Advanced Materials for Agriculture, Food, and Environmental Safety (Tiwari/Advanced) || Gas Barrier Properties of Biopolymer-based Nanocomposites: Application in Food Packaging

Ashutosh Tiwari and Mikael Syväjärvi (eds.) Advanced Materials for Agriculture, Food,

and Environmental Safety, (369–384) 2014 © Scrivener Publishing LLC

369

13

Gas Barrier Properties of Biopolymer-based Nanocomposites: Application

in Food Packaging

Sarat Kumar Swain

Department of Chemistry, Veer Surendra Sai University of Technology,

Burla, Sambalpur, Odisha, India

AbstractA series of biopolymer- and protein-based nanobiocomposites have been pre-

pared with reinforcement of diff erent nanoparticles such as silicon carbide (SiC),

boron nitride (BN), carbon nanotubes and nanoclays. Th e bionanocomposites

were prepared by solution technique at various wt% of nonomaterials and Fourier

transform infrared spectroscopy (FTIR) and fi eld emission scanning electron

microscopy (FESEM) were used for characterizing them. Th e mechanical, ther-

mal, rheological, biodegradable, chemical resistance and oxygen barrier proper-

ties of biopolymer-based nanocomposites were studied. In this chapter, gas barrier

properties of bionanocomposites were investigated for use in food packaging

applications. A substantial reduction in oxygen permeability was achieved due to

uniform distrubution of nanoparticles with biopolymer matrix. Since nanopar-

ticles have a higher aspect ratio than their microscale counterparts, gas barrier

properties were improved. Th e well-dispersed nanomaterials within the biopoly-

mer- and protein-based matrixes created huddles for gas penetration. Th e theories

of substantial reduction in gas permeability of nanocomposites due to insertion

of nanofi llers are studied. Also, antimicrobial properties and detection of gas pro-

duced by food spoilage are discussed.

Keywords: Proteins, nanocomposites, aspect ratio, permeability, antimicrobial

*Corresponding author: [email protected]

370 Advanced Materials for Agriculture, Food, and Environmental

13.1 Introduction

A nanocomposite is a multiphase material derived from the combination of two or more components, including a matrix (continuous phase) and a discontinuous nanodimensional phase with at least one nanosized dimen-sion (i.e., with less than 100 nm). Th e nanodimensional phase can be divided into three categories according to the number of nanosized dimen-sions. Nanospheres or nanoparticles have the three dimensions on the nanoscale. Both nanowhiskers (nanorods) and nanotubes have two nano-metric dimensions, with the diff erence that nanotubes are hollow, while nanowhiskers are solid. Finally, nanosheets or nanoplatelets have only one nanosized dimension. Most nanosized phases have a structural role, act-ing as reinforcements to improve the mechanical properties of the matrix (usually a polymer), since the matrix transfers the tension to the nanore-inforcement through the interface. Nanoreinforcements are especially useful for biopolymers, because of their usually poor performance when compared to conventional petroleum-based polymers. Th e incorporation of nanosized reinforcements into biopolymers may open new possibilities for improving not only their properties but also their cost-price effi ciency.

Nowadays, most materials used for packaging are practically undegrad-able, representing a serious global environmental problem. New bio-based materials have been exploited to develop edible and biodegradable films in a big eff ort to extend shelf life and improve quality of food while reduc-ing packaging waste [1]. However, the use of edible and biodegradable polymers has been limited because of problems related to performance, processing and cost. Starch, for example, has received considerable atten-tion as a biodegradable thermoplastic polymer. However, it has a poor per-formance by itself because of its water sensitivity and limited mechanical properties with high brittleness, which is related to the anarchical growth of amylase crystals with time [2]. Th e application of nanotechnology to these polymers may open new possibilities for improving not only the properties but also the cost-price effi ciency. Th e main advantage of plas-tics compared with other packaging materials is that they are lightweight, can be processed quickly and easily and off er design and printing fl exibil-ity. However, petroleum resources are fi nite and fuel prices have recently been escalating. In addition, the end-of-life management of plastics has also depleted the world’s rights for sustainability. Hence, the emergence of biopolymers as an alternative material option has been promising.

