Materials Literature
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Abstract A kinetic model has been developed on the basis of reaction mechanisms proposed for the anhydride curing of diepoxides, using tertiary amine as catalyst. The model has been tested for the cure reaction of a diglycidylester model compound, bis‐(2,3‐epoxypropyl)‐1,3‐benzenedicarboxylate, with hexahydrophthalic…
Abstract In order to introduce carboxylic acid groups at the surface of poly(ethylene) (PE) films, an attempt was made to covalently link a preadsorbed layer of poly(acrylic acid) (PAAc) on a PE film by an argon or tetrafluoromethane (CF 4 ) plasma treatment. Surface analysis was performed by XPS (X‐ray photoelectron…
Abstract The structural changes and the thermal behavior of silk fibers grafted with methacrylamide (MAA) were investigated as a function of the weight gain. The refractive index parallel to the fiber axis decreased with increasing weight gain, whereas that perpendicular remained almost unchanged. Accordingly, birefri…
LithiumseftiQn characteristics of a ODmplex oxide containing V(V)Cu2V207weinvestigatedLithium illseion was caed outchemicay ushlg anBuLihexie solution and also by the electrochemical GnT method comparativelyThe valence states of copper or vanadium and the stfucturalchImges by lithium insertionwere analyzedbyESRmdXRDme…
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…