Solvent-Free Reactive Extrusion As an Innovative and Efficient Process for the Synthesis of Polyimides

Abstract

Polyimides are commonly synthesized in a 2-step solution polymerization process. Such process requires long reaction times as well as specific care due to the use of potentially harmful solvents. In the present study, the total reaction time for producing polyimides has been lowered to less than 10 min by using a solvent-free continuous reactive extrusion process. The proof of concept was determined with the system based on 3,3',4,4'benzophenone-tetracarboxylic dianhydride (BTDA) and an aliphatic diamine, Jeffamine D-230 within a micro-extruder. Conversion degrees to polyimide, determined with 13 C NMR and DSC analysis, are over 90 mol% after 5 min of extrusion at 180 °C, 200 °C and 225 °C respectively. These syntheses were then transferred to a twin-screw extruder to form linear aliphatic-aromatic polyimides with two types of dianhydride: BTDA and pyromellitic dianhydride (PMDA). Comparison with a conventional solution polymerization process showed no significant differences in the polymers characteristics. The polyimides produced with this method presented glass transition temperatures ranging from 5 to 90 °C. The number average molar masses measured were between 11000 and 15000 g.mol -1 .

Investigation of Polyetherimide Melt-Extruded Fibers Modified by Carbon Nanoparticles

“…Finally, melt-spun fibers are produced by extrusion and drawing the finished PI above its melting point [ 13 ]. Extrusion of thermoplastic polyimides from a melt is more preferable, since it excludes the use of solutions, coagulation bath, and additional processing in order to remove volatiles and achieve thermal imidization of fibers [ 14 ]. However, polyimide fibers were rarely obtained by this method due to the high glass transition temperature due to the high rigidity of polymer chains and strong intermolecular interactions between them [ 15 ].…”

Green Approaches in Rubber Recycling Technologies: Present Status and Future Perspective

“…Instead, they are frequently used for the synthesis of copolymers with a different blocky nature, which enable shuffling of polymer segments. 126,127 Unlike counter-rotating machines, melting in a corotating twin-screw extruder normally happens in the first kneading disc block, ending in highly efficient reactive blending. 128 More importantly, corotating machines are modular, which gives the user a wider processing window.…”

“…Counter-rotating twin-screw extruders are less frequent for reactive extrusion mainly because of the inability for modularity, especially for high-viscosity melts or highly loaded polymer compounds. Instead, they are frequently used for the synthesis of copolymers with a different blocky nature, which enable shuffling of polymer segments. , Unlike counter-rotating machines, melting in a corotating twin-screw extruder normally happens in the first kneading disc block, ending in highly efficient reactive blending . More importantly, corotating machines are modular, which gives the user a wider processing window.…”

Innovative polypropylene based blends by in situ polymerization of a polyimide dispersed phase by reactive extrusion

“…Actually, these reactive processing approaches represent an elegant way to develop well--defined structures of polymer blends at the micro--and nanoscale [15--19] and are compatible with the incorporation of high Tg polymers. Moreover, a recent study by Verny et al [20] explored the synthesis of polyimides in a solvent--free process in a twin--screw extruder. They were able to synthesize a polyimide from pyromellitic dianhydride (PMDA) and Jeffamine D--230, with a complete imidization in less than 5min at 200°C in the molten state.…”