Home About us Contact
|
Home About us Contact | ||
|
|
||
Mechanical Tests (mechanical + test)
Selected AbstractsCOMPARISON OF MECHANICAL TESTS FOR EVALUATING TEXTURAL CHANGES IN POTATOES DURING THERMAL SOFTENINGJOURNAL OF TEXTURE STUDIES, Issue 6 2002W. K. SOLOMON ABSTRACT The changes in the texture of cylindrical samples of potato tissues immersed in water at 60, 70, 80 and 90C for up to 80 min were monitored at each temperature in terms of tangent modulus of elasticity in axial and radial compression tests, and elasticity and viscosity parameters in creep and stress relaxation tests. The magnitude of all mechanical test parameters decreased with an increase in heating time and temperature. The creep and stress relaxation responses of individual potato samples were adequately represented by respective mechanical models (R2= 0.94 to 0.99). The mechanical test parameters followed apparent first-order degradation kinetics due to the effect of thermal softening, and the rate constant was used as an index of the sensitivity of a mechanical test. The radial compression test was relatively more sensitive than the axial test. Based on an overall comparison, the parameters from creep and stress relaxation tests were found to be the most sensitive in describing the textural changes during thermal softening of potatoes. [source] Effect of freeze-drying and gamma irradiation on the mechanical properties of human cancellous boneJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2000O. Cornu Freeze-drying and gamma irradiation are commonly used for preservation and sterilization in bone banking. The cumulative effects of preparation and sterilization of cancellous graft material have not been adequately studied, despite the clinical importance of graft material in orthopaedic surgery. Taking benefit from the symmetry of the left and right femoral heads, the influence of lipid extraction followed by freeze-drying of a femoral head and a final 25-kGy gamma irradiation was determined, with the nonirradiated, nonprocessed counterpart as the control. Five hundred and fifty-six compression tests were performed (137 pairs for the first treatment and 141 pairs for the second). Mechanical tests were performed after 30 minutes of rehydration in saline solution. Freeze-dried femoral heads that had undergone lipid extraction experienced reductions of 18.9 and 20.2% in ultimate strength and stiffness, respectively. Unexpectedly, the work to failure did not decrease after this treatment. The addition of gamma irradiation resulted in a mean drop of 42.5% in ultimate strength. Stiffness of the processed bone was not modified by the final irradiation, with an insignificant drop of 24%, whereas work to failure was reduced by a mean of 71.8%. Freeze-dried bone was a bit less strong and stiff than its frozen control. Its work to failure was not reduced, due to more deformation in the nonlinear domain, and it was not brittle after 30 minutes of rehydration. Final irradiation of the freeze-dried bone weakened its mechanical resistance, namely by the loss of its capacity to absorb the energy (in a plastic way) and a subsequent greater brittleness. [source] Ultraviolet curing of acrylic systems: Real-time Fourier transform infrared, mechanical, and fluorescence studiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2002Carmen Peinado Abstract The photopolymerization of acrylic-based adhesives has been studied by Fourier transform infrared and fluorescence analysis in real time. Real-time infrared spectroscopy reveals the influence of the nature of the photoinitiator on the kinetics of the reaction. Furthermore, the incident light intensity dependence of the polymerization rate shows that primary radical termination is the predominant mechanism during the initial stages of the curing of the acrylic system with bis(2,4,6-trimethylbenzoyl) phenyl phosphine oxide (TMBAPO) as a photoinitiator. The fluorescence intensity of selected probes increases during the ultraviolet curing of the adhesive, sensing microenvironmental viscosity changes. Depending on the nature of the photoinitiator, different fluorescence,conversion curves are observed. For TMBAPO, the fluorescence increases more slowly during the initial stage because of the delay in the gel effect induced by primary radical termination. Mechanical tests have been carried out to determine the shear modulus over the course of the acrylic adhesive ultraviolet curing. In an attempt to extend the applications of the fluorescence probe method, we have undertaken comparisons between the fluorescence changes and shear modulus. Similar features in both curves confirm the feasibility of the fluorescence method for providing information about microstructural changes during network formation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4236,4244, 2002 [source] Investigating mechanical behaviour at a core,sheath interface in peripheral nerveJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 4 2004Rachel L. Tillett Abstract As peripheral nerves bend and stretch, internal elements need to move in relation to each other. However, the way in which intraneural components interact is poorly understood. Previous work identified a distinct core and sheath in the rat sciatic nerve and provides a useful model with which to investigate this interaction. Here we have focused on identifying the mechanical and anatomical characteristics of the interface between core and sheath. Nerve samples, 15 and 20 mm long, of rat sciatic nerves were harvested and placed in a purpose-built jig, and a tensile testing machine was used to pull core from sheath. Mechanical tests of specimens in which core had been previously pulled from sheath by 25% of its initial length achieved a mean pull-out force approximately six times smaller than that achieved using intact controls. These results are consistent with the proposal that core,sheath interactions involve physical connections rather than a viscous fluid interface. Anatomical