posted on 2024-03-07, 20:38authored byOmar Atiq, Eleonora Ricci, Marco Giacinti Baschetti, Maria Grazia De Angelis
The modeling of the barrier properties of semicrystalline
polymers
has gained interest following the possible application of such materials
as protective liners for the safe supply of pressurized hydrogen.
The mass transport in such systems is intimately related to the complex
intercalation between the crystal and amorphous phases, which was
approached in this work through an all-atom representation of high-density
polyethylene structures with a tailored fraction of amorphous–crystalline
connections (tie-chains). Simulations of the polymer pressure–volume–temperature
data and hydrogen sorption were performed by means of molecular dynamics
and the Widom test particle insertion method. The discretization of
the simulation domains of the semicrystalline structures allowed us
to obtain profiles of density, degree of order, and gas solubility.
The results indicated that the gas sorption in the crystalline regions
is negligible and that the confinement of the amorphous phase between
crystals induces a significant increase in density and a drop in the
sorption capacity, even in the absence of tie-chains. Adding ties
between the crystal and the amorphous phase results in further densification,
an increase of the lamella tilt angle, and a decrease in the degree
of crystallinity and hydrogen sorption coefficient, in agreement with
several literature references.