ISSN: 0090-3973
Page Count: 6

Relationships between Tensile Stress Relaxation Behavior and Short-Term Elastic Recovery for Linear Low-Density Polyethylenes

Porzucek, K
ECP, Enichem Polymères France S.A., Centre de Recherches Polymères,

Lefebvre, JM
Laboratoire de Structure et Propriétés de l'Etat Solide, URA CNRS 234, Université des Sciences et Technologies de Lille,

(Received 4 May 1993; accepted 26 October 1994)

Abstract

Tensile stress relaxation is shown to be an experimental way to quantify the short-term elastic recovery of linear low-density polyethylenes (LLDPEs). The evolution of the force decrement ΔF with the logarithm of time is described by two linear equations on both sides of a critical time value tc = 100 s.

The slope p¹ of the ΔF − ln(t) plot below tc increases linearly with the percentage of elongation ε up to the critical ε^c value associated with the onset of the yielding plateau; beyond ε^c, p¹ remains almost constant with ε. This constant p^lp value is a linear function of the Tensile Residual Deformation (TRD) measured at the end of the relaxation: the lower the p^lp value, the lower the TRD. The determination of p^tp thus appears as a predictive tool of the short-term elastic recovery of a material. Results show that the p^lp slope is slightly more sensitive to density evolutions than the TRD value. Assessing the elastic recovery capability through a stress relaxation analysis offers the following advantages: operator-independence, time-saving, and possibility of information storage for further data treatment.

Keywords:
elastic recovery, stress relaxation, Tensile Residual Deformation (TRD)

Paper ID: JTE10411J
DOI: 10.1520/JTE10411J
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