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Tensile Mechanical Properties (tensile + mechanical_property)
Selected AbstractsThe role of a novel p -phenylen-bis-maleamic acid grafted atactic polypropylene interfacial modifier in polypropylene/mica composites as evidenced by tensile propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2009J. M. García-Martínez Abstract Present work is devoted to the study of the tensile behavior of polypropylene (PP)/mica composites with improved interfacial interactions from the matrix side caused by the presence of a p -phenylen-bis-maleamic acid grafted atactic polypropylene (aPP- pPBM) as an interfacial agent. Hence, aPP- pPBM was previously obtained, in our laboratories, by reactive processing in the melt of a by-product (atactic PP) from industrial polymerization reactors. Present article is two-fold, on one hand it has been planned to evidence the so called interfacial effects caused by this novel interfacial agent (aPP- pPBM) yielding better final properties of the heterogeneous system as a whole as revealed by tensile mechanical properties, and on the other to obtain models to forecast the overall behavior of the system. For such purpose, a Box-Wilson experimental design considering the amount of mica particles and of interfacial agent as independent variables was used to obtain polynomials to forecast the behavior of the PP/Mica system in the experimental space scanned. The existence of a critical amount of aPP- pPBM to optimize mechanical properties appears to emerge. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Tailoring mechanical properties of nano-structured Eurofer 97 steel for fusion applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2010M. Kozikowski Abstract EUROFER 97 steel is a candidate structural material for future fusion reactors and Test Blanket Modules (TBMs). In the present work microstructure of Eurofer 97 was modified by hydrostatic extrusion in multi-step process with total true strain exceeding 3. TEM observations showed that HE causes significant grain refinement from about 400 to 80 nm. This is accompanied by improvement of the tensile mechanical properties and microhardness. On the other hand, there is a clear decrease in the resistance to brittle fracture as measured in the Charpy impact tests. In order to improve strength/ductility/fracture toughness balance, the extruded samples were annealed for 1 hour at temperature range of 473-1073K. The results obtained for samples after post-extrusion annealing are discussed in terms of mechanical properties of Eurofer 97 steel. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of ,-irradiation on the physical properties and dyeability of poly(vinyl butyral) blends with polystyrene and poly(ethylene glycol)POLYMER COMPOSITES, Issue 6 2008Horia M. Nizam El-Din Cast films of polymer blends essentially based on poly(vinyl butyral) (PVB) and equal ratios of polystyrene (PS) and poly(ethylene glycol) (PEG) were prepared from benzene and butyl alcohol solutions of the individual polymers. The effect of ,-irradiation on the thermal decomposition and tensile mechanical properties was investigated. Moreover, the effect of ,-irradiation on the dye affinity of PVB/PS and PVB/PEG for basic and acid dyestuffs was studied. The thermogravimetric analysis (TGA) study showed that the unirradiated PVB polymer films prepared in benzene displayed higher thermal stability than the same polymer films prepared in butanol. However, in all cases the thermal stability was found to increase with increasing ,-irradiation dose. On the other hand, PVB/PS blend possesses higher thermal stability than PVB/PEG, as shown from the determination of the weight loss (%) at different heating temperatures, the temperatures of the maximum rate of reaction and the activation energy. While, pure PS films showed the stress-strain behavior of brittle polymers, PVB/PS films showed the behavior of tough polymers with yielding properties. The results of dyeing clearly showed that the solvent type, blend composition, and irradiation dose are determining factors for the dye affinity for basic or acid dyes. For example, unirradiated PVB films prepared from butanol displayed a higher affinity for the basic and acid dyes than the same polymer prepared from the same benzene. However, PVB prepared from butanol showed higher affinity to the dyes than PS prepared from the same solvent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Intracellular Na+ and Ca2+ modulation increases the