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Abstract: PLA/CaSO4 composites were prepared from uncoated and stearic acid coated filler particles in a wide composition range. The strength of interfacial adhesion was estimated quantitatively with three independent methods. Structure was characterized by DSC, XRD and SEM measurements, while mechanical properties by tensile and instrumented impact tests. The results proved that adhesion is twice as strong in composites prepared with the uncoated particles than in those containing the coated filler. Coating changes also local deformation processes around the particles. Although debonding is the dominating micromechanical deformation process in all composites, local plastic deformation is larger around coated particles. The extent of this deformation depends very much also on the local distribution of particles. The final properties and performance of the composites depend unambiguously on the micromechanical deformation processes occurring during loading, on debonding and the subsequent plastic deformation. Stearic acid used for the coating of the filler seems to dissolve in the polymer and locally change its properties. [Copyright &y& Elsevier]

• A sustainable aqueous cellulose nanofiber surface PEGylation. • Effective filler dispersion within PLA through melt-processing. • Rheological percolating CNF network in the composites holding 20 wt.% of PEG. • Load bearing capacity of well entangled cellulose nanofibers. Considering the appealing need for an industrially viable approach, this works aims at demonstrating the rapid and easy melt processing of Polylactide (PLA) bio-composites reinforced with cellulose nanofibrils (CNF). For this purpose and against to their high propensity to self-aggregate on processing, an aqueous CNF-based suspension in the presence of polyethylene glycol (PEG) followed by a gentle drying way were performed to provide melt-processable CNF-based masterbatches. Morphological observations coupled with rheological analyses confirmed how the strategy of the PEG-based masterbatch approach facilitated the formation of a well-dispersed and strongly interacting CNF network within the polymeric matrix. At temperatures above T g , thermo-mechanical characterization showed that the load-bearing capacity of the web-like CNF network was even more apparent and counteracted the PEG plasticizing effect. Thermogravimetric analysis evidenced that in the case of selective positioning at the PLA-PEG interface, CNF mitigated the negative impact of PEG addition on the PLA thermal stability. These results revealed the successfulness of our sustainable organic solvent-free approach to prepare melt-processable CNF masterbatches, which can be readily converted into conventional industrially scalable melt-processing techniques. [ABSTRACT FROM AUTHOR]