banana fiber (BF)-reinforced low-density polyethylene (LDPE) unidirectional composites were fabricated by the compression molding process with 40 wt% fiber loading. The fibers were modified with methylacrylate (MA) mixed with methanol (MeOH) along with 2% benzyl peroxide under thermal curing method at different temperatures (50–90 °C) for different curing times (10–50 min) in order to have better compatibility with the matrix. The effect of fiber surface modification on the mechanical properties (tensile and impact properties) of the composites were evaluated. Monomer concentration, curing temperature, and curing time were optimized in terms of polymer loading and mechanical properties. The mechanical properties were found to be improved based on the improved interaction between the reinforcement and the matrix. Optimized BFs were again treated with 2–5 wt% starch solutions and composites made of 4% starch treated BF showed the highest mechanical properties than that of MA treated composites. Scanning electron microscopy (SEM) was performed to get an insight into the morphology of the composites. Water uptake and soil degradation test of the composites were also investigated.     

Morphology and Mechanical Properties of Polyamide 6/Acrylonitrile-Butadiene-Styrene Blends Containing Carbon Nanotubes

The blends of polyamide 6/acrylonitrile-butadiene-styrene (PA6/ABS), with added styrene-maleic acid copolymer (SMA) compatibilizer, were prepared through melt mixing in an internal mixer. The effects of blend composition and various process conditions, as well as the addition of multi-wall carbon nanotubes (MWCNTs) to the blends, on the morphology and mechanical properties were investigated. The morphology of the blends and blend nanocomposites were observed by scanning electron microscopy (SEM) and analyzed using an image analysis technique. The mechanical behavior of the blends was investigated by tensile and also impact testing. The results showed that the blend composition as well as the processing conditions significantly affected the morphology and mechanical properties of the PA6/ABS blends. Among the various compositions, the blend with 36?wt.% of ABS and 4?wt.% of SMA compatibilizer exhibited the best mechanical properties. Comparing various speeds and times of mixing, it was found that less mixing speed and longer mixing times resulted in the favorable morphology and conditions for achievement of the desired toughness for the polyamide 6. By adding different amounts of MWCNTs to the blends, it was found that the presence of the carbon nanotubes changed the viscosity of the resulting nanocomposite and thus changed the morphology. These nanocomposites also showed an improvement in mechanical properties. The MWCNTs acted as a second compatibilizer, resulting in a synergistic effect on the mechanical properties of the PA6/ABS blend nanocomposites.     

Acrylate Elastomer Toughened and UV Stabilized Polyoxymethylene

Acrylate elastomer (ACE) synthesized ourselves was mixed with antioxidative and UV stabilizer into polyoxymethylene (POM) matrices to investigate the effects of the ACE phase on the mechanical properties and UV stability of POM. For comparison, POM blended with same amount of TPU instead of ACE was used. Dispersion of the elastomer particles in POM matrices was investigated using SEM micrograph. Crystallinities of the specimen before and after UV ageing were also measured. The surface molecular weight and the mechanical properties of modified POM after UV ageing were determined. The result showed that excellent mechanical properties of the POM composites after UV‐irradiation could be obtained by blending with ACE.     

Natural fibre composites from polyethylene waste and hazelnut shell: dimensional stability,physical, mechanical and thermal properties

Within the framework of this study, the physical modification of high-density polyethylene waste foil was performed using finely ground hazelnut flour to produce a composite whose physical, mechanical and flammable properties make it possible to use inside and outside of buildings. Three mixtures were produced with filler shares of 11, 26 and 42 vol.% using equipment that is normally used in polymer processing, and no refining additives were applied. The produced materials were analysed for their processing (mass flow ratio), physical (density and moisture content) and mechanical properties (tensile strength, elongation at break and dynamic thermal analysis) and resistance to environmental factors (swelling and water absorption, thermogravimetric analysis and combustion heat). The particle size distribution of the filler and morphological properties of the composites (scanning electron microscopy) were also investigated. It was vital to obtain an inexpensive material with low absorptivity. The resulting materials are characterised by a low density, acceptable low absorptive and good mechanical properties; also, they can constitute an important fuel once their practical properties have been exploited.     

Influence of SiC Electron Acceptor–Donor Modification on Thermal and Physical Properties of Carbon Fiber/SiC/Epoxy Composites

In this work, the effects of electron acceptor–donor modification on the surface properties of SiC were investigated in the mechanical interfacial properties of carbon fibers-reinforced SiC-impregnated epoxy matrix composites. The surface properties of the SiC were determined according to acid/base values and FT-IR, and contact angle measurements. The thermal and mechanical interfacial properties of the composites were evaluated using a thermogravimetric analysis, critical strain energy release rate mode II (G _IIC), and impact strength testing. As a result, the electron acceptor-treated SiC had a higher acid value and polar component in surface free energy than did the untreated SiC or the electron donor-treated SiC. The G _IIC and impact strength mechanical interfacial properties of the composites had been improved in the specimens treated by acidic solutions due to the good wetting and a high degree of adhesion with electron donor characteristic epoxy resins.     

