The extrusion process is now an old process which was first applied to paper and agro-food industry or earlier for metallurgical industry, almost one century ago. The first published works about reactive extrusion appears in 1987 where chemists adapted twin screw extruder for mixing to reactive mixing. They took advantages to combine efficiently blending under high shear rates and chemical reaction in a continuous processing where solvents are not necessary. From this origin, the reactive extrusion development continuously progress where the current UMR CNRS IMP was always involved with more than 85 published articles. Applications are generally focused on depolymerization, in-situe compatibilization in immiscible systems or chemical modification to adjust targeted properties. This specific process combines sciences in chemistry, heat transfer, rheology and physico-chemistry, where all are evolutionary all along the extruder. It gives an explanation why reactive extrusion process cannot be surely model despite the enormous progress in computing capacity this last 30 years and why this process remains empirical for a large part. This last 15 years, reactive extrusion has lived through major changes for applications with the very increasing interests for polymers from bio-mass. Particularly, biosourced PLA, starch, cellulose, lignin and their acetalized derivatives have been seriously engaged by reactive extrusion. For most of them, the challenge is double : first, to destructure their complex architecture to reach a molten state and then to engage a chemical reaction with short residences times in the extruder. A second strategy consists to first destroy a natural polymer in elementary synthons to then elaborate new architectures by reactive extrusion. In all cases the scientist is forced to adapt its strategy to the existing processing with both its advantages and disadvantages. Through our long experience of reactive extrusion, we are presented this global view with specificities and also considering it appears very new technological developments to adapt the twin screw extruders to chemistry applied to polymers from bio-mass. What are now the possibilities, the perspective … and limitations considering the current knowledge’s and progresses in science and technology?

Interest, progress and limitations of reactive extrusion applied to natural polymers

251st National Meeting (2016)

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