Introduction

There is a significant demand for packaging that exhibit excellent oxygen barrier properties for food and medicine sectors. It is vital for some food packaging to allow maintenance of the product in an appropriate condition, for instance, limited oxygen transference between packed food and atmosphere, in order to prolong product’s shelf life [13, 36, 55]

High oxygen permeability of food packaging not only contributes to limited shelf life of packed food, but also leads to deterioration of food during storage and handling and reduces consumer compliance [56]. In case of food items which are rich in lipid or oil amount, holding under high O2 concentration leads to possible chemical changes in food, for example, lipid oxidation, discoloration, and off-flavor that affect quality of packed food ([73, 102]. Oxygen can also induce deterioration of food quality by microbial spoilage which not only cause mechanical or chemical damage, for instance, accelerating fruit softening and aging, but also bacterial or fungal infection, which cause potential safety risks of some ready-to-eat fresh products. Furthermore, oxygen can accelerate generation of ethylene and the rate of respiration in fruits and vegetables [26, 47, 66]. Food packaging materials with high oxygen barrier properties can ensure quality maintenance of the packed product during the determined shelf life and guarantee its safety [45]. The food packaging industry requires flexible films that not only have high oxygen barrier properties but also should be transparent. In these cases, some polymers like PE, PP, PLA, PHA, PCL, PVAL, etc., have the potential to be applied for production of transparent, light, and flexible films which are appropriate for utilization in the food packaging sector. Nevertheless, their poor barrier properties toward oxygen limit their application for food packaging. Improving these poor oxygen barrier properties would be a challenge in the packaging industry. Recently, many efforts have been made to produce packaging with the least permeability to oxygen, including fabrication of a new hybrid structure, for instance, application of plastic additives and blending different polymers; introducing new crystal into the matrix of polymer; creation of a multilayer structure with an appropriate oxygen barrier material; creation of cross-linked polymer; creation of nanocomposites via incorporation of various nanoparticles, nanosheet, and tubular nano into the polymer matrix; and production of multilayer film with enhanced oxygen barrier properties [163]. The focus of this article is to represent unique new approaches for producing oxygen superior barrier performance packaging compared to the current commercial food packaging.

Principle of Oxygen Mass Transport

Barrier materials can be defined as the materials which have the ability to inhibit or slow down the passage of gases, water vapor, and organic vapor through their borders [99].

Two factors have a critical role in determining the oxygen transmission or permeability rate through the packaging material, including solubility of oxygen in the polymer matrix and its diffusion rate through the polymer matrix. The solubility of oxygen is dependent upon the chemical relationship and also the affinity between the oxygen molecule and the polymer and the rate of diffusion is affected by the size of the permeant and also polymer characteristics, especially the proportion of crystalline and amorphous regions of the polymer [39].

Oxygen transmission rate (OTR) is expressed as cubic centimeters of oxygen, which pass through a square meter of packaging material when oxygen pressure is 1 atm greater than that on the other side of the packaging during 24 h, at a specified temperature. OTR can be calculated as follows [99]:

$$ \frac{\Delta mgas}{\Delta t}=P\ \frac{A\ \Delta p}{L} $$

where\( \kern0.5em \frac{\Delta mgas}{\Delta t} \) is transmission rate of oxygen, P is permeability of the packaging material, A is area contact of the packaging material, ∆P is partial pressure difference across the packaging material, and L is the thickness of the packaging material. OTR is expressed in cubic centimeters (STP)/square meters/day.

In cases that we have laminated or coated film, OTR can be calculated using the “laminate” equation [99]:

$$ \mathrm{OTR}\ \mathrm{Coating}=\frac{{\mathrm{ORT}}_{\mathrm{Uncoated}}\times \kern0.5em {\mathrm{ORT}}_{\mathrm{Coated}}}{{\mathrm{ORT}}_{\mathrm{Uncoated}}-{\mathrm{ORT}}_{\mathrm{Coated}}} $$

Factors Affecting Oxygen Permeability

Many factors can affect oxygen permeability rate through packaging material which can be divided into two major groups including polymer and biopolymer characteristics and environment as demonstrated in Fig. 1 [103, 125, 158].

