The measurements have been made of the sonic moduli (pulse propagation moduli) and the tensile moduli simultaneously on the filaments produced from various polymers to investigate the orientation characteristics of molecules in the drawing process. The tensile moduli have been measured dynamically by giving the sample sinusoidal strain, whose amplitude is about 0.4% and frequency is 0.12cps, and by stress relaxation statically. These three moduli gives different information each on the behavior of polymer molecules during the elongation. The variance of pulse propagation time (ΔT
) has also been measured when the sample is given dynamic strain (Δγ) or stress (ΔS
) of the low frequency of 0.12cps. The physical meanings of the coefficients ΔT
/Δγ and ΔT
are discussed from the point of molecular orientation.
The measuring apparatus consists of pulse propagation viscoelastic meter, strain meter, stress meter, bias current part, drawing device and X-Y recorder. The dynamic tensile moduli have been measured by Lissajous method. Only the change of pulse propagation time has been amplified after the electric current corresponding to the propagation time of the sample, which was not dynamically strained, was cut off by the opposite bias current. The measurements have been made mainly on polypropylene filaments (1050d
) at room temperature (about 30°C). The results are as follows:
(1) The dynamic tensile moduli (E'
) and pulse propagation moduli (Es
) do not change so much for polypropylene filaments of lower draw ratio, but increase much for that of higher draw ratio with the increase of static strain. E
' increases monotonously with the increase of draw ratio. Es
, however, has a minimum at the draw ratio of about 1.5. The reason why the Es
curve passes the minimum seems to be found in the process of crystalline orientation which gives much influence upon the drawing process at the lower elongation. At the higher elongation, E'
increase in accordance with the increase of amorphous orientation.
(2) The propagation moduli on polypropylene filaments were measured during the stress relaxation. The stress relaxation moduli (Er
) decrease monotonously within the measured time. Because of increase of molecular orientation Es
increases to about 100sec and reaches the constant value which corresponds to the strain. R. S. Stein et al
. have reported that crystalline orientation is completed within 1sec from the observation of dynamic birefriengences and dynamic X-ray diffraction. Taking accounts of these results, it is considered that the change of Es
within 100sec has been occasioned by the relaxation of the orientation of the amorphous parts though the orientation is usually complete within 100sec. The change of Es
which is derived from crystalline orientation seems to be too fast to observe.
(3) The change of pulse propagation time (ΔT
) when a filament received dynamic strain (Δγ) or dynamic stress (ΔS
) are recorded on the X-Y recorder with either of them. The coefficients ΔT
/Δγ or ΔT
are defined as“strain-pulse propagation coefficient”or“stress-pulse propagation time coefficient”respectively. The strain-pulse propagation time coefficient is useful as a measure showing the degree of the allowance of molecular strain. The coefficients of polypropylene are positive for lower elongated filaments, negative for moderately elongated filaments, and zero for highly elongated filaments. The change of the coefficient with the increase of the static strain also shows this tendency.