THE ROLE OF VISCOELASTICITY IN POLYMER SINTERING

An experimental study for polymer sintering has been carried out using pairs of powder particles. Although in many cases Newtonian sintering models successfully describe polymer sintering, they predict a faster coalescence rate than that observed with the polypropylene copolymer resins used in this study, indicating that factors other than the surf ace tension and the viscosity play a role in polymer sintering. Observ ations of coalescence under the microscope and rotational molding expe riments suggest that melt elasticity slows down the process. Based on these findings, a mathematical model describing the complete polymer s intering process for viscoelastic fluids has been developed. The appro ach was similar to that of Frenkel (1945) and the convected Maxwell co nstitutive equations were used together with the quasi-steady state ap proximation. The proposed viscoelastic sintering model is capable of p redicting the sintering rate slowdown observed in this study.