Thermal and hydrolytic degradation of poly(1,4‐cyclohexylenedimethylene terephthalate)

Abstract

AbstractThe kinetics of simultaneous thermal and hydrolytic degradation of poly(1,4‐cyclohexylenedimethylene terephthalate) (PCHDT) were evaluated by using a 1.5‐in.‐diam. melt extruder (≈20/1 length/diameter ratio) as a reactor. The effects of extrusion temperature (295°‐330°C), residence time (2.6–17.5 min), and moisture content (<0.001% to 0.2%) of the supply polymer on degradation were determined. The rate of degradation was measured in terms of the rate at which inherent viscosity (I.V.) decreased and the rate at which carboxyl endgroup concentration increased. The contributions of both thermal and hydrolytic degradation to the total degradation of PCHDT could be separated because the hydrolysis was rapid enough that it could be considered as occurring prior to thermal degradation. Thus, the hydrolysis merely adjusted the initial properties of the supply polymer, which was then subjected to thermal degradation. Equations were developed from an analysis of the kinetic data based on a random chain scission mechanism. The activation energies for decrease in I.V. and increase in carboxyl endgroup concentration of PCHDT from thermal degradation were determined as 33.5 and 41 kcal/mole, respectively.