Nill ductility temperature (NDT), which is used as the indicator of BDTT, was defined as the temperature at which [E.
t] at ambient temperature above BDTT, but did not affect BDTT distinctly.
p]) with no crosslinking, showed a lower BDTT than the sample XS21, which has a lower value in [M.
The same type of fracture as that at 2000 was observed at -30[degrees]C close to BDTT, although the patch type fracture length was reduced corresponding to the decrease in [E.
This case is similar to the case of low density polyethylene in which the patchwork type fracture was found in the narrow temperature range near BDTT (14).
The fracture surface of the sample tested at -70[degrees]C, close to BDTT, was composed of a drawing type fracture, which might be similar to a dimple type fracture, at the notch tip and a brittle type fracture (hackle-like structure) in the center.
t] was achieved, and at -60[degrees]C close to BDTT, as well as the sample ES20.
t] However, the fracture mode observed at the notch tip prior to catastrophic failure at lower temperatures close to BDTT varied from the mixed mode composed of patchwork type fracture and dimple type fracture to only a dimple type fracture depending on the increase in the degree of crosslinking.
Now, another type of transition behavior including the brittle fracture, which decides BDTT based on should be considered.