Pitch Compositions Research Articles

Processes and Equipment for the Preparation of Coke Pitch and Graphitoplast Compositions for Pressing of Intermediate Products for Electrical Engineering

This article discusses advanced developments in the field of manufacture of electrical machine brushes. A new method for manufacturing by mixing coke pitch and graphitoplast compositions for making brushes, a new mixer design, and a new graphitoplast composition are presented.

The effect of solvent extraction on petroleum pitch compositions and their pyrolysis behaviors

To concentrate pre-mesogens (molecules can convert to a mesophase quickly) from petroleum pitch and prevent system from suffering from excessive carbonization, the parent pitch was extracted by various solvents with different solubility parameters and the corresponding pitch residues were carbonized. It was found that the dispersive solubility parameter has a major effect on the FTIR structural indices (i.e., the indices calculated from Fourier transform infrared spectroscopy) of the pitch residue; thus, four pitch residues enriched in molecules characterized by different condensation degrees and numbers of alkyl chains were successfully obtained and their carbonization behaviors were identified to determine the carbonization behavior of pre-mesogens.The pitch residue obtained by hexamethylene extraction (A1HEX) formed a large domain texture with good lamellar orientation (d002 = 3.4656 Å, Lc = 24.45 Å) and low softening point (SP = 257 °C) in a short carbonization time (6 h), which is attributed to the removal of molecules with a high alkyl carbon atom percentage (which accelerates the formation of an anisotropic phase) and the enrichment of specific molecules. The concentration of molecules with a low condensation degree (condensation index HAU/CA = 0.5491), fewer alkyl chains (C–H substitution indice, ICHS = 0.1511), and a higher condensation reactivity in A1HEX accelerated the formation of the anisotropic phase and provided alkyl free radicals during thermal treatment, which hindered crosslinking between larger free radicals and contributed to the large domain texture with good lamellar orientation and a low softening point.In addition, because of the lower reactivity of the self-assembled polycyclic aromatic hydrocarbons (PAHs) contained in the anisotropic phase (compared to that of the isolated PAHs in the isotropic matrix), the rapid formation of a mesophase during carbonization prevented excessive condensation to some extent.

Insight into controllability and predictability of pore structures in pitch-based activated carbons

Tailoring porosity of pitch-based activated carbons (PACs) on a large scale is of high importance and usually achieved by introducing additives or templates and adjusting activation conditions. Since pitch is a kind of extraordinarily complex mixtures, it is highly necessary to investigate the effect of pitch composition on pore structure of PACs. Herein, a coal-tar pitch was subdivided by solvent fractionation into toluene-soluble (TS), pyridine-soluble (PS), quinoline-soluble (QS), and quinoline-insoluble (QI) fractions followed by activation using KOH or steam, respectively, to obtain PACs. It is found that the formation of pores in PACs is significantly dependent on pitch composition and activation methods. The light fractions (TS and PS) are more favorable for pore development in the KOH-activated carbons, whereas pores in the H2O-activated carbons are easily achieved by using the heavy fractions (QS and QI). The possible pore-formation mechanisms were also proposed, which indicates that the big differences intrinsically originate from the chemical properties (such as molecular size, structures, reactivity with activation agents and rheological behaviors of the molecular aggregations) of pitch compositions. When commercial pitches are employed for the precursors, a synergistic effect on pore development occurs both in KOH- and H2O-activated PACs seriously depending on their mass percentages of light or heavy fractions. It suggests that the mass percentage can be an index to foresee the porous properties of PACs. These findings open up a significantly important and more practical approach applicable to tailor the pores in PACs on an industrial scale just through adjusting pitch compositions.

Experimental and Statistical Optimization of the Tensile Strength of Carbon Fibers from Pitches with Different Composition

A factorial analysis was used to maximize the tensile strength of the carbon fibers obtained from pitch by means of a rational selection of variables and precursor properties. The combined influence of the fiber diameter, the soaking time at the optimum stabilization temperature, and the effect of the polycondensation degree of the pitch on the tensile strength of the carbonized fibers was assessed using a factorial design. For the first time, the strong influence of the degree of polycondensation of the parent pitch was evidenced, even though less polycondensed pitches were spun at a higher yield and favored the homogeneous fixation of oxygen during stabilization. Fibers prepared from the most polycondensed pitches exhibited the best values of tensile strength. However, very highly polycondensed pitch compositions may hinder oxygen diffusion and the formation of cross-linked structures during stabilization, leading to a poorer mechanical performance that can be overcome by increasing the stabilization time.

Study on the structure of pitch-polymer compositions by fluorescence microscope.