Th e majority of materials currently used for packaging are nondegrad-able, creating environmental problems. Several biopolymers and proteins

Gas Barrier Properties of Biopolymer-based Nanocomposites 371

have been exploited to develop materials for eco-friendly packaging mate-rials. However, the use of biopolymers/proteins have been limited because of their usually poor mechanical and barrier properties, which may be enhanced by adding discontinuous phased reinforcing compounds, form-ing composites. Most reinforced materials have poor matrix–filler interac-tions, which tend to improve depending on filler dimensions. When fi llers of nanodimension are used with bulk materials then the hybrid materials are known as nanocomposites.

Several composites [3] have been developed by adding reinforcing com-pounds to biopolymers/proteins to enhance their thermal, mechanical and barrier properties. Most of these reinforced materials present have poor interactions at the interface of both components. Macroscopic reinforc-ing components usually contain defects, which become less important as the particles of the reinforcing component are smaller. Biopolymers are polymers that are produced by living organisms and represent a special class of polymers that are biodegradable in nature [4]. Th ey are produced from plants from the agricultural non-food crops directly and by means of fermentation, hence rendering them renewable. In another aspect, use of biopolymers promotes organic recycling either through composting, anaerobic digestion or by biomass conversion. Th ese benefi ts have con-tributed to the rising signifi cance of biopolymers. Some examples of bio-polymers include polylactide acid (PLA), polyhydroxy alkanoate (PHA), cellulose and starch-based polymers or thermoplastic starch (TPS). Despite the biodegradability of biopolymers, there exist several factors that limit their applications as packaging materials. First, their mechanical proper-ties are relatively poor compared to many petroleum-based plastics due to their inherent lower stiff ness and strength, as well as brittleness. Second, many are relatively sensitive to water, with some materials dissolving rap-idly, or have a substantial decrease in mechanical performances when they absorb water, especially in moist environments.

Th e introduction of nanofi llers should be explored for sustainable pack-aging as an improvement in properties could take place with the use of less raw materials, thus conserving resources [5]. Th is, in conjunction with degradability of biopolymer, could impart ease in waste management as well. Hence, several research groups started the preparation and charac-terization of various kinds of biodegradable polymers/nanofi ller systems. To date, the work carried out on biopolymeric nanocomposites has been focused mainly on the designing and making of biopolymeric nanocom-posites by selecting an appropriate synthetic method and adjusting their structures and compositions [6].


13.2 Experimental

A series of bionanocomposites were prepared with variable wt% of nano-fi llers by using the solution technique. Th e nanoparticles were dispersed in double-distilled water by continuous stirring at 60°C for 30 minutes and then the solution was treated with ultrasound (120W/180KHz) for 30 min-utes. Th en the biopolymer solution prepared in distilled water was added to diff erent wt% fi ller

solutions. Th e viscous product obtained was fi ltered

and washed with double-distilled water. Th e bionanocomposites obtained were dried in an oven for 24 hours. at a temperature of 50°C.

Th e functionalization of MWCNT was done as per our earlier pub-lication [22]. Th e MWCNTs were treated with concentrated H

2SO

4 and

HNO3 in the volume ratio of 3:1 and sonicated by using ultrasonic cleaner

(120W/60KHz) at 40°C for 24 hours in a fl ask. Th e solution was diluted by distilled water and fi ltered. Th e remaining residue was washed by distilled water. Th en the open ended tubes were polished with hydrogen peroxide and H

2SO

4 in volume ratio of 1:4 with stirring at 70°C for thirty minutes.

Th e resulting solution was diluted by distilled water and centrifuged to get f-MWCNT.

Starch/MWCNT nanocomposites fi lm was prepared by a convenient solution casting and evaporation method. Th e f-MWCNTs were dispersed in double-distilled water with stirring for ten minutes taking in a fl ask. Calculated amount of glycerol was added and homogenized in an ultra-sonic bath for 30 minutes. Th e required quantity of starch was added into the fl ask and the solution was charged by constant stirring with heating at 95°C for 30 minutes to form the plasticized starch. Oxygen permeability of the bionanocomposite was measured with STM F 316-86 by using oxy-gen permeation analyzer (PMI instrument, model GP-201-A, Texas, NY, USA). For testing oxygen permeability the synthesized powdered bionano-composites were converted into fi lms of 5 mm thickness with the help of a polymer press at a pressure of 9 tons. Th e results were recorded as average of the values obtained from fi ve same samples.

