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Viscoelastic and thermoelastic properties of general purpose commercial vulcanized natural rubber
Author(s) -
Nishida Noboru,
Murai Masaki,
Sasaki Naoki
Publication year - 1985
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.1985.070300401
Subject(s) - viscoelasticity , stress relaxation , natural rubber , materials science , vulcanization , thermoelastic damping , relaxation (psychology) , stress (linguistics) , superposition principle , thermodynamics , deformation (meteorology) , composite material , mechanics , physics , creep , thermal , psychology , social psychology , linguistics , philosophy , quantum mechanics
Viscoelastic and thermoelastic properties of general purpose vulcanized natural rubber were investigated focusing attention on its nonideal or irreversible natures. The master curve is not composed by simple horizontal shift of stress–relaxation curves at various temperatures by the time–temperature superposition principle. In order to compose a smooth master curve, both horizontal and vertical shifts are necessary. The relative stress–time relation elucidates the fact that the stress–relaxation mechanism is caused by the chemical scission by oxidation occurring in the network system. The value of vertical shift increases with increasing temperature or strain. This phenomenon has the same meaning as the one derived from the relative stress–time relation. The activation energies are calculated using the horizontal shift factors determined empirically. The result suggests the existence of two concurrent relaxation mechanisms with different activation energies. From the stress–temperature relation at any given strain, energetic and entropic components of the stress–strain curve are obtained. The energetic component is very significant as compared with the case of ideal crosslinked natural rubber. This phenomenon is considered to be caused by the internal friction and/or chemical scission of bonds in the system associated with the deformation process of sample.