Force measurement from viscoelastically recovering Nylon 6,6 fibres

The force generated from viscoelastically stored energy in nylon 6,6 fibres was investigated. A 320 MPa, 24 h tensile creep stress was applied to annealed yarn. Following elastic (short-term) recovery, the yarn was allowed to contract from a loose state to a fixed strain, thereby becoming taut. The resulting force grew to 3.4% of applied creep load over a 2700 h measurement period t, and was predicted to approach a maximum of 3.8% as t → ∞. Increasing humidity reduced force output, but the effect was totally reversible. As the force–time curve follows a Weibull or Kohlrausch–Williams–Watts function, the findings are discussed from a molecular jumps perspective.