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properties and extend shelf-life (16). The fastest growing

barrier application for nanoclays is bottles for beer, carbo-

nated soft drinks and other carbonated beverages (17) and

ﬁlm applications (18).

Most nanocomposite technologies make use of chemical

or otherwise modiﬁcations of layered 2:1 phyllosilicates

(19). The modiﬁcation is needed both to compatibilize

highly hydrophilic clays with the more organic apolar

chemical constitution of most plastic materials and to

increase the clay intergallery space (basal space between

adjacent layers), which facilitates both intercalation and

exfoliation of the clays laminar components in the matrix

during compounding. In the food chain, speciﬁc caution

should be taken because the applied modiﬁcations should

be harmless, comply with migration regulations, and make

use of food contact approved substances as valid modiﬁers.

Unfortunately, for most technologies and producers, this is

not the case, and it will limit the implementation of the

nanocomposites in the food packaging sector.

In this context, it is well known that most nanocomposite

formulations (ﬁrst generation nanocomposites) in the mar-

ket are curren tly making use of some not European union

(EU) listed ammonium salts as organophilic chemical modi-

ﬁers, which have been devised to enhance the properties of

engineering polymers in structural applications . However,

as mentioned above, for food-packaging applications, only

food contact approved materials and additives should be

used, and they should do so below their corresponding

threshold migration levels. In this respect, Nanobiomatters

S .L., Paterna (Spain) and its second-generation nanocom-

posite products traded as NanoBioTer

claim to comply

with the current food contact legislation. Second-generation

nanocomposites are therefore referred to as nanocomposite

technologies, which are speciﬁcally designed to comply with

current regulations and at the same time are cost effective

and speciﬁcally formulated to target speciﬁc materials

(including biopolymers), materials properties, or production

technologies. In essence, second-generation nanocomposites

are materials with targeted speciﬁcations rather than wide-

spectrum generic formulations.

Despite the fact that multilayer solutions are currently

needed in many food-packaging applications including the

above-mentioned carbonated beverages, a monolayer solu-

tion would be of great interest for many reasons, including

recyclability, a technology, and material costs. The nano-

composites technology can also make this possible by

simple melt or solution blending routes. The reason why

in PET bottles, nanocomposites are still devised to be used

in multilayer systems (such as Impermt nanocomposites

of PA from Nanocor) is because PET nanocomposites are

extremely difﬁcult to obtain in a monolayer case because

of the high temperature needed to process the polymer,

which causes degradation of the organophilic chemical

modiﬁcation of the layered clay particles.

Companies are already developing packaging materials

based on nanotechnologies that claim to extend the shelf

life of foods and drinks. Several large beer makers,

including South Korea’s Hite Brewery and Miller Brewing

Company, are already offering the technology. However,

nanocomposites for packaging have been developed for a

limited number of polymers, e.g., PAs, thermosetting

epoxies and, to some extent, PET (20), and their food

contact status remains unclear.

Table 1 summarizes the companies and the barrier

technologies that have been developed for improving the

properties of thermoplastics materials. From Table 1,

nanoclay companies developing nanocomposite materials

in the food-packaging sector are NanoBioMatters S.L.

and Nanocor (part of Amcol International). Nanobio-

matters S.L. (Paterna, Spain) offers a wide range of

commercially available food contact compliant nanoclays

and plastic masterbatchs for enhancing physical pro-

perties such as barrier to gases, vapors, and ultraviolet

(UV) light and thermal and mechanical properties, as

well as specialty grades that can exhibit active properties

such as antimicrobial, oxygen scavenging and antioxidant

performance (21). The Nanocor company is currently

producing nanocomposites for use in plastic beer bottles

that give the contents a 6-month shelf life (22). TetraPak

and Eastman are developing nanocomposites of PET

materials (23–26), and ICI is developing also nanocompo-

sites of PET (27). Ube (Allied Signa Bayer) (28) and EMS

Chemie is developing nanocomposites of PA-based sys-

tems (29).

