Preparation and Characterization of High-Density Polyethylene with Alternating Lamellar Stems Using Molecular...

Area of Science:

• Materials Science
• Polymer Science
• Computational Chemistry

Background:

• Mechanical recycling is crucial for reducing plastic pollution and maintaining polymer properties.
• Molecular dynamics (MD) simulations offer insights into polymer structural deformation and reorganization.
• Understanding high-density polyethylene (HDPE) behavior during recycling requires detailed structural analysis.

Purpose of the Study:

• To simulate structural deformations in HDPE during mechanical recycling using MD.
• To investigate the creation of alternate lamellar orientations in HDPE models.
• To identify a reliable model for mimicking industrial plastic behavior.

Main Methods:

• Preparation of stacked lamella-oriented HDPE united atom (UA) models with varying chain numbers (2, 10, 15, 20).
• Utilizing MD simulations to analyze structural deformation, lamellar orientation, and entanglement.
• Employing one-dimensional density profiles and local order parameter analyses for characterization.

Main Results:

• HDPE models with 2, 10, and 15 chains exhibited desired alternating lamellar orientations and entangled segments.
• The 20-chain model showed multi-nucleus crystal growth, deviating from lamellar-stack orientation.
• Models demonstrated densities of 0.90-0.94 g/cm³, crystallinity ≥42%, stress yield ~100-120 MPa, and elongation at break ~250%.

Conclusions:

• The 10-chain alternate lamellar-stack orientation model is a reliable miniature representation of HDPE.
• This model effectively mimics industrially relevant plastic behavior under various conditions.
• MD simulations are valuable tools for optimizing mechanical recycling processes for polymers like HDPE.