Journal of Materials Research

Articles

Thermomechanical properties dependence on chain length in bulk polyethylene: Coarse-grained molecular dynamics simulations

Junhua Zhao, Shijo Nagao and Zhiliang Zhanga1 c1

a1 NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway

Abstract

Mechanical and thermodynamical properties of bulk polyethylene have been scrutinized using coarse-grained (CG) molecular dynamics simulations. Entangled but cross-link-free polymer clusters are generated by the semicrystalline lattice method for a wide range chain length of alkane modeled by CG beads, and tested under compressive and tensile stress with various temperature and strain rates. It has been found that the specific volume and volumetric thermal expansion coefficient decrease with the increase of chain length, where the specific volume is a linear function of the bond number to all bead number ratios, while the thermal expansion coefficient is a linear rational function of the ratio. Glass-transition temperature, however, does not seem to be sensitive to chain length. Yield stress under tension and compression increases with the increase of the bond number to all bead number ratio and strain rate as well as with decreasing temperature. The correlation found between chain length and these physical parameters suggests that the ratio dominates the mechanical properties of the present CG-modeled linear polymer material.

(Received June 22 2009)

(Accepted September 01 2009)

Key Words:

  • Polymer;
  • Simulation;
  • Stress/strain relationship

Correspondence:

c1 Address all correspondence to this author. e-mail: zhiliang.zhang@ntnu.no

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