Fig. 1
figure 1

Factors affecting oxygen permeability of packaging materials

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Polymer Characteristics

Many parameters influence molecular organization of the polymer which contribute to creation of specific properties of the polymer matrix; these parameters will be discussed in the following part:

Pendent Chain

Pendent chains or side chains are oligomeric or polymeric branches which extend from the backbone chain of a polymer. Pendent chains significantly affect characteristics of the polymer, predominantly its crystallinity and density (Ryan [147]). Ghasemnejad-Afshar et al. [46] have studied the effect of side branch on gas separation performance of polyimide branched with the side groups C4H9, C3H7, CH3, and CF3. Results illustrated that membranes with larger side branch groups are more rigid. As a consequence of restriction in chain mobility, the free volume in the membrane’s structure increased which accordingly enhanced the permeation of gases into the membrane. The findings indicated that the membrane with C4H9, as the largest side branch, has the greatest diffusivity and permeation [46].

Degree of Crystallinity

The polymer matrix is consisted of two distinguishable regions: crystalline and amorphous. In crystalline regions, polymer chains are arranged in a regular, periodic manner with strong interactions, while amorphous regions behave quite differently; in these regions, polymer chains are arranged irregularly and have less density and present more free volumes compared to crystalline regions. Since the crystallites are impermeable, permeant molecule must seek out amorphous zones in order to pass through the polymer matrix. Therefore, a polymer with higher degree of crystallinity compared to the polymer with fewer degree of crystallinity provide less amount of permeation [152]. It has also been demonstrated that the arrangement of crystalline lamellae in semicrystalline polymers can significantly influence gas barrier characteristics. In particular, when the arrangements of the lamellae stacks are perpendicular to the direction of gas diffusion, the highest barrier properties will be achieved. In a study, the self-assembly nucleator approach was applied to design the arrangement of crystalline lamellae in the PLA matrix. Octamethylenedicarboxylic dibenzoylhydrazide (TMC-300) and graphene were used as active nucleators for PLA. A multilayer sheet consisting of PT (PLA+TMC-300) alternating with PTG (PLA+TMC-300+graphene) was prepared by multilayer coextrusion. Under isothermal processing as a result of the induced impact of graphene, the melted TMC-300 self-assembles into solid-state fibrils that were perpendicular to PT/PTG layered interface. As a result, a reduction of 85.4% in O2 permeability was achieved compared to the blended control sample [88,86,90]. Gupta et al. [52] have studied the effect of modified chitosan on the oxygen permeability of PDLA/PLLA blend and pristine PLA. The results indicated that incorporation of 3wt% modified chitosan into blended polymer increased the degree of crystallinity. Consequently, oxygen permeability reductions have been found to be nearly 56 and 84%, respectively, compared to blended PDLA/PLLA and pristine PLA ([52](.

Formulation

It should be taken into consideration that formulation of the compounds has a key role in molecular arrangement and properties of final produced polymer particularly in the case of biomaterials such as polysaccharide- and protein-based materials, which have poor oxygen barrier properties [15, 27, 98, 111, 166]. For instance, the presence of additives such as plasticizers can affect permeability of packaging. For some polymers, it is essential to use plasticizer in order to achieve desired properties, but plasticizers generally increase the permeability of the polymer. Zhang et al. [164] have investigated the impacts of glycerol and sorbitol as plasticizer on the oxygen permeability of edible film based on gum ghatti (GG). The results revealed that oxygen permeability of films marginally increased with increasing glycerol concentration. Whereas, increasing sorbitol concentration had no significant effect on oxygen permeability. SEM micrograph showed that the structure of glycerol-GG films was more regular and smoother compared to sorbitol-GG films. It was also indicated that crystallinity degree decreased with increasing glycerol concentration [164]. On the other hand, incorporation of some filler like nanoparticles into the polymer matrix can enhance its barrier properties. Especially, the insertion of fillers that have high adhesion and compatibility with the polymer matrix can improve barrier properties of the packaging [122].

