Tensile Strength (tensile + strength)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Tensile Strength

  • high tensile strength
  • lower tensile strength
  • maximum tensile strength
  • ultimate tensile strength

  • Terms modified by Tensile Strength

  • tensile strength measurement

  • Selected Abstracts

    High-Temperature Tensile Strength of Er2O3 -Doped ZrO2 Single Crystals

    José Y. Pastor
    The deformation and fracture mechanisms in tension were studied in single-crystal Er2O3 -doped ZrO2 monofilaments processed by the laser-heated floating zone method. Tensile tests were carried out between 25° and 1400°C at different loading rates and the dominant deformation and fracture mechanisms were determined from the shape of the stress,strain curves, the morphology of the fracture surfaces, and the evidence provided by monofilaments deformed at high temperature and broken at ambient temperature. The tensile strength presented a minimum at 600°,800°C and it was controlled by the slow growth of a crack from the surface. This mechanism was also dominant in some monofilaments tested at 1000°C and above, while others showed extensive plastic deformation before fracture at these temperatures. The strength of plastically deformed monofilaments was significantly higher than those which failed by slow crack growth due to the marked strain hardening capacity of this material. [source]

    Temperature Dependence of Tensile Strength for a Woven Boron-Nitride-Coated Hi-NicalonÔ SiC Fiber-Reinforced Silicon-Carbide-Matrix Composite

    Shuqi Guo
    The temperature dependence of tensile fracture behavior and tensile strength of a two-dimensional woven BN-coated Hi-NicalonÔ SiC fiber-reinforced SiC matrix composite fabricated by polymer infiltration pyrolysis (PIP) were studied. A tensile test of the composite was conducted in air at temperatures of 298 (room temperature), 1200, 1400, and 1600 K. The composite showed a nonlinear behavior for all the test temperatures; however, a large decrease in tensile strength was observed above 1200 K. Young's modulus was estimated from the initial linear regime of the tensile stress,strain curves at room and elevated temperatures, and a decrease in Young's modulus became significant above 1200 K. The multiple transverse cracking that occurred was independent of temperature, and the transverse crack density was measured from fractographic observations of the tested specimens at room and elevated temperatures. The temperature dependence of the effective interfacial shear stress was estimated from the measurements of the transverse crack density. The temperature dependence of in situ fiber strength properties was determined from fracture mirror size on the fracture surfaces of fibers. The decrease in the tensile strength of the composite up to 1400 K was attributed to the degradation in the strength properties of in situ fibers, and to the damage behavior exception of the fiber properties for 1600 K. [source]

    Modeling the Ultimate Tensile Strength of Unidirectional Glass-Matrix Composites

    R. E. Dutton
    The ultimate tensile strengths of a unidirectional glass-matrix composite were measured as a function of fiber volume fraction. The results were compared with predictions, using a refined solution of the stress field generated by an axisymmetric damage model, which incorporated the effect of stress concentration in the fiber caused by the presence of a matrix crack both before and after deflection at the fiber/matrix interface. Two possible locations for the fiber failure were considered: (1) at a transverse matrix crack, near a bonded fiber/coating interface and (2) at the tip of a debond, at the fiber/coating interface. At low fiber volume fractions, the measured ultimate tensile strength matched the prediction calculated, assuming no crack deflection. For higher volume fractions, the predictions calculated for a debonded crack matched the observed values. The model results were relatively insensitive to debond length and interfacial shear stress for the range of values in this study. In comparison, the global load-sharing model, which does not account for the stress singularity at the fiber/matrix interface, was found to overpredict the values of the ultimate tensile strength for all fiber volume fractions. An important contribution of the present work was to introduce the use of fiber volume fraction as a parameter for testing theoretical predictions of the mode of fiber failure. [source]

    Hochdynamische Materialeigenschaften von Ultrahochleistungsbeton (UHPC)

    Markus Nöldgen Dipl.-Ing.
    Baustoffe; Versuche; Dynamische Einwirkungen Abstract Der vorliegende Bericht liefert einen Beitrag zur Werkstoffbeschreibung von Ultrahochleistungsbetonen unter hochdynamischer Belastung. Grundlage für die Ermittlung der Werkstoffeigenschaften ist eine Hopkinson-Bar Versuchsreihe, die Werte für die dynamische Zugfestigkeit, den dynamischen E-Modul und die dynamische Bruchenergie unter Dehnraten von 102 · s,1 liefert. Ein Vergleich mit den Ergebnissen dieser Parameter für Normalbeton und hochfesten Betonen ermöglicht eine Einordnung des Ultrahochleistungsbetons in etablierte Ansätze und Berechnungsvorschriften und liefert einen Bewertungsansatz für die maßgebenden mechanischen Vorgänge. Unter Einbeziehung der Bruchenergie und der Spannungs-Rissöffnungs-Beziehung für UHPC in das RHT-Betonmodell werden Hydrocode Simulationen durchgeführt, die den Versuch am Hopkinson-Bar adäquat abbilden können. Material Properties of Ultra High Performance Concrete (UHPC) at High Strain Rates The presented paper is a contribution to the material description of Ultra High Performance Concrete (UHPC) under high-speed dynamical loading conditions. Based on a series of Hopkinson-Bar experiments dynamical material parameters such as the Tensile Strength, Young's Modulus and Fracture Energy are derived at high strain rates of 102 · s,1. A comparison with the results of these parameters for normal and high strength concrete leads to a qualitative and quantitative evaluation of UHPC at high strain rates. With the extension of the established RHT material model for UHPC by the material's Fracture Energy and Stress-Crack-Opening-Relation the Hopkinson-Bar experiments are simulated appropriately. [source]

