2026/07/01 by Nguyen Tien Dat, Tien Dat Nguyen, Quentin Barbero +4
Chemical Engineering · Materials Science · #Rheology and Fluid Dynamics Studies #Polymer crystallization and properties #Polymer Foaming and Composites
paper · doi:10.1016/j.ces.2026.124783
Polycarbonate (PC) and polymethyl methacrylate (PMMA) are two of the most widely used transparent engineering plastics but their recycling rates remain low despite their large-scale production. Reactive extrusion is a continuous recycling route for many polymers, but their flow-mixing behavior remains unclear for immiscible PC/PMMA blends. Here we for the first time characterize the residence time distribution (RTD) with KBr (quantitative tracer), carbon black (visual tracer) in a dual stage extruder system: single screw extruder (SSE) and twin screw extruder (TSE). In this study, the PC content was investigated in the range of 75% to 91%. From rheological analysis at 250 circ , shear thinning was the main mechanism in all mixtures and flow regime transitioned from elastic (PCMA-1) to viscous (PCMA-3) with increasing PC content. The axial dispersion model fitted experimental RTD curves with R 2 = 0.94-0.97. All the flow behavior was plug-flow-like, with PCMA-2 had the highest Péclet number ( N Pe = 102) and PCMA-3 had the lowest ( N Pe = 56). The screw speed (240 - 360 rpm) of the twin screw extruder (TSE) enhanced the axial dispersion of the material, without changing the mean residence time ( t ¯ m =29 - 40 min). A power-law based model predicted the Péclet number from processing variables with a R 2 = 0.92 and assessed its sensitivity to these variables. These quantitative RTD–rheology correlations provide a basis for applying optimal processing conditions for co-recycling of PC/PMMA in a future work.