Customer Service:
Mon - Fri: 8:30 am - 6 pm EST


ASTM D256-10

Standard Test Methods for Determining the Izod Pendulum Impact Resistance of Plastics

1.1 These test methods cover the determination of the resistance of plastics to standardized (see Note 1) pendulum-type 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. A measure of a plastic's notch sensitivity may be obtained with Test Method D by comparing the energies to break specimens having different radii at the base of the notch.

Note 4—Caution must be exercised in interpreting the results of these standard test methods. The following testing parameters may affect test results significantly:

Content Provider
ASTM International [ASTM]

Others Also Bought

ASTM D638-10
Standard Test Method for Tensile Properties of Plastics
ASTM D790-10
Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating ...
ASTM D1238-10
Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer

As the voice of the U.S. standards and conformity assessment system, the American National Standards Institute (ANSI) empowers its members and constituents to strengthen the U.S. marketplace position in the global economy while helping to assure the safety and health of consumers and the protection of the environment.