Abstract:

The main problem in the investigation and prediction of stress relaxation is  the long time periods (not in seconds or minutes but in days or even months) of measurements for each kind of textile, especially in  cases where users need to know the behaviour of the textile in prolonged time usage. Previously it was found that the rate of relaxation on the log scale can be described by two straight lines and the values of relaxation can be predicted over a long time by the rate of relaxation of the second linear dependency. The present paper shows  investigations of 29.4 tex polyester yarn’s relaxation behaviour at different levels of elongation, i.e. at 3, 5, 7 and 10%. Investigations show that the place of the break-point of relaxation depends on the level of elongation – by increasing the level of elongation the time decreases till the break-point. This phenomenon is clearly visible at higher levels of elongation, while at low levels (3 and 5%) the difference is quite small. Using the data presented, it is possible to predict long-lasting relaxation without long-lasting experiments; only shorter than 1000 second tests are needed.