features of this interface were characterised using transmission electron microscopy. It appeared that sheath was derived from epineurium and most of the perineurium, whilst core consisted of endoneurium and a small proportion of the perineurium: the plane of cleavage appeared to involve the innermost perineurial cell layer. [source] Processability and mechanical properties of commercial PVC plastisols containing low-environmental-impact plasticizersJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 3 2009Paola Persico Preliminary results are presented concerning the use of less-toxic plasticizers such as dioctyl adipate (DOA) and acetyl tributyl citrate (ATBC) in plastisol formulations for rotational molding technology. The DOA and ATBC plasticizers have been studied by comparing the effects of their content, molecular architecture, and polarity on the rheological behavior of liquid plastic systems and on the mechanical properties of the ultimate products prepared with PVCs having different particle sizes and molecular-weight distributions. Rheological tests have confirmed the differences in solvent power of the diethylhexyl phthalate (DOP), DOA, and ATBC plasticizers. The glass transition temperatures measured on rotomolded samples have shown that the use of ATBC leads to a more nearly rigid system as a consequence of the branched structure and polarity of this plasticizer when compared with DOA. Mechanical tests carried out on final products after natural and forced environmental aging revealed a slight decrease in their performance. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers [source] Effect of clay exfoliation and organic modification on morphological, dynamic mechanical, and thermal behavior of melt-compounded polyamide-6 nanocompositesPOLYMER COMPOSITES, Issue 2 2007Smita Mohanty Abstract Polyamide-6/clay nanocomposites were prepared employing melt bending or compounding technique followed by injection molding using different organically modified clays. X-ray diffraction and transmission electron microscopy were used to determine the molecular dispersion of the modified clays within the matrix polymer. Mechanical tests revealed an increase in tensile and flexural properties of the matrix polymer with the increase in clay loading from 0 to 5%. C30B/polyamide-6 nanocomposites exhibited optimum mechanical performance at 5% clay loading. Storage modulus of polyamide-6 also increased in the nanocomposites, indicating an increase in the stiffness of the matrix polymer with the addition of nanoclays. Furthermore, water absorption studies confirmed comparatively lesser tendency of water uptake in these nanocomposites. HDT of the virgin matrix increased substantially with the addition of organically modified clays. DSC measurements revealed both , and , transitions in the matrix polymer as well as in the nanocomposites. The crystallization temperature (Tc) exhibited an increase in case of C30B/polyamide-6 nanocomposites. Thermal stability of virgin polyamide-6 and the nanocomposites has been investigated employing thermogravimetric analysis. POLYM. COMPOS., 28:153,162, 2007. © 2007 Society of Plastics Engineers [source] Magnetorheological elastomers based on isobutylene,isoprene rubberPOLYMER ENGINEERING & SCIENCE, Issue 3 2006Yinling Wang Magnetorheological (MR) elastomers are a group of smart materials whose modulus can be controlled by the application of an external magnetic field. In this paper, MR elastomers based on isobutylene,isoprene rubber were prepared by the common manufacturing procedure of rubber and the corresponding MR effect, mechanical properties, and thermal stability were investigated. The results showed that MR effect varied with the volume content of iron particles and a maximum of 20% in MR effect was obtained at 15 vol% of iron particles. The relationship between MR effect and microstructure was discussed in detail. Mechanical tests showed that iron particles could improve the tensile strength and hardness. However, compared with carbon black with the same volume content, the reinforcing effect was far worse. TG analysis showed the thermal stability of isobutylene,isoprene rubber was improved by incorporation of iron particles. POLYM. ENG. SCI. 46:264,268, 2006. © 2006 Society of Plastics Engineers [source] Association of Geometric Factors and Failure Load Level With the Distribution of Cervical vs.JOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2006Trochanteric Hip Fractures Abstract We experimentally studied the distribution of hip fracture types at different structural mechanical strength. Femoral neck fractures were dominant at the lowest structural strength levels, whereas trochanteric fractures were more common at high failure loads. The best predictor of fracture type across all failure loads and in both sexes was the neck-shaft angle. Introduction: Bone geometry has been shown to be a potential risk factor for osteoporotic fractures. Risk factors have been shown to differ between cervical and trochanteric hip fractures. However, the determinants of cervical and trochanteric fractures at different levels of structural mechanical strength are currently unknown. In addition, it is not known if the distribution of fracture types differs between sexes. The aim of this experimental study on excised femora was to investigate whether there exist differences in the distribution of cervical and trochanteric fractures between different structural mechanical strength levels and different sexes and to identify the geometric determinants that predict a fracture type. Materials and Methods: The sample was comprised of 140 cadavers (77 females: mean age, 81.7 years; 63 males: mean age, 79.1 years) from whom the left femora were excised for analysis. The bones were radiographed, and geometrical parameters were determined from the digitized X-rays. The femora were mechanically tested in a side impact configuration, simulating a sideways fall. After the mechanical test, the fracture