Control Tests of Uniformity in the Manufacture of Carbon Black

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Abstract Twenty-five years ago, a pneumatic tire for an automobile cost twenty-five dollars and gave service of about 3500 miles. Today a pneumatic tire costs only one-half as much and can be relied upon to give service of about 25,000 miles. These improvements are the result of various factors, such as the use of cord fabric, organic accelerators, antioxidants, and other carefully chosen raw materials. Among these latter, it is safe to say that carbon black is unquestionably the raw material which has contributed most of all to the increased mileage of pneumatic tires. Years ago when the reënforcing properties imparted to rubber by carbon black first became recognized, this product was furnished without any particular requirements other than freedom from impurities. Later, as the percentage of carbon black incorporated in rubber mixtures continued to increase, certain measures were taken to control the grit content. Ultimately, with the aim of furnishing the rubber industry with a product of the highest quality and greatest uniformity, the most important producers of carbon black, in coöperation with the laboratories of rubber factories, proceeded to develop a series of check tests and various other tests, which have led in turn to the development of the present-day specifications of carbon black.