Reconstruction of the Entanglement Network and Its Effect on the Crystallization and Mechanical Strength of Sintered Polymers

Large-scale molecular dynamics simulations are carriedout to studythe reconstruction of the entanglement network and the subsequentcrystallization in the sintering process of polymers. The re-entanglednetwork is quickly initiated by a melting explosion and then slowlyadjusted by reptation. A two-step dependence of crystallization half-timeon the initial entanglement length is observed, which is caused bythe different complexity of entanglement. Rather than the commonlyconsidered entanglement length, the number of entangled chains perchain plays an important role in the following crystallization kinetics,and the number of entangled particles per powder particle dominatesthe impact resistance of sintered polymers. The critical number 12of entangled neighboring chains or particles is identified for thecrystallization kinetics or mechanical strength, relating to the coordinatenumber of dense packing. A better reconstruction of the entanglementnetwork is achieved with a longer relaxation time, resulting in ahigher tensile strength because of strain hardening at large strains.