SYNOPSISInstrumented impact testing has been used to study castor-oil-based polyurethanes. The energy-absorbed capacity of these materials in impact is dependent on several factors, such as the type of isocyanate, NCO/OH ratio, and testing temperature. An approximate but simple method for the low-temperature impact testing was proposed. A change from ductile response to brittle fracture was observed as the temperature of the specimen was reduced. This characteristic ductile-brittle transition temperature is to be found highly sensitive to crosslinking degree. 0 1995 John Wiley & Sons, Inc.

An approximate but simple method for the low temperature mechanical testing of polymers is frequently used. It consists of quenching the polymer sample into liquid nitrogen and then installing it on the testing apparatus. The required test temperature is determined by the time where the experiment is started. In this work, the time‐temperature patterns of two quenched impact test samples, in high density polyethylene and polyurethane, were first measured and then compared with the values obtained from a graphical method of unsteady‐state heat conduction. The agreement between experimental data and calculated values is better than 8% in terms of relative error.

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