tensile properties of developing engineered articular cartilageARTHRITIS & RHEUMATISM, Issue 4 2010Roman M. Natoli Objective Significant collagen content and tensile properties are difficult to achieve in tissue-engineered articular cartilage. The aim of this study was to investigate whether treating developing tissue-engineered cartilage constructs with modulators of intracellular Na+ or Ca2+ could increase collagen concentration and construct tensile properties. Methods Inhibitors of Na+ ion transporters and stimulators of intracellular Ca2+ were investigated for their ability to affect articular cartilage development in a scaffoldless, 3-dimensional chondrocyte culture. Using a systematic approach, we applied ouabain (Na+/K+ -ATPase inhibitor), bumetanide (Na+/K+/2Cl, tritransporter inhibitor), histamine (cAMP activator), and ionomycin (a Ca2+ ionophore) to tissue-engineered constructs for 1 hour daily on days 10,14 of culture and examined the constructs at 2 weeks or 4 weeks. The gross morphology, biochemical content, and compressive and tensile mechanical properties of the constructs were assayed. Results The results of these experiments showed that 20 ,M ouabain, 0.3 ,M ionomycin, or their combination increased the tensile modulus by 40,95% compared with untreated controls and resulted in an increased amount of collagen normalized to construct wet weight. In constructs exposed to ouabain, the increased percentage of collagen per construct wet weight was secondary to decreased glycosaminoglycan production on a per-cell basis. Treatment with 20 ,M ouabain also increased the ultimate tensile strength of neo-tissue by 56,86% at 4 weeks. Other construct properties, such as construct growth and type I collagen production, were affected differently by Na+ modulation with ouabain versus Ca2+ modulation with ionomycin. Conclusion These data are the first to show that treatments known to alter intracellular ion concentrations are a viable method for increasing the mechanical properties of engineered articular cartilage and identifying potentially important relationships to hydrostatic pressure mechanotransduction. Ouabain and ionomycin may be useful pharmacologic agents for increasing tensile integrity and directing construct maturation. [source] Shear stress magnitude and duration modulates matrix composition and tensile mechanical properties in engineered cartilaginous tissueBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2009Christopher V. Gemmiti Abstract Cartilage tissue-engineering strategies aim to produce a functional extracellular matrix similar to that of the native tissue. However, none of the myriad approaches taken have successfully generated a construct possessing the structure, composition, and mechanical properties of healthy articular cartilage. One possible approach to modulating the matrix composition and mechanical properties of engineered tissues is through the use of bioreactor-driven mechanical stimulation. In this study, we hypothesized that exposing scaffold-free cartilaginous tissue constructs to 7 days of continuous shear stress at 0.001 or 0.1,Pa would increase collagen deposition and tensile mechanical properties compared to that of static controls. Histologically, type II collagen staining was evident in all construct groups, while a surface layer of type I collagen increased in thickness with increasing shear stress magnitude. The areal fraction of type I collagen was higher in the 0.1-Pa group (25.2,±,2.2%) than either the 0.001-Pa (13.6,±,3.8%) or the static (7.9,±,1.5%) group. Type II collagen content, as assessed by ELISA, was also higher in the 0.1-Pa group (7.5,±,2.1%) compared to the 0.001-Pa (3.0,±,2.25%) or static groups (3.7,±,3.2%). Temporal gene expression analysis showed a flow-induced increase in type I and type II collagen expression within 24,h of exposure. Interestingly, while the 0.1-Pa group showed higher collagen content, this group retained less sulfated glycosaminoglycans in the matrix over time in bioreactor culture. Increases in both tensile Young's modulus and ultimate strength were observed with increasing shear stress, yielding constructs possessing a modulus of nearly 5,MPa and strength of 1.3,MPa. This study demonstrates that shear stress is a potent modulator of both the amount and type of synthesized extracellular matrix constituents in engineered cartilaginous tissue with corresponding effects on mechanical function. Biotechnol. Bioeng. 2009; 104: 809,820 © 2009 Wiley Periodicals, Inc. [source] | ||||||||||