Table 1. Summary of suppliers and of the barrier nanotechnology they are developing or offering at a commercial level

Company Material Application Development status

NanoBioMatters S.L. Nanocomposites/EVOH/PET/LDPE/PLA/PHB/PCL Film Commercial

NanoBioMatters S.L. Active nanocomposites Biocide, antioxidant Film Commercial

Nanocor/Amcol Int. Nanocomposites Development

EMS Chemie Nanocomposites/PA Film Commercial

Ube Nanocomposites/PA Film Commercial

Allied Signal Nanocomposites/PA Development

Bayer Nanocomposites/PA Development

Honeywell Nanocomposites/PA Commercial

ICI/DuPont Nanocomposites/PET Film Development

Eastman Nanocomposites/PET Bottles Development

TetraPak Nanocomposites/PET Bottles Laboratory

ICI Nanocomposites/melamine Bottles Development

PPG Industries Nanocomposites/epoxy Bottles Development

PA, polyaniline; PCL, polycapro lactone; PHB, polyhydroxybutyrate.

808 NANOCOMPOSITE PACKAGING MATERIALS

NANOCOMPOSITES RESEARCH DEVELOPMENTS TO

ENHANCE BARRIER PROPERTIES

Several research studies published in the scientiﬁc litera-

ture detail barrier improvements for plastic-clay nano-

composites. Table 2 summarizes the most relevant works

reporting barrier improvements in nanocomposites of

plastics of interest in food-packaging applications.

PET is one of the most widely studied materials

regarding nanocomposites, Sa

nchez-Garcı

a et al. (30)

reported improvements in oxygen permeability of about

55% in melt mixed nanocomposites of PET with 5 wt.-%

nanoclay (based on a food contact approved montmorillo-

nite (MMT) traded as NanoBioTer), with regard to the

pure PET. Limonene permeability improvements of about

68% for composites containing 5 wt.-% of nanoclay and a

water vapor permeability improvement of about 43% in

nanocomposites containing 1 wt.-% of nanoclay were also

reported. Ke et al. (31) reported a 25% oxygen permeabil-

ity reduction for PET containing 1 wt.-% of organically

modiﬁed montmorillonite [organical montmorillonite

(OMT), containing an interlayer agent comprising a –

COOH group in its structure] by using an in situ inter-

layer polymerization route. More recently, Choi, W.J et al.

claimed to have obtained a 94% oxygen permeability

reductions in PET containing 5 wt.-% of MMT (MMT-Na-

with chlorotitanium triisopropoxide used as a catalyst)

nanocomposites by an in situ polymerization process

(32). Fifty percent oxygen permeability reduction for

PET–MMT nanocomposites obtained by melt blending

in a rheometer was also reported by Vidotti, et al. (33).

Lai et al. (34) studied amorphous ﬁlms of poly(ethylene

terephthalate-co-ethylene naphthalate) (PETN) and

PETN/Cloisite 30B (MMT-(OH)

; MMT modiﬁed with

methyl bis(2-hydroxyethyl) (hydrogenated tallowalkyl)

ammonium cation)) nanocomposites prepared in a twin

screw extruder. The PETN containing 2 wt.-% of the MMT-

(OH)

clay showed a 50% reduction in O

permeability

compared with the neat PETN. So, to enhance the polar

interactions between the organoclay and the PETN ma-

trix, the organoclay surface was treated with a diepoxide,

diglycidyl ether of bisphenol A (DGEBA). Therefore, with

the addition of epoxy (by melt intercalation and the weight

ratio of epoxy to PETN was (0.75/100) in the ﬁnished

composite), a permeability reduction higher than 88% was

obtained with compared the neat PETN (34).

For the case of polyamides, Yano et al. (35) reported

that the polyamides have a reduction of the water permea-

tion coefﬁcient of about 54% with only 2 wt.-% of an OMT

(MMT-intercalated with an ammonium salt of dodecyla-

mine) compared with the unﬁlled polymer. Picard et al.

