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Molecular Dynamics Simulations on the Demolding Process for Nanostructures with Different Aspect Ratios in Injection Molding

College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China
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Micromachines 2019, 10(10), 636; https://doi.org/10.3390/mi10100636
Received: 26 August 2019 / Revised: 15 September 2019 / Accepted: 22 September 2019 / Published: 23 September 2019
Injection molding is one of the most potential techniques for fabricating polymeric products in large numbers. The filling process, but also the demolding process, influence the quality of injection-molded nanostructures. In this study, nano-cavities with different depth-to-width ratios (D/W) were built and molecular dynamics simulations on the demolding process were conducted. Conformation change and density distribution were analyzed. Interfacial adhesion was utilized to investigate the interaction mechanism between polypropylene (PP) and nickel mold insert. The results show that the separation would first happen at the shoulder of the nanostructures. Nanostructures and the whole PP layer are both stretched, resulting in a sharp decrease in average density after demolding. The largest increase in the radius of gyration and lowest velocity can be observed in 3:1 nanostructure during the separation. Deformation on nanostructure occurs, but nevertheless the whole structure is still in good shape. The adhesion energy gets higher with the increase of D/W. The demolding force increases quickly to the peak point and then gradually decreases to zero. The majority of the force comes from the adhesion and friction on the nanostructure due to the interfacial interaction. View Full-Text
Keywords: demolding process; molecular dynamics simulation; polypropylene; injection molding; nanostructure; depth-to-width ratio demolding process; molecular dynamics simulation; polypropylene; injection molding; nanostructure; depth-to-width ratio
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Weng, C.; Yang, D.; Zhou, M. Molecular Dynamics Simulations on the Demolding Process for Nanostructures with Different Aspect Ratios in Injection Molding. Micromachines 2019, 10, 636.

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