In this work, the results of studies on the evaluation of colloidal structure of coal-tar pitch compositions with selected waste polymers by fluorescence microscope. For pitch-polymer compositions containing 10–50 wt% waste polymer, softening point, coking value and content of components insoluble in toluene and quinoline were carried out. The results indicate that pitch-polymer compositions can be treated as microheterogeneous systems, colloidal and biphase, generally exhibiting uniform dispersion of particles composed of polymer macromolecules and probably of α components of coal-tar pitch.

Influence of modifiers and coking conditions on the yield and quality of pitch coke

In the coking of pitch with different softening temperatures, coke particles of different type and structure are added. The coking temperature is 500 and 1200°C. The yield and quality of the pitch coke and compositions obtained are determined. In all cases, the introduction of coke particles is found to increase the yield and change the structure of the coke composition obtained. The microstructure of the composite coke may be regulated by introducing small coke particles of different structure in the high-temperature pitch prior to coking: particles of regular pitch coke increase the proportion of isotropic and finely fibrous structures; particles of acicular coke facilitate the appearance of fibrous and needle structures.

The viscosity of pitches and coke pitch compositions

The viscosity of three coal pitches that have softening temperatures of 361, 386, and 393 K and dust pitch compositions containing a fine fraction (−0.074 mm) of baked oilcoke in amounts of 15, 30, and 50% is measured on a vibratory viscosimeter at T = 430–750 K. The characteristics of the viscous flow of these materials are determined based on the results of this investigation. This allowed specialists working in the aluminum industry to come to some practical conclusions.

00/00760 Properties of gas sparged coal tar pitch compositions

00/00760 Properties of gas sparged coal tar pitch compositions

Properties of gas sparged coal tar pitch compositions

Two pitches have been modified to varying degrees by gas sparging at 400°C for various times. The process gas used was either 1% oxygen in nitrogen or 5% hydrogen in nitrogen. Results indicate that for pitch A, the product is independent of sparge gas and that sparging does not benefit the carbon yield with respect to the raw pitch. Some improvement in toluene insoluble content is observed, however, it would appear that this does not translate to the formation of additional carbon. Overall, the results indicate that the predominant reaction giving rise to the hardening of the pitch is stripping of volatile matter. Pitch B shows different behaviour, whilst with the hydrogen sparge gas the results are similar to pitch A, the oxygen sparge gas shows marked improvement in the yield of carbon from the raw pitch. The improvement in pitch B with oxygen is presumably due either to an oxidative molecular growth mechanism or to the incorporation of oxygen functionality into the pitch and a consequential reduction in volatility.

Investigation of thermochemical transformations of cellulose triacetate, petroleum pitch, and compositions based on them by differential-thermal and mass-spectrometric analyses

-- The effect of preliminary thermooxidative treatment on the pyrolysis processes of CTA, petroleum pitch, and CTA—pitch compositions [40:60% by wt.] has been investigated. -- The polyconjugated aromatic systems which are contained in pitch or which are developed during thermooxidation apparently aid in the occurrence of thermal transformations in the CTA which are connected up with reactions of splitting out and with the development of three-dimensional structures, which leads to a loss in the ability of the composition to melt during subsequent pyrolysis.

4590055 Pitch-based carbon fibers and pitch compositions and precursor fibers therefor

The invention provides carbon fibers having mechanical properties equival to or even better than those of the polyacrylonitrile-based carbon fibers from a bituminous material, e.g. coal tar pitch, as the starting material. The starting pitch is first partially hydrogenated in tetrahydroquinoline under specific conditions followed by a heat treatment to give a pitch composition suitable for spinning which can be characterized by several parameters including the proportions of the carbons and hydrogens having different chemical shifts in the NMR analysis. The pitch composition for spinning is then subjected to spinning under specific conditions including the temperature condition for controlling the viscosity behavior of the molten pitch composition determined by use of the Andrade's equation and the pitch filament is then infusibilized in an oxidative atmosphere and carbonized in an inert atmosphere into carbon fibers having a tensile strength of at least 200 kg/mm2 and a tensile modulus of at least 10 tons/mm2.

Prestige coatings from coal‐tar pitch

Coal‐tar pitch, either in its simple form or as part of more complicated formulations, is being increasingly used in modern times for the heavy‐duty protection of steelwork, concrete, non‐ferrous metals, etc. wherever the utmost in resistance to corrosion is required. Wailes Dove Bitumastic Ltd., of Hebburn, Co. Durham, have been specialists in coal‐tar pitch compositions for over 100 years and are in the vanguard of research to extend its possibilities to keep pace with modern needs for corrosion prevention. This report traces the development of coal‐tar pitch from its use as a simple, single material to its use in the most modern and advanced type of coatings.