(36) measured that the diffusion rate slowed down by

about 55% going from neat PA to polyamide 6 containing

13 wt.-% OMT (organically modiﬁed with a dihydroxy

methyl tallow quaternary ammonium) nanocomposite

prepared by melt mixing. Pinnavaia et al. (37) reported

that the rate of water absorption in PA6 nanocomposites

was lowered by 40% compared with the neat polymer.

Table 2. Relevant reported reductions (%) in oxygen and water vapor permeability of nanocomposites of some widely

used polymers

Matrix Type of clay Clay content O

Permeability H

O Permeability

PET (30) MMT 5% 55%

PET (30) MMT 1% 43%

PET (31) MMT 1% 25%

PET (32) MMT 5% 94%

PET (33) MMT 5% 50%

PETN (34) MMT 2% 50%

PA (35) MMT 2% 54%

PA (36) MMT 13% D 55%

Nylon6 MMT 6% 28%

Copolyamide-Nylon6 MMT 6% 54%

LDPE MMT 7% 24%

LLDPE MMT 5% 15%

LDPE MMT 5% 30%

EVOH MMT 5% 75%

PP CaCO

3% 30%

PP MMT 4% 50%

PP MMT 5% 57%

PS MMT 7% 60%

PI MMT 5% 69%

PI MMT 0.5% 46% 48%

PI MMT 4% 82%

Natural Rubber Latex MMT 2% 66%

PVC SiO

3% 40% 45%

Resin Epoxy Zirconium phosphate/phosphonate 5% 59%

PU Natural Unmodiﬁed MMT 5% 41%

PU MMT 3% 30% 50%

PSF MMT 3% 72% 30%

PA, polyaniline; pp, polypropylene.

NANOCOMPOSITE PACKAGING MATERIALS 809

Russo et al. (38) reported an oxygen barrier improvements

for the PA6 (nylon 6) with 6 wt.-% of Cloisite 30B of about

28% compared with the pure PA6. They also study the

copolyamides of PA6 containing 6 wt.-% of Cloisite 30B,

and the oxygen permeability reduction was of about 54%

compared with the pure copolyamide (38). Moreover, Jiang

et al. (39) published that the barrier performance of

exfoliated PA6 with an OMT (OMT was synthesized by a

cation-exchange reaction between Na-montmorillonite

and octadecylammonium salt) was improved markedly

by adding a small amount of the clay, having a toluene

and ethanol permeation rate in the composite sheet 3–4

times slower than in neat PA6.

Regarding polyethylene, Supong Arunvisut et al. pub-

lished that a low-density polyethylene LDPE containing

7 wt.-% of OMT (MMT was mixed with Di(hydrogenated

tallowalkyl) dimethyl ammonium chloride) exhibited a

decreased oxygen permeability of 24% compared with the

pure material (40). Ali Durmus et al. (41) measured a

reduction in the oxygen permeability of ca. 15% with the

addition of 5% OMT traded as Cloisite 20A [MMT modiﬁed

with dimethyl dihydrogenated tallow quaternary ammo-

nium salt, MMT(2Me

HT)] to linear LDPE (LLDPE). Fi-

nally, Zhong et al. (42) reported that incorporating 5 wt.-%

of the MMT(2Me

HT) clay, the oxygen permeability of an

LDPE maleic anhydride grafted polyethylene (MAPE) sys-

tem prepared by melt mixing decreased by 30%.

Lagaron et al. (43) reported many signiﬁcant results

where nanotechnology was satisfactorily applied to im-

prove packaged food quality and safety by increasing the

barrier properties to oxygen of an ethylene-vinyl alcohol

copolymer (EVOH) under dry and humid conditions using

nanoclays (MMT and kaolinite). The authors measured a

reduction in oxygen permeability of more than 75% in dry

conditions and a reduction of 71% for the nanocomposites

of EVOH at 85% RH.

Regarding poly(ethylene-co-vinyl acetate), Muralidhar-

ana et al. (44) reported the characterization of ethylene

vinyl acetate (EVA)/MMT (natural sodium MMT clay)

nanocomposite membranes with different clay loadings.

