A NEW TECHNIQUE FOR THE STUDY OF HIGH-POLYMER DEGRADATION REACTIONS

Abstract

A quartz spoon gauge, recording pressures automatically, is described. The gauge, representing a closed reaction system, can be used for investigations of the degradation of polymers. It has been tested by degrading polymethylmethacrylate over a temperature range of 300 to 400 °C. The important features of the gauge are as follows: (1) The pressure exerted by gases during degradation is continuously recorded at appropriate chart speeds via an electrical transducer (maximum displacement ± 0.038 cm; spoon gauges used in this work had sensitivities in the region of 0.035 cm/atm). (2) Only small quantities of polymers are needed; 20 to 40 mg of polymer in the form of films was deposited on the walls of the reaction vessels; however, much smaller samples could be used, the limit being given by mechanical vibrations set up in the system. (3) Temperature equilibrium between the reaction vessels and a thermostated bath is reached within about 30 seconds.Useful results for polymethylmethacrylate were obtained up to 400 °C, which is a temperature about 100° higher than that reached by previous workers, not neglecting the initial parts of the reactions. The reproducibility of the results has been indicated by average curves obtained from several runs at any one particular temperature and their standard deviations.