FRACTURE OF UN-NOTCHED BIAXIALLY COLD ROLLED HIGH DENSITY POLYETHYLENE IN TENSION

The fracture surfaces of un-notched tensile specimens prepared from HDPE biaxially rolled at room
temperature and drawn to failure in tension were analyzed using scanning electron microscopy (SEM). The
HDPE sheets were reduced to a thickness of about 80% the initial during the rolling process and the tensile
test was conducted at -40 degrees Celsius and at a strain rate of 100%/min. In comparison to a melt processed sheet of
the same material and thickness, the rolled material exhibited greater work hardening capacity,
homogeneous yield behavior, and improved elongation to failure. The fracture surface manifested in a plane
roughly 45 degrees to the draw direction, and revealed three distinct zones: 1) the damage zone, 2) a fracture
surface associated with slow crack propagation, and 3) a fracture surface associated with rapid crack
propagation. The cross-sectional dimensions of sub-microlayers observed from the fracture surface
suggested that they could have resulted from the affine deformation of spherulitic crystals during the rolling
process.
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