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Internal stresses and activation volumes from the stress relaxation behavior of polyethylene at large deformations
Author(s) -
Kubát J.,
Seldén R.,
Rigdahl M.
Publication year - 1978
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1978.070220620
Subject(s) - materials science , stress relaxation , low density polyethylene , polyethylene , high density polyethylene , composite material , stress (linguistics) , relaxation (psychology) , internal stress , deformation (meteorology) , annealing (glass) , residual stress , creep , psychology , social psychology , linguistics , philosophy
The internal stress level in polyethylene has been determined as a function of strain by analyzing the stress relaxation behavior at room temperature. Also the influence of annealing on the magnitude of the internal stresses was studied, both with HD and LD polyethylene. The maximum initial strain was comparatively high: 20% and 40% for HDPE and LDPE, respectively. The internal stresses were found to be introduced during the initial deformation of the sample prior to the relaxation experiment. For both LDPE and HDPE the internal stress varied with the initial deformation in a manner resembling that of a stress–strain curve. In no case was a permanent residual internal stress (due to the molding process, etc.) observed. The activation volume v , evaluated from the stress relaxation kinetics, was found to be related to the effective stress σ * according to v σ * ≈ 10 kT , where k is the Boltzmann constant and T is the absolute temperature. This is in agreement with results reported earlier for both metals and polymers.