A Preliminary Study of the After-Effect or Drift in Rubber Under Constant Load

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Abstract
Similar vulcanized rubber bands were subjected to four different tensions which produced immediate strains of approximately two to five times their original length. During the life of the bands this elongation was augmented an additional one to two hundred percent by the so‐called after‐strain or drift. Observations were taken at constant temperature. The average life of the bands was about 33 weeks. No correlation was found between the magnitude of the load and the time that the specimen could bear its load. Drift for all stresses continued to the breaking point. In all cases the initial time rate of drift was comparatively high. It declined with time to a positive minimum, passed through an inflection, and then steadily increased for the remaining life of the band. The inflection occurred after some weeks or months of drift. No correlation was found between the magnitude of the load and the time of inflection in the drift rate. During the interval between one and eighty minutes, the magnitude of the drift in at least one specimen was directly proportional to the log of the time. It then deviated from the log law and for three weeks closely followed a decreasing power law.