The role of viscoelastic adhesive contact in the sintering of polymeric particles

The sintering of polymeric particles is analyzed by considering the growth of contact between viscoelastic spheres driven by adhesive intersurface forces. This process is dominant during the initial phase of sintering and is succeeded by a viscous sintering step that is driven by surface tension and accommodated by viscous flow. The intersurface forces in this work are described by a cohesive zone model. A new formulation of adhesive contact that does not require the cohesive zone to be smaller than the contact radius, together with finite element simulations is used to study the growth of contact. The results of this paper establish conditions that determine the dominant mechanism of contact growth during sintering. These conditions are described using a "deformation map." For a Maxwell material, if particle radius R_max ≤ 20δ_c, where δ_c is a characteristic separation in the Dugdale-Barenblatt model, then the coalescence is driven by adhesive intersurface forces.