Mechanical Properties of Highly Filled Elastomers III. Influence of Particle Size and Content of Filler on Thermal Expansion and Bulk Moduli

摘要

Model substances were prepared of a polyurethane rubber filled with different amounts of various fractions of sodium chloride. Eight filler fractions were used with sizes between 1 micron and 480 micron. The amount of filler was varied between 0 and 50 per cent. by volume. An experimental method is described, by which thermal expansion and bulk modulus of an isotropic material may be simultaneously determined as functions of temperature. The materials were investigated for thermal expansion and bulk modulus. All filled and unfilled samples show a glass-rubber transition, at which temperature the thermal expansion coefficient increases considerably and the bulk modulus decreases sharply. These temperatures do not depend on amount or size of filler. The levels of the bulk moduli and the thermal expansion coefficients are independent of filler size, but depend considerably on the amount of filler. These levels may be predicted by means of a simple macroscopic theory (Frohlich-Sack-Van der Poel), describing the bulk modulus, the thermal expansion and the density of the composite material in terms of the corresponding properties of the components and of their relative amounts. (Author)