Abstract

The utility of the T-R test for determining the freezing points of elastomeric compounds and their tendency to crystallize has been demonstrated. The freezing point is not appreciably influenced by elongation, but from an operational standpoint it is preferable to employ 50 per cent extension of the sample. To determine the tendency to crystallize on cold storage a 50 per cent test elongation is optimum. To determine if a stock crystallizes on stretching the determination must be made at a series of elongations, or a minimum of two test elongations such as 50 and 200–300 per cent. Materials which crystallize almost immediately at low temperature are readily recognized. All materials which crystallize exhibit sluggish retraction characteristics, whether the crystallization is spontaneous, induced by cold storage, or by extension. The T-R test is simple to perform, highly reproducible, and very versatile. A complete characterization of the low-temperature properties of an elastomeric compound can be made by means of the T-R test in a shorter time than by any other method or combination of methods.