patterns were classified into cervical and trochanteric. Results: The overall proportion of cervical fractures was higher in females (74%) than in males (49%) (p = 0.002). The fracture type distribution differed significantly across load quartiles in females (p = 0.025), but not in males (p = 0.205). At the lowest load quartiles, 94.7% of fractures in female and 62.5% in males were femoral neck fractures. At the highest quartiles, in contrast, only 52.6% of fractures in females and 33.3% in males were cervical fractures. Among geometric variables, the neck-shaft angle was the best predictor of fracture type, with higher values in subjects with cervical fractures. This finding was made in females (p < 0.001) and males (p = 0.02) and was consistent across all failure load quartiles. Conclusions: Femoral neck fractures predominate at the lowest structural mechanical strength levels, whereas trochanteric fractures are more common at high failure loads. Females are more susceptible to femoral neck fractures than males. The best predictor of fracture type across all structural strength levels and both sexes was the neck-shaft angle. [source] Early bone in-growth ability of alumina ceramic implants loaded with tissue-engineered boneJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2006Yasuaki Tohma Abstract To enhance early bonding of an alumina ceramic implant to bone, we evaluated a method of seeding the implant surface with bone marrow mesenchymal cells that differentiated to osteoblasts and bone matrix prior to implantation. The usefulness of the method was evaluated in Japanese white rabbits. In our study, an alumina ceramic test piece loaded with differentiated osteoblasts and bone matrix by a tissue engineering technique was implanted into rabbit bones. Three weeks after the procedure, evaluation of mechanical bonding and histological examination were performed. Histological examination of the noncell-loaded implant surfaces showed no bone infiltration into the implant gap. However, the cell-loaded implant surfaces exhibited new bone infiltration into the implant gap with mechanical bonding. In the mechanical test, the average failure load was 0.60 kgf for the noncell-loaded side and 1.49 kgf for the cell-loaded side. Preculturing mesenchymal cells on the surface of the alumina ceramic prior to implantation increased the debonding strength by two and half times. The present findings indicate early bonding between the implant and bone three weeks after the procedure. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] COMPARISON OF MECHANICAL TESTS FOR EVALUATING TEXTURAL CHANGES IN POTATOES DURING THERMAL SOFTENINGJOURNAL OF TEXTURE STUDIES, Issue 6 2002W. K. SOLOMON ABSTRACT The changes in the texture of cylindrical samples of potato tissues immersed in water at 60, 70, 80 and 90C for up to 80 min were monitored at each temperature in terms of tangent modulus of elasticity in axial and radial compression tests, and elasticity and viscosity parameters in creep and stress relaxation tests. The magnitude of all mechanical test parameters decreased with an increase in heating time and temperature. The creep and stress relaxation responses of individual potato samples were adequately represented by respective mechanical models (R2= 0.94 to 0.99). The mechanical test parameters followed apparent first-order degradation kinetics due to the effect of thermal softening, and the rate constant was used as an index of the sensitivity of a mechanical test. The radial compression test was relatively more sensitive than the axial test. Based on an overall comparison, the parameters from creep and stress relaxation tests were found to be the most sensitive in describing the textural changes during thermal softening of potatoes. [source] Coaxial electrospinning of PC(shell)/PU(core) composite nanofibers for textile applicationPOLYMER COMPOSITES, Issue 5 2008Xiao-Jian Han To develop a novel functional composite material for textile application, a coaxial electrospinning technique was investigated to electrospin two different polymer solutions into core-shell structured nanofibers in which polyurethane and polycarbonate were used as core and shell materials, respectively. The resultant nanofibers were subsequently characterized by means of scanning electron microscope, transmission electron microscopy, fourier transform infrared spectroscopy, and tensile mechanical test. Furthermore, water vapour transmission rate and pliability of the resulting nonwoven mats were also measured. The preliminary results indicated that it is feasible to attach composite nanofibers, with possible fictionalization on the shell material, onto a substrate fabric. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Anterior Cruciate Ligament Reconstruction Using Chitin-coated Fabrics in a Rabbit ModelARTIFICIAL ORGANS, Issue 1 2010Tomoyuki Kawai Abstract Experimental anterior cruciate ligament (ACL) reconstruction was carried out in a rabbit model, in which a chitin-coated polyester graft was used as the scaffold, and a noncoated graft was used as a control graft. After 8 weeks implantation, a mechanical test of the knee and histometric measurement of the graft and surrounding tissues were carried out. A tensile test of the femur-graft-tibia specimen showed that the knee treated with the coated graft had a peak resistance force of 42.2 ± 12.7 N, which was significantly greater than the 19.2 ± 15.3 N of the knee treated with the control graft. The histometric measurement revealed that the area of bone tissue within the section of the coated graft in the femoral bone tunnel was 3.43 ± 1.73 mm2, which was significantly greater than the area of 0.29 ± 0.37 mm2 of the control graft. Similarly, the area of soft tissue within and around the midsubstance of the coated graft located in the articular cavity was significantly greater than that of the control graft. The chitin coating enhanced the formation of bone tissue in the femoral bone tunnel and soft