Processing Properties

The results of processing conducted during production of polymer can noticeably influence its permeability properties. For instance, creation of pinholes and microvoids contributed to the higher transmission rate of gases, since gas molecules require free volume for movement and diffusion through the polymer matrix [75]. Processing which initiates higher degree of cross-linking or increases molecular orientation in polymer will improve barrier properties, since these approaches further increase density and crystallinity of polymer, which make the path to permeate more difficult. As an illustration, graphene oxide nanosheet/cellulose nanofiber (GONS/CNF) nanocomposite film with ultra-low oxygen permeability was manufactured through layer-by-layer coating. In this procedure, GONS and CNF were dispersed into distilled water with ultrasonic treatment. The achieved mixture was repeatedly coated onto a glass plate until a film with a thickness of approximately 30–40 μm was manufactured. The images of SEM and GI-WAXS manifested that the exfoliated GONS and CNF were highly oriented along the film direction, which is the reason of ultra-low oxygen permeability (F. [137]).

Physical Interaction between Penetrant and Barrier Material

Some interactions between penetrant and barrier material can lead to trapping of diffusing molecule and slow down the permeation rate. For instance, presence of polar or functional groups that cause interaction between polymer and penetrant or hydrogen bonds formation will also trap diffusing molecules [31, 41]. Paine [118] investigated the oxygen uptake capacity of three polymers, including poly (cyclohexylmethyl methacrylate) (CHMA), poly (cyclohexenylmethyl acrylate (CHAA), and polyvinylidene fluoride (PVDF). The findings of this study showed that both polyCHMA and polyCHAA have greater capacity for oxygen uptake compared to PVDF. One possible explanation for this could be the existence of cyclic ring units, which are capable of scavenging oxygen molecules [118].

Environment

External factors such as temperature and humidity also can influence the value of permeability.

Temperature

Penetrant molecules in order to diffuse through the polymer matrix require enough energy to overcome the interactions that exist between polymer chains. On the other hand, increasing temperature causes more motion in polymer chains and creates free volume, which accelerate oxygen transmission rate. The transport equation (which stated was in section 2) is affected by increasing temperature in two ways, including the flow of gas and the partial pressure difference [99]. Öner et al. [113] have investigated the influence of temperature on oxygen-barrier performance of nanobiocomposites based on poly (3-hydroxybutyrate-co-3-hydroxyvalerate) and boron nitride (PHBV/BN). The PHBV nanocomposites showed an increase in oxygen permeability as temperature was increased, with an Arrhenius behavior, as was expected (M [113]).

Humidity

Since absorbed water could have a plasticizing effect on some packaging materials, high humidity can increase packaging permeability. Exposure of polymer to an environment with high level of humidity or product with high moisture content can also lead to swelling of the polymer which will increase permeability. In the case of polar polymers like cellophane and PVA, contact with high humidity has a plasticizing effect on them that disturbs their barrier properties [39]. For instance, chitosan-based films exhibit good oxygen barrier but are degraded when exposed to high humidity, due to their great water solubility [86]. In an investigation, the impact of moisture on the oxygen permeability of polyvinyl alcohol (PVOH) and PVOH–kaolin dispersion barrier coatings was examined. The oxygen permeability was measured at different humidity levels, and the material properties were characterized under the same conditions, including polymer crystallinity, kaolin concentration, and kaolin orientation. The experimental results indicated that the water is able to plasticize the PVOH material of the coatings, and the incorporation of kaolin as filler failed to inhibit or overcome such phenomenon substantially. It was also revealed that the crystallinity degree of the PVOH was affected dramatically by the humidity, since water melts polymer crystallites, which further increased oxygen permeability [112].

Collected Comparative Oxygen Barrier Properties of Plastic

In Fig. 2. oxygen and water vapor barrier properties of some commercial petro- and bio-based materials for food packaging have been illustrated, which were measured at 23 °C and 85% RH.

