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Effect of Crystallinity on Water Vapor Sorption, Diffusion, and Permeation of PLA-Based Nanocomposites

The effects of crystalline morphology and presence of nanoparticles such as cellulose nanofibers (CNFs), organically modified nanoclay (C30B), or a combination of both on water vapor sorption and diffusion in polylactide (PLA) were evaluated by a quartz spring microbalance (QSM). It was found that the large spherulite size induced by high-temperature processing leads to an increase in water sorption and a substantial reduction of diffusion with increasing crystallinity. Contrarily, small-sized spherulites, arising after low-temperature processing during solvent-casting, showed a different behavior with a slight decrease in both water vapor sorption and diffusion with increasing crystallinity. These observations suggest that solvent-casting at low temperatures should not be used to predict the properties a material will show after industrial-scale processing. From the analysis of the nanocomposite materials, it was concluded that nanoparticles affected the material′s properties not only by themselves but also by modifying the crystalline morphology. Interestingly, this led to CNF showing similar performance to C30B, decreasing water diffusivity (21 vs 27%) on isothermally crystallized materials despite its less favorable geometry. Additionally, the incorporation of 1 wt % CNF and C30B decreased water vapor transmission rate (WVTR) by 24% under an amorphous state but by 44% in a crystallized state, which makes hybrid CNF/C30B composites a promising food packaging material

Impact of thermal processing or solvent casting upon crystallization of PLA nanocellulose and/or nanoclay composites

Here, we present how processing (solvent casting or isothermal crystallization) impacts crystallinity of poly(lactic acid) (PLA) and its nanocomposites (PLA/1 wt % cellulose nanofibers (CNFs), PLA/1 wt % nanoclay (C30B) or PLA/1 wt % CNF/1 wt % C30B. Polarized optical microscopy demonstrated a heterogeneous nucleation process during isothermal crystallization leading to smaller homogeneously distributed spherulites. With solvent casting, no effect on morphology was observed with respect to the nanoparticles, but an increased spherulite size was observed at higher temperatures. This fact raises significant concerns regarding the suitability of solvent casting as a lab‐scale procedure to investigate materials. Additionally, combining the reinforcing agents, CNF, and C30B, did not increase nucleation rate, in contrast with the general tendency, where the incorporation of both particles led to improved properties (e.g., thermomechanical and barrier properties). However, a combination of C30B and CNF did lead to an overall increase in the rigid amorphous fraction and a reduced mobile amorphous fraction

Chemically extracted nanocellulose from sisal fibres by a simple and industrially relevant process

International audienceA novel type of acetylated cellulose nanofibre (CNF) was extracted successfully from sisal fibres using chemical methods. Initially, a strong alkali treatment was used to swell the fibres, followed by a bleaching step to remove the residual lignin and finally an acetylation step to reduce the impact of the intermolecular hydrogen bonds in the nanocellulose. The result of this sequence of up-scalable chemical treatments was a pulp consisting mainly of micro-sized fibres, which allowed simpler handling through filtration and purification steps and permitted the isolation of an intermediate product with a high solids content. An aqueous dispersion of CNF could be obtained directly from this intermediate pulp by simple magnetic stirring. As a proof of concept, the dispersion was used directly for preparing a highly translucent CNF film, illustrating that there are no large aggregates in the prepared CNF dispersion. Finally, CNF films with alkali extracts were also prepared, resulting in flatter films with an increased mass yield and improved mechanical strength

Faba bean protein films reinforced with cellulose nanocrystals as edible food packaging material