tissue in the articular cavity, and increased the attachment strength of the graft to the bone. Thus, the efficacy of the chitin coating for the ACL reconstruction scaffolds was demonstrated. [source] Impact of ageing on the antinociceptive effect of reference analgesics in the Lou/c ratBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2002Didier Jourdan Research on the evolution of experimental pain perception and on the achievement of analgesia with ageing has led so far to contradictory results. This study investigated in the rat the impact of ageing on the antinociceptive effect of reference analgesics, acetaminophen (50, 100, 200, 400 mg kg,1 po), aspirin (50, 100, 200, 400 mg kg,1 sc), clomipramine (5, 10, 20, 40 mg kg,1 sc) and morphine (1.25, 2.5, 5, 10 mg kg,1 sc). Lou/c rats were chosen because they provide a model of healthy ageing and they do not develop obesity with age. Three groups of 40 rats each (mature (4 months), middle-aged (18 months) and old (26 months)), were treated with each drug at 14 days interval. Two tests were used: a thermal test (tail immersion in 48°C water and measurement of reaction latency) and a mechanical test (paw pressure and measurement of struggle threshold). Results confirm the increased mechanical sensitivity to pain and no change in thermal sensitivity for old rats compared to mature and middle-aged animals. They show a marked decrease in the effect of morphine with age and no age-related effect for acetaminophen, aspirin or clomipramine. Plasma levels of morphine and metabolites are not different in the three age groups. It is likely that the influence of age on morphine analgesia is linked mainly to pharmacodynamic rather than pharmacokinetic changes. British Journal of Pharmacology (2002) 137, 813,820. doi:10.1038/sj.bjp.0704944 [source] Fatigue damage analysis in a duplex stainless steel by digital image correlation techniqueFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 2 2008A. EL BARTALI ABSTRACT Strain field measurements by digital image correlation today offer new possibilities for analysing the mechanical behaviour of materials in situ during mechanical tests. The originality of the present study is to use this technique on the micro-structural scale, in order to understand and to obtain quantitative values of the fatigue surface damage in a two-phased alloy. In this paper, low-cycle fatigue damage micromechanisms in an austenitic-ferritic stainless steel are studied. Surface damage is observed in real time, with an in situ microscopic device, during a low-cycle fatigue test performed at room temperature. Surface displacement and strain fields are calculated using digital image correlation from images taken during cycling. A detailed analysis of optical images and strain fields measured enables us to follow precisely the evolution of surface strain fields and the damage micromechanisms. Firstly, strain heterogeneities are observed in austenitic grains. Initially, the austenitic phase accommodates the cyclic plastic strain and is then followed by the ferritic phase. Microcrack initiation takes place at the ferrite/ferrite grain boundaries. Microcracks propagate to the neighbouring austenitic grains following the slip markings. Displacement and strain gradients indicate probable microcrack initiation sites. [source] Concrete canal lining cracking in low to medium plastic soils,IRRIGATION AND DRAINAGE, Issue 2 2002H. Rahimi sol plastique; gonflement; revêtement bétonique; Iran Abstract Failure of concrete irrigation canal linings in the form of cracking, rupture, uplifting and opening of joints, causes loss of water and money in many countries. Following the appearance of extensive cracking of concrete linings in one of the Shoeybieh sugar cane industry farms in the Khoozestan province of Iran, extensive research work was conducted to identify the main causes. In this paper, the final results of the research are presented. The testing program consisted of laboratory as well as field tests, including identification, chemical and mechanical tests of soil samples taken from the borrow pits and canal embankments. Dispersivity tests were performed using pin-hole and chemical methods. Swelling tests were conducted using the ASTM standard and ISSMFE method. The field test includes measurement of deformations of the concrete lining and embankment of an actual lined canal resulting from the filling of the canal with water. The canal was 60 m in length. The deformations were recorded by surveying the elevations of steel bars driven to different depths under the canal lining and at different points in the canal and its embankment sections. The results of laboratory tests showed the soil to have low to medium plasticity with a classification of CL-ML, having less than 1% soluble content, and being nondispersive. Swelling tests conducted by the ASTM and ISSMFE methods showed completely different results. The ISSMFE method resulted in a high free swell potential, while the ASTM method indicated a low to medium potential. The results of full-scale field tests were all in favor of the ISSMFE method. The greatest difference between the results of the two methods was found to be due to the different compaction methods used during construction of the canal, as well as the moisture content of the soil sample being prepared for the swell tests. The flocculent structure and lower compaction water content of soil samples in the ISSMFE method resulted in much higher free swell. The similarity between compaction methods used in the field and the static effort used in the ISSMFE method, as well as very low soil water content of the canal embankments during lining operations, were found to be the main reasons for swelling of the soil and the eventual cracking of the concrete linings. Copyright © 2002 John Wiley & Sons, Ltd. RÉSUMÉ L'écroulement du revêtement bétonique des canaux d'irrigation en forme de fissure, de la rupture, de la sous-pression et de l'ouverture des joints, est