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Tensile Tester (tensile + tester)
Selected AbstractsStress and elastic-constant analysis by X-ray diffraction in thin filmsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-2 2003F. Badawi Residual stresses influence most physical properties of thin films and are closely related to their microstructure. Among the most widely used methods, X-ray diffraction is the only one allowing the determination of both the mechanical and microstructural state of each diffracting phase. Diffracting planes are used as a strain gauge to measure elastic strains in one or several directions of the diffraction vector. Important information on the thin-film microstructure may also be extracted from the width of the diffraction peaks: in particular, the deconvolution of these peaks allows values of coherently diffracting domain size and microdistortions to be obtained. The genesis of residual stresses in thin films results from multiple mechanisms. Stresses may be divided into three major types: epitaxic stresses, thermal stresses and intrinsic stresses. Diffraction methods require the knowledge of the thin-film elastic constants, which may differ from the bulk-material values as a result of the particular microstructure. Combining an X-ray diffractometer with a tensile tester, it is possible to determine X-ray elastic constants of each diffracting phase in a thin-film/substrate system, in particular the Poisson ratio and the Young modulus. It is important to notice that numerous difficulties relative to the application of diffraction methods may arise in the case of thin films. [source] Elongational rheology by different methods and orientation numberJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007John R. Collier Abstract The elongational rheology of polymer melts was measured by the authors using the hyperbolic convergent die technique and the results were compared with the same samples measured using a Meissner type device or an Instron tensile tester. Polyethylene and polystyrene samples were tested at Eidgenössische Technische Hochschule-Zürich or Virginia Polytechnic Institute, and the polyisobutylene was part of a world wide "Round Robin" comparison. A modified Weissenberg number, i.e., an Orientation number, is suggested to explain the agreement between techniques for some samples and lack of agreement for others. The Orientation number is the product of Hencky strain, elongational strain rate, and average relaxation time. When it is less than one a relaxation dominant regime results, when greater than one an orientation dominant regime results, and near one a transition occurs. For the hyperbolic convergent die technique, in which the polymers are transversely constrained by the walls, the extrudates in the transition regime have slight surface defects and the pressure fluctuates more than in the other regimes. If the transition occurs after significant time, i.e., lower elongational strain rates, in the free boundary Meissner and Instron devices, the samples apparently experience more relaxation since unconstrained transversely (and perhaps differential thinning) leading to disagreement with the hyperbolic die measurements. The orientation related body forces are magnitudes larger than the shearing forces and cause slip at the wall in the hyperbolic dies in the orientation dominant regime. Even in the relaxation dominant regime, shear near the wall is a minor contributor to the necessary pressure force. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Characterization of spreadability of nonaqueous ethylcellulose gel matrices using dynamic contact angleJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2008Keat Theng Chow Abstract This study reports the characterization of spreadability of nonaqueous ethylcellulose (EC) gel matrices intended for topical drug delivery using a newly developed method based on dynamic contact angle. EC solutions were prepared using three grades of EC and propylene glycol dicaprylate/dicaprate. Dynamic contact angles of sessile drops of EC solutions on silicone elastomer were measured using a dynamic contact angle analyzer equipped with axisymmetric drop shape analysis-profile. Roughness of silicone elastomer, viscosity of EC solutions and compressibility of semisolid EC gels were determined by the atomic force microscope, cone-and-plate rheometer and tensile tester, respectively. The silicone elastomer employed as a substrate was demonstrated to have similar hydrophilic/lipophilic properties as the human skin. Spreadability of EC solutions was dependent on EC concentration, polymeric chain length and polydispersity. EC gel spreadability was governed by viscosity and the extent of gel-substrate interaction. From the apparent contact angle values, most EC gel formulations tested were found to be moderately spreadable. Linear correlation observed between spreading parameter and compressibility of EC gel verified the applicability of dynamic contact angle to characterize EC gel spreadability. Thus, the feasibility of employing dynamic contact angle as an alternative technique to measure gel spreadability was demonstrated. The spreadability demonstrated by EC gel would facilitate application on the skin indicating its potential usefulness as a topical dosage form. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97: 3467,3482, 2008 [source] Orthotropic elastic constants for polyimide filmPOLYMER ENGINEERING & SCIENCE, Issue 2 2001Seo Hyun Cho The orthotropic constants of polyimide film have been characterized using the theory of elasticity of an anisotropic material. Experimental techniques coupled with the mechanics of orthotropic materials are used to determine all 9 independent orthotropic elastic constants (3 tensile moduli, 3 shear moduli, and 3 Poisson's ratios) and 3 coefficients of thermal expansion. Vibrational holographic interferom-etry is used to determine the orthotropic axes of symmetry. For this polyimide film, the two principal axes coincided with the machine and transverse directions. It is also used to evaluate the 2 in-plane Poisson's ratios by measuring residual stresses in 2-D and 1-D square membranes. Using other instruments such as a high pressure gas dilatometry apparatus, a tensile tester, a pressure-volume-temperature apparatus, a thermornechanical analyzer, and a torsion pendulum, the 7 other orthotropic constants and the 3 coefficients of thermal expansion are determined. [source] Development of a New Tissue-Engineered Sheet for Reconstruction of the StomachARTIFICIAL ORGANS, Issue 10 2009Masato Araki Abstract We have developed tissue-engineered digestive tracts composed of collagen scaffold and an inner silicon sheet and successfully used it to repair defects in parts of the esophagus, stomach, and small intestine. However, some improvements were demanded for clinical usage because the silicon sheet presented technical difficulties for suturing and endoscopic removal. New tissue-engineered sheet (New-sheet) was composed of a single-piece and reinforced collagen scaffold with biodegradable copolymer. One beagle dog was used to evaluate whether New-sheet could withstand suturing in comparison with native digestive tracts using a tensile tester. Seven beagle dogs had a 5-cm circular defect created in the stomach. New-sheet soaked with autologous peripheral blood or bone marrow aspirate was sutured to the gastric wall. Endoscopic, histological, and immunohistochemical assessment was performed to evaluate regeneration of the stomach up to 16 weeks. Tensile strength testing showed that the mucosal side of New-sheet had strength almost equivalent to the mucosa of the esophagus (P = 0.61). Endoscopically, regeneration of the mucosa started from the circumference after 4 weeks, but a small linear ulcer was still evident at 16 weeks. The regenerated stomach shrank by 60,80% of its original size and histologically showed villous mucosa and underlying dense connective tissue. Immunohistochemically, the regenerated area expressed ,-smooth-muscle actin but was negative for basic calponin, irrespective of the source of soaked blood. New-sheet shows sufficient strength for suturing, no dehiscence, and better biocompatibility for clinical use, although further examination will be necessary to create a functional digestive tract. [source] | |||||||||||||