TY - JOUR
T1 - The effect of annealing on the elastoplastic and viscoelastic responses of isotactic polypropylene
AU - Drozdov, Aleksey D.
AU - Christiansen, Jesper de Claville
PY - 2003
Y1 - 2003
N2 - Observations are reported on isotactic polypropylene (i) in a series of tensile tests with a constant strain rate on specimens annealed for 24 h at various temperatures in the range from 110to 150 C, (ii) in two series of creep tests in the subyield region of deformations on samples not subjected to thermal treatment and on specimens annealed at 140 C, and (iii) in a series of tensile relaxation tests on non-annealed specimens. Constitutive equations are derived for the elastoplastic and non-linear viscoelastic responses of semicrystalline polymers. A polymer is treated as an equivalent transient network of macro-molecules bridged by junctions (physical cross-links, entanglements and lamellar blocks). The network is assumed to be highly heterogeneous, and it is thought of as an ensemble of meso-regions with different activation energies for separation of strands from temporary nodes. The elastoplastic behavior is modelled as sliding of junctions in meso-domains with respect to their reference positions driven by macro-deformation. The viscoelastic response is attributed to detachment of active strands from temporary junctions and attachment of dangling chains to the network. Constitutive equations for isothermal deformations with small strains are derived by using the laws of thermodynamics. Adjustable parameters in the stress–strain relations are found by fitting the experimental data.2003 Elsevier Science B.V. All rights reserved.
AB - Observations are reported on isotactic polypropylene (i) in a series of tensile tests with a constant strain rate on specimens annealed for 24 h at various temperatures in the range from 110to 150 C, (ii) in two series of creep tests in the subyield region of deformations on samples not subjected to thermal treatment and on specimens annealed at 140 C, and (iii) in a series of tensile relaxation tests on non-annealed specimens. Constitutive equations are derived for the elastoplastic and non-linear viscoelastic responses of semicrystalline polymers. A polymer is treated as an equivalent transient network of macro-molecules bridged by junctions (physical cross-links, entanglements and lamellar blocks). The network is assumed to be highly heterogeneous, and it is thought of as an ensemble of meso-regions with different activation energies for separation of strands from temporary nodes. The elastoplastic behavior is modelled as sliding of junctions in meso-domains with respect to their reference positions driven by macro-deformation. The viscoelastic response is attributed to detachment of active strands from temporary junctions and attachment of dangling chains to the network. Constitutive equations for isothermal deformations with small strains are derived by using the laws of thermodynamics. Adjustable parameters in the stress–strain relations are found by fitting the experimental data.2003 Elsevier Science B.V. All rights reserved.
KW - Semicrystalline polymer
KW - Temporary network
KW - Isotactic polypropylene
KW - Annealing
KW - Non-linear viscoelasticity
KW - Elastoplasticity
U2 - 10.1016/S0927-0256(03)00040-5
DO - 10.1016/S0927-0256(03)00040-5
M3 - Journal article
SN - 0927-0256
VL - 27
SP - 403
EP - 422
JO - Computational Materials Science
JF - Computational Materials Science
IS - 4
ER -