la cause de la perte d' eau et par conséquence des fonds publics de plusieurs pays dans le monde entier. Après avoir observé ce phénomène dans des canaux d'irrigation d'un grand projet de canne à sucre à Shoeybieh dans la région de Khozestan, située au sud de l'Iran, une équipe de recherche a été engagée pour trouver les causes principales de cetécroulement. Cet article présente les résultats finaux de cette recherche. Le programme consiste de deux types d'essai, en laboratoire et sur le terrain. Les échantillons du sol pour l'essai mécanique et chimique ont été pris dans des emprunts de terre et la digue du canal. Les essais de dispersivité ont été faits par les méthodes de pin-hole et de chimique. La méthode del ISSMFE et la standard del ASTM ont été utilisés pour les essais de gonflement du sol. Le mesurage de la déformation d'un canal revêté en béton et aussi de digue du canal a été fait par rempliz le canal avee de l'eau. Le canal avait une longueur de 60 m. La déformation a été observée en examinant les élévations à plusieurs points sur la profondeur du canal en dessous de la partie revêtée et aussi la digue du canal par un instrument spécifique. Les résultats des essais de laboratoire montrent que les sols qui ont une plasticité entre petite et moyenne situés dans la classification de CL-ML ayant moins d'un pour cent de contenude soluble sont non-dispersifes. Les essais de gonflement par les méthodes de l'ASTM et l'ISSME montrent des résultats tout à fait différents. La méthode ISSMFE montre un potentiel de gonflement assez élevé, tandis que la méthode ASTM montre un potentiel entre petit et moyen. Les résultats des essais en champs d'étude confirme la méthode ISSMFE. La plus grande différence entre le résultat de deux méthodes est à cause d'usage de plusieurs méthodes de compaction dans la période de la construction du canal. La structure floculée du sol ayant une humidité moins compactée dans la méthode ISSMFE montre un gonflement plus élevée du sol. Les méthodes similaires de compaction utilisées dans le champs d'étude et énergie statique utilisée par la méthode ISSFE, et aussi une petite humidité de digue du canal en période de revêtement sont les causes principales de gonflement et éventuellement de fissure. Copyright © 2002 John Wiley & Sons, Ltd. [source] Efficient utilization of plastic waste through product design and process adaptation: A case study on stiffness enhancement of beams produced from plastic lumberADVANCES IN POLYMER TECHNOLOGY, Issue 3 2008Cristian Pio Abstract The aim of the present work is the development of a method for structural reinforcement of beams obtained by in-mold extrusion of plastics from solid urban waste. The beams obtained by in-mold extrusion are commonly used for outdoor furniture and structures. The material used for such applications is mainly composed of low-density polyethylene derived from bags and films, with small amounts of high density polyethylene and polypropylene, as well as traces of polyethylene terephthalate. This material is usually referred to as "plastic lumber." Plastic lumber products have a low stiffness, which results in high deflections under flexural loads, particularly under creep loading. In this study, reinforcing rods of high aspect ratio were incorporated into plastic lumber beams in specific positions with respect to the cross section of the beam. The reinforcement of the plastic lumber beams with fine rods is introduced in the typical intrusion process used for the production of unreinforced beams. Glass fiber reinforced pultruded rods were chosen for this purpose from a preliminary evaluation of different materials. Different diameter glass fiber reinforced pultruded rods, including surface-abraded systems to increase the roughness, were used for the reinforcement of plastic lumber beams. The reinforced beams were tested in terms of flexural stiffness, creep resistance, and pullout resistance of the embedded rods. The results obtained from the mechanical tests showed a significant enhancement of flexural stiffness and creep resistance behavior. The performance at higher stress levels was shown to be significantly dependent on the interfacial adhesion between rods and polymer matrix. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:133,142, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20131 [source] Modification of polypropylene by melt vibration blending with ultra high molecular weight polyethyleneADVANCES IN POLYMER TECHNOLOGY, Issue 3 2002Kejian Wang Abstract A novel vibration internal mixer was used to prepare polypropylene/ultra high molecular weight polyethylene PP/UHMWPE blends with two additional adjustable processing parameters (vibration frequency and vibration amplitude) as compared with those prepared in the steady mode. Microscopy, mechanical tests, and differential scanning calorimetry showed that vibration influenced the blend morphology and the product properties. The good phase homogeneity of the blends might be due to the variation of shear rate either spatially or temporally in blending. Additionally, the vibration internal mixer could be used to analyze the dependency of viscosity on the shear rate. Vibration enhanced the interpenetration of UHMWPE into PP and vice versa. Subsequently, the formed crystals of two components were connected, and there was epitaxy between PP and UHMWPE crystals. Moreover, the crystalline aggregates, with the amorphous UHMWPE, formed a complex network-like continuous structure, which improved the elongation ratio at the break and the yield strength. The higher the vibration frequency and/or the larger the vibration amplitude at a fixed average rotation speed of the mixer, the more significant these effects were. The larger amount of the connected crystals, especially of , form of PP in the bulk , form PP as well as with the continuous phase structure, led to a higher tensile properties of PP/UHMWPE vibration blended. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 164,176, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/adv.10020 [source] Curing behavior and mechanical properties of hollow glass microsphere/bisphenol a dicyanate ester compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010Jinhe Wang Abstract Hollow glass microsphere (HGS)/bisphenol A dicyanate ester (BADCy) composites have been prepared by mechanical mixing, followed by a stepped curing process. The effect of HGS on the curing behavior of BADCy was studied using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The mechanical properties of the composites were examined by mechanical tests, and the improvements of the mechanical properties were investigated by scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). The results show that HGS is catalytic for the polycyclomerization of the BADCy, which is advantageous to reduce the maximal processing temperature. The impact strength, flexural strength, flexural modulus and storage modulus of BADCy are improved. The improvements of the mechanical properties without sacrificing thermal properties, the ability of lowing processing temperature and the low cost make HGS good filler for cyanate ester resin. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Microstructure and physical properties of open-cell polyolefin foamsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2009M. A. Rodriguez-Perez Abstract The cellular structure, physical properties, and structure,property relationships of novel open-cell polyolefin foams produced by compression molding and based on blends of an ethylene/vinyl acetate copolymer and a low-density polyethylene have been studied and compared with those of closed-cell polyolefin foams of similar chemical compositions and densities and with those of open-cell polyurethane foams. Properties such as the elastic modulus, collapse stress, energy absorbed in mechanical tests, thermal expansion, dynamic mechanical response, and acoustic absorption have been measured. The experimental results show that the cellular structure of the analyzed materials has interconnected cells due to the presence of large and small holes in the cell walls, and this structure is clearly different from the typical structure of open-cell polyurethane foams. The open-cell polyolefin foams under study, in comparison with closed-cell foams of similar densities and chemical compositions, are good acoustic absorbers; they have a significant loss factor and lower compressive strength and thermal stability. The physical reasons for this macroscopic behavior are analyzed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Poly(lactic acid) properties as a consequence of poly(butylene adipate- co -terephthalate) blending and acetyl tributyl citrate plasticizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Maria-Beatrice Coltelli Abstract This study was aimed at the modulation of poly(lactic acid) (PLA) properties by the addition of both a low-molecular-weight plasticizer, acetyl tributyl citrate (ATBC), and a biodegradable aliphatic,aromatic copolyester, poly(butylene adipate- co -terephthalate) (PBAT). PLA/PBAT, PLA/ATBC, and PLA/PBAT/ATBC mixtures with 10,35 wt % ATBC and/or PBAT were prepared in a discontinuous laboratory mixer, compression-molded, and characterized by thermal, morphological, and mechanical tests to evaluate the effect of the concentration of either the plasticizer or copolyester on the final material flexibility. Materials with modulable properties, Young's modulus in the range 100,3000 MPa and elongation at break in the range 10,300%, were obtained. Moreover, thermal analysis showed a preferential solubilization of ATBC in the PBAT phase. Gas permeability tests were also performed to assess possible use in food packaging applications. The results are discussed with particular emphasis toward the effects of plasticization on physical blending in the determination of the phase morphology and final properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis and characterization of fullerene grafted poly(,-caprolactone)JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Weihua Kai Abstract The fullerene grafted poly(,-caprolactone) (PCL) was successfully synthesized with a graft efficiency of 80%. The fullerene moieties grafted onto the PCL chain aggregate into 1,2 ,m particles so that a physical pseudo -network is formed. Because of the existence of the network structure, the fullerene grafted PCL film can retain its shape at much higher temperatures than that of pure PCL film, as observed in dynamic mechanical tests. It shows a hydrophobic gelling behavior in chloroform solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Analysis of the mechanical behavior of a titanium scaffold with a repeating unit-cell substructureJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Garrett Ryan Abstract Titanium scaffolds with controlled microarchitecture have been developed for load bearing orthopedic applications. The controlled microarchitecture refers to a repeating array of unit-cells, composed of sintered titanium powder, which make up the scaffold structure. The objective of this current research was to characterize the mechanical performance of three scaffolds with increasing porosity, using finite element analysis (FEA) and to compare the results with experimental data. Scaffolds were scanned using microcomputed tomography and FEA models were generated from the resulting computer models. Macroscale and unit-cell models of the scaffolds were created. The material properties of the sintered titanium powders were first evaluated in mechanical tests and the data used in the FEA. The macroscale and unit-cell FEA models proved to be a good predictor of Young's modulus and yield strength. Although macroscale models showed similar failure patterns and an expected trend in UCS, strain at UCS did not compare well with experimental data. Since a rapid prototyping method was used to create the scaffolds, the original CAD geometries of the scaffold were also evaluated using FEA but they did not reflect the mechanical properties of the physical scaffolds. This indicates that at present, determining the actual geometry of the scaffold through computed tomography imaging is important. Finally, a fatigue analysis was performed on the scaffold to simulate the loading conditions it would experience as a spinal interbody fusion device. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2009 [source] The effects of RANKL inhibition on fracture healing and bone strength in a mouse model of osteogenesis imperfectaJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2008Demetris Delos Abstract Currently, the standard treatment for osteogenesis imperfecta (OI) is bisphosphonate therapy. Recent studies, however, have shown delayed healing of osteotomies in a subset of OI patients treated with such agents. The current study sought to determine the effects of another therapy, RANKL inhibition, on bone healing and bone strength in the growing oim/oim mouse, a model of moderate to severe OI. Mice [73 oim/oim and 69 wild-type (WT)] were injected twice weekly with either soluble murine RANK (RANK-Fc) (1.5 mg/kg) or saline beginning at 6 weeks of age. At 8 weeks of age, the animals underwent transverse mid-diaphyseal osteotomies of the right femur. Therapy was continued until sacrifice at 2, 3, 4, or 6 weeks postfracture. At 6 weeks post-fracture, greater callus area (6.59,±,3.78 mm2 vs. 2.67,±,2.05 mm2, p,=,0.003) and increased radiographic intensity (mineral density) (0.48,±,0.14 vs. 0.30,±,0.80, p,=,0.005) were found in the RANK-Fc versus saline oim/oim group, indicating a delay in callus remodeling. Despite this delay, mechanical tests at 6 weeks postfracture revealed no significant differences in whole bone properties of stiffness and failure moment. Further, RANKL inhibition resulted in a greater failure moment and greater work to failure for the nonfractured contralateral WT bones compared to the nonfractured saline WT bones. Together, these results demonstrate that RANKL inhibition does not adversely affect the mechanical properties of healing bone in the oim/oim mice, and is associated with increased strength in intact bone in the WT mice. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:153,164, 2008 [source] EFFECTS OF TEXTURAL CHANGES IN COOKED APPLES ON THE HUMAN BITE, AND INSTRUMENTAL TESTSJOURNAL OF TEXTURE STUDIES, Issue 5-6 2003HARUKA DAN A multiple-point sheet sensor was used to measure the bite force applied to raw and cooked apple specimens during the first bite with incisors. Wedge penetration tests were compared with human bite measurements on the same samples. The shape of the force-time curves during biting of cooked apples clearly differed from that for raw apples. The first curve of cooked apple biting became jagged, and the maximum force was reduced. The second curve emerged following the first curve in most subjects as a characteristic feature of cooked apple biting, whereas it was not seen in the bite curve of a raw specimen or the wedge penetration curve of a cooked specimen. The maximum force for tissue fracture decreased for cooked apples, but the duration of biting increased. No adequate counterparts for the impulse of biting could be obtained from the load-displacement curves of the wedge penetration tests. The existence of parameters only measurable by bite tests and not by mechanical tests suggests the necessity of directly measuring the human bite. [source] Controlling and Testing the Fracture Strength of Silicon on the MesoscaleJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2000Kuo-Shen Chen Strength characterizations and supporting analysis of mesoscale biaxial flexure and radiused hub flexure single-crystal silicon specimens are presented. The Weibull reference strengths of planar biaxial flexure specimens were found to lie in the range 1.2 to 4.6 GPa. The local strength at stress concentrations was obtained by testing radiused hub flexure specimens. For the case of deep reactive ion-etched specimens the strength at fillet radii was found to be significantly lower than that measured on planar specimens. This result prompted the introduction of an additional isotropic etch after the deep reactive ion etch step to recover the strength in such regions. The mechanical test results reported herein have important implications for the development of highly stressed microfabricated structures. The sensitivity of the mechanical strength to etching technique must be accounted for in the structural design cycle, particularly with regard to the selection of fabrication processes. The scatter of data measured in the mechanical tests clearly illustrated the need to use a probabilistic design approach. Weibull statistics may be the appropriate means to describe the data, although a simple two-parameter Weibull model only provides a moderately good fit to the experimental data reported in this study. [source] Organoclay Nanocomposites from Ethylene,Acrylic Acid CopolymersMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2006Sara Filippi Abstract Summary: A study of the structure,property relationships for nanocomposites prepared by melt compounding from ethylene,acrylic acid copolymers of varied composition and molecular architecture, and organoclays modified with different ammonium ions has been made by DSC, POM, SEM, TEM, WAXD, and rheological and mechanical tests. Within the series of clays investigated, the best levels of dispersion were displayed by those organically modified with quaternary ammonium ions containing two long alkyl tails. The relevant nanocomposites were shown to possess mixed exfoliated and intercalated morphology. The spacing of the intercalated clay stacks, most of which comprise few silicate layers, was found to be independent of clay loading, in the range of 2,50 phr, and to change with the molecular architecture of the matrix polymer. An indication that the excess surfactant present in some of the clays, and the organic material added in others to expand the interlayer spacing, were expelled from the clay galleries during melt blending and acted as plasticisers for the matrix polymer, was obtained from WAXD and rheological characterisations. TEM micrograph of the nanocomposite of EAA1 with 11 phr of 15A. [source] Influence of Reactice Processing on the Properties of PP/Glass Fiber Composites Compatibilized with SilaneMACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2006Afonso H. O. Felix Abstract Summary: Composites of PP reinforced with 20 wt.