Abstract
The thermal stress with polypropylene monofilament drawn in hot state is measured preventing from any shrinkage. The stress-temperature curve shows that thermal stress increases at first and then decreases with temperature.
The maximum thermal stress may be inferable to be the force which is a restrictive condition with manufacturing the polypropylene to fiber form. The stages of experimental processes taken may be explained by the following:
1. When the temperature coefficient of thermal stress is positive, the frozen strain is gradually removed.
2. In the case of heating the sample at various constant temperatures, each thermal stress has almost the same maximum value.
3. Voigt model is suitable for these explanations, and the activation energy is calculated from the equation; Where ST is thermal stress at T°C, S0 the maximum stress, t heating time and τ relaxation time.
4. The obtained value of activation energy is nearly equal to that of viscous flow.
5. When the temperature coefficient of thermal stress is negative, the relaxation of restrictive force by heat appears.