    Compatibilization and development of layered silicate nanocomposites based of unsatured polyester resin and customized intercalation agent

    Luigi Torre
    Abstract In this study a procedure for the preparation of compatibilized nanoclays was used to produce effective nanocomposites based on unsatured polyester (UP) resin. A compatibilization procedure of the filler with a selected surfactant has been developed and optimized, the effect of organic modifiers on the synthesized nanocomposites properties was studied. Moreover, polyester/clay nanocomposites were prepared. In particular, samples were prepared using two different mixing methods. The properties and formation processes of the nanocomposites obtained using the two methods were compared. X-ray diffraction studies revealed the formation of intercalated/exfoliated nanocomposites structures. The effect of processing parameters, used for both the compatibilization procedure and the preparation of nanocomposites, was studied. Dynamic mechanical, thermal analysis, and rheological tests were performed to investigate the formation mechanism of UP/montmorillonite nanocomposite. In particular, mechanical properties of nanocomposites were studied using dynamic mechanical analysis and tensile tests. Mechanical, rheological, and thermal characterization have confirmed the validity of the used approach to compatibilize the nanoclay and to produce nanocomposites. Tensile strength and Young's modulus were modified by the loading of the organoclays. Furthermore, the rheology of the nanocomposite formulation provided processing information, while mechanical and dynamic mechanical characterization was performed on the nanocomposites produced with the newly compatibilized formulation. The results have shown that nanocomposites with better mechanical properties can be obtained through the selection of an appropriate compatibilization process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Morphologies and mechanical properties of HDPE induced by small amount of high-molecular-weight polyolefin and shear stress produced by dynamic packing injection molding

    Zhanchun Chen
    Abstract To better understand the effect of a small amount of high-molecular-weight polyethylene (HMWPE) on the mechanical properties and crystal morphology under the shear stress field, the dynamic packing injection molding (DPIM) was used to prepare the oriented pure polyethylene and its blends with 4% HMWPE. The experiment substantiated that the further improvement of tensile strength along the flow direction (MD) of high-density polyethylene (HDPE)/HMWPE samples was achieved, whereas the tensile strength along the transverse direction (TD) still substantially exceeded that of conventional molding. Tensile strength in both flow and TDs were highly enhanced, with improvements from 23 to 76 MPa in MD and from 23 to 31 MPa in TD, besides the toughness was highly improved. So, the samples of HDPE/HMWPE transformed from high strength and brittleness to high strength and toughness. The obtained samples were characterized via SEM and TEM. For HDPE/HMWPE, the lamellae of the one shish-kebab in the oriented region may be stretched into other shish-kebab structures, and one lamella enjoys two shish or even more. This unique crystal morphology could lead to no yielding and necking phenomena in the stress,strain curves of HDPE/HMWPE samples by DPIM. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Preparation and characterization of interpenetration polymer network films based on poly(vinyl alcohol) and poly(acrylic acid) for drug delivery

    Yu-Mei Yue
    Abstract A series of full interpenetrating polymer network (full-IPN) films of poly(acrylic acid) (PAA)/poly (vinyl alcohol) (PVA) were prepared by radical solution polymerization and sequential IPN technology. Attenuated total reflectance-Fourier transform infrared spectroscopy, swelling properties, mechanical properties, morphology, and glass transition temperature of the films were investigated. FTIR spectra analysis showed that new interaction hydrogen bonds between PVA and PAA were formed. Swelling property of the films in distilled water and different pH buffer solution was studied. Swelling ratio increased with increasing PAA content of IPN films in all media, and swelling ratio decreased with increasing PVA crosslink degree. Tensile strength and elongation at break related not only to the constitution of IPNs but also to the swelling ratio of IPNs. Mechanical property of glutaraldehyde (0.5%) for poly(vinyl alcohol) crosslinking was better than that of glutaraldehyde (1.0%). DSC of the IPN films showed only a single glass transition temperature (Tg) for each sample, and Tg data showed a linear relationship with network composition. Morphology was observed a homogeneous structure, indicating the good compatibility and miscibility between PAA and PVA. Potential application of the IPN films in controlled drug delivery was also examined using crystal violet as a model drug. The release rate of the drug was higher at 37°C than 25°C for all IPNs and also increased slightly with decreasing of poly(acrylic acid) content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