The solvent uptake was minimum for composites with

3 wt.-% of the nanoclay and increased with increasing

ﬁller content, presumably because of aggregation of the

clay ﬁller at higher loading. They claimed a reduction in

the diffusion coefﬁcient of benzene, toluene and xylene of

about 50%, 48%, and 40% for the nanocomposite with 3%

clay, respectively.

In regard to propylene, Avella et al. (45) measured a

reduction in barrier properties both to oxygen and to

carbon dioxide of about 30% on nanocomposites of poly-

propylene containing 3 wt.-% of CaCO

. Giuliana Gorrasi

et al. (46) reported that samples of polypropylene contain-

ing 1 and 2 wt.-% of organomodiﬁed ﬂuorohectorite

showed a linear decrease in the diffusion coefﬁcient until

about the 3% of solvent sorbed dichloromethane vapor.

Mittal et al. (47) prepared polypropylene nanocomposites

containing different volume fractions of an OMT (MMT

modiﬁed with an dialkyl imidazolium salt) and measured

oxygen permeability reductions of about 50% for samples

containing 4 wt.-% of the nanoﬁller (47). Finally, nano-

composites of polypropylene with 5 wt.-% of an OMT (a

MMT modiﬁed with a nondisclosed alkyl ammonium salt)

also showed a reduction in the oxygen permeability of

about 57% and a reduction in the dioxide permeability of

about 48%. The composites were prepared by a solvent

blending method by Frounchi et al. (48).

In the case of polystyrene, Meneghetti et al. (49)

synthesized polystyrene (PS)/clay nanocomposites via in

situ polymerization with an OMT (the MMT was ion

exchanged with zwitterionic surfactant (C18DMB)) that

resulted in an intercalated morphology. The oxygen per-

meability decreased by more than 60% over pure PS for

the intercalated nanocomposite containing a 0.07 volume

fraction of clay.

Regarding polyimides, Yano et al. (50) claimed that only

a 2 wt.-% addition of a synthetic mica led to a decrease in

the gas permeability coefﬁcient to a value less than one

tenth that of the pure polyimide. Huang et al. (51) reported

a decrease in the oxygen permeability of about 69% with a

5 wt.-% of OMT clays (MMT modiﬁed with alkylammonium

ions) in a polyimide prepared by in situ polymerization.

Yeh et al. (52) reported that a polyimide prepared by

solvent casting containing an OMT (MMT modiﬁed with

an alkyl ammonium salt) (0.5 wt.%) exhibited about a (53)

48% and 46% decrease in H

O and O

permeability,

respectively (52). Jin-Hae Chang et al. obtained an 82%

reduction in the water permeability coefﬁcient with the

addition of 4 wt.-% of OMT (Na–MMT modiﬁed with an

ammonium salt of hexadecylamine) in a polyimide (PI)

nanocomposite ﬁlm, as compared with the same PI ﬁlm

without nanoclay, both prepared by solution casting.

In the case of the natural rubber latex prepared by

casting, the addition of 2 wt.-% of natural sodium MMT

yielded a reduction in oxygen permeability of about 66%

compared with the unﬁlled material (54). Liang et al. (55)

discussed a reduction in nitrogen permeability of ca. 22%

in an isobutylene–isoprene rubber (IIR) containing 5 wt.-%

of OMT (MMT modiﬁed with butyl alcohol).

Concerning poly(vinyl-chloride) (PVC), Zhu et al. (56)

reported the barrier properties to O

and H

O of nano-

composites of PVC prepared by melt mixing as a function

of nanoﬁller content. The PVC nanocomposites containing

3 wt.-% of SiO

led to an oxygen permeability reduction of

about 40% and for the case of water of 45% compared with

the same unﬁlled material.

In the case of epoxy resins, Tsai et al. (57) reported the

preparation of novel nanocomposites of an epoxy resin

containing zirconium phosphate/phosphonate derivative

(Zr-P). The oxygen permeability decreased by about 59%

and the nitrogen permeability decreased by about 53% for

the nanocomposite containing 5 wt.-% of Zr-P compared

with the unﬁlled material.

