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Solid‐phase rheology of an anisotropic polymer (vectra A)
Author(s) -
Devens Douglas A.,
Denn Morton M.
Publication year - 1995
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.1995.220061103
Subject(s) - materials science , rheology , viscoelasticity , viscoplasticity , stress relaxation , deformation (meteorology) , thermotropic crystal , phase (matter) , stress (linguistics) , relaxation (psychology) , composite material , constitutive equation , polymer , thermodynamics , creep , finite element method , liquid crystalline , psychology , social psychology , physics , chemistry , linguistics , organic chemistry , philosophy
The solid‐phase rheology of a thermotropic polyester which is liquid crystalline in the melt (Vectra A) was studied for one‐dimensional finite‐amplitude deformations, including step‐strain and recovery, step‐stress and recovery, and step‐strain followed by small‐amplitude oscillations. The rheology is complex, and cannot be described by existing models. Below a critical strain, which is history‐dependent, Vectra A deforms as a linear viscoelastic solid. Above the critical strain the deformation is both viscoplastic and viscoelastic. There appears to be a maximum recoverable strain of about 0.03, beyond which all deformation is nonrecoverable. A large number of relaxation modes is required to describe the stress, and one time scale is inadequate to describe the time‐dependence of yielding and plastic flow.