8.3 Self-Reinforcement Behavior of NR
153
Figure 8.8 shows how to measure WAXD of the notched NR specimen under
stretching (the tear mode), that is, a setup at the synchrotron beam line for simultaneous time-resolved WAXD and tensile measurements [87]. The sample width of
8 mm is assumed to be large enough for the notch depth (a X ) of 0.5–1.0 mm. Usage
of the X-ray beam from the synchrotron radiation source makes it possible to carry
out the time-resolved observation of crack growth from the tip of notch as shown.
Figure 8.9 shows an example of experimental results [87]. At the horizontal axis,
X = 0 is the tip position of the notch, which is the starting point of the crack growth
(λ = 1). At λ = 1, the specimen is in amorphous state; hence, crystallinity (χ ) is zero
regardless of X (not shown in the figure). Immediately after the stretching, however,
template crystallization began at the tip of growing crack, and χ increased to 12% at
Fig. 8.8 Time-resolved WAXD measurement of a notched natural rubber vulcanizate under tear
stress (from Fig. 2 in Ref. [87])
Fig. 8.9 Dependence of
degree of crystallization (χ)
at the crack tip on strain ratio
(λ) (modified Fig. 9 in Ref.
[87])
153
Figure 8.8 shows how to measure WAXD of the notched NR specimen under
stretching (the tear mode), that is, a setup at the synchrotron beam line for simultaneous time-resolved WAXD and tensile measurements [87]. The sample width of
8 mm is assumed to be large enough for the notch depth (a X ) of 0.5–1.0 mm. Usage
of the X-ray beam from the synchrotron radiation source makes it possible to carry
out the time-resolved observation of crack growth from the tip of notch as shown.
Figure 8.9 shows an example of experimental results [87]. At the horizontal axis,
X = 0 is the tip position of the notch, which is the starting point of the crack growth
(λ = 1). At λ = 1, the specimen is in amorphous state; hence, crystallinity (χ ) is zero
regardless of X (not shown in the figure). Immediately after the stretching, however,
template crystallization began at the tip of growing crack, and χ increased to 12% at
Fig. 8.8 Time-resolved WAXD measurement of a notched natural rubber vulcanizate under tear
stress (from Fig. 2 in Ref. [87])
Fig. 8.9 Dependence of
degree of crystallization (χ)
at the crack tip on strain ratio
(λ) (modified Fig. 9 in Ref.
[87])