Expanding the application field of post-consumer poly(ethylene terephthalate) through structural modification by reactive blending

With the aim of up-grading the material properties of post-consumer PET, making them suitable for extrusion of thermoformable thick sheets, a series of polyepoxy chain extenders have been comparatively evaluated as melt viscosity modifiers for a toughened compatibilized blend containing up to 80 wt % of bottle-grade post-consumer recycled poly(ethylene terephtalate) (r-PET). Combinations of a commercial modifier with pentaerythritol were also successfully employed to cause simultaneous hyperbranching and controlled chain scission, thereby modifying the melt rheology of the material without excessively increasing the molecular weight, as highlighted by common technological melt viscosity measurements such as online torque and off-line melt flow rate (MFR). Since the high melt fluidity of PET plays a critical role on its flame resistance, the combined effect of chain extenders and halogen-free phosphorated additives on the fire resistance of the modified toughened blends was also investigated. Preliminary results indicate that the chemical reactions among polymer and additives must be taken into careful account to prevent unfavorable effects on the ultimate melt rheology and mechanical properties.