Films of carrot cellulose nanofibrils (CCNFs) with the addition of low-viscosity chitosan (CHIT) were prepared by the vacuum filtration. The chitosan content in the films varied from 9 to 33% (dry wt. basis). The surface morphology of the films was investigated by scanning electron microscopy, and it was found that chitosan was dispersed in the CCNF matrix. The interaction between CCNFs and CHIT was evaluated in terms of Fourier transform infrared spectroscopy (FTIR). The obtained results suggested physical interactions rather than hydrogen bonding between CCNFs and CHIT. This finding also supports the results of the water wettability experiment. The addition of chitosan to the nanocellulose matrix causes an increase in the water contact angle, i.e., the surface of the composites becomes more hydrophobic. This increase is probably connected to an interaction between nanocellulose and chitosan forming a denser structure. Analyses of thermal properties showed that the composites are stable under high temperature, and the degradation occurred above 300°C. It was found that the addition of CHIT to CCNF matrices caused a decrease in the Young's modulus-the higher that the concentration of chitosan in the composite was, the lower the Young's modulus (decreased from 14.71 GPa for CCNFs to 8.76 GPa for CCNF/ CHIT_5). Additionally, the tensile strength of composites, i.e., the maximum force that causes a fracture decreased after the addition of chitosan (decreased from 145.83 MPa for CCNFs to 129.43 MPa for CCNF/CHIT_5). The results indicated the highest inhibitory effect of the investigated composites against E. coli and S. epidermidis. Whereas M. luteus was inhibited only by the higher concentration of chitosan in the tested composites, inhibition was not found against C. krissii and all tested filamentous fungi.

In order to improve optical properties of materials made of nanocellulose and also minimalize costs, small amounts of mineral fillers such as different forms of calcium carbonate are added. In this work nanocellulose was obtained from apple pomace. The precipitated calcium carbonate (PCC) in amount of 3.74 ± 1.36% of a sample dry matter was deposited on cellulose fibers during isolation process. Isolated cellulose was then treated with ultrasonic method in order to obtain apple cellulose nanofibrills (ACNF)/ PCC nanocomposites. Different ultrasonication conditions were applied in order to evaluate how time (0-60 min) and power (0-400 W) influence on the ACNF/PCC nanocomposites properties. Moreover structure, chemical composition, morphology and rheological properties of both cellulose and composites were characterized. Also the mechanical properties of nanopapers made of ACNF/PCC nanocellulose were measured. The nanofibril structure of ultrasound processed cellulose was confirmed. In all cases samples were pseudoplastic fluids with quite low viscosity. The mean hydrodynamic diameter of particle dispersions decreased the most after use of ultrasounds for 60 min and the obtained dispersions were also the most homogeneous. The elastic modulus of obtained nanopapers were 2-3 GPa and tensile strength 60-70 MPa and in general ultrasonication improved their rigidity.

In this research, it was proposed to use carrot cellulose nanofibrils (CCNF) isolated from carrot pomace modified with silver nanoparticles (AgNPs) as a filler of polylactic acid (PLA) composites matrix. The new procedure was based on two steps: first, the preparation of nanocellulose modified with metal nanoparticles, and then the combination with PLA. Two concentrations—0.25 mM and 2 mM—of AgNO3 were used to modify CCNF. Then, PLA was mixed with the filler (CCNF/AgNPs) in two proportions 99:1 and 96:4. The influence of CCNF/AgNPs on mechanical, hydrophilic, thermal, and antibacterial properties of obtained nanocomposites was evaluated. The greatest improvement of mechanical properties was observed for composite containing CCNF with 2 mM of AgNPs, which obtained the lowest Young modulus and highest strain at break. The degradation temperature was lower for PLA with CCNF/AgNPs, but crystallization temperature wasn’t influenced. The addition of CCNF/AgNPs also increased hydrophilicity. The transmission rates of oxygen, nitrogen, and carbon dioxide also increased after the addition of CCNF/AgNPs to PLA. The antibacterial function against Escherichia coli and Bacillus cereus was obtained after the addition of AgNPs but only at the contact surface with the material made, suggesting the lack of migration of nanoparticles from the composite.

No abstract