    ABSTRACT Tensile strength (TS), elongation at break (EAB) and elastic modulus (EM) of edible films prepared from 5, 7 and 9% whey protein isolate (WPI) plasticized with different levels of glycerol (Gly) (WPI : Gly = 3.6:1, 3:1 and 2:1) were investigated in order to completely characterize WPI-Gly films. On increasing protein concentration an increase in TS and EAB was observed. On the other hand, increasing Gly led to a decrease in TS and EM, while EAB increased. The addition of pullulan (Pul) into the film forming solution (FFS) increased EAB while TS, EM and thermal properties were reduced. This suggested that Pul had a similar effect as plasticizers. Films with higher Pul content showed lighter protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fourier transform infrared spectroscopy showed that hydrogen bonding was high in WPI : Pul films as compared with the control. This is attributed to the protein-polysaccharide interactions brought about by the dominance of Pul in the FFS. PRACTICAL APPLICATIONS This work describes some physical properties of films based on blends of whey protein isolate (WPI) and pullulan (Pul), made after a previous study on some characteristics of films based on pure WPI plasticized by glycerol. The most studied proteins in the edible films technology being gluten and WPI, the use of Pul in mixture with WPI is considered as a new investigation to explore the utilization of WPI-Pul in edible film and coating materials applied to food products. Furthermore, the use of WPI-Pul films and coatings could potentially extend the shelf life and improve the stability of the coated products as shown by the resultant properties in this investigation and previous works. [source]

    Properties of Poly(lactide)-Coated Paperboard for the Use of 1-Way Paper Cup

    J.-W. Rhim
    ABSTRACT:, Poly(lactide)-coated paperboards were prepared by a solution coating method, and the effect of coating to improve properties of paperboard used for the manufacturing of 1-way paper cups was tested. Surface of PLA-coated paperboards was smooth and shiny like PE-coated paperboard, and the coating weight and thickness increased linearly with increasing PLA concentration of coating solution. Tensile strength (TS) and elongation at break (E) of the paperboard also increased after PLA coating. Water vapor barrier or water-resistant properties tested, such as water vapor permeability (WVP), water absorptiveness (WA), and contact angle (CA) of water drop, indicated that water resistance of the paperboard was improved through surface coating with PLA. The increase in water resistance of PLA-coated paperboards was mainly due to the hydrophobicity of PLA and the improvement of water barrier properties increased depending on the PLA concentration. In addition, PLA-coated paperboard showed strong heat sealing property when coated with more than 1 w/v% of PLA. Wet strength of PLA-coated (3, w/v%) paperboard was comparable to or greater than that of PE-coated paperboard. All the test results indicated that the PLA-coated paperboard can be exploited for the manufacturing of 1-way paper cups as an alternative to the PE-coated paperboard. [source]

    Physical Properties of Gelidium corneum,Gelatin Blend Films Containing Grapefruit Seed Extract or Green Tea Extract and Its Application in the Packaging of Pork Loins

    Y.-H. Hong
    ABSTRACT:, Edible Gelidium corneum,gelatin (GCG) blend films containing grapefruit seed extract (GFSE) or green tea extract (GTE) were manufactured, and the quality of pork loins packed with the film during storage was determined. Tensile strength (TS) and water vapor permeability (WVP) of the films containing GFSE or GTE were better than those of the control. The film's antimicrobial activity against Escherichia coli O157:H7 and Listeria monocytogenes increased with increasing antimicrobial concentration, resulting in a decrease in the populations of bacteria by 0.77 to 2.08 and 0.91 to 3.30 log CFU/g, respectively. Pork loin samples were inoculated with E. coli O157:H7 and L. monocytogenes. The samples packed with the GCG film containing GFSE (0.08%) or GTE (2.80%) had a decrease in the populations of E. coli O157:H7 and L. monocytogenes of 0.69 to 1.11 and 1.05 to 1.14 log CFU/g, respectively, compared to the control after 4 d of storage. The results showed that the quality of pork loins during storage could be improved by packaging them with the GCG film containing GFSE or GTE. [source]

    Mechanical Properties, Water Vapor Permeabilities and Solubilities of Highly Carboxymethylated Starch-Based Edible Films

    K.W. Kim
    ABSTRACT: Tensile strength (TS), elongation (E), water vapor permeabilities (WVP) and solubilities were determined for highly carboxymethylated starch (HCMS)-based edible films plasticized with sorbitol (S), xylitol (X), mannitol (M) and glycerol (G). TS and E of HCMS-based film increased as the concentration of plasticizer S, M or × increased. TS of the HCMS-based film containing combined plasticizers were higher than those of films containing single plasticizer. The WVP of HCMS-based films seemed to decreased as the concentration of M, X or G plasticizer increased. Increasing plasticizer concentrations in HCMS-based film resulted in decreasing solubility of the films. [source]

