Formulation Development for the Production of Poly(lactic acid)-based Films for Use as Biodegradable Packaging Materials for Dried Longan

Abstract

Biodegradable polymer nanocomposites have been developed in this study as materials for use in the packaging of moisture-sensitive products. Poly(lactic acid) (PLA) was the main component of the nanocomposites with poly(butylene adipate-co-terephthalate) (PBAT) as flexibility enhancer. Tetrabutyl titanate (TBT) was also added as a compatibilizer to enhance the interfacial affinity between PLA and PBAT by inducing the formation of some PLA/PBAT via transesterification during the melt blending process, thereby improving the mechanical properties of the blends. Silver-loaded kaolinite (AgKT) synthesized via chemical reduction was also incorporated into the compatibilized blends for further property improvement. Herein, we report a novel biodegradable quaternary nanocomposite system with intercalated-exfoliated clay dispersion that was uniquely achieved by increasing the interlamellar space between kaolinite layers through silver nanoparticle insertion. The resultant compressed sheets of nanocomposites containing as little as 4 phr modified clay reduced the elongation at break from 213.0 ± 5.85 % to 53.8 ± 1.81 %, enhanced thermal stability (initial decomposition temperature increased from 378 C to 399 C) and exhibited a water vapor permeability (WVP) reduction of 41.85 %.

Novel biodegradable nanocomposite blown films based on compatibilized poly(lactic acid)-poly(butylene adipate-co-terephthalate) blend are fabricated for use as a model package for dried longan by using a twins-screw extruder and blowing machine. Content of each component was used similarly to that for sheet fabrication. Silver-loaded kaolinite (AgKT) dispersing in the polymer matrix in intercalated-exfoliated fashion functions as an excellent property improver of the blend. The emphasis of this research work is enhancement of film moisture barrier property by inducing polymer crystallization coupled with formation of AgKT tortuous path. Additionally, controlled silver release which provides long-term antibacterial activity is attributed to AgKT’s layered structure. The amount of released silver ions herein also complies with migration levels specified by the standard for food-contact plastic packages. Dried longan shelf lives as eventually predicted by experimental moisture sorption isotherm and by Peleg model are almost identical (~308 days) for the nanocomposite films being over two folds of that obtained from the compatibilized blend package at ambient condition. The percentage of biodegradabilities of both compatibilized blend and nanocomposite films as compared to cellulose (100%) are 81.58 and 82.85, respectively, complying with the standards for effectiveness degradation for use as shopping plastic bags. On the basis of these properties, the developed nanocomposites are considered to be promising candidates for use in bio-packaging applications to replace non-biodegradable and petro-based plastics.