Characteristics of both thermoplastic and thermoset composite materials as they pertain to marine vehicle applications are discussed. Comparison of various material selection factors such as strength, damage and moist...
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Characteristics of both thermoplastic and thermoset composite materials as they pertain to marine vehicle applications are discussed. Comparison of various material selection factors such as strength, damage and moisture resistance, and flammability and toxicity as well as cost and availability of thermoset and thermoplastic composite materials are presented. Methods for testing and reducing the flammability and toxicity are discussed. Many commercially available composite systems are reported to provide favorable characteristics for marine applications. Although there seems to be a need for improved production technology for thermoplastics, they present potential advantages in physical properties over thermoset composites.
Measurements of the complex permittivity were used to assess the amorphous phase miscibility in blends of poly(butylene terephthalate) (PBT) and several poly(ester-ether) (PEE) segmented block copolymers. In addition,...
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An investigation of the influence of crystalline morphology on fatigue crack propagation (FCP) resistance in a slightly branched polyethylene is presented. Various thermal histories have been utilized to generate samp...
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An investigation of the influence of crystalline morphology on fatigue crack propagation (FCP) resistance in a slightly branched polyethylene is presented. Various thermal histories have been utilized to generate samples with different crystalline microstructures and the samples were characterized thoroughly using standard methods. Estimation of tie molecule densities was obtained from measurements of brittle fracture stress. Differences in FCP behaviour for the quenched and annealed samples were shown to be dictated by a competing effect between the degree of crystallinity and tie molecule density. Further, larger spherulite size and distribution appeared to have a deleterious effect on fatigue properties. In general, crystalline microstructure is shown to have a significant influence on fatigue crack propagation behaviour.
The preparation of nylon-6/hollow glass microspheres composites by the RIM procedure, leading to a new material with reduced density and increased stiffness, is described. The shear moduli of these composites show a l...
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The preparation of nylon-6/hollow glass microspheres composites by the RIM procedure, leading to a new material with reduced density and increased stiffness, is described. The shear moduli of these composites show a linear dependency on the filler concentration. By means of a modified Kerner equation the shear moduli of the various glass spheres were calculated. A linear dependency between the shear modulus of a glass sphere and its wall thickness is demonstrated. A direct method for the determination of the shear moduli of those glass spheres having a density lower than the matrix material is presented.
作者：
ODIJK, TDepartment of Polymer Technology
Faculty of Chemical Engineering and Materials Science Delft University of Technology 2600 GA Delft P.O. Box 5045 Netherlands
A simple theory is presented for the lengthening of charged micelles with increasing salt concentration. An electrostatic end effect is incorporated in the current theory of micellar aggregation. At low salt concentra...
The orthorhombic superconductor YBa2(Cu1−xNix)3O7−δ with nominal values of x=0.02 and 0.05 and Tc=86.5 and 79.5 K, respectively, was investigated by x-ray-absorption fine-structure (XAFS) measurements about the Ni an...
The orthorhombic superconductor YBa2(Cu1−xNix)3O7−δ with nominal values of x=0.02 and 0.05 and Tc=86.5 and 79.5 K, respectively, was investigated by x-ray-absorption fine-structure (XAFS) measurements about the Ni and Cu K edges. The sample was carefully characterized by various means including optical and electron microscopy. In the sample with x=0.02, the Ni was predominantly dissolved in the 1:2:3 phase. The maximum solubility found in the nominal 5% phase was x=0.04, with the excess precipitating out as NiO. The Ni atoms in the 1:2:3 phase were found to have 4.75±0.4 oxygen neighbors at 1.95±0.03 Å. The best fit to the next neighbor was 5.1±1.2 Y atoms at 2.96±0.02 Å, though the data are also consistent with a mixed shell of Y and Ba atoms. Although the Ni atoms have a first-neighbor environment of oxygen atoms somewhat similar to the Cu site, the more distant neighbor distances are quite different. It is concluded from both the extended and near edge XAFS that most, if not all, of the Ni atoms do not substitute in either Cu site of the 1:2:3 phase, but are in some defect site.
作者：
VROEGE, GJDepartment of Polymer Technology
Faculty of Chemical Engineering and Materials Science Delft University of Technology P.O. Box 5045 2600 GA Delft The Netherlands
We extend previous work [G. J. Vroege and T. Odijk, Macromolecules2 1, 2848 (1988)] on the formation of nematic liquid crystals from uncharged semiflexible polymers to the charged case. The polyelectrolytes are modele...
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We extend previous work [G. J. Vroege and T. Odijk, Macromolecules2 1, 2848 (1988)] on the formation of nematic liquid crystals from uncharged semiflexible polymers to the charged case. The polyelectrolytes are modeled as long slender worm‐like cylinders interacting via both hard‐core and electrostatic repulsions in the second virial approximation. Analogously to rod‐like polyelectrolytes it is possible to describe the result of charge by introducing an effective diameter and a twisting effect. We then calculate numerically the orientational distribution function as a function of concentration. We determine the effect of charge on the phase transition and—in the nematic phase—its influence on the order parameter and the global persistence length (directly connected to the splay elastic modulus). Although the phase transition concentrations are clearly dependent on charge, the properties of the nematic phase at the transition are not—in contrast to the result for rod‐like polyelectrolytes.
Fluorine-containing polyglutamates, which have been synthesized by ester exchange reaction, were investigated from the standpoint of their higher order structure and O2 and N2 permeabilities. The right-handed a helix ...
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