Effect of the carbon filler on the curing kinetics of epoxycyanate cooligomer

The influence of carbon fibre on the curing kinetics of the prepolymer based on bisphenol A cyanurate and epoxy resin has been studied using infra‐red spectroscopy. It was found that curing process of prepolymer is very complicated. It is shown that in curing the prepolymer a number of the sequential transformations of ones cycle structure into others occurs. An introduction of the carbon fiber (CF) of two types, original CF and modified CF (MCF) containing phosphate groups, affect strongly the prepolymer curing. Both CF and MCF accelerate the conversion rate of epoxy groups. In the case of cyanate groups, the former does not practically affect their conversion whereas the latter decelerates strongly this process. In the paper the influence mechanism of CF is considered.     

Study of the adsorption of sulfur dioxide on dealuminated zeolites Y by thermal desorption and powder X-ray diffraction

Sulfur dioxide is adsorbed on zeolites Y in two forms. The amount of the stable form (T_des=350–390 K) changes in proportion to the sodium content in the zeolite The stable form is localized in a large void at a distance of 1.8 å from the S_II position and causes redistribution of sodium cations. The weakly bound form (T_des=286–300 K) makes the main contribution to the adsorption of SO₂ on highly siliceous zeolites Y and is formed by adsorbate-adsorbate interaction, and it is apparently delocalized in a large void. Out-of-framework aluminum compounds that are formed during dealumination decrease the free volume of the zeolite without changing the nature of interaction of SO₂ with the zeolite.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 535–541, March, 1991.     

Nature and centers of localization of extraframework particles in Y zeolite dealuminated by silicon tetrachloride

X-ray diffraction, XPS, and NMR have been used to investigate the nature and centers of localization of nonframework particles in Y zeolite dealuminated by silicon tetrachloride. It has been established that the reaction products formed upon dealumination consist mainly of aluminum compounds that migrate from the volume of the zeolite to the surface and are also partially localized in internal supercages and small cages (sodalite cells). Water washing removes the particles localized in the supercages but does not affect the particles localized in sodalite cells. It has been shown that, by plotting maps of electron density on the basis of x-ray powder diffraction patterns, the sites of localization of extraframework particles can be determined. The results are consistent with those obtained by other methods, and the maps of electron density give a graphic picture of changes in internal structure of the Y zeolite.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1729–1734, August, 1989.The authors wish to express their appreciation to V. M. Mastikhin for assistance in taking the²⁷Al and²⁹Si NMR spectra.     

Thermochemical transformations of epoxy oligomers in the presence of lead-containing carbon fibers

The aim of the paper is to consider the possibilities of use of differential thermal analysis in studying the interaction between active metal-carbon (lead containing in particular) fibers with epoxide oligomers. The authors examined epoxides of various chemical structure: aliphatic, aromatic, alicyclic, alicyclic-aliphatic. It was ascertained, that lead-containing carbon fibers activate the catalytic decomposition of epoxides and, at the same time, essentially influence their structurization.     

Silver nanoparticles on fibers and films of <Emphasis Type="Italic">Bombyx mori</Emphasis> silk fibroin

Possibility of obtaining silver nanoparticles on fibers and films of silk fibroin was studied. A comparative assessment of the effect of reducing agents on the morphology and size of silver particles on the fiber surface was made.     

Interaction at the Interface of Phosphorus-Containing Carbon Fibers and Diglycidil Ether of Bisphenol-A

Two-component blends of phosphorus-containing carbon fibers (PCF) and diglycidyl ether of bisphenol-A (DGEBA) are investigated. It is found that PCF are better wetted by the epoxy oligomer considered than unmodified carbon fibers. It is stated that the equilibrium work of adhesion of the epoxy oligomer to PCF increases considerably. Heating the two-component blends is accompanied by conversion of epoxy groups and formation of a gel-fraction nonextractable from the fiber surface. The investigation results indicate that chemical bonds are formed at the fiber-oligomer interface, which causes grafting of the DGEBA immediately to the surface of PCF without the use of intermediate compositions usually employed in such cases. It is shown that a transition layer is formed whose morphology differs from that of the fibers and polymer in the blend volume.     

Principles of Structure and Phase Composition Formation in Composite Master Alloys of the Al–Ti–B/B4c Systems Used for Aluminum Alloy Modification

Russian Physics Journal - The principles of formation of structure and properties of materials produced by self-propagating hightemperature synthesis (SHS) from the Al–Ti–B/B4C powder...