Prediction of polymer processing characteristics using the C. W. Brabender plasti‐corder torque rheometer

The Brabender Plasti‐Corder is shown to be an effective tool for predicting the processing characteristics of thermoplastic polymers. Procedures for determining the molding temperature range, the relative melt viscosity over a continuous temperature range, and the stability of molding and experimental curtain coating materials are presented. Molding temperature ranges can be determined by first establishing the Brabender torque which corresponds to the maximum viscosity at which a material will just fill the cavity in a particular injection system under full injection pressure and maximum injection rate. This torque is constant for any material to be molded in this system. A Brabender torque‐temperature curve is then obtained on the pertinent resin and the temperature which corresponds to the torque associated with the maximum viscosity is the minimum molding temperature. Maximum molding temperature is the temperature at which the log of the torque deviates from a linear dependence on temperature. The stability of thermoplastic compositions can be shown by a Brabender torque‐time curve at constant temperature. An unstable polymer shows decreasing torque with time if the decomposition predominantly consists of chain scission.