Production and characterization of PLA_PBS biodegradable blends reinforced with cellulose nanocrystals extracted from hemp fibres

Poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) were blended and bionanocomposite films were prepared by solvent casting method adding 1 or 3 wt% of cellulose nanocrystals extracted from Carmagnola carded hemp fibres. Both unmodified (CNC) and surfactant modified (s-CNC) cellulose nanocrystals were loaded to PLA matrix or to PLA_PBS blend in order to produce binary or ternary formulations while the thermal, morphological, mechanical, optical and barrier properties of all the produced systems were deeply investigated. Mechanical analysis showed increased values of Young's modulus in binary and ternary formulations, more evident in the CNC based formulations. The presence of both CNC and s-CNC and the addition of PBS to PLA matrix provoked an improvement of barrier properties. This behaviour could be related to the synergic ability of cellulose nanocrystals to increase the tortuous path of gas molecules with the increase in the crystallinity degree induced by the presence of PBS. The disintegration in composting conditions of different PLA and PLA_PBS based bionanocomposites was also investigated. The results showed that all the formulations disintegrated in less than 17 days while s-CNC were able to promote the disintegration behaviour although the PBS presence hinders the disintegrability. During the composting, the main chemical parameters were investigated in order to assess changes in the composition of the tested mixtures. The organic matter (OM) loss occurred in both control and in the PBS_PLA based bionanocomposites composts in the 90 days of treatment. Neverthless the total organic C content showed values >20; moreover a low concentration in heavy metals in both composts as recommended by the Italian and European law was observed.