Asphalts and pitches

Petroleum asphalt or coal-tar pitch as coatings The question of whether coal-tar pitch or petroleum asphalt is the more suitable for the coating of underground pipelines has raised a good deal of controversy. Asphalt and pitch are both waterproof materials, and they resemble one another in physical type. In the right circumstances both can be very effective in preventing the access of water to buried or submerged steel surfaces. 

Mineral based adhesive systems involve materials such as sodium silicate but use of this, particularly for fibreboard, is reducing. Bitumens, asphalts and pitches could be put under this category. 

Anisole is a high-boiling, mobile, straw-colored liquid with excellent thermal stability. It is immiscible in water and glycols but completely miscible with most common solvents. It is useful as a solvent for many organic compounds and it has unusual solvency for asphalts and pitches. 

CPA. Copolymer alloy membranes (CPAs) are made by alloying high molecular weight polymeries, plasticizers, special stabilizers, biocides, and antioxidants with poly(vinyl chloride) (PVC). The membrane is typically reinforced with polyester and comes in finished thicknesses of 0.75—1.5 mm and widths of 1.5—1.8 m. The primary installation method is mechanically fastened, but some fully adhered systems are also possible. The CPA membranes can exhibit long-term flexibiHty by alleviating migration of the polymeric plasticizers, and are chemically resistant and compatible with many oils and greases, animal fats, asphalt, and coal-tar pitch. The physical characteristics of a CPA membrane have been described (15). 

Asphalt [8052-42-4] is defined by the American Society for Testing and Materials (ASTM) (1) as a dark brown to black cementitious material in which the predominating constituents are bitumens that occur in nature or are obtained in petroleum processing. Bitumen is a generic term defined by ASTM as a class of black or dark-colored (soHd, semisoHd, or viscous) cementitious substances, natural or manufactured, composed principally of high molecular weight hydrocarbons, of which asphalts, tars, pitches, and asphaltites are typical. 

Canadian and European practice (2—4) and geologists and archaeologists in the United States use bitumen or asphaltic bitumen as a synonym for asphalt, and apply asphalt to the mixture of bitumen and inorganic matter that is used for paving purposes. On the other hand, pitches and tars are derived from the destmctive distillation of coal, cmde oils, and other organic materials. 

Gilsonitc sometimes is used in place of asphalt or pitch. It is easily pulverized and is generally reduced on hammer mills with air classification. 

In the limit of high viscosity, immobile liquid bridges formed from materials such as asphalt or pitch fail by tearing apart the weakest bond. Then adhesion and/or cohesion forces are Lilly exploited, and binding ability is much larger. 

Hoiberg, A. J., (ed.). Asphalts, Tars and Pitches, Interscience Publishers (John Wiley) (1965) ANSI/AWWA C213-79, Standard for Fusion Bonded Epoxy Coatings for the Interior and Exterior of Steel Water Pipelines... 

The production of carbon fibres is based on the pyrolysis of organic fibres or precursors. The main starting materials are polyacrylonitrile (PAN) and pitch (coal tar or petroleum asphalt). They can be classified according to their mechanical performances ... 

Macado ML, Beatty PW, Fetzer JC, et al Evaluation of the relationship between PAH content and mutagenic activity of fumes from roofing and paving asphalts and coal tar pitch. Eundam Appl Toxicol 21 492-499, 1993... 

Asphalt is one of the bitumens, to which also belong tar and pitch. Bitumen, as well as asphalt, is a mixt of hydrocarbons associated sometimes with mineral matter. The org constituents are sol in CSa and may be roughly divided into asphaltines and carhenes. The former are in sol in ether and mineral oils, whereas the latter are insol in CC14 or in CHClj... 

Crude oils are classified chemically according to the structures of tire larger molecules in the mixture. Classification methods use combinations of the words paraffinic, naphthenic, aromatic, and asphaltic. For instance, crude oil which contains a predominance of paraffinic molecules will yield very fine lubricating oils from the gas-oil fraction and paraffin wax from the residuum. Oh the other hand, if the larger molecules are aromatic and asphaltic, the heavier fractions of the crude oil are useful for pitch, roofing compounds, paving asphalts, and other such applications. 

In analytical chemistry in the early 1990s, NMR was routinely used to study (1) polymers, polymer networks, and copolymers, and (2) asphalt, bitumens, Lars, and pitches, amuiig numerous examples that could be cited. 

The heavy, viscous petroleum substances impregnating the tar sands are called asphaltic oils. Other names used to describe these oils include maltha, brea, and chapapote. Asphaltic petroleums are most commonly confused with, but are not related to asphaltites (gilsonite, glance pitch, and grahamite) the asphaltic pyrobitumens (elaterite, wurtzilite, albertite, and impsonite) the native mineral wax (ozokerite) and the pyrogenous distillates of bituminous substances (tar and pitch). 

The presence of tar sands in North America was notedby American Indians several centuries ago. Pitch recovered from surface deposits was used for waterproofing canoes, It is reported llial Columbus observed asphalt from Pitch Lake in Trinidad and used the material for repairing his ships on his third voyage to the West Indies in 1498. The same bitumen deposit was reported by Sir Walter Raleigh in 1595. For several centuries the material was used for repairing vessels,... 

Bitumen. Naturally occurring, solid or semisolid, hydrocarbons including asphalt, mineral pitch, petroleum and naphtha. The ASTM designates them as the fraction of hydrocarbons which are sol in CS2. They are rich in C and H and burn with a sooty flame... 

Hoiberg, A.J. 1964. Bituminous Materials Asphalts, Tars, and Pitches. John Wiley Sons, New York. 

Rostler, F.S. 1965. In Bituminous Materials Asphalt, Tars and Pitches. A. Hoiberg (Editor). Interscience, New York, 11(1) 151. 

Hoiberg, A. J. Bituminous Materials Asphalts, Tars and Pitches Interscience ... 

Tars and Asphalts. These solid and semisolid substances are also known as bitumens, waxes, resins, and pitch. They are very complex substances and relatively little is known regarding their chemical composition. There is little doubt that these materials were foamed... 

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