Air-blown asphalts

Air-blown asphalts, more resistant to weather and changes ia temperature than the types mentioned previously are produced by batch and continuous methods. Air-blown asphalts, of diverse viscosities and flow properties with added fillers, polymers, solvents, and ia water emulsions, provide products for many appHcations ia the roofing industry. 

Built-up roofing constitutes several pHes of a saturated roofing felt (low melt, flexible asphalt saturant) with each ply mopped in place and the stmcture covered by air-blown asphalts of from 60° to 105°C softening point, with the hardness selected depending primarily on roof slope. These roofs are usually surfaced with mineral aggregates. 

Air-blown asphalt asphalt produced by blowing air through residua at elevated... 

Samples. Two straight-reduced asphalts from Romashkino-type (29° API gravity) crude petroleum, 100 penetration (SR-100) and 125 penetration (SR-125), and three air-blown asphalts of different degrees of oxidation, 100, 50, and 25 penetration (AB-100, AB-50, and AB-25) were investigated. The air-blown asphalts were derived from SR-125. The properties of the asphalts are given in Table I. 

The increase in asphaltenes in air-blown asphalts results from chemical reactions occurring in the asphalt upon oxidation, resulting in the formation of molecular aggregates. 

The early sulfur cements were used to join clay sewer pipe, clay tile, cast iron pipe, paving brick, acid reaction vessels, and for similar applications. The composition of the materials varied but were mostly sulfur containing 1-10% of an organic polysulfide. Silica, carbon black, and wood rosin also were used frequently. However, the compositions varied considerably, and one promising material contained 60% air blown asphalt and 40% sulfur (49). 

Other dermatologic problems among commercial roofers not necessarily related to coal tar exposure include scars/keloids and fiberglass dermatitis (Emmett 1986). Few dermatologic problems have been associated with asphalt apart from the occasional thermal burn. Asphalt is derived from petroleum and is made up of the non-volatile hydrocarbons left after petroleum has been refined into gasoline and other products. Air-blown asphalts, which are produced from petroleum residue at temperatures between 400 F and 600 °F, are primarily used in roofing materials. In addition to thermal burns, irritant contact dermatitis occurs from the defatting action of repeated exposure to these chemicals (Mackison et al. 1981). 

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