The International Organization for Standardization (ISO) standard "ISO 4649 Rubber, vulcanized or thermoplastic - Determination of abrasion resistance using a rotating cylindrical drum apparatus" describes two methods for determining the resistance of rubber to abrasion by means of a rotating cylindrical drum apparatus. These methods involve determining the volume loss resulting from the abrasive action of a test piece rubbing over a specified class of abrasive layer. Method A is for a non-rotating test piece and method B is for a rotating test piece. The result for each method can be reported as relative volume loss or abrasion resistance index.
These test methods are suitable for comparative testing, quality control, specification compliance testing, referee purposes and research and development studies. No close relationship can be inferred between the results of this wear test and service performance.
The wear loss is generally more uniform when a rotating test piece is used because the entire surface of the test piece is in contact with the abrasive layer throughout the test period. However, there is considerable experience in using a non-rotating test piece.
For the purposes of this standard, the following terms and definitions apply:
In principle, a cylindrical rubber test piece is slid over an abrasive layer of a specified abrasive class for a specified distance under a specified pressure. The test piece may be rotating or non-rotating during the test. The abrasive layer is attached to a rotating cylindrical drum on which the test piece is held and passed. The mass loss of the test piece is determined and used together with the density of the test piece material to calculate the volume loss. The volume loss of the test piece is compared to the volume loss of a reference compound tested under the same conditions.
An abrasive machine is used in these tests. This apparatus consists of a laterally movable test piece holder and a rotatable cylinder to which the abrasive layer is fixed. The cylinder shall have a diameter of 150 mm plus/minus 0,2 mm and a length of approximately 500 mm and shall be rotated at a speed of 40 r/min plus/minus 1 r/min, the direction of rotation being as shown in the figure. The test piece holder shall have a cylindrical opening adjustable from 15,5 mm to 16,3 mm in diameter and a device for adjusting the length of the test piece protruding from the opening to 2 mm plus/minus 0,2 mm. The holder shall be mounted on a rotating arm attached to a slide that can be moved laterally on a shaft. The lateral displacement of the holder shall be 4,20 mm plus/minus 0,04 mm for each revolution of the drum. Suitable attachments can be provided to rotate the test piece during the test run (preferably at a speed of 50 revolution for every 1 revolutions of the drum) by rotating the test piece holder (method B). With this lateral movement, the test piece passes over any area of the abrasive layer four times.
The rotary arm and the test piece holder must be vibration-free during operation and positioned so that the test piece is pressed onto the drum with a vertical force of 10 N plus/minus 0,2 N. For examination of extremely soft or hard materials, the force can be changed to 5 N plus/minus 0,1 N or 20 N plus/minus 0,4 N, respectively. The force is generated by adding masses to the top of the test piece holder.
The abrasive sheet should be attached to the drum using three equally spaced double-sided adhesive tape strips running the full length of the drum. The margins where the test piece does not touch should be of equal width. Care should be taken to hold the abrasive sheet firmly so that a uniform abrasive surface is provided over the entire area of the drum. One strip should be placed where the ends of the abrasive sheet meet. Ideally, the ends should meet exactly, but the gap between them should not exceed 2 mm. The adhesive tape should be approximately 50 mm wide and not more than 0,2 mm thick. The abrasive run begins with the test piece in contact with the abrasive sheet.
To prevent the abrasive layer from being damaged by the test piece holder, a device that shuts off the device just before the lower edge of the test piece holder touches the layer is recommended.
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