EPR spectroscopic and X-Ray diffraction studies of carbon fibers with different mechanical properties

The carbon fibers obtained by carbonization of polyacrylonitrile fibers were studied by electron paramagnetic resonance and X-ray diffraction analysis in the range of small and wide scattering angles. Their elastic and strength characteristics were also studied. The concentration of the paramagnetic centers was correlated with the mechanical properties of carbon fibers. The wide-angle X-ray diffraction study did not reveal essential structural differences in the carbon fiber samples with different mechanical properties. At the same time, the small-angle X-ray scattering study showed that the fiber nanostructures with different mechanical properties differ substantially.     

Fracture toughness of the epoxy/ATPEI-CTBN-ATPEI triblock copolymer/NMA blend system

The shortcoming of epoxy resin is the brittleness of this material though it shows excellent chemical, mechanical and electric properties. To improve fracture toughness of epoxy resin, rubbery materials that show high values in toughness but low values in glass transition temperature and mechanical properties, and thermoplastics that show high values in thermal and mechanical properties but relatively small increase in toughness were blended with epoxy. ATPEI-CTBN-ATPEI triblock copolymer, which consists of rubbery and thermoplastics blocks, was synthesized, and the triblock copolymer was blended with epoxy resin. The effects of parameters such as contents of the triblock copolymer, cure temperature, and contents of catalyst on the morphology of the blend systems were studied. From 30 wt% of the contents of the triblock copolymer, fracture toughness and impact energy absorption of the blend systems were increased significantly. This was due to the generation of nodular morphology in the system.     

电子辐照聚酰亚胺薄膜力学性能演化机理研究北大核心CSCD

利用空间综合辐照试验系统和X射线光电子能谱分析(XPS)、热重等分析测试对空间电子辐射环境下聚酰亚胺薄膜力学性能演化及机理进行了研究。研究发现,聚酰亚胺薄膜的拉力、抗拉强度和断裂伸长率随着电子辐照注量的增加先增加而后指数减小。由热重分析可知,电子辐照可引起聚酰亚胺薄膜的失重温度显著降低,在以失重10%作为判据的条件下,其失重温度由595℃下降为583℃。由XPS分析可知,电子辐照诱发聚酰亚胺薄膜化学价键的断裂和交联,在电子辐照初期,C—N键的断裂及引发的交联是导致力学性能增加的主要原因,而随着辐照注量的增加,C=O双键、—N(CO)键的断裂、新的C—N键的形成以及N元素的析出是导致聚酰亚胺薄膜力学性能降低的主要原因。     

Discontinuous basalt and glass fiber reinforced PP composites from textile prefabricates: effects of interfacial modification on the mechanical performance

Spun and blown basalt fibers and their PP matrix composites were investigated. The composites were manufactured by hot pressing technology from carded and needle punched prefabricate using PP fiber as matrix material. Glass and blown basalt fibers were treated with reaction product of maleic acid-anhydride and sunflower oil while spun basalt fibers had a surface coating of silane coupling agent. Fibers were investigated with tensile tests while composites were subjected to static and dynamic mechanical tests. The results show that blown basalt fibers have relatively poor mechanical properties, while spun basalt fibers are comparable with glass fibers regarding geometry and mechanical performance. The static and dynamic mechanical properties of glass and spun basalt fiber reinforced composites are similar and are higher than blown basalt fiber reinforced composites. Results were supported with SEM micrographs.     

Effect of Mixing Sequence on Phase Morphology and Mechanical Properties in Polyamide 6/Butadiene (Core) Styrene Acrylonitrile-G-Maleic Anhydride (Shell) Latex/Organoclay Ternary Nanocomposites

Ternary nanocomposites based on polyamide-6, maleated butadiene (core) -acrylonitrile-styrene (shell) rubber particles (PB-g-SAM), and modified montmorillonite (organoclay) were prepared by a twin-screw extruder. The glassy shell of the core-shell particles can act as a barrier which can resist the entrance of clay into the rubber phase. The influence of mixing sequence on the phase morphology and mechanical properties were studied. The microstructure of the ternary nanocomposites was characterized by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. It was found that the clay in the polyamide nanocomposites was partially exfoliated, exhibiting a mixture of exfoliated structures. The organoclay plates affected the interfacial adhesion between the polyamide-6 and the core-shell particles. The location of the organoclay plates in the blends with different mixing sequences produced differences of the mechanical properties. The results of mechanical testing revealed that the optimum mixing sequence to achieve balanced mechanical properties was mixing the polyamide-6 and organoclay first followed by mixing with the core-shell particles.     

Effect of fiber content and surface treatment on the mechanical properties of natural fiber composites produced by rotomolding

In this study, natural fibers (agave, coir, and pine) were surface treated with maleated polyethylene (MAPE) with two main objectives: (1) to improve the mechanical properties of natural fiber composites produced by rotational molding and (2) to increase the fiber content in the composite. The rotomolded composites were produced at 0, 10, 20, 30, and 40% wt. of fiber contents (treated or untreated) and characterized in terms of morphology and mechanical properties (hardness, impact, tension, and flexion). The results showed that MAPE surface treatment was more successful for agave and coir than for pine fibers due to their respective chemical composition. In general, surface treatment led to better fiber distribution and a more uniform composite morphology allowing the possibility to use higher fiber contents in rotational molding. At low fiber contents (10 and 20% wt.), the mechanical properties were improved using treated fiber composites (TFC) compared to the neat polymer and untreated fiber composites (UFC). Although the mechanical properties of TFC decreased at high fiber contents (30 and 40% wt.), they were substantially higher (about 160, 400, and 100% for impact, tensile, and flexural properties, respectively) than for UFC.