Reconstruction of the Entanglement Network and Its Effect on the Crystallization and Mechanical Strength of Sintered Polymers
Ran Chen, Shengming Jiang, Chuanfu Luo
Abstract
Large-scale molecular dynamics simulations are carried out to study the reconstruction of the entanglement network and the subsequent crystallization in the sintering process of polymers. The re-entangled network is quickly initiated by a melting explosion and then slowly adjusted by reptation. A two-step dependence of crystallization half-time on the initial entanglement length is observed, which is caused by the different complexity of entanglement. Rather than the commonly considered entanglement length, the number of entangled chains per chain plays an important role in the following crystallization kinetics, and the number of entangled particles per powder particle dominates the impact resistance of sintered polymers. The critical number 12 of entangled neighboring chains or particles is identified for the crystallization kinetics or mechanical strength, relating to the coordinate number of dense packing. A better reconstruction of the entanglement network is achieved with a longer relaxation time, resulting in a higher tensile strength because of strain hardening at large strains.