Some new operational modes and parameters of stress relaxation for the viscoelastic characterization of solid polymers. II. The "vertical-shift" mode and intrinsic "time-strain clock"

Kytopoulos, VN; Bourkas, GD; Sideridis, E

dc.contributor.author	Kytopoulos, VN	en
dc.contributor.author	Bourkas, GD	en
dc.contributor.author	Sideridis, E	en
dc.date.accessioned	2014-03-01T01:19:33Z
dc.date.available	2014-03-01T01:19:33Z
dc.date.issued	2003	en
dc.identifier.issn	0021-8995	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/15565
dc.subject	poly(propylene) (PP)	en
dc.subject	relaxation	en
dc.subject	modeling	en
dc.subject	viscoelastic properties	en
dc.subject	modulus	en
dc.subject.classification	Polymer Science	en
dc.subject.other	YIELD	en
dc.title	Some new operational modes and parameters of stress relaxation for the viscoelastic characterization of solid polymers. II. The "vertical-shift" mode and intrinsic "time-strain clock"	en
heal.type	journalArticle	en
heal.identifier.primary	10.1002/app.11167	en
heal.identifier.secondary	http://dx.doi.org/10.1002/app.11167	en
heal.language	English	en
heal.publicationDate	2003	en
heal.abstract	As in part I of this study, in the same manner in the present part II as well, by the same modus operandi way, an attempt was made to introduce, by means of a given operational mode, some further practical parameters for a "by-eye" but well-proven experimental viscoelastic characterization of a polymeric solid. Thus, through consideration of the peculiar vertical shift behavior of the apparent modulus ((E) over tilde) of isotactic polypropylene (iPP) and based on the KWW model, it is shown that, in an empirical and a formalistic sense, a relevant effective or equivalent (single) characteristic relaxation time can be introduced which can give some new interpretations for the linear and nonlinear viscoelastic behavior of a polymeric material, as that of a "time-strain clock," which, as an intrinsic function, is responsable for a functional time-strain shift of the relaxation time and, at the same time, for a shift toward to a more linear or to a more nonlinear behavior. In the above context of attempts, another functional relationship was shown, the so-called spectral shift function and its corresponding parameter of nonlinearity strength, through which some further interpretations and characterizations connected with the existence of the permanent internal stress could be made. Finally, the introduction of the so-called spectral isostrains and their corresponding "spectral inversion point" complete the "set" of the operative parameters proposed for the above-mentioned purpose. (C) 2002 Wiley Periodicals, Inc.	en
heal.publisher	JOHN WILEY & SONS INC	en
heal.journalName	JOURNAL OF APPLIED POLYMER SCIENCE	en
dc.identifier.doi	10.1002/app.11167	en
dc.identifier.isi	ISI:000179267600004	en
dc.identifier.volume	87	en
dc.identifier.issue	2	en
dc.identifier.spage	138	en
dc.identifier.epage	148	en