| Izod Impact
Izod Impact testing
is done by clamping a specimen in the base of a pendulum
testing machine so that it is cantilevered upward with the
notch facing the direction of impact. The pendulum is released,
and the force consumed in breaking the sample is calculated
from the height the pendulum reaches on the follow-through.
The Izod impact test
indicates the energy required to break notched specimens
under standard conditions. It is calculated as ft. lb. per
inch of notch and is usually calculated on the basis of
a one inch specimen although the specimen used may be thinner
in the lateral direction.
The Izod value is
useful in comparing various types of grades of a plastic.
In comparing one plastic with another, however, the Izod
impact test should not be considered a reliable indicator
of overall toughness or impact strength. Some materials
are notch-sensitive and derive greater concentrations of
stress from the notching operation. The Izod impact test
may indicate the need for avoiding sharp corners in parts
made of such materials. For example, nylon and acetal-type
plastics, which in molded parts are among the toughest materials,
are notch sensitive and register relatively low values on
the Izod impact test. ASTM D-256.
|