Abstract
In this study, we present the development of eco-friendly biocomposites composed of polylactic acid (PLA) and microcrystalline cellulose (MCC), using melt extrusion and compression molding processes. In all the studied samples, the PLA/MCC ratio was always 1:1, whereas the plasticizer triethyl citrate (TEC) was responsible for the improved dispersion of the MCC in PLA. Tensile tests proved that the developed biocomposites containing TEC show improved ductility and crystallinity, as confirmed by the X-ray diffraction (XRD) study. Furthermore, the water vapor and oxygen permeability of the biocomposites were found to decrease as the TEC content increases in the formulation. Nonetheless, migration analyses to a dry food simulant prove that the migration of TEC is slightly above the acceptable limits when biocomposites with 15 wt % TEC were used. Taking this into account, in combination with the ranking of all the developed biocomposites according to their performance through the technique for order of preference by similarity to ideal solution (TOPSIS) analysis, we concluded that the PLA/MCC samples with 10 wt % TEC can be considered the most suitable biocomposites for eco-friendly food packaging applications. These findings place the developed PLA/MCC biocomposites among the strong candidates for biobased food packaging materials able to be produced at a large scale following industrially applicable methods since they are cost-effective and have improved properties compared to the pure biopolymer.
Highlights
The continuously increasing number of human inhabitants on Earth impels the intensified production of consumption goods, which leads unavoidably to the generation of millions of tons of wastes
The chemical structures of polylactic acid (PLA), triethyl citrate (TEC), and microcrystalline cellulose (MCC) are shown in Figure 1a, and the chemical compositions of the obtained biocomposite films were characterized by FTIR-ATR spectroscopy
Since the PLA/MCC_10%TEC biocomposite was ranked second, according to the TOPSIS evaluation, and its food migration levels are within the accepted limits, we propose it as the most suitable biocomposite for eco-friendly food packaging applications
Summary
The continuously increasing number of human inhabitants on Earth impels the intensified production of consumption goods, which leads unavoidably to the generation of millions of tons of wastes. An excellent alternative to petroleum-derived polymers in terms of performance and costs is the polylactic acid (PLA) biopolymer, mostly used in the packaging industry.[1,5−8] Despite its strong points, like being eco-friendly, having high tensile strength and stiffness and being biodegradable,[7,9] PLA is brittle, has low heat deflection temperature, and low thermal stability during processing. Such constraints, in combination with the so-far limited supply, induce great limitations for its large-scale use in flexible packaging. Diverse research efforts have focused on the combination of PLA with other materials,[10−22] such as natural fibers,[10,23−25] activated biochar,[26] microcrystalline cellulose (MCC),[11−13,27] and nanocellulose,[14,15,28,29] or blending PLA with other biodegradable polymers, such as natural rubbers,[16,17] thermoplastic polyurethane and elastomers,[18−20] polyhydroxyalkanoates (PHA),[21] polycarbonate (PC),[22] poly(butylene succinate),[30] and poly(butylene succinate-co-adipate).[10,30] to form highly flexible materials with ideal properties for food packaging, PLA and PLA blends have been combined with numerous plasticizers such as poly(ethylene oxide) (PEO), polyethylene glycol (PEG), triethyl citrate (TEC), tributyl citrate (TBC), acetyl-tributyl citrate
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