This International Standard specifies a method for the determination of the temperature at which plastics that are not rigid at normal ambient temperature exhibit brittle failure under specified impact conditions. A supplementary technique using notched specimens develops brittleness values at a much higher temperature than are observed for unnotched specimens of the same plastic material. The method utilizes a statistical technique to quantify the brittleness failure temperature. Provisions are made for the testing of sufficient specimens to permit the calculation of the brittleness temperature on a statistical basis. Statistical techniques have been developed to quantify the brittleness temperature as is defined in 3.1. The method establishes the temperature at which there is a 50 % chance of failure in either unnotched or notched specimens. This method has been found useful for specification purposes, although it does not necessarily measure the lowest temperature at which the material may be used. In the measurement of the brittleness temperature, the precision of the measurement should preferably be ± 5 °C at the worst when establishing values used in material specifications.