    Biomechanical findings in rats undergoing fascial reconstruction with graft materials suggested as an alternative to polypropylene ,,

    M.L. Konstantinovic
    Abstract Aims Graft materials used for pelvic floor reinforcement should still be considered as investigational and, therefore, evaluated experimentally and within clinical trials. The present report describes our biomechanical findings in rats implanted with selected novel implant materials, which in recent years have been suggested as alternatives to plain polypropylene (PP) meshes. Methods Full thickness abdominal wall defects were primarily repaired by the implant of interest. Experiments involved eight different implant materials: two partly degradable synthetic implants, that is, a hybrid of polyglactin 910 with PP (Vypro II) and collagen coated PP (Pelvitex); two non-cross linked (Surgisis, InteX,n LP) and two cross-linked materials (Pelvicol, Pelvisoft) and two porous modifications of InteX,n LP and Pelvicol implants. At different time points (7, 14, 30, and 90 days), the implants and surrounding host tissue (explant) were harvested and tensiometry was performed. Tensile strength and location of breakage were recorded. Results In general resorbable non-cross linked collagen matrices and porous materials were weaker after 90 days; similar behavior was seen for implant materials alone and their construction with the surrounding native tissue. Both non-porous and porous modification of InteX,n LP appeared at 90 days as a very thin layer of collagen that was two-thirds, respectively one-third of the initial thickness. Conclusions In experimental conditions, sufficient strength was obtained only after 3 months, and PP containing constructs appeared as the strongest though reconstruction with Pelvicol showed comparable outcomes. Lower values for strength of non-cross linked and porous collagen materials are questioning their efficacy for pelvic floor reconstruction. Neurourol. Urodynam. 29:488,493, 2010. © 2009 Wiley-Liss, Inc. [source]

    Characterization and properties of activated nanosilica/polypropylene composites with coupling agents

    POLYMER COMPOSITES, Issue 11 2009
    Ong Hui Lin
    In this work, nanosilica/polypropylene composites containing 1 wt% of silica nanoparticles were prepared by melt mixing in a Thermo Haake internal mixer. Prior compounding, nanosilica was subjected to surface activation using sodium hydroxide (NaOH) solution. The effectiveness of the activation process was evaluated by measuring the amount of hydroxyl groups (OH) on the surface of nanosilica via titration method and supported by FTIR analysis. Two coupling agents namely 3-aminopropyl triethoxysilane (APTES) and neopentyl (diallyl)oxy, tri(dioctyl) phosphate titanate (Lica 12) were used for surface treatment after activation process. The mechanical properties of polypropylene matrix reinforced with silica nanoparticles were determined by tensile and impact test. Hydroxyl groups on the nanosilica surface played an important role in enhancing the treatment with silane coupling agents. To increase the amount of hydroxyl groups on the nanosilica surface, the optimum concentration of NaOH is 1 mol%. Tensile strength, tensile modulus, and impact strength of nanosilica/PP composites improved with activation process. As the coupling agent is concerned, APTES coupling agent is more pronounced in enhancing the mechanical properties of the composites when compared with Lica 12 coupling agent. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source]

    Preparation and characterization of chitosan/KSF biocomposite film

    POLYMER COMPOSITES, Issue 8 2009
    Aylin Alt
    Chitosan,clay biocomposites have been prepared in which KSF-montmorillonite (KSF) is used as filler and diluted acetic acid is used as solvent for dissolving and dispersing chitosan and montmorillonite, respectively. The effect of KSF loadings in biocomposites has been investigated. The characterization with different methods (FTIR, DSC, TGA, SEM, and XRD) on chitosan/KSF biocomposites systems was examined. Morphology and properties of chitosan biocomposites have been studied compared with those of pure chitosan. The FTIR and SEM results indicated the formation of an intercalated-and-exfoliated structure at low KSF content and an intercalated-and-flocculated structure at high KSF content. The thermal stability and the mechanical properties of the composites were also examined by DSC, TGA/DTG, and tensile strength measurements, respectively. The dispersed clay improves the thermal stability of the matrix systematically with the increase of clay loading. Tensile strength of a chitosan film was enhanced until the clay ratio up to 2 wt% and elongation-at break decreased with addition of clay into the chitosan matrix. The XRD results confirmed the intercalation of the biopolymer in the clay interlayer by the decrease of 2, values while the chitosan,clayratio increases. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source]

    Tailoring viscoelastic and mechanical properties of the foamed blends of EVA and various ethylene-styrene interpolymers

