Mesophase Content Research Articles

An NMR method for quantitative determination of the carbonaceous mesophase content of a petroleum pitch

Quantitative measurements of the carbonaceous mesophase content of a petroleum pitch, Ashland 240, have been achieved using high-temperature pulsed proton nuclear magnetic resonance ( 1H NMR) spectroscopy. A simple signal analysis procedure allows the anisotropic (mesophase) and isotropic phases of the pitch to be distinguished quantitatively. When pitches containing various proportions of mesophase were analysed by the 1H NMR method and by an optical point counting method, a one-to-one correspondance was observed between the mesophase contents obtained by the two methods. This one-to-one correspondance between determinations by optical and NMR methods confirms the results of preliminary studies with a coal-based pitch. The NMR technique is more rapid and convenient than currently used optical methods of mesophase determination for monitoring and analysing the progress of mesophase development in such pitches.

Crystal lattice deformation and the mesophase in poly(ethylene terephthalate) uniaxially drawn by solid-state coextrusion

The development of crystalline and mesophase structure on drawing of poly(ethylene terephthalate) (PET) has been studied. The uniaxial drawing has been done by solid-state coextrusion from 50 to 90°C. The unit-cell parameters of stress-induced crystallites in extrudates have been determined as a function of extrusion draw ratio ( EDR) up to 4.4 and at an extrusion temperature ( ET) above T g, at 70 and 90°C. The higher the EDR, the longer the c-axis chain direction, the shorter the a and b axes and the smaller the unit-cell volume. In comparison with the conventional lattice parameters obtained by Bunn and Fisher, the highest elongation of the c axis is near 10%. These features imply that the lattice of stress-induced crystallites is far from the closest packing. Coextrudates made below the T g of PET differ markedly from those made above T g. Wide-angle X-ray diffraction (WAXD) patterns of PET extruded at 50°C (below T g) even at high draw ratio exhibit small and/or imperfect crystallites. They appear much as a mesophase. The distance between macromolecular chains ranges from 3.2 to 5.4 Å. The shortest value in the mesophase approaches the interplanar crystal distance of 3.4 Å for the (100) crystal face, on which the benzene rings lie. The crystalline peak separation of the PET, WAXD curve has been evaluated to obtain absolute crystallinities and the content of mesophase and amorphous phase.

Rheological characteristics of mesophase pitch

Rheological characteristics of two pretreated petroleum pitches, during their transformation to mesophase, have been studied by using rotalional viscometer. Simultaneously, the formation, growth, coalescence of mesuphase spheres, and the alignment of coalesced mesophase were observed by Hot-Stage-Cinema-Microscope, discussed with the results of viscosity change and the Q.I. content. It is found that both pretreated pitches were Newtonian fluids at low temperature, but behaved pseudoplastics as increase of mesophase content above 390C. Shear thinning behaviour was also apparent in the shear rate range of 1.9–20 sec−1 at temperature above 390C. The apparent viscosity-temperature curves of this pyrolysed pitches were much affected by the pretreatment conditions.

Anomalous capillary flow of coal tar pitches

Capillary flow of liquid coal tar pitch into a coke bed was studied. Anomalies in the flow could not be attributed to a plugging effect for mesophase content lower than 20 wt%. The flow behaviour of small pitch droplets can be correlated with the change in physicochemical properties, as measured by the glass transition temperature, on penetration into the coke bed.

181. Quantitative determination of mesophase content in pitch

181. Quantitative determination of mesophase content in pitch

Quantitative determination of mesophase content in pitch

A quantitative microscopy method for measuring the mesophase content in pitch has been developed because conventional solubility methods often do not reflect mesophase contents accurately. The general technique utilizes area measurements on photomicrographs of polished specimens to determine volume percent mesophase. Slight modifications to the general method are necessary to overcome unique problems associated with measurements on low (0–15%), intermediate (15–70%) and high (70–100%) mesophase content pitches. Typical data are presented for samples from each regime. The limitations of the method are discussed.

