Response Surface Analysis for Competition between Thermooxidation and Polycondensation Reactions of PET Flakes. Part 1: Low Vacuum Atmosphere

摘要

This work was accomplished employing solid-state polymerization (SSP) under less severe vacuum intensity (30 mmHg) in static mode at different times and temperatures. The influence of these parameters on intrinsic viscosity measurements was performed using Response Surface Methodology. The effect of temperature on intrinsic viscosity gains showed to be less pronounced than expected due to SSP being surface diffusion-controlled. The SSP efficiency for temperature as high as 230°C and dwell times higher than approximately 330 min showed lower increment on intrinsic viscosity than at immediately lower temperatures, although above approximately 215°C. This effect is a consequence of higher conversion rates of side reactions with increasing temperatures, their cumulative effect with increasing dwell time, and lower increment of polycondensation convertion rate with temperature under less severe vacuum intensity. The process temperatures and intervals determined, which allow PET recycling into new injected bottles, were moderates.