    POLYMER COMPOSITES, Issue 3 2003
    I-Chun Liu
    Foamed materials (EVA/ESI) have been prepared from blends of ethylene-vinyl acetate copolymer (EVA) and ethylene-styrene interpolymers (ESI) in the presence of various amounts of dicumyl peroxide (DCP). Four ESIs of different compositions were employed in this study; their styrene contents ranged from 30 to 73 wt% and their Tg ranged from ,2 to 33°C. It has been found that microcellular morphology, degree of crosslinking and expansion ratio were strongly affected by the DCP concentration and the type of ESI employed. A minimum degree of crosslinking was required for making good foams and the same degree of crosslinking could be achieved by employing a smaller amount of DCP for an EVA/ESI blend having a higher styrene content. In contrast to other EVA blends, such as EVA/LDPE, these EVA/ESI blends exhibited no existence of any optimum DCP concentration, and the , glass transition temperatures of the foams varied with the ESI type, covering a wide span from 0°C to 37°C. Therefore, it was possible to tailor the Tg of an EVA/ESI blend by choosing an appropriate type of ESI. Furthermore, by correctly tailoring the Tg, the EVA/ESI foam could be made into a rubbery material with a custom-designed damping factor. Tensile strength and modulus of the EVA/ESI foams increased generally with an increase in the styrene content, with the exception that ESIs with very low styrene content will confer on the blend a high modulus at small strain and a large elongation at break. [source]

    Gamma-irradiation effects on polypropylene-based composites with and without an internal lubricant

    Witold Brostow
    Polypropylene (PP) based materials for nonreusable syringe applications have been investigated, some of them containing an internal liquid lubricant. Hardness, tensile properties, and friction measured by two distinct procedures have been determined. We report three series of results: for nonirradiated samples; for samples directly after stopping the irradiation; and also for samples after accelerated aging equivalent to 2 years of shelf life. We find that effects of irradiation and aging on Shore A and Shore D hardness are small. Tensile strength at break, elongation at yield, and elongation at break all decrease after irradiation and then decrease still more after aging; these results are quantified but expected. By contrast, results from pin-on-disk tribometry are quite varied. In some cases , irradiation and aging both increase friction, in other cases both decrease friction. We also have a case when irradiation increases friction while aging decreases it,as well as vice versa. Possible mechanisms of all these types of behavior are advanced. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source]

    Evaluation of mechanical properties of adjacent flow weldline

    Koji Yamada
    Weldlines occur at the interface of two adjacent flows of material behind an obstructive pin in a cavity in injection molding (meldline or hot weldline). Tensile strength of such "adjacent flow weldline" in injection molded polystyrene plates was evaluated by a mechanical step-by-step milling technique. The strength when the milling depth was 1/5 of the thickness from each surface was about the same and independent of the distance from the pin. In contrast, the strength without milling decreased once and then increased along the flow direction. This demonstrates that the strength of a weldline is predominantly dependent on the properties of the surface layer of the weldline. The depth of the surface layer was defined as the depth of the weld, Dw. Dw reduced monotonously along the flow direction and faded away with the V-notch, resulting in an increase of strength along the direction. On the other hand, it was considered that the farther from the pin, the flow-induced molecular orientation in the surface layer is greater. It caused a decrease of the strength along the flow direction. The sequence of decrease and increase in tensile strength of adjacent flow weldline is due to the complex effect of these two contradictory factors. POLYM. ENG. SCI., 45:1180,1186, 2005. © 2005 Society of Plastics Engineers [source]

    Development of orientation and mechanical properties of extrusion cast polyamide 11 films in biaxial stretching process

    Sangkeun Rhee
    The development of orientation of extrusion cast polyamide 11 films in the biaxial stretching process was studied with birefringence and wide angle X-ray diffraction (WAXD) pole figures. White-Spruiell biaxial orientation factors of the crystalline phase were calculated with the pole figure data. Both biaxially stretched films were developed. Planarity of hydrogen bonding planes with respect to the film surface was observed from WAXD pole figures. Mechanical properties of the films were studied. Tensile strength and elongation at break were successfully correlated with the out-of-plane birefringences. [source]

