Thermal degradation of polymers at low rates

Abstract

Samuel 1. Madorsky I n meas uring the rates of thermal degradation of polym e rs at constant tempe rat u res in the r ange of 200 0 to 500 0 C, one encoun ters a distortion of t he initial p arts of t he rate cur ves during the time required to h eat the sp ecimen to t he p yrolys is tempe raL ure. This distortion has been largely overcome b y using a new apparatus, based o n an elecLronie ba lance, in which the d egradat ion of t he specimen is carried out at very low rates. The apparatus is eq uipped with an electronic thermostat that con trols t he temperature Lo within ± O.lo C, and also wi th an a u tomatic recorder t hat m easures both the temperatu re and the loss of weight of t he specimen. P yrolysis experimen ts were carri ed out in a vacuum in t his apparatus on pure specimens of poly styrene, p oly (a-meth ylsty rene), polyme thyle ne, high-molecula r-weigh t polyet hylene, and low-molecula r-weight polyethyle ne. T he ini tial rates of d egradation, in percent of sample p er minu te, varied fr o m 0.008 to 0.095. Except for the initial parts of the rate curves, in some cases up to about 30 percent loss of weight, t he r ate curves at low rates res emble closely t hose previously obtained at h igh rates of degradation .