Fig. 2
figure 2

Oxygen and water vapor barrier properties of some commercial petro- and bio-based materials for food packaging [14, 101]

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Novel Approaches for Producing High Oxygen Barrier Packaging Materials

Nanocomposite

In the last few decades, polymer nanocomposites, in the field of nanotechnology, has attracted enormous attention because of their unique characteristics, especially gas barrier properties [94, 108, 132]. It has been shown that incorporation of nanofillers into the polymer matrix improves oxygen barrier properties [5, 61], since these nanofillers are impermeable and do not permit diffusion of gas molecules and make them to follow a longer and more torturous pathway to pass through the nanocomposite [34, 37, 100] as illustrated in Fig. 3. Furthermore, nanofillers insertion in the polymer matrix increases crystallinity degree which acts as an obstacle and does not allow the permeation of gas molecules through them. It has also been indicated that the molecular orientation of polymer chains that are around the nanofillers will be affected and contributed to formation of a restricted or rigid amorphous fraction which has lower permeability and further enhances barrier properties [68, 143]. Three parameters have a critical role in determining barrier properties of nanocomposite including filler characteristics (volume fraction, aspect ratio), the intrinsic barrier property of the polymer matrix, and the state of nanofillers dispersion in the polymer matrix (intercalation, exfoliation, flocculation or agglomeration, specific interface, free volume and in the case of nanosheets the orientation of nanoplatelets) [107]. The fundamental point of manufacturing nanocomposites is that we can use commercially available polymers for making high oxygen barrier films. Therefore, it is a cost-effective and practical procedure to reach uncomplicated and scale-up manufacturing and thus has attracted intensive attention from both academic and industrial fields (Y. [91]). In a study by Ramos et al. [134], nano-biocomposite films based on PLA were prepared by incorporating modified montmorillonite (D43B) at two different concentrations of 2.5 and 5 wt%. It was reported that D43B at both concentrations reduced the oxygen transmission rate by formation of intercalated nanocomposites [134]. In another study, the octadecylamine (ODA) modified graphene oxide (mGO-ODA)/maleic anhydride grafted polypropylene (MAPP) nanocomposites (mGO-ODA/MAPP) were prepared and applied successfully as gas barrier materials. The result indicated that 60% mGO-ODA/MAPP exhibited 94.1 and 95.0% reduction for H2GTR and O2GTR, respectively, compared to the pure nylon film [90]. In another study, PLA/titanium oxide nanocomposite films were prepared by the casting method. The effect of titanium oxide nanoparticles and its concentration (1, 3, and 5wt %) on oxygen transmission rate of nanocomposites were investigated, and it was shown that oxygen transmission rate was decreased when the concentration of titanium oxide was increased [1]. Also, in the case of PLA as a biodegradable polymer, it has been proved in many researches that incorporation of nanocellulose in the PLA matrix will enhance oxygen barrier properties. These kinds of bio-based hydric polymers have semicrystalline behavior, which makes them appropriate materials for food packaging [78, 92, 109].

