The shape accuracy and residual stress distribution of a nano-molded semicrystalline polymer are studied by molecular dynamics simulations.Semicrystalline polyethylene flakes are obtained by continuous cooling inside ...The shape accuracy and residual stress distribution of a nano-molded semicrystalline polymer are studied by molecular dynamics simulations.Semicrystalline polyethylene flakes are obtained by continuous cooling inside templates with four shapes.We find that the curvature of contour curve near template corners decreases with corner angle.A simple 2D shape model of minimum surface energy is proposed to understand the shapes for repulsive and attractive templates.The confinement of template induces highly ordered chain packing in surface region.According to the spacial distribution of local stress,we find the contracting stress caused by volume shrinkage during cooling concentrates on the chains perpendicular to the direction of relative stress principal.The distribution of von Mises stress indicates the outer layer of semicrystalline polymer flake has lower distortion.Our results provide a theoretical insight for better nano-molding techniques.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.21873093,21790340,22073092 and 22103080)the National Key R&D Program of China(No.2020YFA0713601)the Key Research Program of Frontier Sciences,CAS(No.QYZDY-SSW-SLH027).
文摘The shape accuracy and residual stress distribution of a nano-molded semicrystalline polymer are studied by molecular dynamics simulations.Semicrystalline polyethylene flakes are obtained by continuous cooling inside templates with four shapes.We find that the curvature of contour curve near template corners decreases with corner angle.A simple 2D shape model of minimum surface energy is proposed to understand the shapes for repulsive and attractive templates.The confinement of template induces highly ordered chain packing in surface region.According to the spacial distribution of local stress,we find the contracting stress caused by volume shrinkage during cooling concentrates on the chains perpendicular to the direction of relative stress principal.The distribution of von Mises stress indicates the outer layer of semicrystalline polymer flake has lower distortion.Our results provide a theoretical insight for better nano-molding techniques.
