Determination of young's modulus of elastomers by use of a thermomechanical analyzer

This work used a conventional thermomechanical analyzer (TMA) to measure the depth of indentation at room temperature of elastomers and Finkin's equation to calculate Young's moduli of elastomers, which have been measured by Drutowski, from the radius of contact of an indentor on thin sheets of sample. Data obtained from the TMA are compared with those measured by radius of contact and Hertz contact theory and are found in good agreement. Measurements of Young's modulus as a function of temperature at different heating rates by TMA were made for an acrylic elastomer. The results are compared with theory and the deviations from theory are discussed.     

Determination of internal energy contribution to the thermoelasticity of natural rubber during compression by use of a thermomechanical analyzer

A method for measuring the internal energy change of elastomers under compression is demonstrated using a conventional thermomechanical analyzer. The method is rapid and convenient and has a major advantage in that only a very small sample is required. Results are reported for natural rubber cured with two different crosslinking agents. The results are compared with previous work on similar materials in tension and torsion.     

Development and characterization of poly(trimethylene terephthalate)‐based bicomponent meltblown nonwovens

Poly(trimethylene terephthalate) (PTT)‐based mono and bico meltblown webs have been produced by using a Reicofil® Bi‐Component Meltblown Line at TANDEC, located at the University of Tennessee, Knoxville, TN. Thermal and flow properties of PTT were first examined by DSC (differential scanning calorimetry) and with a Melt Indexer for an effective experimental design through the Surface Response Methodology (SRM). The processability of meltblowing in a wide range of operating windows was extensively investigated. Melt temperature, melt throughput, air temperature, airflow rate, and DCD (distance of collector to die) were considered as primary process control variables. The produced webs were characterized for fiber diameter, bulk density, air permeability, hydrostatic head, tensile properties, and heat shrinkage. Non‐round and curly or twisted fibers were observed in the bico PP/PTT webs by SEM (scanning electrical microscope). The PTT grade studied is quite suitable for the meltblown process. The PTT/PP‐based bico webs showed enhanced barrier properties and heat resistance. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1280–1287, 2002     

Gd2O(CO3)2 · H2O Particles and the Corresponding Gd2O3: Synthesis and Applications of Magnetic Resonance Contrast Agents and Template Particles for Hollow Spheres and Hybrid Composites

The solution approach was employed to yield multifunctional amorphous Gd₂O(CO₃)₂ · H₂O colloidal spheres by reflux of an aqueous solution containing GdCl₃ · 6H₂O and urea. By elongating the reaction time, crystalline rhombus‐ shaped Gd₂O(CO₃)₂ · H₂O with at least 87% yield could be formed and were also accompanied by some rectangular particles. High‐resolution synchrotron powder X‐ray diffraction provides crystal structure information, such as cell dimensions, and indexes the exact crystal packing with hexagonal symmetry, which is absent from the Joint Committee on Powder Diffraction Standards file, for the crystalline rhombus sample. Particle formation was studied based on the reaction time and the concentration ratio of [urea]/[GdCl₃ · 6H₂O]. After a calcination process, the amorphous spheres and crystalline rhombus Gd₂O(CO₃)₂ · H₂O particles convert into crystalline Gd₂O₃ at temperatures above 600 °C. For in vitro magnetic resonance imaging (MRI), both Gd₂O(CO₃)₂ · H₂O and Gd₂O₃ species show the promising T₁‐ and T₂‐weighted effects and could potentially serve as bimodal T₁‐positive and T₂‐negative contrast agents. The amorphous Gd₂O(CO₃)₂ · H₂O contrast agent further demonstrates enhanced contrast of the liver and kidney using a dynamic contrast‐enhanced MR imaging (DCE‐MRI) technique for in vivo investigation. The multifunctional capability of the amorphous Gd₂O(CO₃)₂ · H₂O spheres was also evidenced by the formation of nanoshells using these amorphous spheres as the template. Surface engineering of the amorphous Gd₂O(CO₃)₂ · H₂O spheres could be performed by covalent bonding to form hollow silica nanoshells and hollow silica@Fe₃O₄ hybrid particles.     

Empirical correlation of flow properties of poly(vinyl chloride)

Empirical correlations of flow properties of poly(vinyl chloride) were made using data reported by a number of investigators. Correlation was made by plotting the reduced variable viscosity η/η₀ versus \documentclass{article}\pagestyle{empty}\begin{document}$ (\eta _0 \dot \gamma \bar M_w )/(_\rho RT) $\end{document} or \documentclass{article}\pagestyle{empty}\begin{document}$ (\eta _0 \dot \gamma \bar M_w ^{0.5} )/(_\rho RT) $\end{document} for unplasticized PVC and versus \documentclass{article}\pagestyle{empty}\begin{document}$ (\eta _0 \dot \gamma \bar M_w ^{0.5} )/(_\rho RTW_2 ^a ) $\end{document} with polymer concentration, W₂, for PVC containing plasticizer.     

Corterra PTT纤维在纺织业中的应用前景

PTT纤维具有高弹性和手感柔软的特点 ,非常适合生产针织物和机织物。PTT短纤亦可生产非织造布 ,概述了PTT纤维在纺织行业的技术进展。     

Flow properties of poly (vinyl chloride)

A detailed review of the material published to date on the flow properties of poly(vinyl chloride) is given. The dependence of viscosity on concentration molecular weight, molecular weight distribution, shear and temperature for concentrated and molten poly (vinyl chloride) is considered. Polymer blends and plastisols are also included.     

Low Dose of X‐Ray‐Excited Long‐Lasting Luminescent Concave Nanocubes in Highly Passive Targeting Deep‐Seated Hepatic Tumors

Chromium‐doped zinc gallate, ZnGa₂O₄:Cr³⁺ (ZGC), is viewed as a long‐lasting luminescence (LLL) phosphor that can avoid tissue autofluorescence interference for in vivo imaging detection. ZGC is a cubic spinel structure, a typical agglomerative or clustered morphology lacking a defined cubic shape, but a sphere‐like feature is commonly obtained for the nanometric ZGC. The substantial challenge remains achieving a well‐defined cubic feature in nanoscale. The process by which dispersed and well‐defined concave cubic ZGC is obtained is described, exhibiting much stronger LLL in UV and X‐ray excitation for the dispersed cubic ZGC compared with the agglomerative form that cannot be excited using X‐rays with a low dose of 0.5 Gy. The cubic ZGC reveals a specific accumulation in liver and 0.5 Gy used at the end of X‐ray excitation is sufficient for imaging of deep‐seated hepatic tumors. The ZGC nanocubes show highly passive targeting of orthotopic hepatic tumors.