Materials Literature
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The lithium surface immersed in tetrahydrofuran(THF)containing various salts was analyzed by X-ray Photoelectron SpectroscopyThe lithium surface was covered with the native film which consists of Li2CO3 Li20and LiOHDuring the immersion of lithium in the LiBF40r LiClO4rHF eltrolytesthe chemical compositions of the nati…
Abstract Novel fluorinated methacrylate polymers were synthesized. The purpose was to produce polymers with low refractive indices and increased resistance to optical radiation damage. Six different fluorinated substituents were appended on the monomer before polymerization. Optical‐quality samples were prepared, and…
Abstract The uncatalysed and catalysed polymerization of a hydroxyl‐terminated polybutadiene with toluene diisocyanate has been studied in toluene solution at four different temperatures. The rate constants ( k 1 , k 2 ) and the activation parameters ( Ea 1 , Ea 2 , Δ S 1 ‡ , Δ S 2 ‡ ) for the isocyanate groups in the…
Abstract Using a commercial epoxy/carbon fiber prepreg as a model system, cure kinetics of an autocatalytic‐type reaction were analyzed by a general form of conversion‐dependent function first proposed for degradation kinetics of polymers and composites. The characteristic feature of conversion‐dependent function was…
Abstract 2,2′‐Bis(2‐oxazoline) was used as a chain extender during processing in a twin‐screw extruder with the aim of counteracting degradation phenomena in recycled poly(ethylene terephthalate) (PET). The same experiments were performed on fiber‐grade PET for comparison purposes. Rheological characterization showed…
Abstract The thermal degradation of a poly(vinyl chloride) (PVC) resin was studied using a non‐isothermal thermogravimetric technique. Kinetic parameters such as activation energies, reaction orders, and preexponential factors are calculated using integral and differential methods reported in the literature. Advantage…
The crystal structure of silk fibroin ( Bombyx mori ) was reexamined by using newly collected intensity data. Four molecules pass through a rectangular unit cell with parameters, a = 9.38 A, b = 9.49 A, 2 and c (fiber axis) = 6.98 A, and the space group P2 1 -C 2 . The sheet formed by hydrogen bond is arranged paralle…
Regionalization within the glandular epithelium of araneid silk glands has been revealed by several authors using various experimental methods. The relationship of this regionalization to the potential complexity of silk is discussed. We also review studies on the regulation of secretory protein synthesis in araneid s…
The thermal behavior of silk proteins in silkworms has been investigated in detail. As the temperature of the amorphous random-coil fibroin of Bombyx mori is raised, water is evaporated off up to 100° C. Intra- and intermolecular hydrogen bonds are broken between 150 and 180° C. The glass transition is observed at 175…
Three silks are discussed to exemplify the extreme variability of spider silks. Orb weaver radial silk is rather similar to many other typical silks whether found in spiders or insects. The capture silks of the ecribellate and cribellate orb webs are highly atypical. Indeed they are not so much materials as mechanical…
Color evaluation, surface morphology, amino acid composition, solubility and molecular weight distributions are used to describe the initial degradative changes in Bombyx mori silk fibroin resulting primarily from irradiation with UV and visible light. The biochemical techniques are more sensitive detectors of the ini…
The mechanical properties of major ampulate gland silk fibers extracted from Nephila clavipes (Araneae, Tetragnathidae) spiders are presented. Stress-strain response at conventional tensile testing rates (ca. 10%/s), and at very high strain rates (ca. 1,000,000%/s) are characterized. Fiber surface topography indicates…
Models for the molecular networks present in the frame and viscid silks of the spider, Araneus diadematus, have been developed from the non-Gaussian mechanical behaviour of these silks when tested in their elastomeric state. Frame silk contains a short chain network, crosslinked by β-sheet crystals, where the network…
Larvae of the silkworm, Bombyx mori, control the molecular orientation of their cocoon fiber with several sophisticated spinning techniques. This chapter reviews the interactions of behavior, morphology, and biochemistry in the production of silkworm silk. Numerous physical and chemical variables can induce transition…
General Biology Silks are produced by the more than 30,000 known species of spider [1], and by most of the 113,000 species in the insect order Lepidoptera [2]. In addition, silks are produced by members of several other insect orders [3]. For every silk that has been characterized in any detail, over 1000 uncharacteri…
Molecular-based magnets with high magnetic-ordering temperatures, T(c), can be obtained by mild chemistry methods by focusing on the bimetallic and mixed-valence transition metal micro-cyanide of the Prussian blue family. A simple orbital model was used to predict the electronic structure of the metal ions required to…
In a thin film geometry symmetric block copolymers self-assemble to form well-oriented multilayered structures, ideally suited for study by reflectivity techniques. Neutron reflectivity was performed on selectively deuterated poly(styrene-b-methyl methacrylate) copolymers to determine quantitatively the spatial distri…
We report here the parallel implementation of an original algorithm allowing a fast calculation of the distance matrix D of a graph representing a given chemical structure (molecule, polymer, crystal, etc.). Our algorithm fits perfectly in the SIMD parallel architecture of the Connection Machines CM-200 as we shall sh…
A new method for detecting the initial susceptibility of ferromagnetic materials by recording an induced voltage is described and applied to measurements on grain oriented silicon steel. The significantly different results in dependence of the initial susceptibility on the crystallographic directions can be interprete…
Coatings with Pd-Ni predeposit alloys have been processed using various aluminizing treatments : low and high activity cements, pack and vapor phase coatings. Their metallurgical structure has been investigated with a special emphasis on the repartition of the various metallic elements throughout the coating section.…