    Synthesis and properties of BCDA-based polyimide,clay nanocomposites

    P Santhana Gopala Krishnan
    Abstract Bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA)-based polyimide,clay nanocomposites were prepared from their precursor, namely polyamic acid, by a solution-casting method. The organoclay was prepared by treating sodium montmorillonite (Kunipia F) clay with dodecyltrimethylammonium bromide at 80 °C. Polyamic acid solutions containing various weight percentages of organoclay were prepared from 4,4,-(4,4,-isopropylidenediphenyl-1,1,-diyldioxy)-dianiline and BCDA in N -methyl-2-pyrrolidone containing dispersed particles of organoclay at 20 °C. These solutions were cast on a glass plate using a Doctor's blade and then heated subsequently to obtain nanocomposite films. The nanocomposites were characterized using Fourier transform infrared spectroscopy, differential scanning calorimetry, thermal mechanical analysis, dynamic mechanical analysis, polarizing microscopy, scanning electron microscopy, transmission electron microscopy, wide-angle X-ray diffraction (WAXD) and thermogravimetric analysis. The glass transition temperature of the nanocomposites was found to be higher than that of pristine polymer. The coefficient of thermal expansion of the nanocomposites decreased with increasing organoclay content. WAXD studies indicated that the extent of silicate layer separation in the nanocomposite films depended upon the organoclay content. Tensile strength and modulus of the nanocomposite containing 1% organoclay were significantly higher when compared to pristine polymer and other nanocomposites. The thermal stability of the nanocomposites was found to be higher than that of pristine polymer in air and nitrogen atmosphere. Copyright © 2007 Society of Chemical Industry [source]

    Mechanical properties and thermal analysis of low-density polyethylene,+,polypropylene blends with dialkyl peroxide

    Kamil, irin
    Abstract Polypropylene,+,low density polyethylene (PP,+,LDPE) blends involving 0, 25, 50, 75 and 100,wt% of PP with dialkyl peroxide (DAP) were prepared by melt blending in a single-screw extruder. The effects of adding dialkyl peroxide on mechanical and thermal properties of PP,+,LDPE blends have been studied. It was found that at lower concentrations of peroxide (e.g., 0,0.08,wt% of dialkyl peroxide) LDPE component is cross-linked and Polypropylene (PP) is degraded in all compositions of PP,+,LDPE blends. Mechanical properties (Tensile strength at break, at yield and elongation at break), Melt flow index (MFI), hardness, Scanning Electron Microscope (SEM) and thermal analyses (DSC) of these blends were examined. Because of serious degradation or cross-linking the mechanical properties and the crystallinty (%) of those products were decreased as a result of increasing peroxide content. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Pan-milling mixing , a novel approach to forming polymer blends and controlling their morphology

    Zhe Chen
    Abstract A novel technique (pan-milling mixing) was developed to control the morphology and thus enhance the mechanical properties of polypropylene/polyamide 6 (PP/PA6) systems. Through pan-milling at ambient temperature, PP/PA6 pellets of particle size 2,4,mm can be effectively pulverized to well-mixed micrometre fine powders in the solid state. During pan-milling of mixtures of PP and PA6, the polymer molecules undergo chain scission and form copolymers that compatibilize the two polymers in situ. By press moulding the finely mixed PP/PA6 powder obtained at a temperature between the melting points of PA6 and PP (for example 200,°C), a blend can be obtained in which the PA6 powder, retained throughout the process in the solid state, is well dispersed in the PP matrix. The mechanical properties of the system are much better than that of PP/PA6 blends prepared by common twin screw extrusion mixing and injection moulding. Tensile strengths of the fine PA6 particle filled PP/PA6 (70/30) blend is 29.3,MPa, which is 6.1,MPa higher than that of a conventionally prepared PP/PA6 blend. The Izod notched impact strength of a fine PA6 particle-filled PP/PA6 (70/30) blend is 6.34,kJ,m,2, which is 1.72,kJ,m,2 higher than that of a conventionally prepared PP/PA6 blend. Morphological analysis shows that the domain size of PA6 in the system is much smaller than that of the PP/PA6 blend, and can be controlled by the processing conditions such as temperature. © 2001 Society of Chemical Industry [source]

    Effect of Cog Threads under Rat Skin

    Hyo Jook Jang MD
    Background. The aging face loses the tensile strength of structural integrity. Cog threads have been used recently to tighten lax skin and soft tissue. Objective. A comparative study of the effects of cog, monofilament, and multifilament threads under rat skin. Methods. Each cog, monofilament, and multifilament thread was inserted under the facial skin of a cadaver and the panniculus carnosus of rat dorsal skin. The maximum holding strength (MHS) of the thread and the tearing strength of the skin around the thread were measured with a tensiometer. The thickness of the capsule around the thread and the myofibroblasts was observed histologically. Results. In the cadaver, the MHS of the cog thread was 190.7 ± 65.6 g. It was greater than that of the monofilament (22.4 ± 7.7 g) or multifilament (40.4 ± 19.7 g) thread. In the rat, the MHS of the cog thread was 95.1 ± 18.8 g. It was greater than that of the monofilament (4.3 ± 1.3 g) or multifilament (10.9 ± 2.1 g) thread in the second week. The thickness of the capsule around the cog thread was 93.0 ± 3.2 ,m. It was thicker than the monofilament thread's capsule, 39.2 ± 12.1 ,m, in the fourth week. The number of myofibroblasts presented significantly more in the cog (96.0 ± 72.4) than in the monofilament thread (4.3 ± 4.4). The rumpled in-between skin suspended by each of the three different threads returned to its original state in 2 weeks. Conclusion. The cog thread placed under the rat skin immediately pulled the skin and subcutaneous tissue. The myofibroblasts around the thread played a role in fibrous tissue contracture 4 weeks postinsertion of the thread. These findings could be the basis for clinical application. THIS STUDY WAS SUPPORTED BY A GRANT FROM THE KOREA HEALTH 21 R&D PROJECT, MINISTRY OF HEALTH AND WELFARE, REPUBLIC OF KOREA. [source]