13.3 Objective

Even though research activities have intensifi ed over the last decade, there is still a limited amount of literature on the applications of biopolymeric nanocomposites-based primary, secondary and tertiary packaging. Th is indicates that an understanding on such bio-based nanocomposites as sus-tainable packaging materials is very much still in its infancy and much is


needed to assess their performance and potential. In the present study, the sustainability of biopolymer-based nanocomposites for packaging applica-tions has been discussed along with their theories and gas permeability properties. Th e main objective of the present review is to compare diff er-ent kinds of nanofi llers suitable for various biopolymers in order to enable the materials to be used for food packaging materials. Th e oxygen perme-ability of nanocomposites of diff erent fi llers was compared with the virgin polymer/biopolymers.

13.4 Background of Food Packaging

13.4.1 Oxygen Penetration

Oxygen (O2) is responsible for the deterioration of many foods either

directly or indirectly. Food deterioration by indirect action of O2 includes

food spoilage by aerobic microorganisms [7]. Th e incorporation of O2

scavengers into food packaging can maintain very low O2 levels, which is

useful for several applications. In particular, attention has been focused on the photocatalytic activity of nanocrystalline titania (TiO

2) under ultra-

violet radiation. Industries estimate the food expiration date, taking into consideration the distribution and storage conditions to which the food product is predicted to be exposed. However, it is known that such con-ditions are not always the real ones, and foods are frequently exposed to temperature abuse; this is especially worrying for products which require a cold chain. Moreover, micropores or sealing defects in packaging sys-tems can lead to an unexpected high exposure of oxygen in food products, which can result in undesirable changes. When integrated into food pack-aging, nanosensors can detect certain chemical compounds, pathogens and toxins in food [8].

Food spoilage is also caused by microorganisms, whose metabolism produces gases which can be detected by conducting polymer nanocom-posites (CPC) or metal oxides. Th is can be used for quantification and/or identification of microorganisms based on their gas emissions. Sensors based on CPC consist of conducting particles embedded into an insulating polymer matrix; the resistance changes of the sensors produce a pattern that corresponds to the gas under investigation. Oxygen allows aerobic microorganism to grow during food storage [9]. Th ere has been increasing interest in developing nontoxic and irreversible oxygen sensors to assure oxygen absence in oxygen-free food packaging systems, such as packaging under vacuum or nitrogen [10].


Th e use of biopolymers by the food industry has faced feasibility prob-lems related mainly to their relatively high cost and poor overall perfor-mance when compared to those of synthetic polymers [11]. However, since industries are concerned with sustainable development, the production cost of biopolymers has decreased, allowing biopolymer-based materials to be increasingly developed. More importantly, nanocomposites promise to expand the use of edible and biodegradable films, since the addition of nanoreinforcements has been related to improvements in overall perfor-mance of biopolymers, enhancing their mechanical, thermal and barrier properties, usually even at very low contents. Th us, nanoparticles have an important role in improving feasibility of the use of biopolymers for sev-eral applications, including food packaging [12].

However, there are many safety concerns about nanomaterials, as their size may allow them to penetrate into cells and eventually remain in the system. Th ere is no consensus about categorizing nanomaterials as new materials. On one hand, the properties and safety of the materials in its bulk form are usually well known, but the nanosized counterparts fre-quently exhibit diff erent properties from those found at the macroscale. Th ere is limited scientific data about migration of most types of nanopar-ticles (NPs) from the packaging material into food, as well as their eventual toxicological eff ects. It is reasonable to assume that migration may occur, hence the need for accurate information on the eff ects of NPs to human health following chronic exposure is imperative [13].

13.4.2 Antimicrobial Systems

Antimicrobial food packaging systems have received considerable atten-tion since they help control the growth of pathogenic and spoilage micro-organisms on food surfaces, where microbial growth predominates. Antimicrobial nanocomposite systems are particularly interesting, since materials in the nanoscale range have a higher surface-to-volume ratio when compared with their microscale counterparts. Nanomaterials are thus more effi cient, since they are able to attach more copies of microbial molecules and cells. Nanoscale materials have been investigated for anti-microbial activity as growth inhibitors or killing agents [14].

Silver is well known for its strong toxicity to a wide range of microorgan-isms, besides some processing advantages such as high temperature stabil-ity and low volatility. Silver nanoparticles have been shown to be eff ective antimicrobials, even more eff ective than larger silver particles, thanks to their larger surface area available for interaction with microbial cells. In fact, the most common nanocomposites used as antimicrobial fi lms for


food packaging are based on silver nanoparticles, whose antimicrobial activity has been ascribed to diff erent mechanisms, namely: (a) adhesion to the cell surface, degradation of lipopolysaccharides and formation of “pits” in the membranes, largely increasing permeability; (b) penetration inside bacterial cell, damaging DNA, and; (c) releasing antimicrobial Ag+ ions by dissolution of silver nanoparticles. Besides their antimicrobial activity, silver nanoparticles have been reported to absorb and decompose ethylene, which may contribute to their eff ects on extending shelf life of fruits and vegetables [15].

