Volume changes during stress relaxation in polyethylene

Autor: Rodney Rychwalski, Josef Kubát, M. Delin, M. J. Kubát
Rok vydání: 1995
Předmět:
Zdroj: Rheologica Acta. 34:182-195
ISSN: 1435-1528
0035-4511
DOI: 10.1007/bf00398438
Popis: This paper presents the results of an experimental study of the stress relaxation behaviour of PE where the focus was on determination of the volume changes taking place during the relaxation process. The dimensions of the samples were followed using a specially designed non-disturbing extensometer. The extensometer data were confirmed in experiments where the volume was measured with a specially designed liquid stress dilatometer. The bulk of the results was obtained with LDPE and LLDPE. High density polyethylene was shown to behave similarly. The decrease in volume, corresponding to an increasing Poisson's ratio, during relaxation was approximately linear with log time. Volume vs. stress diagrams were linear; the values of the apparent bulk modulus calculated from them were only slightly higher than those obtained from the stress-strain curves. Gruneisen parameter was measured and compared with reported values. Possible similarities between the volume change during stress relaxation and that occuring during the process of physical ageing are discussed.
Databáze: OpenAIRE
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