    Use of a Deep Polypropylene Suture during Earlobe Repair: A Method to Provide Permanent Reinforcement in the Prevention of Recurrent Earlobe Tract Elongation

    Joseph F. Greco MD
    Background. Cosmetic repair of elongated or lacerated earlobe tracts is a commonly encountered dermatologic procedure. For esthetic purposes, patients may choose to repierce the repaired lobe over the original site. Subsequent piercing within a scarred area potentially increases the risk of recurrent tract elongation secondary to the reduced tensile strength of the scar. Objective. To strengthen a damaged earlobe by incorporating a nonabsorbable, dermal polypropylene suture during earlobe repair. Methods. The technique is described within the text. Results. A deep polypropylene suture placed within a repaired earlobe tract provides a permanent barrier above which repiercing can be performed. Conclusion. Permanent reinforcement of the repaired earlobe serves to reduce the possibility of recurrent elongation of the earlobe tract. The technique is relevant when repeat piercing is desired over the original site. JOSEPH F. GRECO, MD, CHRISTINE S. STANKO, MD, AND STEVEN S. GREENBAUM, MD, HAVE INDICATED NO SIGNIFICANT INTEREST WITH COMMERCIAL SUPPORTERS. [source]

    Modelling increased soil cohesion due to roots with EUROSEM

    S. De Baets
    Abstract As organic root exudates cause soil particles to adhere firmly to root surfaces, roots significantly increase soil strength and therefore also increase the resistance of the topsoil to erosion by concentrated flow. This paper aims at contributing to a better prediction of the root effects on soil erosion rates in the EUROSEM model, as the input values accounting for roots, presented in the user manual, do not account for differences in root density or root architecture. Recent research indicates that small changes in root density or differences in root architecture considerably influence soil erosion rates during concentrated flow. The approach for incorporating the root effects into this model is based on a comparison of measured soil detachment rates for bare and for root-permeated topsoil samples with predicted erosion rates under the same flow conditions using the erosion equation of EUROSEM. Through backwards calculation, transport capacity efficiencies and corresponding soil cohesion values can be assessed for bare and root-permeated topsoils respectively. The results are promising and present soil cohesion values that are in accordance with reported values in the literature for the same soil type (silt loam). The results show that grass roots provide a larger increase in soil cohesion as compared with tap-rooted species and that the increase in soil cohesion is not significantly different under wet and dry soil conditions, either for fibrous root systems or for tap root systems. Power and exponential relationships are established between measured root density values and the corresponding calculated soil cohesion values, reflecting the effects of roots on the resistance of the topsoil to concentrated flow incision. These relationships enable one to incorporate the root effect into the soil erosion model EUROSEM, through adapting the soil cohesion input value. A scenario analysis shows that the contribution of roots to soil cohesion is very important for preventing soil loss and reducing runoff volume. The increase in soil shear strength due to the binding effect of roots on soil particles is two orders of magnitude lower as compared with soil reinforcement achieved when roots mobilize their tensile strength during soil shearing and root breakage. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Instability investigation of cantilevered seacliffs

    Adam P. Young
    Abstract Wave action is a fundamental mechanism in seacliff erosion, whereby wave undercutting creates an unstable cantilevered seacliff profile and can lead to large catastrophic cliff failures, thus threatening coastal infrastructure. This study investigated the instability of two such failures that occurred in Solana Beach, California, by combining terrestrial LIDAR scanning, cantilever beam theory and finite element analysis. Each landslide was detected by evaluating the surface change between subsequent high resolution digital terrain models derived from terrestrial LIDAR data. The dimensions of failed cantilever masses were determined using the surface change measurements and then incorporated into failure stress analysis. Superimposing stress distributions computed from elastic cantilever beam theory and finite element modeling provided a method to back-calculate the maximum developed tensile and shear stresses along each failure plane. The results of the stress superposition revealed that the bending stresses caused by the cantilevered load contributed the majority of stress leading to collapse. Both shear and tensile failure modes were investigated as potential cliff failure mechanisms by using a comparison of the back-calculated failure stresses to material strengths found in laboratory testing. Based on the results of this research, the tensile strength of the cliff material was exceeded at both locations, thus causing the cliffs to collapse in tension. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Crust strength: a wind tunnel study of the effect of impact by saltating particles on cohesive soil surfaces