Fig. 3
figure 3

Torturous pathway of diffusing molecules around nanoparticles

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Cheng et al. [23] manufactured biodegradable films as packaging materials that could act as barrier for oxygen, by mixing a guar gum (GG) solution with a nanocrystalline cellulose (NCC) dispersion using a novel circular casting technology [23]. In a study, an active nanocomposite of Halloysite nanotubes and PE was prepared as ethylene scavenging packaging, but it was also found that oxygen barrier properties of nanocomposite was improved compared to neat PE [146]. It was demonstrated that the antimicrobial nanocomposite film of HDPE/cu-nanofiber, which were prepared by the melt mixing method, also showed better barrier properties toward oxygen compared to neat HDPE [12]. Majeed et al. have prepared montmorillonite (MMT)/rice husk (RH) hybrid filler-filled LDPE nanocomposite films, containing 0, 2, 3, 4, 5, and 6 wt% MMT (based on the total weight) by extrusion blown film. The findings of this study showed that addition of MMT into the LDPE/RH system improved the O2 barrier properties [97]. It was shown that the oxygen permeability coefficient of GONS/PVA nanocomposite at a low GONS loading of 0.72 vol% was declined about 98% (H.-D. [48, 64] have demonstrated that incorporation of different montmorillonite type (hydrophylic vs. organically modified) into chitosan/PVOH blends enhances its oxygen barrier properties. In an investigation, the effect of encapsulating the polymer within a nanoplatelet shell on oxygen permeability was examined. The Pickering suspension polymerization method was applied for manufacturing few-layered GO nanoplatelets encapsulated polystyrene (PS) microparticles. The oxygen permeability was reduced by 96 and 34% in obtained PS/GO composite film containing 2 wt% of GO, respectively, compared to the PS control film and the solution mixed PS/GO composite film [101]. Risyon et al. [138] have developed polylactic acid (PLA)/halloysite nanotubes (HNTs) bionanocomposite films for extending the shelf life of packaged cherry tomatoes. The PLA/HNTs bionanocomposite films were demonstrated to have great oxygen barrier properties especially at 3.0 wt% of HNTs and had the potential to prolong the shelf life of cherry tomatoes [138]. Vaezi et al. [149] examined the oxygen barrier properties of a bio-nanocomposite based on cationic starch (CS)/montmorillonite (MMT)/nanocrystalline cellulose (NCC). CS nanocomposites with 5 wt% NCC and MMT showed the best improvement in the barrier properties against oxygen and also water vapor [149]. Pengwu et al. have developed a high barrier polyhydroxyalkanoates (PHA) nanocomposite by compounding graphene oxide grafted by long alkyl chain quaternary salt (GO-g-LAQ). The GO-g-LAQ was capable of improving the interfacial adhesion between GO and PHA due to its hydrophobic nature. As a result of the condensed crystal structure of PHA and the impermeable property of GO sheets, PHA/GO-g-LAQ nanocomposite showed improved oxygen barrier property [157]. The impact of different types of boron nitride particles (BNPs) including silanized flake type BN (OSFBN) and silanized hexagonal disk type BN (OSBN) on oxygen permeability of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was examined. As a consequence of higher crystallinity degree in the presence of BN particles, all the obtained nanocomposites had lower oxygen permeability compared to the neat PHBV. The best barrier properties was obtained by incorporating 2 wt% OSFBN, for which a reduction of oxygen permeability up to 36% was observed in comparison to the neat PHBV (Mualla [114]). The influence of nanofillers on the oxygen barrier properties of some nanocomposites prepared by different methods is summarized in Table 1. It should be noted that the values of the permeability coefficients in the literature are often given in different units of measurement. To facilitate the comparison of gas permeability, the values of gas barrier properties reported in the literatures have been converted into the same units (m2 s-1 Pa-1). As evidenced, incorporation of scarce amount of graphene oxide has resulted in significant reduction in oxygen permeability compared to O-MMT and MMT. As an illustration, application of 0.4 wt% graphene oxide into the PLA matrix contributed to 68% reduction in oxygen permeability, while incorporation of 7.9 wt% O-MMT caused only 24% reduction, which indicated the critical role of the nanofiller type. In addition, apart from the polymer kind, in most of cases, by increasing nano amount, greater oxygen permeability reduction was achieved.

Table 1 Oxygen permeability of polymer/nanocomposites
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Multilayer Polymer

Multilayer polymer packaging had gained a lot of attention due to its excellent gas barrier properties. The first multilayer films were introduced in the food packaging industry by polymers coated with thin metal films, known as metalized plastics. Metalized plastics have been utilized in the food industry since the early 1970s [142]. The main problem associated with metalized packaging is their opaqueness, which limits their application. Recently, the demand for transparent packaging materials with equivalent gas barrier properties to metalized plastics has increased significantly, since they allow content visibility. Furthermore, elimination of metallic components provides better recyclability and microwave compatibility [81]. In the following parts, we will discuss about different approaches of making transparent multilayer films.

Thin Metal Oxide Films

The first alternative for metalized plastics was transparent silicon oxide (SiOx) coating which, besides providing oxygen barrier properties, also prevents from moisture ingress or aroma loss. In the 1980s, application of these thin films in the food packaging sector became very popular. Although thin metal oxide films exhibit good oxygen barrier properties, these coatings fall short of their predicted performance, mainly due to microscopic defects like pinholes that form during the deposition process and also their surface roughness. It has been shown that barrier trends logarithmically with surface roughness and smoother films illustrate a better oxygen barrier characteristic [29, 57].

