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A method for determining the abrasion resistance properties of reinforced vulcanizates was required for evaluating new GR-S type elastomers and carbon blacks developed for use in automobile tire treads. In spite of the fact that past experiences revealed that most laboratory machines are unsatisfactory for testing GR-S vulcanizates, a program for evaluating several machines was undertaken. A Lambourn abrader similar to the one recently adopted by the British Standards Institution for testing elastomer vulcanizates appeared to be most promising, for which reason efforts were expended on constructing a similar machine. The abrader that was constructed and operated to simulate wear brought about by a tire slipping on road surfaces embodied the following four modifications of the British machine: 1. All parts and accessories were either obtained or fabricated in the United States. 2. The electrical eddy current type of brake used in the original Lambourn machine was replaced with a hydraulic, gear pump braking system. 3. Intermittent talcing of the test wheel during operation was specified. 4. A revolution counter equipped with a friction drive wheel, one foot in circumference, was installed to ride on the test wheel for the purpose of conveniently determining test run distances. The conditions for testing vulcanizates were standardized to obtain abrasion loss values that could be expressed in terms of loss in cubic centimeters per 3000 feet of running at 24 per cent slip. Adjustments were made in calculating abrasion ratings from volume loss values to bring them more in line with reported service test ratings.

was no extensive shift of the center of the band with different organic solvents, although such a shift was shown to occur with" benzene-azophenol.413 On this same graph is also given the curve for eight times the original concentration in ligroin (Curve 3), showing the exact position and strength of the first weak band. In the absorption curve of the entire band, this first band appears so weak that some observers have missed it entirely. Summary 1.The absorption spectra of benzene-azobenzene have been determinedin a number of solvents, and there has been shown to be no extensive shift of the band with a change of typical organic solvents as was the case with benzene-azophenol.2. It has been shown that the absorption band of benzene-azobenzene is not simple but consists of a smaller band on the lower frequency side of the principal band which adds to the principal band to produce the observed absorption curve.

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