    M. A. Rice
    Abstract A wind tunnel study examined the effect of distributions of saltating particles on sediment surfaces which were characterized by distributions of their tensile strength. The sediments consisted of varying proportions of large sand-sized particles with a fine particle cement. The energies of the impacting particles and the surface strengths were compared with the mass of material lost from the surface. It is important to consider distributions of parameters rather than mean values only, since abrasion and erosion may occur from surfaces not predicted from average strength and saltation velocities. At the impact velocities used in this study (mean velocity 4·4 m s,1, with standard deviation of 0·51), surfaces containing less than 12 per cent fine material were easily eroded, but insignificant erosion occurred when the fine particle content exceeded 60 per cent. Small amounts of cementing material were easily ruptured, allowing the large sand grains to be moved (largely in creep) by the bombarding particles. A significant amount of energy was lost to the bed. As the percentage of fine material increased, the surface became more difficult to break up and less energy was lost to the bed. The probability that erosion will occur for known energy distributions of impacting particles and surface strength can be calculated and the mass loss increases exponentially with a decrease in the percentage of fine cementing particles. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Tensile strength equation for HSS bracing members having slotted end connections

    Sang-Whan Han
    Abstract In the previous study, the authors investigated the effect of w/t ratios on the behaviour of bracing members under symmetric cyclic loading in compression and tension. In this study, 11 bracing members with slotted end sections made of cold-formed square hollow structural sections (HSS) were tested. The w/t ratios ranged from 8 to 28. Unlike the test results of other former studies obtained under compression-oriented cyclic loading, the results of this study showed that bracing members having a smaller w/t ratio (<14) had less deformation and less energy dissipation capacity, and a shorter fracture life compared with other specimens. Such inferior behaviour resulted from early fracture at the slotted end section. This study compares tensile strength obtained from the design equations in the AISC LRFD manual and Eurocode 3 using the actual strengths of the tested specimens. This study found that for preventing early fracture in HSS bracing members, design fracture strength should be larger than design yield strength. Design strength equations are proposed for bracing members in special concentrically braced frames (SCBF). The proposed design equations are verified by experimental tests conducted under symmetric cyclic loading in tension and compression using two HSS bracing members designed according to the proposed equation. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Mechanical behavior of bovine periodontal ligament under tension-compression cyclic displacements

    Tatsuya Shibata
    In the present study, the mechanical response of bovine periodontal ligament (PDL) subjected to displacement-controlled tension,compression harmonic oscillations and subsequent rupture was examined. Specimens including dentine, cementum, PDL, and alveolar bone were extracted from different depths and locations of bovine first molars. They were immersed in a saline solution at room temperature and clamped on their bone and dentine extremities. The samples were tested at ±35% of the PDL's width, with a frequency of 1 Hz. The mechanical parameters evaluated were hysteresis, phase lag, and the modulus of the stress,stretch ratio curves in tension and compression. The tensile strength and the corresponding stretch ratio were also recorded. Stress,stretch ratio curves indicated a non-linear, time-dependent response with hysteresis and preconditioning effects. The hysteresis and phase lag in compression were much higher than in tension, suggesting that the dissipated energy was higher in compression than in tension. The root depth and location did not play essential roles for the tension or compression data, with the exception of limited statistical differences for tensile strength and corresponding stretch ratio. Thus, biological variability in the specimens, as a result of different bone contours, PDL width, and fiber orientation, did not affect the energy-absorbing capacity of the PDL. The evolution of the stress rate with stress demonstrated a constant increase of stiffness with stress. The stiffness values were twofold higher in tension than in compression. The data also showed that the stiffness of the PDL was comparable with data reported for other soft tissues. [source]

    Environmental Behavior and Stress Corrosion Characteristics of Nano/Sub-Micron E950 Aluminum Alloy,

    Eli Aghion
    The corrosion performance and stress corrosion resistance of E950 Aluminum alloy with nano/sub-micron structure were evaluated in 3.5% NaCl solution. The results obtained indicated that the corrosion and stress corrosion resistance of E950 alloy were relatively reduced compared to that of the conventional coarse-grained alloy (Al,4.65%Mg). In particular, the inherently improved ultimate tensile strength of E950 alloy was significantly decreased under stress corrosion conditions. [source]

    Anisotropic Behavior of Radiopaque NiTiPt Hypotube for Biomedical Applications

    Zhicheng Lin
    This paper presents the first characterization of anisotropic stress,strain behavior in micron-sized specimens cut directly from hypotubes, the starting material for the manufacture of endovascular stents and other biomedical devices, of a new radiopaque alloy NiTiPt. Experimental results show that NiTiPt hypotube has very different anisotropic characteristics when compared to its NiTi counterpart including higher tensile strength and strain, higher stress,strain nonlinearity, smaller hysteresis loop, and sharper tails during loading,unloading. [source]