Hybrid Coating

An innovative approach to achieving enhanced barrier properties of polymers can be presented by coating micro-layers of material with appropriate gas barrier properties on them. Various materials from natural or synthetic bases can be utilized for coating. For instance, in a study, modified whey protein was coated on PLA in order to improve its oxygen barrier properties. Comparison of neat PLA versus PLA coated with whey protein isolate showed improvement of about 90% in the oxygen barrier properties [155]. In another study, cellulose nanocrystals, which were obtained from cotton linters and Kraft pulp, were coated on PET to enhance PET oxygen barrier characteristics. The result illustrated that the oxygen permeability value of coated PET was hundreds of times lower than pure PET over a board range of time [135]. In a study, a biodegradable PLA-based hybrid coating material was obtained via coating PLA film by prepared PLA/SiO2 hybrids. In this study, 3-isocyanatopropyltriethoxysilane was employed as a silane coupling agent in order to promote adhesion between dissimilar materials (silica and PLA). Oxygen barrier properties of coated PLA improved by 69.7% compared to neat PLA [9]. High-strength regenerated cellulose/attapulgite (ATT) composite films (RC/ATT) with good oxygen barrier performance were prepared from cellulose/LiOH/urea solutions with different ATT contents ranging from 5 to 20 wt%. The RC/ATT composite films exhibited relative low oxygen permeability below 0.5 cm3 μm/day m2 kPa, which could even reach 0.32 cm3 μm/day m2 kPa with 20 wt% ATT content (C. [154]). In a study, functional antimicrobial LDPE films with coatings containing different amounts of pyrogallol (PGL), a natural phenolic substance, and polyurethane were prepared. Coatings with pyrogallol caused the barrier properties for water, and oxygen was increased from 0.78–0.32 to 470 ± 23.2–273 ± 57.1 (g mm)/(m2 h kPa), respectively. These findings indicate that the barrier properties of the LDPE/PGL films were highly improved compared to those of neat LDPE [42, 25] have explored the mass transfer of renewable films based on gelatin (Ge), glycerol (Gly), and epoxidized soybean oil (ESO) for application in food packaging. The results illustrated that gelatin sample containing 20% Gly and 20% ESO present appropriate gas barrier properties [25]. In another study, the oxygen transfer rate (OTR) and water vapor permeability (WVP) of polyethylene terephthalate (PET) films were adjusted via coating of polyphenols and gelatin mixture (PGM) with different concentrations while maintaining the other properties of modified PET films. The results showed that OTR was decreased (63.5±0.02 to 38.1±0.03g/in2/day) with respect to uncoated film (82 ± 3.5) [69]. Lu et al. [95] reduced the oxygen permeability of biaxially oriented PP/LDPE film by coating nanofibrillated cellulose (NC) solution on it. The result showed that oxygen transmission rate of the coated film was as low as 24.02 cc/m2/day compared to non-coated film (67.03 cc/m2/day) [95].

Layer by Layer Assembly

Layer by layer assembly has received extensive, worldwide attention over the past two decades, due to its relatively inexpensive deposition technique and typically for producing multifunctional thin film such as enhanced gas barrier properties film which has less than a micron thick ([4]; M A [130]). Generally, the following steps are done in order to prepare the LBL film as shown in Fig. 4: often the negatively charged substrate is immersed into a mixture of positively charged material (polyelectrolytes or nanoparticles) for a given amount of time, ranging from seconds to tens of minutes. The substrate is then removed from the mixture, rinsed with deionized water, optionally dried in a stream of filtered air (or nitrogen), and then immersed into a mixture of negatively charged material, rinsed and dried. This simple procedure is then repeated to deposit a given number of cationic and anionic pairs layers [131]. Individual layers can range from angstroms to hundreds of nanometers in thickness, although many factors can influence their thickness, including pH, buffer, ionic strength, temperature, the molecular weight of the deposition species, and the relative humidity of the fabrication environment [2, 51].

Fig. 4
figure 4

Procedure of layer by layer assembly in production of multilayer films

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Layer by Layer Assembly of Polymers

