Effect of Particle-Surface Treatment on Dynamic Mechanical Properties of Polystyrene Powder Compacts

Abstract

Powdered polystyrene was treated with concentrated sulfuric acid at various temperatures and then compacted into specimens having various void fractions. The dynamic mechanical properties of the compacts were measured by the vibratory method in the same manner as shown in our previous papers.
The mechanical loss factor Q^-1 of the compacts increased with increases in treating temperature, void fraction and strain amplitude of vibration. The dynamic modulus σ₀/ε₀ which was defined as the ratio of a stress amplitude σ₀ to a strain amplitude ε₀ decreased with increases in treating temperature and void fraction, but varied quite little with increasing strain amplitude. The relation between the mechanical loss factor and the value, which was defined by the cohesive force between particles, the static compressive force superimposed on vibration force and the frictional coefficient between polystyrene itself, was united into a function independent of the treating temperature and the void fraction. This fact can be interpreted by Mindlin's model with respect to the inelastic behavior of a pair of particles in contact subjected to a cyclic force: The increase in the mechanical loss factor of powder compacts is attributed to the friction at weak junctions between particles.