-% of short glass fibers were prepared by extrusion using VTES as a coupling agent. The addition of VTES was performed via in-situ functionalization of PP and by a two-step process in which PP was functionalized before the composite preparation. The obtained samples were characterized using rheometry, mechanical tests and microscopy. Both processes allowed the fiber/matrix interaction to increase. It was found that the VTES content affected the viscosity of the system by means of three different mechanisms: reduction of , -scission reactions, decrease of fiber sliding and plasticizing effect on the matrix. Whereas the first two mechanisms increased the viscosity of the final composite after unreacted VTES removal, the third one reduced the viscosity during the process and contributed to fiber-length preservation. The effects of VTES and peroxide contents on the Young's modulus were closely related to their effects on the final fiber length, indicating the effectiveness of using VTES as a coupling agent. Comparison between in-situ functionalization and the two-step process with prefunctionalization showed that in-situ functionalization led to a lower degree of chain breakage, even when it was performed in the presence of peroxide. Scanning electron micrographs of PP/glass fiber composite prepared without coupling agent. [source] Enhanced Mechanical Performance of Self-Bundled Electrospun Fiber Yarns via Post-TreatmentsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 10 2008Xuefen Wang Abstract A new route to high-performance electrospun polymer fibers was developed using a self-bundling electrospinning technique combined with post-treatments such as stretching and annealing under conditions similar to those used for conventional fibers. Self-bundled electrospun PAN fiber yarns were characterized by SEM, mechanical tests, polarized FT-IR spectroscopy and WAXD. The obtained results revealed that the PAN nanofiber yarns possessed enhanced alignment, a higher degree of crystallinity and higher molecular orientation after treatments, resulting in a remarkable improvement in mechanical performance, approaching the strength value of the corresponding conventional fibers. [source] Study of the modification of the properties of (PP/EPR) blends with a view to preserving natural resources when elaborating new formulation and recycling polymersPOLYMER COMPOSITES, Issue 6 2009Nizar Mnif The aim of the present work is to study how CaCO3, very abundant on earth, can be blended with polypropylene/ethylene propylene rubber (PP/EPR) either to preserve natural resources when elaborating virgin formulations or to simulate mixtures of waste made of CaCO3 filled PP with PP/EPR which could result from end-of-life-vehicles (ELV). The article focuses on the studies of PP/EPR blends, used in the manufacture of automobile fenders, in the presence of nano-CaCO3 and compatibilizers. Blends of various compositions (with and without compatibilizer and nanoparticles) were prepared using a corotating twin-screw extruder. The results were compared with the ones presented by a commercial (PP/EPR) blend. The experiments included mechanical tests, differential scanning calorimetry, scanning electron microscopy, and dynamic mechanical analysis experiments. The presence of the compatibilizers in the (PP/EPR) blends decreases the size of elastomer particles, improves the adherence to the interface and improves the mechanical properties. The nano-CaCO3 would also seem to act as a nucleating agent in the PP/EPR matrix; it increases the cristallinity and the Young modulus of the blends. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Use of different alkylammonium salts in clay surface modification for epoxy-based nanocompositesPOLYMER COMPOSITES, Issue 3 2009G. Ipek Nakas Layered silicates become widely used reinforcement material in the polymer nanocomposite production in recent years due to their high aspect ratio, ease of processing, and low cost. In this present study, the aim was to evaluate the usability of a raw clay source (Resadiye, Turkey) in the production of epoxy/clay nanocomposites and to investigate the effects of different surface modifiers. For this purpose, raw Na,montmorillonite clay was first purified and then surface modified by using different types of alkylammonium salts: tetramethyl ammonium bromide, benzyl triethyl ammonium bromide, dodecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, and octadecyl trimethyl ammonium bromide. Purification and surface modification of this clay were evaluated by using the following analyses; X-ray diffraction (XRD), cation exchange capacity (CEC), particle size distribution, and dissolved organic content. These analyses simply indicated that surface modification increased both interlayer spacing between the silicate layers and CEC of the clay. These improvements were directly proportional with the chain length of the surface modifier. Nanocomposite specimens were produced by adding 0.5 wt% surface modified clay into the epoxy matrix. These specimens were characterized by XRD, Si-mapping facility of SEM, and mechanical tests. XRD results indicated an exfoliated structure whereas Si-mapping showed the uniform distribution of clay particles in epoxy, leading to improved mechanical properties, for instance more than 100% increase in fracture toughness of the neat epoxy specimen. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] | |||||||||||||||||||