Much of the early LbL gas barrier work was done using only polymers, rather than particle-filled or nanostructural systems. Leväsalmi and McCarthy [87] showed that layered structural films which consisted of PAH (a strong poly cation) and PSS (a strong poly anion) have good gas barrier properties due to its dense ionically crosslinked structure [87]. Yang et al. [159] have also reported that the multilayer film of PEI and PAA form a dense network, which has super gas barrier performance (Y.-H. [159]). In a study, the LBL approach was applied to produce a biodegradable multilayer film of sodium alginate/PEI on biaxially oriented PLA. Oxygen permeability of the prepared film was found to be three orders of magnitude less than the uncoated biaxially oriented PLA film [50]. In another study, a multilayer film of fish gelatin/PLA was prepared in order to reduce oxygen permeability. It was found that the oxygen permeability value of the multilayer film reduced more than eightfold compared to pure PLA film [62]. Joo et al. have developed whey protein isolate (WPI)-coated multilayer films using PET film as a substrate. In order to improve the interfacial compatibility between PET film and water-based WPI coating solution, various surface pretreatments (corona discharge, plasma, and primer coating) were applied to PET. Oxygen transmission rates of surface-pretreated multilayer films with WPI coating layer [PET/WPI/nylon/ LLDPE] were significantly lower, about 43–234 times, than the multilayer films without WPI film layer [74]. Apicella et al. [3] developed a multilayer film based on PET polymer, which indicated excellent barrier properties toward oxygen. In this investigation, an active layer of PET containing 10 wt% polymeric oxygen scavenger, named Amosorb DFC 4020E, were sandwiched between two layers of neat PET polymer. [3].

Layer by Layer Assembly of Polymers and Nanomaterials

LbL films exhibit unique properties when incorporated with nanoparticles. Nanoparticle-based LbL films have super barrier gas properties [119]. In a study, a polymer/nanoclay multilayer ultrathin film with only 52 nm thickness was prepared via LBL assembly of 12 polymer and 4 clay layers. The obtained film presented oxygen permeability orders of magnitude even lower than EVOH and SiOx [126, 127]. In another study, a quadlayer film which consisted of CH/CR/CH/MMT was deposited on PET film, using the LBL technique. This multilayered thin film was able to reduce the oxygen permeability value of PET by two orders of magnitude compared to pure PET film, under the same conditions (Galina [85]). In another study, a high barrier multilayer film based on PET substrate was achieved by LBL assembly of similarly cationic charged layers of PEI and successive anionic charged layer of clay. Transmission electron microscopy images of the prepared film illustrated a nanobrick wall structure of clay nanoplatelets within the polymeric mortar, which resulted in enhanced oxygen barrier properties [53]. The impact of deposition of multilayered hybrid thin film composed of cellulose nanocrystals (CNCs) and gibbsite nanoplatelets (GNPs) onto different selected substrates on the oxygen barrier properties was examined. The substrates were an uncoated kraft cardboard, a polyethylene-coated cardboard, a low density virgin PE, and a smart paper. The results revealed that the oxygen barrier properties of all the substrates were significantly improved after the deposition of thin multilayered hybrid film [20]. Other studies related to oxygen barrier properties of multilayer film are summarized in Table 2. As illustrated in majority of cases, the reduction in oxygen permeability was higher than 90% that reveals the efficiency of multilayer film in improving oxygen barrier properties. It is worth mentioning that multilayer films compromising of polymer and nanofiller demonstrated enhanced oxygen barrier characteristics, which are analogs to multilayer films containing SiOx coating.

Table 2 Oxygen permeability of multilayer polymer
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Introducing New Crystals Phase or Shape in the Polymer Matrix

It has been shown that increasing the degree of crystallinity contributed to enhancement of gas barrier properties of packaging, since crystallites act as impermeable obstacles and make the diffusing molecules to take a longer pathway around them. It has been also illustrated that crystalline zones can influence their surrounding polymer chains and cause formation of a restricted or rigid amorphous fraction which has lower chain movement and improved oxygen barrier properties compared to amorphous fraction as illustrated in Fig. 5 [143]. In a study, combined techniques of solution blending and isothermal recrystallization were applied for formation of film comprised of PVA and GO, in order to introduce new crystals into the polymer mortar. It was found that during isothermal recrystallization process, GO sheets act as nucleating agents and contributed to formation of PVA crystals around the GO sheets. Transmission electron microscopy images revealed that newly formed PVA crystals have filled the empty spaces that existed between GO sheets and have formed ultra huge impermeable fractions that inhibit oxygen diffusion through the polymer matrix [22]. In another study, the effect of crystallinity degree on oxygen permeability values of films prepared via in situ polymerization of L-lactide with silane-modified nanosilica and MMT and also pure PLA and commercial PLA was evaluated. The results showed that the difference in crystallinity between commercial PLA and pure polymer results in different oxygen permeability with commercial PLA having permeability 76% higher than pure PLA, which is the result of its lower crystallinity degree compared to pure PLA. These are two unmodified PLAs; therefore, the difference in permeability can be attributed only to the different crystalline content in these two samples. Also, it was demonstrated that the presence of nanoparticles in the polymer matrix increases crystallinity degree which positively affects permeability and contributed to improved oxygen barrier properties [115].

