抄録
It is generally known that the cause of a filament shrinkage by heat-treatment is a partial decline of frozen strain set up during manufacture of the filament. The present paper concers with the thermal stress which works on the filament preventing these shrinkage. The thermal stress shows maximum value (fmax.) at a temperature (Tmax.), which varies according to the cramp length (≤ initial length of the filament). Between these values, we found the following linear relation: fmax.=k(T0-Tmax.), where k, T0 are constants. When the appearance of thermal stress is to release the frozen secondary bonds on the chain molecule in a set form filament fibre, the variation of the thermal stress in drawn P. P. monofilament due to elongation, is discussed. The results obtained are as follows:
1. Two effects differing in principle are dependent upon the difference in the thermal relaxation curves of the elongated P. P. fibres (specially in low elongation), which are normal stress relaxation curve obtained by heating and the thermal stress curve due to the unbroken secondary bonds caused by elongation.
2. Drawing of P. P. fibre below the elastic limit (relaxated for 30 min. after loading), the thermal stress of the fibre does not vary, but above it, the stress decreases.
3. The constant relation is found between fmax. and its yield point.
