SynopsisA new method is presented for the rapid and consecutive determination of the Young's and bulk moduli of polymeric materials. Usually these properties are determined by separate measurements. However, by using an undersized specimen in a standard compressibility device it has been found possible consecutively to determine both moduli on the same specimen in a single test procedure. The initial loading of the undersized specimen results in a decrease in length and an increased diameter. From these changes Young's modulus may be calculated. Once the bore of the tester is filled, the application of additional pressure results in a decrease in the volume of the polymer, from which the bulk modulus may be calculated. Both of these determinations may be made within minutes, and the values of the moduli are in agreement with published values.Young's modulus and the bulk modulus are both important fundamental properties of the solid state. Generally, they are determined by separate and independent measurements. Or the bulk modulus is calculated from other moduli values. However, there appears to be no one method by which both moduli can be measured directly and simply on the same specimen in the same apparatus. It is the purpose of this paper to describe a new rapid isothermal technique for accomplishing such measurements.The modulus of a Hookean solid under load is defined as the ratio of the applied stress to the resulting strain. Young's modulus E is rather easily determined in tension and in compression.' I n both cases it is the simple unit load divided by the unit deformation of the specimen. Bulk modulus B is taken as the ratio of hydrostatic pressure to volume strain, and is generally more difficult to determine than is E. In either instance, different test equipments and different specimens are required for each of these measurements.We have recently found that a Matsuoka-Maxwell type tester2 can be used to determine both E and B consecutively on the same polymer specimen in a single test procedure. Briefly, the apparatus consists of a hardened steel inner bushing, the inner surface of which is lapped and polished to 0.635 cm. (0.2500, +O.OOOl, -0.OOOO in.) in diameter. This inner bushing is tightly fitted into an outside steel casing. 1147
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