Titanium dioxide (TiO2) is widely used as a photocatalytic disinfect-

ing material for surface coatings. Titanium dioxide photocatalysis, which promotes peroxidation of the phospholipids present in microbial cell membranes, has been used to inactivate food-related pathogens. A TiO

2

powder-coated packaging fi lm able to reduce E. coli contamination on food surfaces has been developed; and the effi cacy of TiO

2-coated fi lms

exposed to sunlight to inactivate fecal coliforms in water has been dem-onstrated. Metal doping improves visible light absorbance of TiO

2, and

increases its photocatalytic activity under UV irradiation. It has been dem-onstrated that doping TiO

2 with silver greatly improved photocatalytic

bacterial inactivation. Th is combination was explored by Hulleman et al., who have obtained eff ective antibacterial activity from a polyvinyl chloride nanocomposite with TiO

2/Ag+ nanoparticles [16].

Carbon nanotubes have also been reported to have antibacterial prop-erties. Direct contact with aggregates of carbon nanotubes have been demonstrated to kill E. coli, possibly because the long and thin nano-tubes puncture microbial cells, causing irreversible damage and leakage of intracellular material. On the other hand, there are studies suggesting that carbon nanotubes may also be cytotoxic to human cells, at least when in contact to skin, which would aff ect people manipulating the nanotubes in processing stages rather than consumers [17]. Anyway, once present in the food packaging material, the nanotubes might eventually migrate into food. Th en, it is mandatory to know any eventual health eff ects of ingested carbon nanotubes.

13.4.3 Detection of Gases Produced by Food Spoilage

Food spoilage is caused by microorganisms whose metabolism pro-duces gases, which may be detected by several types of gas sensors which have been developed to translate chemical interactions between parti-cles on a surface into response signals. Nanosensors to detect gases are usually based on metal oxides or, more recently, conducting polymer


nanocomposites, which are able to quantify and/or identify microorgan-isms based on their gas emissions. Sensors based on conducting polymers (or electroactive conjugated polymers) consist of conducting particles embedded into an insulating polymer matrix [18]. Th e resistance changes of the sensors produce a pattern corresponding to the gas under investi-gation. Conducting polymers are very important because of their electri-cal, electronic, magnetic and optical properties, which are related to their conjugated π electron backbones. Polyene and polyaromatic conducting polymers, such as polyaniline, polyacetylene and polypyrrole, have been widely studied. Electrochemically polymerized conducting polymers have a remarkable ability to switch between conducting oxidized (doped) and insulating reduced (undoped) states, which is the basis for several appli-cations. Nanosensors containing carbon black and polyaniline have been developed which have been demonstrated to be able to detect and identify three foodborne pathogens by producing a specifi c response pattern for each microorganism.

13.4.4 Diff erent Fillers for Nanocomposites

13.4.4.1 Nanoclay as Fillers

Nanoclays have been the most studied nanofi llers due to their high avail-ability, low cost, good performance and good processability. Th e clays for nanocomposites usually are bidimensional platelets with very tiny thick-nesses (frequently around 1 nm) and several micrometers in length. In con-trast with the typical tactoid structure of microcomposites (conventional composites), in which the polymer and the clay tactoids remain immis-cible, the interaction between layered silicates and polymers may produce two types of nanoscale composites, namely: intercalated nanocomposites, which result from penetration of polymer chains into the interlayer region of the clay, producing an ordered multilayer structure with alternating polymer/inorganic layers, and exfoliated nanocomposites, which involve extensive polymer penetration, with the clay layers delaminated and ran-domly dispersed in the polymer matrix. Exfoliated nanocomposites have been reported to exhibit the best properties due to their optimal clay- polymer interactions.