[EN] In the present work, transparent films were obtained by the solution casting method from faba bean protein isolate (FBP), reinforced with different cellulose nanocrystals (CNCs) content (1, 3, 5 and 7 wt%), obtained by acid hydrolysis of pine cone, and using glycerol as plasticizer. The influence of different CNCs loadings on the mechanical, thermal, barrier, optical, and morphological properties was discussed. Microstructurally, the FTIR and FESEM results corroborated the formation of intramolecular interactions between the CNCs and proteins that lead to more compact and homogeneous films. These interactions had a positive influence on the mechanical strength properties, which is reflected in higher tensile strength and Young's modulus in reinforced films with respect to the control film, resulting in stiffer films as the CNCs content increases. Thermal stability of the FBP films was also improved with the presence of CNCs, by increasing the characteristic onset degradation temperature. In addition, the linkages formed between the CNCs, and proteins reduced the water affinity of the reinforced films, leading to a reduction in their moisture content and water solubility, and an increase in their water contact angle, obtaining more hydrophobic films as the CNCs content in the matrix increased. The addition of CNCs in the FBP film also considerably improved its barrier properties, reducing its water vapour transmission rate (WVTR) and oxygen transmission rate (OTR). The present work shows the possibility of obtaining biobased and biodegradable films of CNC-reinforced FBP with improved mechanical, thermal and barrier properties, and low water susceptibility, which can be of great interest in the food packaging sector as edible food packaging material.This research was supported by the Ministry of Science and Inno-vation (MICI) [MAT2017-84909-C2-2-R] . S. Rojas-Lema thanks the Generalitat Valenciana (GVA) for the financial support through a San-tiago Grisolia grant (GRISOLIAP/2019/132) . D. Garcia-Garcia wants to thank the Ministry of Science, Innovation and Universities for their financial support through the "Jose Castillejo" mobility grant (CAS19/00332).Rojas-Lema, S.; Nilsson, K.; Trifol, J.; Langton, M.; Gómez-Caturla, J.; Balart, R.; Garcia-Garcia, D.... (2021). Faba bean protein films reinforced with cellulose nanocrystals as edible food packaging material. Food Hydrocolloids. 121. https://doi.org/10.1016/j.foodhyd.2021.10701912

The effect of pine cone lignin on mechanical, thermal and barrier properties of faba bean protein films for packaging applications

In the present work, faba bean protein (FBP) films plasticized with glycerol and reinforced with different amounts (2.5, 5.0, 7.5 and 10% by weight of FBP) of lignin extracted from pine cones (PL) have been obtained by solution casting. The results obtained showed an elongation at break of 111.7% with the addition of 5% PL to the FBP film, which represents an increase of 107% compared to the FBP control film. On the other hand, it was observed by thermogravimetric analysis (TGA) that the incorporation of lignin improved the thermal stability of the FBP film, leading to an increase in the protein degradation temperature, being this increase higher in the sample film reinforced with 10% PL. The barrier properties of the FBP films were also affected by the presence of lignin, leading to a decrease in water vapor permeability (WVP) in comparison to the unreinforced film. The results show that the sample reinforced with 2.5% PL had the lowest WVP value, with a reduction of 25% compared to the control film. Chemical analysis by Fourier transform infrared spectroscopy (FTIR) confirmed the formation of intramolecular interactions between lignin and proteins which, together with the inherent hydrophobicity of lignin, resulted in a decrease of the moisture content in the films reinforced with PL. This research work has allowed the development of biobased and biodegradable films with attractive properties that could be of potential use in sectors such as packaging

The effect of pine cone lignin on mechanical, thermal and barrier properties of faba bean protein films for packaging applications

In the present work, faba bean protein (FBP) films plasticized with glycerol and reinforced with different amounts (2.5, 5.0, 7.5 and 10% by weight of FBP) of lignin extracted from pine cones (PL) have been obtained by solution casting. The results obtained showed an elongation at break of 111.7% with the addition of 5% PL to the FBP film, which represents an increase of 107% compared to the FBP control film. On the other hand, it was observed by thermogravimetric analysis (TGA) that the incorporation of lignin improved the thermal stability of the FBP film, leading to an increase in the protein degradation temperature, being this increase higher in the sample film reinforced with 10% PL. The barrier properties of the FBP films were also affected by the presence of lignin, leading to a decrease in water vapor permeability (WVP) in comparison to the unreinforced film. The results show that the sample reinforced with 2.5% PL had the lowest WVP value, with a reduction of 25% compared to the control film. Chemical analysis by Fourier transform infrared spectroscopy (FTIR) confirmed the formation of intramolecular interactions between lignin and proteins which, together with the inherent hydrophobicity of lignin, resulted in a decrease of the moisture content in the films reinforced with PL. This research work has allowed the development of biobased and biodegradable films with attractive properties that could be of potential use in sectors such as packaging