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Atomistic-scale insights into the crosslinking of polyethylene induced by peroxides

Evidence and attribution

Authority of statements

Prose sections below (Summary, Methods, Findings, etc.) are curated summaries of the publication identified by doi, title, and pdf_path in the front matter above. They are not new primary claims by this wiki.

For definitive numerical values, reaction schemes, and interpretations, use the peer-reviewed article (and optional records under normalized/papers/ when present)—not this page alone.

Summary

ReaxFF molecular dynamics is combined with FTIR mapping and wide-angle X-ray scattering (WAXS) to dissect peroxide-induced crosslinking of polyethylene (PE)—motivated by dicumyl peroxide (DCP) chemistry in high-voltage cable XLPE insulation. The study reports non-monotonic behavior of crosslink extent with curing temperature (moderate heating to ~500 K helps; excessive temperature can hurt), density effects, and peroxide loading trade-offs between byproduct formation and XLPE yield. Electric field in the MD protocol is found to have little effect on crosslinking, and an alternative peroxide is argued to be less efficient than DCP under the modeled conditions. Adri C. T. van Duin is a corresponding author with Penn State and Dow collaborators. The Polymer article emphasizes joint simulation/metrology loops so atomistic radical pathways can be checked against bulk spectroscopic markers.

Methods

  • ReaxFF MD of PE + peroxide mixtures under varied temperature, density, stoichiometry, and optional field (see Polymer for simulation cells).
  • FTIR and WAXS on cured samples to validate structural and crosslink trends.

MD application (Polymer Methods). Engine / code: ReaxFF in LAMMPS. Ensemble / duration: NVT-MD with 2.25 ns equilibration at each target temperature, timestep 0.25 fs, Berendsen thermostat (100 fs damping). System & sweeps: butane/decane + DCP-family chemistry across ~300–900 K (varied increments) and mass densities 0.2–1.0 kg/dm³; representative DCP/alkane cells (e.g., 40 DCP radicals with 500 butane molecules) are shown in the figures. PBC bulk supercells for each state point. Barostat / pressure: N/A — NVT protocol quoted here. Electric field: the article reports MD tests where an external electric field has almost no effect on crosslinking relative to the no-field cases. Enhanced sampling: N/A — not used.

Findings

  • Atomistic models reproduce key experimental trends for crosslinking extent and byproduct burden across the processing window explored.
  • High DCP:PE can increase byproducts without proportionally increasing XLPE quality, informing formulation choices.

The non-monotonic temperature trend is interpreted as a competition between radical initiation efficiency and side reactions that consume peroxide without network formation.

Limitations

  • Industrial XLPE recipes include additives and multiphase morphology not fully captured in idealized MD cells.
  • ReaxFF for hydrocarbon + peroxide chemistry should be spot-checked against QM when new initiators are studied.

Wiki prose here is a navigation aid. Definitive numbers, protocol details, and figure-level claims should be taken from the peer-reviewed article at pdf_path (and any Supporting Information cited there), not from this page alone.

Relevance to group

Industry-facing ReaxFF application to polyolefin crosslinking with experimental validation—parallel to other group polymer reactive MD papers.

Citations and evidence anchors

  • DOI: https://doi.org/10.1016/j.polymer.2019.121901 (papers/Akbarian_Polymer_2019.pdf).