Effect of annealing on the viscoelastic and viscoplastic responses of low-density polyethylene

Aleksey D. Drozdov, Qiang Yuan

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Two series of tensile tests with constant crosshead speeds (ranging from 5 to 200 mm/min) and tensile relaxation tests (at strains from 0.03 to 0.09) were performed on low-density polyethylene in the subyield region of deformations at room temperature. Mechanical tests were carried out on nonannealed specimens and on samples annealed for 24 h at the temperatures T = 50, 60, 70, 80, and 100 °C. Constitutive equations were derived for the time-dependent response of semicrystalline polymers at isothermal deformations with small strains. A polymer is treated as an equivalent heterogeneous network of chains bridged by temporary junctions (entanglements, physical crosslinks, and lamellar blocks). The network is thought of as an ensemble of mesoregions linked with each other. The viscoelastic behavior of a polymer is modeled as a thermally induced rearrangement of strands (separation of active strands from temporary junctions and merging of dangling strands with the network). The viscoplastic response reflects sliding of junctions in the network with respect to their reference positions driven by macrostrains. Stress-strain relations involve five material constants that were found by fitting the observations. Fair agreement was demonstrated between the experimental data and the results of numerical simulation. This study focuses on the effects of strain rate and annealing temperature on the adjustable parameters in the constitutive equations.

Original languageEnglish
Pages (from-to)1638-1655
Number of pages18
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume41
Issue number14
DOIs
StatePublished - 11 Jun 2003
Externally publishedYes

Keywords

  • Annealing
  • Low-density polyethylene
  • Relaxation
  • Structure-property relations
  • Tension

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