Biodegradability, physical, mechanical and antimicrobial attributes of starch nanocomposites containing chitosan nanoparticles.

This study aimed to develop a plasticized starch (PS) based film loaded with chitosan nanoparticles (CNPs, 1, 2, 3, and 4%) as a reinforcing and antibacterial agent. We examined the morphology, biodegradability, mechanical, thermo-mechanical, and barrier properties of the PS/CNPs films. The antimicrobial activity against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria was investigated by colony forming unit (CFU) and disc diffusion methods. A dense structure was obtained for all PS/CNPs films and, thus, their complete biodegradation occurred in more days than neat PS. The increase in the CNPs percentage led to improved mechanical behaviour and barrier properties. PS-CNPs composite films revealed inhibition zones against both E. coli and S. aureus, with the 100% reduction in CFU against S. aureus. The current study exhibited that PS-CNPs films were more effective in inhibiting bacteria growth than neat PS film, confirming the composite films potential application as antimicrobial food packaging.

Biodegradability and mechanical properties of reinforced starch nanocomposites using cellulose nanofibers.

In this study the effects of chemical modification of cellulose nanofibers (CNFs) on the biodegradability and mechanical properties of reinforced thermoplastic starch (TPS) nanocomposites was evaluated. The CNFs were modified using acetic anhydride and the nanocomposites were fabricated by solution casting from corn starch with glycerol/water as the plasticizer and 10 wt% of either CNFs or acetylated CNFs (ACNFs). The morphology, water absorption (WA), water vapor permeability rate (WVP), tensile, dynamic mechanical analysis (DMA), and fungal degradation properties of the obtained nanocomposites were investigated. The results demonstrated that the addition of CNFs and ACNFs significantly enhanced the mechanical properties of the nanocomposites and reduced the WVP and WA of the TPS. The effects were more pronounced for the CNFs than the ACNFs. The DMA showed that the storage modulus was improved, especially for the CNFs/TPS nanocomposite. Compared with the neat TPS, the addition of nanofibers improved the degradation rate of the nanocomposite and particularly ACNFs reduced degradation rate of the nanocomposite toward fungal degradation.

Solvent-free acetylation of cellulose nanofibers for improving compatibility and dispersion.

Cellulose nanofibers (CNFs), as bio-materials derived from wood or non-wood plants, have the advantages of being biodegradable, renewable, low cost, and having good mechanical properties compared to synthetic nanofibers. CNFs have been used as reinforcement in polymeric matrices, however, due to their polar surface, their dispersibility in non-polar solvents and compatibility with hydrophobic matrices are poor. In this work, the chemical modification of CNFs, using acetic anhydride in the presence of pyridine as a catalyst, was studied with the aim of changing the surface properties. Native and chemically modified CNFs were characterized in terms of dynamic absorption, thermal stability, surface chemistry, morphology, and crystal structure. The reaction of acetylation between the acetyl groups and the hydroxyl groups of the CNFs was examined using Fourier transform infrared (FT-IR) analysis, while its extent was assessed by titration. The ester content of CNFs was higher for the acetylated samples compared to the control samples. It was also shown that the crystallinity decreased moderately as a result of esterification. Thermal stability of the modified nanofibers was slightly increased. Unlike native CNFs, a stable aqueous suspension was obtained with the modified nanofibers in both ethanol and acetone. The contact angle measurements confirmed that the surface characteristics of acetylated CNFs were changed from hydrophilic to more hydrophobic. In addition, the obtained acetylated CNFs showed more hydrophobic surface, which is in favor of enhancing the hydrophobic non-polar mediums.