Th e hydrophilicity of the surface of most clays make their dispersion in organic matrices diffi cult. Organoclays, produced by interactions of clays and organic compounds, have found an important application in polymer nanocomposites. An adequate organophilization is essencial for successful exfoliation of clays in most polymeric matrices, since organophilization


reduces the energy of clays and improves their compatibility with organic polymers. Organo-montmorillonite (MMT) has been produced, for exam-ple, by exchanging inorganic cations of MMT with organic ammonium ions, improving compatibility of MMT with organic polymers, leading to a more regular organization of the layers, and decreasing the water uptake by the resulting nanocomposite.

Th e most widely known theories to explain the improved barrier prop-erties of polymer–clay nanocomposites are based on a theory developed by Nielsen (Figure 13.1), which focuses on a tortuous path around the clay plates, forcing the gas permeation to travel a longer path to diff use through the film. Th e increase in path length is a function of the high aspect ratio of the clay filler and the vol% of the filler in the composite. Nielsen’s model predicts permeability of systems at clay loading rates of less than 1%, but experimental data deviate significantly from predicted values at higher loading rates and more extensively in certain polymers.

Th e improved barrier properties of polymer-clay nanocomposites seem to be due to an increased tortuosity of the diff usive path for permeants, forcing them to travel a longer path to diff use through the fi lm. Th e increase in path length is a function of the aspect ratio of the clay and the volume fraction of the fi ller in the composite. Nielsen’s model has been used eff ectively to predict permeability of systems at clay loadings of less than 1%, but some experimen-tal data have reported much lower permeabilities than predicted at higher loadings, and a new proposed model to predict permeability of nanocompos-ites focused on the polymer-clay interface as an additional governing factor to the tortuous path, thus providing a correction factor to Nielsen’s model.

Th e oxygen permeability of polyacrylonitrile (PAN)/clay nanocompos-ites was measured with variation of clay concentration along with diff erent frequencies and powers of ultrasound waves [19]. It was found that oxygen

Permeant

Clay

Figure 13.1 Tortuous path of a permeant in a clay-based nanocomposite.


permeability of nanocomposites decreased substantially with an increase in clay loading (Figure 13.2). It was marked that the oxygen permeability was further reduced with an increase in power and frequency of ultrasound. Th is may be due to the removal of microvoids by the application of ultrasound.

Th e oxygen permeability of the virgin polymethylmethacrylate (PMMA) and PMMA/clay nanocomposites can be studied from Figure 13.3. Th e

24

22

20

18

16

14

12

100 1

Clay content, wt %

Oxy

ge

n p

erm

ea

bili

ty, l

it/m

in/c

m2

2 3 4

Figure 13.2 Oxygen permeability of PAN/clay nanocomposites as a function of clay

content at 5 psi pressure [19].

17.0

16.5

16.0

15.5

15.0

14.5

14.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Clay content, wt %

Oxy

ge

n fl

ow

ra

te, l

it/m

in/c

m2

Figure 13.3 Oxygen fl ow rate of PMMA and PMMA/clay nanocomposites with variation

of clay content at a constant pressure (5 psi) [20].


oxygen fl ow rate through all the nanocomposites was observed to be less in comparison to the virgin PMMA at diff erent pressures up to 5 psi; the fl ow rate was found to decrease with an increase in percentage clay loading. Th e fl ow rate of PMMA/clay nanocomposites was reduced by 17% as compared to virgin PMMA at 3% clay concentration. Th is is due to the tortuous path created as a result of exfoliation of clay during sonication [20].

Th e oxygen fl ow rate of the soy/clay bionanocomposites was found to be decreased in proportion to clay loading of 2% (Figure 13.4). At 8% clay concentration, the oxygen permeability was reduced by 6 times as com-pared to the virgin protein. Th is is because the clay nanoparticles act as physical obstacle, retarding the movement of the gas [21].

13.4.4.2 Carbon Nanotube as Fillers

Carbon nanotubes may consist of a one-atom thick single-wall nanotube, or a number of concentric tubes called multiwalled nanotubes, having extraordinarily high aspect ratios and elastic modulus. Several polymers have been found to have their tensile strength/modulus improved by addi-tion of carbon nanotubes, such as polyethylene naphtalate, polyvinyl alco-hol, polypropylene and a polyamide. Th e polylactic acid not only had its tensile properties improved by carbon nanotubes, but also had its water vapor transmission rate decreased by 200%.

