Volume 23, Issue 3 (May 1995)
Relationships between Tensile Stress Relaxation Behavior and Short-Term Elastic Recovery for Linear Low-Density Polyethylenes
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 εc value associated with the onset of the yielding plateau; beyond εc, p1 remains almost constant with ε. This constant plp value is a linear function of the Tensile Residual Deformation (TRD) measured at the end of the relaxation: the lower the plp value, the lower the TRD. The determination of ptp thus appears as a predictive tool of the short-term elastic recovery of a material. Results show that the plp 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.