We measured the linear and nonlinear elastic moduli of polymer material plastisol. The layer of material was polymerized between two coaxial solid cylinders with diameters 6-8 times greater than the thickness of the layer. During the polymerization process mechanical stresses arose within the material. Comparing the measured values of the elastic parameters of the material, polymerized between the cylinders, to the values measured in the material, polymerized between flat parallel plates, under uniaxial compression it became possible to evaluate these stresses. Measurements in the flat and cylindrical geometry have been carried out by the method of static shear deformations up to 0.4-0.6 of the layer thickness. Nonlinear effects are well pronounced under such deformations, which allows to estimate their contribution to the elastic properties exhibited by the material and measure the nonlinear Landau parameters. Shear strain was created by certain tension applied to one of the plastisol boundaries in plane geometry. The second boundary was fixed and could not move in the direction of shear deformation. However, bindings allowed this boundary to move in the direction perpendicular to the direction of shear deformation. The shear strain in a cylindrical geometry was created by the rotation of one of the cylinders applying a certain stress tangentially to the lateral surface. The pattern of stress-strain curves and the measured values of static shear modulus appeared to be significantly different in cylindrical geometry and planar geometry, whereas the thickness of plastisol was the same. Landau parameter A, measured in plane geometry with the uniaxial compression applied, was equal to -392 kPa.

43.25.Dc Nonlinear acoustics of solids

43.25.Ba Parameters of nonlinearity of the medium

Department of Acoustics, Faculty of Physics, M.V.Lomonosov Moscow State University, GSP-1, Moscow 119991, Russia.