Abstract

Due to the high brittleness of the poly (lactic acid) (PLA), the main purpose of this work is to obtain a more ductile material than neat PLA, and the subsequent characterization by different techniques. In order to plasticize neat PLA, some plasticizers from renewable resources, such as non-epoxidized and epoxidized and soybean oils, have been used. Neat PLA has been plasticized with 20 wt% of plasticizers and the properties of different blends have been studied. Impact test results have showed that PLA became more ductile with the addition of vegetable oils. Furthermore, PLA/epoxidized vegetable oil blends showed higher tensile and impact strength values than that for blends plasticized with non-epoxidized oils. Fourier transform infrared spectroscopy (FTIR) technique has showed that the band related to the epoxy group did not completely disappear in the spectra of PLA/epoxidized vegetal oil suggesting an incomplete reaction between the epoxy group of epoxidized vegetable oils and the functional groups of PLA. Finally, by differential scanning calorimetry (DSC) technique has observed that after the addition of vegetable oils, both the glass transition temperature (Tg) and the cold crystallization temperature (Tcc) values of the neat poly (lactic acid) were decreased considerably.

Abstract

In this study, cellulose nanofiber (CNF)-reinforced poly (lactic acid) (PLA) bionanocomposites were manufactured through industrially scalable equipments. The compatibility differences between hydrophobic PLA and hydrophilic CNF was counteracted using a water-based polyethylene glycol (PEG)/CNF masterbatch approach, hence minimizing CNF self-agglomeration during drying. Polarized light microscopy showed a progressive refinement of the CNF distribution into PLA upon increasing the PEG content. Rheological experiments provided further evidences about the efficiency of the PEG carrier sytem. Indeed the formation of strong CNF interactions or a three-dimensional CNF network was highlighted for the masterbatch-based composites holding 20 wt.% of PEG, corroborating the successfulness of our sustainable approach to disperse effectively CNF through melt blending techniques. Under thermo-mechanical loading, the rigid percolated CNF structure mastered the viscoelastic response of the plasticized composites, demonstrating the load-bearing capacity of well-entangled CNF in the glassy as well as in the rubbery state. This rapid and straightforward physical method is a suitable approach for preparing dried and concentrated melt-processable CNF masterbatches that can be adopted in conventional melt-processing methods at an industrial scale.