Tensile properties of rubber compounds at high rates of stretch

With the aim of determining whether the tensile properties of a rubber compound measured at high stretching rates offer any better indication of resistance to abrasive wear than the properties measured at the usual testing rates, a special apparatus was developed for stretching ring specimens to rupture by means of a falling weight.Tensile properties of the ring specimens were determined from a study of the position of the weight as a function of time.The position of the weight was recorded at equal time intervals on a paper tape, one e nd of which was fixed to the weight.The tape was pulled through a spark gap as the weight fell.The timing of the sparks was controlled by a tuning fork.Specimens were stretched to the point of rupture in about one-half to three quarters of a second.The work of extension was determined as a function of the elongation of the specimen from the instantaneous positions and corresponding speeds of the weight.Stress-strain relationships were then obtained from the work of extension.T ests were ma de on a range of cures of each of four rubber compounds.One of these was a pure gum compound, and each of the other three contained 25 volumes of a filler per 100 volumes of crude rubber.The three fillers used were channel black, soft black, and clay.A comparis0n of these data with similar data for a rate of stretch which lies in the range of speeds common to the usual routine tests fails to show that the tensile properties measured at the high stretching rates offer any better indication of resistance to abrasive wear than the properties measured at the usual testing rates.