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1. Scope*
1.1 These test methods cover the determination of the
resistance of plastics to “standardized” (see Note 1) pendulumtype
hammers, mounted in “standardized” machines, in breaking
standard specimens with one pendulum swing (see Note 2).
The standard tests for these test methods require specimens
made with a milled notch (see Note 3). In Test Methods A, C,
and D, the notch produces a stress concentration that increases
the probability of a brittle, rather than a ductile, fracture. In
Test Method E, the impact resistance is obtained by reversing
the notched specimen 180° in the clamping vise. The results of
all test methods are reported in terms of energy absorbed per
unit of specimen width or per unit of cross-sectional area under
the notch. (See Note 4.)
NOTE 1—The machines with their pendulum-type hammers have been
“standardized” in that they must comply with certain requirements,
including a fixed height of hammer fall that results in a substantially fixed
velocity of the hammer at the moment of impact. However, hammers of
different initial energies (produced by varying their effective weights) are
recommended for use with specimens of different impact resistance.
Moreover, manufacturers of the equipment are permitted to use different
lengths and constructions of pendulums with possible differences in
pendulum rigidities resulting. (See Section 5.) Be aware that other
differences in machine design may exist. The specimens are “standardized”
in that they are required to have one fixed length, one fixed depth,
and one particular design of milled notch. The width of the specimens is
permitted to vary between limits.
NOTE 2—Results generated using pendulums that utilize a load cell to
record the impact force and thus impact energy, may not be equivalent to
results that are generated using manually or digitally encoded testers that
measure the energy remaining in the pendulum after impact.
NOTE 3—The notch in the Izod specimen serves to concentrate the
stress, minimize plastic deformation, and direct the fracture to the part of
the specimen behind the notch. Scatter in energy-to-break is thus reduced.
However, because of differences in the elastic and viscoelastic properties
of plastics, response to a given notch varies among materials.