The stress relaxation behavior of nylon 1010 samples with the initial strain of 1%

2.8% and 5.1% were investigated under various temperatures for not less than 10 h.The samples were measured at 20

40

60 and 80 ℃ separately.The stress relaxation rate

the residual stress and the activation volume under different experimental conditions were obtained.The results show that there was a certain permanent residual stress in the relaxation process.The reason is that the effect of the crystalline regions in the semi-crystalline nylon leads to a permanent modulus of the system.During the relaxation process

nylon samples with different initial strains showed similar trends.When the relaxation rate reached the maximum

the values of activation volume remained constant for a short period of time

which is in accordance with the principle of stress-aided thermal activation.At this stage the activation unit of the polymer was relaxed

and the relaxation rate -d/dt and the effective stress * showed an exponential relation.With further relaxation

the stress decreased to a certain threshold

activation volume would gradually increase and the independent movement of activation unit was restricted.The internal stress of the polymer gradually relaxed by the cooperative movement of multiple activation units.At this final stage

the value of stress assisted work was constant.The relaxation rate -d/dt and the effective stress * exhibited power-law relation and the power exponent is *V/(kT).