Th e oxygen permeability of virgin PMMA and PMMA/functionalized multiwalled carbon nanotube (f-MWCNT) nanocomposites has been

Clay content, wt %

0

1.2

1.0

0.8

0.6

0.4

0.2

2 4 6 8

Oxy

ge

n p

erm

ea

bili

ty, l

it/m

in/c

m2

Figure 13.4 Oxygen permeability values of the soy/clay bionanocomposites as a function

of clay weight percent at a pressure of 5 psi [21].


studied [22], as shown in Figure 13.5. Th e oxygen permeability of PMMA/f-MWCNT nanocomposites with 1.75 wt% of MWCNTs loading is about eight times less than that of virgin PMMA. Th e reduction of permeability arises from the longer diff usive path of the penetration of the oxygen in the presence of MWCNTs. Th e incorporation of MWCNT in PMMA matrix is particularly excellent at maximizing the path length due to the high aspect ratio. Furthermore, the presence of MWCNT introduces a torturous path for which the oxygen travels longer diff usive path. Hence oxygen perme-ability of PMMA/MWCNT nanocomposites is less than that of PMMA matrix. Th e tremendous decrease in oxygen permeability with increasing MWCNT (wt%) is due to good dispersion of MWCNTs in polymer matrix of PMMA/f-MWCNT composites.

13.4.4.3 Other Nanomaterials

Silica nanoparticles (nSiO2) have been reported to improve tensile proper-

ties of polypropylene, starch, starch/polyvinyl alcohol, besides decreasing water absorption by starch and improving oxygen barrier of polypropylene prepared nanocomposites of polyvinyl alcohol with nSiO

2 by radical copo-

lymerization of vinyl silica nanoparticles and vinyl acetate. Th e nanocom-posites had improved thermal and mechanical properties when compared to the pure polyvinyl alcohol, due to strong interactions between nSiO

2

and the polymer matrix via covalent bonding.

Oxy

ge

n p

erm

ea

bili

ty /

(cm

2/m

in)

1.0

0.8

0.6

0.4

0.2

0.00.00 0.35 0.70

MWCNT / wt%

1.05 1.40 1.75

Figure. 13.5 Oxygen permeability of PMMA/f-MWCNT nanocomposites at constant

pressure of (0.5 psi) [22].


Polymer-based composites which have been shown to provide barrier to oxygen are being studied for packaging applications. Th e oxygen per-meability of virgin chitosan and chitosan/BN composites can be seen in Figure 13.6. As chitosan is a porous polymer, the dispersion of boron nitride in chitosan matrix may provide the huddles for oxygen entrance, whereas virgin chitosan may have voids for oxygen permeation [23]. Oxygen per-meability of chitosan/BN composites was conducted to measure the eff ect of boron nitride concentrations on the chitosan matrix. Th e oxygen fl ow rate through all the composites was observed to be less in comparison with the virgin chitosan at pressure 0.010 MPa (Figure 13.6). It was found that the fl ow rate decreased with an increase in percentages of boron nitride loading. Th e substantial reduction in oxygen permeability may be due to the dispersion of boron nitride within the chitosan matrix. Th e oxygen fl ow rates through all composites were also observed to be less in comparison with the virgin chitosan at diff erent pressures up to 0.013 MPa.

Oxygen permeability of the synthesized cellulose/BN nanobiocompos-ites was conducted to measure the eff ect of boron nitride concentrations on oxygen barrier properties of the cellulose matrix [24]. Th e oxygen fl ow rate through all the nanobiocomposites was observed to be less in compar-ison to the virgin cellulose at constant pressures of 2 psi (Figure 13.7a). It was found that the fl ow rate was decreased with an increase in percentage of boron nitride loading. Th e remarkable reduction in oxygen permeability was due to nanostructure dispersion of boron nitride within the cellulose matrix at diff erence pressure up to 2 psi (Figure 13.7b).

Boron nitride, wt %0 2

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4 6 8 10

Oxy

ge

n p

erm

ea

bili

ty, l

/min

/cm

2

Figure 13.6 Oxygen permeability of the composites as a function of boron nitride content

at a pressure of 0.010 MPa [23].


13.5 Conclusion

Bionanocomposites were prepared by solution technique with dispersion of reinforced nanomaterials with biopolymer matrix. Th is technology was developed to improve barrier performance to gases such as oxygen. It also enhances the barrier performance to ultraviolet rays, as well as adding strength, stiff ness, dimensional stability, and heat resistance. New plastics created with this technology demonstrate an increased shelf life and are less likely to shatter. Once perfected, these plastics will off er these improved characteristics at competitive prices. It will also make them attractive for use in food and beverage packaging and pharmaceutical packaging applications.

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