synopsisThe complete steady-state flow properties of molten poly(ethy1ene terephthalate) for shear stresses 34.14 X 1CP dynes/cm* were determined. A single, complete master curve had been constructed in earlier work by Gregory and Watson; the curve interrelates the shear stress, shear rate, temperature, and molecular weight (inherent viscosity) by using a temperature superposition scheme from the literature and a similar molecular weight superposition scheme.Equations in agreement with theory and with other published experimental data were derived from the master curve. Results presented here make possible the direct calculation of the melt viscosity of poly(ethy1ene terephthalate) a t shear stresses S4.14 X 1P dynes/cm'. The effects of a unit temperature change and/or a unit change in inherent viscosity (I.V.) on the melt viscosity were determined. For poly(ethy1ene terephthalate) with a 0.6 I.V., a 0.0025 change in Z.V. accounts for about the same change in melt viscosity as a l 0 C change in temperature.

SynopsisThe kinetics of simultaneous thermal and hydrolytic degradation of poly( 1,P-cyclohexylenedimethylene terephthalate) (PCHDT) were evaluated by using a 1.5-in.-diam. melt extruder (=20/1 length/diameter ratio) aa a reactor. The effects of extrusion temperature (295°-3300C), 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 a t 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. INTRODUCTIONPoly( 1,4-cyolohexylenedimethylene terephthalate) (PCHDT) is a synthetic polyester which was discovered by Tennessee Eastman Company1 and became the basis for Kodel polyester fiber. It currently finds extensive use as a carpet fiber.During the melt extrusion of PCHDT to produce fibers, the extrusion temperature and the moisture in the supply polymer cause degradation. In this paper, we discuss the thermal and hydrolytic degradation of this polyester during passage through a 1.Bin.-diam. melt extruder.In earlier work, Gregory and Watson used a laboratory extruder to determine the effects of oxygen and temperature on the degradation of PCHDT.2 They found that the oxygen content of the gas used to purge the polymer during drying prior to extrusion had no measurable effect on degradation when I.V. and carboxyl endgroup concentration were used as responses. Gregory and Watson2 also showed that the overdl kinetio equations describing thermal degradation of PCHDT were in agreement with a random chain scission mechanism. 3254 WAMPLER AND GREGORYSeveral workers have investigated the thermal -degradation of poly-(ethylene terephthalate) (PET) 3--6 and other p~lyesters.~ Investigations by Ritchie3 on the mechanism of thermal degradation of PET, using related model compounds, showed that the initial breakdown in the decomposition is a primary alkyl-oxygen scission of the P-hydrogen type. Poh14 interpreted his chemical and infrared examinations of the products of degradation of PET as typical of random chain scission to produce new endgroups and shorter chains. Marshall and Todd6 studied the kinetics of degradation of PET in an oxygen-free atmosphere by measuring the change of melt viscosity as a function of time. They calculated the initial rate of degradation from the decrease in melt viscosity and found it to be ...