Reactive extrusion of PLA, PBAT with a multi-functional epoxide: Physico-chemical and rheological properties

• Reactive extrusion of PLA and PBAT with a multifunctional epoxide (Joncryl).
• Thermo-rheological complexity and TTS failure for the modified polymers.
• Mixture of linear and randomly branched chains topology predicated by rheology.
• Chain extension/branching balance assessed by solution viscometry/rheology/SEC.

The aim of this work was to highlight the presence of long chain branching, LCB, due to the incorporation of a multifunctional epoxide, named Joncryl ®, as a chain extender, into both poly (lactic acid) (PLA) and poly (butylene-adipate-co-terephtalate) (PBAT) polymers. The modified polymers were prepared using a twin-screw reactive extrusion system. It has been demonstrated through this study that these modified biopolymers are thermo-rheologically complex. This complexity may be attributed to the formation of covalent bonds between both polymer and chain extender and leads to a failure of the time-temperature superposition (TTS). The linear viscoelastic properties were predicated on the use of the so-called Van-Gurp–Palmen plots, from which the topology of the modified PLA and PBAT has been studied and analyzed. Indeed, they exhibited a typical feature of a mixture of linear and randomly branched polymers. Furthermore, the resulting linear and branched chains, due to the reactive highly functionalized epoxide, are discussed using rheological investigations (relaxation spectra, flow activation energy) coupled with solution viscometry (solution viscometry properties, hydrodynamic radius) and physico-chemical properties (size-exclusion chromatography).

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