In the aim of producing fully organic bionanocomposite based on poly(lactide) (PLA), cellulose nanowhiskers (CNW) were grafted by n-octadecyl-isocyanate (CNW-ICN) applying an in situ surface grafting method. The compatibilizing effect of the long aliphatic grafted chain was investigated by thermal, mechanical and permeability analysis of solvent cast nanocomposite films. The grafted CNW-ICN could be successfully dispersed in the polymer matrix. The gained compatibility brought about a nucleating effect, decreasing the half time of isothermal crystallization from 25 min for the neat PLA to 8.4 min for the nanocomposite including 2.5 wt% CNW-ICN, e.g., tensile strength was improved by 10 MPa for the same 2.5 wt% CNW-ICN/PLA composite. Mechanical reinforcement was also effective in the rubbery state of PLA and increased the tensile modulus of the rubbery plateau providing thereby thermal resistance to the polymer. Oxygen barrier properties did not change significantly upon the inclusion of CNW-ICN, even when the quantity of CNW-ICN was increased to 15 wt%. More interestingly, the water vapour permeability of the CNW-ICN nanocomposite was always lower than the one of ungrafted CNW composites, which led to the conclusion that the hydrophobic surface graft and improved compatibility could counteract the effect of inclusion of hydrophilic structures in the matrix on water vapour transport. In conclusion, the surface grafting of CNW with isocyanates might be an easy and versatile tool for designing fully organic bionanocomposites with tailored properties

Poly(lactic acid) is one of the most promising biobased and biodegradable polymers for food packaging, an application which requires good mechanical and barrier properties. In order to improve the mechanical properties, in particular the flexibility, PLA plasticization is required. However, plasticization induces generally a decrease in the barrier properties. Acetyl tributyl citrate (ATBC) and poly(ethylene glycol) 300 (PEG), highly recommended as plasticizers for PLA, were added up to 17 wt% in P(D,L)LA. In the case of PEG, a phase separation was observed for plasticizer contents higher than 5 wt%. Contrary to PEG, the T g decrease due to ATBC addition, modelled with Fox's law, and the absence of phase separation, up to 17 wt% of plasticizer, confirm the miscibility of PLA and ATBC. Contents equal or higher than 13 wt% of ATBC yielded a substantial improvement of the elongation at break, becoming higher than 300%. The effect of PLA plasticization on the barrier properties was assessed by different molecules, with increasing interaction with the formulated material, such as helium, an inert gas, and oxygen and water vapour. In comparison to the neat sample, barrier properties against helium were maintained when PLA was plasticized with up to 17 wt% of ATBC. The oxygen permeability coefficient and the water vapour transmission rate doubled for mixtures with 17 wt% ATBC in PLA, but increased five-fold in the PEG plasticized samples. This result is most likely caused by increased solubility of oxygen and water in the PEG phase due to their mutual miscibility. To conclude, ATBC increases efficiently the elongation at break of PLA while maintaining the permeability coefficient of helium and keeping the barrier properties against oxygen and water vapour in the same order of magnitude.

properties of poly(lactic acid) and its morphological changes induced by aroma compound sorption. Polymer International, Wiley, 2010Wiley, , 59 (6), pp.818-826. 10.1002Wiley, /pi.2793 Barrier properties of poly(lactic acid) and its morphological changes induced by aroma compound sorption Gael Colomines, a Violette Ducruet, b Cécile Courgneau, b Alain Guinault a and Sandra Domenek b * The barrier properties of poly(lactic acid) (PLA) play a key role in food packaging applications. For their optimization, the influence of crystallinity on the barrier properties of PLA and the interaction of PLA with the aroma compound ethyl acetate were investigated. PLA film samples with various crystallinities were fabricated by flat die extrusion and thermocompression and compared to PLA Biophan  . The degree of crystallinity had no effect on the oxygen permeability. However, an increase of crystallinity caused a decrease in ethyl acetate sorption. The sorption isotherm of ethyl acetate obtained using microgravimetry showed a steep increase with increasing aroma activity, a form which is consistent with a plasticization effect. This behaviour was verified using differential scanning calorimetry and dynamic mechanical analysis. Sorption caused a marked decrease in the glass transition temperature well below room temperature to approximately 0• C. Furthermore, PLA underwent a solvent-induced crystallization when equilibrated in ethyl acetate atmosphere at an activity of 0.5. The results obtained show the importance of considering possible interactions between polymer and foodstuff during the optimization step of polymeric materials for food packaging applications.

Science Arts & Métiers (SAM)is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Polylactide (PLA), a biodegradable polymer obtained from biomass, was formulated with a nucleating agent, talc, and a plasticizer, acetyl tributyl citrate, and cold crystallized in α and α form. The barrier properties of crystallized PLA were investigated as a function of the formulation and the crystalline form, thanks to three molecules with increasing polymer interactions, i.e. helium, oxygen and ethyl acetate (EA). Contrary to expectation, the oxygen diffusion coefficient in neat and formulated PLA did not decrease with crystallization. Even an increase of the diffusion coefficient was noticed for the most interacting probe, EA, in formulated PLA. Conditioning of neat and formulated PLA in an atmosphere containing EA vapour caused a modification of the material structure by plasticization and induced crystallization even at small EA activities. The plasticizing effect caused the glass transition temperature T g to shift to below ambient temperature. In the case of neat PLA induced crystallization in solely the α form was obtained, and in the case of formulated PLA a blend of α and α forms was observed.