KINETICS OF THERMAL DEGRADATION OF POLY(VINYL CHLORIDE) BY COLOR

摘要

Thermogravimetric monitoring of poly(vinyl chloride) PVC blends degradation kinetics by the loss of HC1 is complicated by simultaneous evaporation of plasticizer and loss of the degradation product, HC1. Degradation kinetics monitoring by total color change due to forming conjugated polyenes was not affected by the plasticizer loss. Isothermal degradation kinetics monitored by thermogravimetric analysis (TGA) in real-time was compared with batch spectroscopic data. Thermal degradation of PVC films plasticized with diethylhexyl phthalate (DEHP) and tri-isooctyl trimelitate (TOTM) was monitored by color change, by optical density at 350 nm, and by TGA at 160°C, 180°C and 200°C. Plasticizer-free PVC powder degradation kinetics was obtained by TGA at temperatures from 160°C to 220°C. Apparent activation energies of plasticizer-free PVC powder degradation monitored by weight loss was≈152 kJ/mol. Activation energies obtained from the kinetics of color change at different temperatures ranged from 165 kJ/mol to ≈180 kJ/mol, by optical density change at 350 nm, ≈147 kJ/mol. Spectroscopic kinetics monitoring appear to be equivalent to monitoring kinetics by HCl emission.