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Mechanical Measurements (mechanical + measurement)
Selected AbstractsMeasuring anisotropic thermal conduction in polyisobutylene following step shear strainsAICHE JOURNAL, Issue 3 2000Hadjira Iddir The connection between polymer chain orientation and several macroscopic properties in a polymer melt was studied using mechanical and optical techniques. Anisotropic thermal conductivity following shear deformation was measured using forced Rayleigh light scattering, the refractive index tensor is followed using birefringence measurements, and the stress was measured mechanically in a parallel-plate rheometer. The thermal diffusivity measured in the flow and neutral directions increased and decreased, respectively, immediately following the deformation. These quantities then relaxed to the equilibrium value on the time-scale of the stress-relaxation memory. Comparison of the difference between measured flow and neutral direction thermal diffusivities with the analogous flow-induced birefringence in the same deformation provided indirect evidence for a linear relation between stress and thermal diffusivity at two different values of strain. Mechanical measurements were used to characterize the memory of the fluid. [source] Carbon Nanotube Fibers: Monitoring a Micromechanical Process in Macroscale Carbon Nanotube Films and Fibers (Adv. Mater.ADVANCED MATERIALS, Issue 5 20095/2009) The evaluation of mechanical properties of carbon nanotube (CNT) fibers is inherently difficult. On p. 603, Sishen Xie and co-workers report that Raman scattering,a generic methodology independent of mechanical measurements,can be used to determine the interbundle strength and microscopic failure process for various CNT macroarchitectures. Raman data are used to predict the moduli of CNT films and fibers, and to illustrate the influences of the twisting geometries on the fibers' mechanical performances. [source] Monitoring a Micromechanical Process in Macroscale Carbon Nanotube Films and FibersADVANCED MATERIALS, Issue 5 2009Wenjun Ma The evaluation of mechanical properties of carbon nanotube (CNT) fibers is inherently difficult. Here, Raman scattering,a generic methodology independent of mechanical measurements,is used to determine the interbundle strength and microscopic failure process for various CNT macroarchitectures. Raman data are used to predict the moduli of CNT films and fibers, and to illustrate the influences of the twisting geometries on the fibers' mechanical performances. [source] Melt amination of polypropylenesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2005Q.-W. Lu Abstract Amine (primary and secondary) functional polypropylenes were prepared by the melt blending of maleated polypropylenes with small diamines, including hexamethylenediamine (primary,primary diamine), p -xylylenediamine (primary,primary diamine), and N -hexylethylenediamine (primary,secondary diamine), at various diamine/anhydride molar ratios in a batch mixer and a twin-screw extruder. The experimental conversion data by Fourier transform infrared nearly agreed with the assumption of a complete reaction between the primary amine and anhydride. Chain extensions of the maleated polypropylenes by the diamines were monitored by the torques during mixing and further evaluated by rheological (dynamic shear rheometry) and mechanical measurements. We show that these amino polypropylenes are very effective adhesion promoters and compatibilizers of thermoplastic polyurethanes with polypropylene. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4217,4232, 2005 [source] Use of PP Grafted with Itaconic Acid as a New Compatibilizer for PP/Clay NanocompositesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 15 2006Edwin Moncada Abstract Summary: Functionalized PP samples with different percentages of grafted IA, i.e., 0.7, 1 or 1.8 wt.-%, with similar molecular weights were used as compatibilizers in PP/clay nanocomposites. PP nanocomposites containing 1 wt.-% of organically modified clays, i.e., montmorillonite, natural hectorite and synthetic hectorite and 3 wt.-% of grafted PP with three different percentages of grafted IA as compatibilizers and two commercial PP samples of different molecular weights were prepared by melt blending. The nanocomposites were characterized by XRD, TEM and tensile mechanical measurements. It was found that the molecular weight of PP used as matrix as well as the percentage of grafted IA of the compatibilizer affected the degree of intercalation/exfoliation of the clay and consequently the mechanical properties of the nanocomposites. Values of 2,137 MPa for the modulus and 51 MPa for the tensile strength were obtained when natural hectorite was used and 2,117 and 40 MPa were obtained when montmorillonite was used. A comparative study was carried out, where PP grafted with maleic anhydride was used as the compatibilizer. Inferior mechanical properties were obtained for nanocomposites prepared by using this compatibilizer, where values of 1,607 MPa for the tensile modulus and 43 MPa for tensile strength were obtained. This result indicated that IA-grafted PP was far more efficient as compatibilizer for the formation of nanocomposites than commercially available maleic anhydride-grafted PP. Model showing interaction of the organically modified clay with grafted PP used as compatibilizer. [source] Effects of synthesis conditions on crystal morphological structures and thermal degradation behavior of hydrotalcites and flame retardant and mechanical properties of EVA/hydrotalcite blendsPOLYMER COMPOSITES, Issue 2 2007Longchao Du The effects of synthesis methods and reaction conditions on the crystal morphological structures and thermal degradation behavior of hydrotalcites have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), particle size analysis (PSA), and differential thermal analysis (DTA). The flame retardant and mechanical properties of ethylene,vinyl acetate (EVA) blends with the corresponding hydrotalcites have been estimated by limiting oxygen index (LOI), UL-94, and mechanical measurements. The results from the XRD, TEM, and PSA demonstrate that the hydrotalcites synthesized by ultrasound method have larger crystal sizes and particle size distribution than those by mechanical stirring method. Higher reaction temperature, longer dripping time, and lower solution concentration can increase the crystal and particle sizes of ultrasound-synthesized hydrotalcites, whereas the longer ultrasound aging time can increase the crystal sizes and decrease the particle sizes of hydrotalcites because of the smashing conglomeration. The DTA data give a positive evidence that the hydrotalcite samples prepared by mechanical stirring method with longer alkaline dripping time have higher thermal degradation temperature than those by ultrasound method, since the ultrasound-synthesized hydrotalcites have more lattice defects than stirring-prepared hydrotalcites. The data from LOI, UL-94, and mechanical tests show that the ultrasonic-synthesized hydrotalcites have better flame retardant properties, whereas the stirring-synthesized hydrotalcites have better tensile strength in the EVA/hydrotalcite blends. POLYM. COMPOS., 28:131,138, 2007. © 2007 Society of Plastics Engineers [source] 4336: Acute mechanical effect of riboflavin corneal cross-linkingACTA OPHTHALMOLOGICA, Issue 2010A PENNOS Purpose To study the acute mechanical effect of corneal cross-linking in vitro. Methods Twenty porcine eyes were harvested from a local abattoire. The epithelium was removed using a rotating brush and corneal buttons having diameter of 8 mm were excised using a Barron's PKP trephine. The buttons were left immersed for four hours in Dextran solution (20%W/V) in order to regulate their hydration. The buttons were immersed in riboflafin 0.1% in dextran 20% and separated in two groups (10 buttons each) where one group was irradiated for 30 minutes with UV light while the other group was not irradiated and served as control. After treatment mechanical measurements were performed by means of a purposely-developed device featuring a stepping motor and a load cell. The motor shaft has a spherical tip that compresses the corneal button against a flat surface mounted on the load cell. The slope of force versus normalized deformation was recorded for each specimen. Results The control group had an average slope of 3.55 (± 1.81) while the irradiated group had 4.47 (±1.80). This difference was not statistically significant. (p=0.27) Conclusion This compressibility test did not reveal statistically significant changes between the two groups immediately after UV corneal cross-linking. It remains to be elucidated whether different tests (e.g. elongation) may yield different results. 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