In-line rheo-optical characterization of PET hydrolysis and chain extension during extrusion

The thermo-mechanical degradation of PET during extrusion was studied in the transient state. Active agents, water, causing hydrolysis by chain scission and pyromellitic dianhydride PMDA, extension, were added to flow as pulses. They change molecular weight, affecting its melt elasticity, which followed in-line a rheo-optical detector set an instrumented slit-die, measuring synchronously, pressure drop birefringence (Δn12). effect shearing level, 90º kneading blocks with different lengths, also quantified. results, residence time distribution curves, show degree extension for each pulse type concentration. Thus, assuming collinearity full orientation along first normal stress difference N1 can be monitored in-line.