# A Review of the Synthesis and Applications of Polymer-Nanoclay Composites
## 3 Application
### Food Packaging  
Polymer/nanoclay composites act as a barrier against the permeation of many gases, such as oxygen, carbon dioxide, water vapors and volatile compounds (flavors and taints); this gas barrier property, along with its basic mechanical, optical and thermal properties, makes these composites excellent candidates for food packing materials [53]. In recent decades, as a result of their advantages over other conventional materials (such as plastics), a variety of polymer/nanoclay materials have been developed with reduced permeability to gases and improved thermal and mechanical properties [150]. Innovative polymer/nanoclay composites may also be designed as an intelligent packaging material to control permeability to select gases, such as CO\({}_{2}\) and CH\({}_{4}\), thereby extending the shelf life of preserved  
Figure 5: The publication statistics related to various types of nanocomposites out of a total of 2725 publications—topic: “nanocomposites and applications” [151]. food [159]. The US military in collaboration with NASA [160], applied nanoclays as barrier enhancers for ethylene vinyl alcohol (EVOH) to develop an long-shelf-life packaging material (nonrefrigerated food). The developed material using EVOH/nanoclay composites has a shelf life of three to five years without refrigeration. [PERSON] et al. [161] developed an antimicrobial food packaging material using poly(e-caprolactone) (PCL)/nanoclay composites with mainly intercalated structures. It inhibited about 90% of the growth of Escherichia coli and Staphylococcus aureus, and significant reduced water vapor permeability (WVP) values up to 56%. [PERSON] et al. [162] investigated the antibacterial activity of low-density polyethylene (LDPE)/Silver-MMT nanoclay films on negative E. coli bacteria. Films with 5% of Ag+ cetyltrimethylammonium bromide (CATB) content exhibited an excellent E. coli growth inhibition (70% reduction). [PERSON] et al. [163] introduced nanokaolin into semolina protein film, which resulted in a significant enhancement of the film's barrier properties (antioxidant properties) and tensile strength. [PERSON] et al. [164] evaluated the significance of nanoclay content on the water vapor barrier behavior and optical properties of PSBA-MMT nanoclay films. The best optical properties were achieved with latex-clay 30:70 films, which decreased the light transmittance by 15%. [PERSON] et al. [165] prepared a mixed membrane using poly(ether-b-amide)/MMT nanoclay composites and evaluated the gas permeation properties at different pressure and clay loadings. The results indicated that the composite material helped decrease the CO\({}_{2}\) permeation and increase the permselectivity of CO\({}_{2}\)/CH\({}_{4}\) and CO\({}_{2}\)/H\({}_{2}\). The permeation of soluble CO\({}_{2}\) gas was reduced by 28% for the highest clay loading and the CO\({}_{2}\)/CH\({}_{4}\) selectivity was improved to 9 at 6 wt% clay loading at all pressures. [PERSON] et al. [166] developed a laminate with an exceptional gas barrier property using polyamide 11/graphene composites. The laminate film reduced permeability to CO\({}_{2}\) by more than one order of magnitude and reduced H\({}_{2}\)S permeability to an undetectable level. [PERSON] et al. [167] studied the diffusion behavior of Irganox(r) 1076 antioxidant (BASF, Ludwigshafen, Germany) in a novel food contact packaging film consisting of high-density polyethylene (HDPE)/closiite(r) 15A (BYK Additives & Instrument, Wesel, Germany) nanoclay composites. The diffusion coefficients were determined according to [PERSON]'s law, which showed that the maximum diffusion rate reduction of the antioxidant reached 78% with a three wt% nanoclay loading. The composite material delivered great potential for the plastic packaging industry. [PERSON] et al. [168] applied the sequential buildup of the layer-by-layer (LBL) surface coating strategy in food packaging applications; this strategy was considered inexpensive, effective, facile and eco-friendly.