Abstract
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.
Highlights
The main function of food packaging is to maintain the quality and safety of food products during storage, transportation, and to extend the shelf-life of food products by preventing unfavorable factors or conditions, such as spoilage microorganisms, chemical contaminants, oxygen, moisture, light, or external force
Atomic Force Microscope (AFM) images of carrot cellulose nanofibrils (CCNF)/AgNPs were obtained with visible silver nanoparticles attached to the cellulose nanofibrils (Figure 1c)
The nanocomposites based on polylactic acid (PLA) reinforced nanocellulose obtained from carrot pomace and silver nanoparticles were prepared by the solvent casting method
Summary
The main function of food packaging is to maintain the quality and safety of food products during storage, transportation, and to extend the shelf-life of food products by preventing unfavorable factors or conditions, such as spoilage microorganisms, chemical contaminants, oxygen, moisture, light, or external force. In order to perform such functions, packaging materials provide physical protection and create proper physicochemical conditions for products [1]. Reducing petroleum non-biodegradable polymers, such as polyethylene (PE), low- (LDPE) and high-density polyethylene (HDPE), or polypropylene (PP), usually used for producing food packaging, is an urgent need [2]. The ideal packaging materials are biodegradable and obtained from renewable biological resources, usually called biopolymers, with proper mechanical and barrier properties. Biopolymers have been considered as a potential environmentally-friendly substitute for the use of non-biodegradable and Polymers 2020, 12, 812; doi:10.3390/polym12040812 www.mdpi.com/journal/polymers
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