Mesophase from electrode‐binder coal‐tar pitch: An appraisal of structural techniques

AbstractAn electrode‐binder coal‐tar pitch containing mesophase and resulting from combined mild thermal treatment under nitrogen and hot filtration (to remove ash, etc.) has been examined by solvent analysis and magnetic resonance (high‐resolution 1H‐nuclear‐magnetic and electron‐spin resonance) spectroscopy, X‐ray diffraction and polarised light microscopy. At ambient temperature, residues and filtrates with higher mesophase contents tend to exhibit higher concentrations of unpaired electrons and higher stacks in crystalline regions. Room‐temperature 100 MHz 1H‐n.m.r. spectra of solvent extracts of the treated pitch fractions confirm the predominance of aromatic over aliphatic hydrogen in all samples; heat‐treated samples have lower content of hydrogen α to the rings but greater amounts of methylene and methyl hydrogen more remote from the rings than before the heat treatment.

Rheological investigation of coal-tar pitch during its transformation to mesophase

Rheological characteristics of two coal-tar pitches, during their transformation to mesophase, have been followed by rotational viscometry. In certain instances samples were also taken, enabling the mesophase microstructure to be correlated with the flow behaviour. Flow curves established that the pitches are Newtonian liquids at low temperatures, but non-Newtonian character appears at temperatures above 380 °C. Scanning the viscosity-temperature curve of a binder pitch showed that the viscosity began to change, as a result of polymerization processes, at about 240 °C. In both pitches the apparent viscosity, at all rates of shear, increased very rapidly at temperatures above 420 °C when the mesophase content was in excess of 25%. Shear-thinning behaviour was apparent and a peak in the apparent viscosity-temperature curves appeared at all the rates of shear investigated. It is suggested that the systems can be regarded as emulsions. Initially an emulsion of mesophase in isotropic liquid exists but this transforms, at higher temperatures, to one of isotropic liquid in mesophase. The maximum in the apparent viscosity appears to correspond to the phase inversion point.

Process for producing high mesophase content pitch fibers : Schulz, D. A. (Union Carbide Corporation, New York, USA) US Pat 3 919 376 (11 November 1975)

Process for producing high mesophase content pitch fibers : Schulz, D. A. (Union Carbide Corporation, New York, USA) US Pat 3 919 376 (11 November 1975)

Process for producing high mesophase content pitch fibers : Singer, L. S. (Union Carbide Corporation Inc, New York, USA) US Pat 3 919 387 (11 November 1975)

Process for producing high mesophase content pitch fibers : Singer, L. S. (Union Carbide Corporation Inc, New York, USA) US Pat 3 919 387 (11 November 1975)

Production of Carbon Solids from Coke covered with Mesophase

It is attempted to produce carbon solids from coke powder covered with mesophase without binder pitch. The coke powders used were a calcined coke and a green coke (not calcined), and the pitches were a coal-tar pitch and the petroleum heavy oils. A mixture of coke powder of 5 or 10 wt% and pitch was heat-treated at 430°C for a certain period. The mesophase in the heat-treated pitch exists on the surface of the coke powder and this coke covered with the mesophase was separated from the heat-treated pitch by quinoline treatment as quinoline insoluble part. Carbon solids were prepared by carbonization of the molding made of quinoline insoluble part (QI) and measured these physical properties.The obtained results are as follows;1) Compressive strength of the carbon solids increased with increasing the mesophase content in QI. When the mesophase content in QI was 50 wt%, the compressive strength was 600-1300 kg/cm2 at HTT 1000°C and 300-500 kg/cm2 at 2800°C.2) The carbon solids made of the green coke covered with the mesophase from coal-tar pitch had the highest strength and bulk density. Also, high strength carbon solids could be obtained from the coke much covered with the mesophase from petroleum heavy oils.3) The values of the electric resistance and the coefficient of thermal expansion were comparable to those of carbon solids prepared from coke and binder pitch, and were varied with the mesophase content in QI.From these results, it is confirmed that high strength carbon solids are prepared from the coke powder covered with mesophase.