Reactive extrusion (REX) for PLA and PLA copolymer based nanocomposites (AIMPLAS, ES)

The core of the REX pilot line consists in a LEISTRITZ 27 MAXX twin-screw extruder with length to diameter (L/D) ratio of 56, equipped with several side feeders, vacuum venting, and liquid injection ports, that is used as a continuous reactor for polymerization of PLA and its copolymers by Ring Opening Polymerization (ROP) of lactide. The polymerization is being carried out in presence of NPs obtained in other BIOMAC PLs, thus allowing the in-situ polymerization of PLA nanocomposites to obtain pellets that will be used in agricultural (TeC2) and packaging (TeC3) applications.

pilot lines templates image
pilot lines templates image

The main upgrade of PL11 was the implementation of in-line monitoring of lactide conversion to PLA by Near-infrared (NIR) spectroscopy, that was carried out with BIOMAC partner IRIS. Currently, a reflexion NIR probe was implemented in the extruder die where the maximum conversion is expected. Nevertheless, it also allows the monitoring of lactide conversion in different positions of the extruder. In addition, transmission NIR probes are being developed to be placed in the extruder die to improve the monitoring performance with transparent polymers like PLA.

Within BIOMAC project, The REX processing parameters (screw and extruder configuration, temperature profile, throughput, and residence time) were optimized to achieve a production capacity from 6 to 10 kg/h of PLA and PLA nanocomposites.