Fig. 5
figure 5

Effect of isothermal recrystallization on crystallinity degree of nanocomposite matrix

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Cross-Linked Polymers

Cross-linking can minimize the gasps and spaces that exist in the polymer matrix and by this way improves gas barrier performance [28]. In the case of nanocomposite, cross-linking can also connect neighboring nanoparticles and form huge impermeable obstacles for diffusing molecules and contribute to improved oxygen barrier properties [8]. In a study, borate was utilized as a cross-linking agent in order to enhance oxygen barrier properties of PVA/GO nanocomposite. It was demonstrated that cross-linking networks joined GO sheets with each other and formed large impermeable regions which contributed in a significant reduction in oxygen permeability of cross-linked nanocomposite [83]. In another similar study, boric acid induced cross-linking in PVA/GO nanocomposite which was also confirmed by FTIR through the formation of a B–O–C bond. Then, the prepared cross-linked nanocomposite was deposited on the nylon. Coated nylon film exhibits dramatic reduction of oxygen gas permeability compared to uncoated nylon film [89]. In another study by Lazar et al. [86], multilayer nanocoating which consisted of cross-linkable CH and PAA were deposited on PET substrate. In this study, glycidyl methacrylate was applied in order to functionalize CH via formation of acrylic functionalities within the film. After deposition, films were cross-linked by the use of a free radical initiator. Cross-linking of film was confirmed by FTIR results and also by the reduction in thickness of film after cross-linking. Moreover, the results of this study revealed a considerable reduction in oxygen permeability value [86]. In an investigation, a ternary polysaccharide polyelectrolyte complex (PPC) material based on crystalline nanocellulose (CNC), chitosan (CS), and carboxymethyl cellulose (CMC) was manufactured by an immediate high-shear homogenization procedure. CS and CMC were ionically cross-linked and formed a homogeneous continuous matrix. CNC was incorporated as nanoreinforcement into the formed network. The developed PPC film exhibited improved barrier properties, ascribed to the even distribution and good interfacial compatibility of CNC within the CS/CMC matrix [24]. Zhuang et al. [165] have prepared an antibacterial chitosan-citric biomembrane with enhanced oxygen barrier performance by in situ cross-linking. The obtained film exhibited a low oxygen transmission rate (below 0.1 cm3/m−2/day−1 at 40% RH), as a result of the increased diffusion length arising from the hydrogen-bonding, ionic, and covalent cross-linking [165].

Conclusion

In recent years by established new regulation for single use packaging materials and banding equal multilayer structure such as polymer-polymer, more and more approaches have emerged in the food packaging industry, and future developments hold great potential for food packaging material with excellent oxygen barrier properties intended to protect oxygen-sensitive food products from deterioration and prolong their shelf life. This review highlights many processes that were tried to prepare, “superbarrier” packaging toward oxygen including layer-by-layer assembly, coating, incorporation of nanoparticles, increasing ratio of crystalline to amorphous regions in polymer via introducing new crystals, and the combination of different methods. Compared to the pure polymer matrix, the gas barrier performance of polymer via these approaches was improved. The results of the scientific literature had illustrated that these prepared materials can also replace other preferred materials like aluminum foil and solve the opaqueness problem associated with metalized packaging. In this review, we highlighted the manufacturing methods of polymer with their respective improvement in gas barrier properties. This literature review showed that the barrier properties could be significantly improved with these techniques and the results could vary from case to case. Lastly, the percentages of oxygen permeability reduction by different strategies are also thoroughly discussed. Owing to increased demand on biopolymer in the past few years that typically have poor barrier characteristics toward oxygen compared to conventional polymer, it would be necessary to conduct more research on improving biopolymer oxygen barrier properties by applying techniques, which would make them capable of competing with synthetic polymers.