A New Plastometer

Abstract AT THE Swampscott meeting of the American Chemical Society an analysis was given of the meaning of plasticity when this term names a property of solids that concerns the molding of plastics such as rubber. A function for plasticity was deduced with some suggestions on the adoption of a C. G. S. unit of plasticity. Also, a design of a plastometer, based upon this analysis, was outlined. It is the purpose of this paper to give a full description of such a plastometer. Original Plastometer A detailed drawing of the instrument as first conceived in February, 1927, is given in Figure 1. The rubber sample, 1, in the form of a cylinder 1 cm. long, 1 sq. cm. cross section, is held between two vertical round rods, A and B, which will be designated as upper and lower plungers. These plungers consist of contacting end caps, 15, 20, of steel mounted upon porcelain tubes, 19, which in turn are cemented into sockets 16, 21. The lower socket, 21, slides through a bushing 22. Its nether end is cut obliquely, and by means of a spring is pressed into contact with the surface of a cylindrical wedge, 23, movable in and out by means of a drum nut, 25, fitted to the threaded end, 24, of the wedge. The height of the sample may be read to 0.001 inch off the scale on the drum nut, 25. The upper socket, 16, slides in a tube, 17, and has a bearing shoulder for the spring, 9, called the force spring. The upper plunger, together with other parts bearing upon it from above, is carried by a light spring, 27.