For polyurethanes, Choi et al. (58) claimed to have

obtained a reduction in the oxygen permeability of about

41% for the PU containing 5 wt.-% of OMT (clay modiﬁed

with hydroxyl end group) obtained by a ﬁlm-casting

method. Osman et al. (59) reported a reduction of the

oxygen transmission rate of about 30% and a reduction in

the water permeation of 50% for a polyurethane (PU)

containing 3 vol.-% of OMT [the inorganic cations of the

MMT were exchanged with the organic ammonium ion

bis(2-hydroxyethyl) hydrogenated tallow ammonium].

810 NANOCOMPOSITE PACKAGING MATERIALS

Regarding polysulfones (PSF), Yeh et al. (60) developed

and characterized PSF containing OMT (MMT modiﬁed

with intercalating agent dodecylamine) nanocomposites,

which were prepared via a solution dispersion method.

Compared with the neat PSF, membranes of nanocompo-

site PSF materials containing low nanoclay loading (3 wt.-

%) showed about 30% and 72% reductions in H

O and O

permeability, respectively.

Even though many studies in the literature report about

barrier enhancements in polymer and biopolymer matrices,

it is clear from the modeling results (see Figure 1) that the

expected improvements are not yet experimentally at-

tained or reproducible. This is the result of lack of (a)

complete exfoliation of the nanoﬁller, (b) good compatibility

between the ﬁller and matrix, and/or (c) good puriﬁcation

and appropriate selection of raw materials and surface

modiﬁcations. In general, there is still a need for a deeper

understanding of the composition-structure-processing-

properties relationships in nanoclay-based nanobiocompo-

sites both at a laboratory and at an industrial scale. More-

over, because most extensive studies related to nanoclays

have been carried out using few nanoclay grades (based

mostly on MMT), in many cases from the same commercial

supplier, there is still a lot of room for variation and

maturation in the nanoclay-based composites area.

Most applications of nanocomposites in plastics have

made use of laminar clays and in some cases of carbon

nanotubes. However, other types of reinforcing elements

such as biodegradable ﬁbers obtained by electrospinning

are promising in several application ﬁelds (61, 62). The

electrospinning method is a simple and versatile technology

that can generate ultraﬁne ﬁbers, typically in the range

from 50 to 500 cm

, of many materials . The produced ﬁbers

have large surface-to-mass ratios (up to 10

higher than a

microﬁber), excellent mechanical strength, ﬂexibility, and

lightness. The obtaining procedure is not mechanical but

electrostatic and is applied to the polymer in solution or to

polymer melts. As a result of the latter, it is a suitable

technique for the generation of ultra-ﬁne ﬁbers of biode-

gradable materials, which are in general easy to dissolve. It

has been reported that around 100 different polymers

(including biopolymers) and polymer blends have been

nanofabricated by electrospinning. Even though signiﬁcant

body of literature report about the characterization of

nanoﬁbers, not many studies exist that examine the proper-

ties of nanocomposites of materials containing these ﬁbers.

One of the most interesting aspects of the electrospinning

methodology is the possibility of the incorporation of various

substances, including ﬁllers such as clays as well as bioac-

tive agents in the electrospun ﬁbers. This advantage has

already been considered in the controlled release of bioac-

tive principles in the pharmaceutical and biomedical ﬁelds

(62) and can also be applied to the controlled release of

active and bioactive food-packaging applications (3).

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NANOTECHNOLOGY AND PACKAGING

SUSAN SELKE

Michigan State University

School of Packaging, East

Lansing, Michigan

WHAT IS NANOTECHNOLOGY

In recent years, a lot of public attention has been given

to nanotechnology, with both claims and fears making

headlines. What may easily be obscured in all the hype

is just what nanotechnology is and isn’t. The simplest

deﬁnition of nanotechnology is that it is technology

involving structures with one or more dimensions that

lie between 1 and 100 nanometers (1 nm = 0.000000001

m). It has been discovered that at these very small sizes,

particles of ‘‘ordinary’’ materials can have properties that

are signiﬁcantly different from those the material has

when its particles are larger. Among these properties

can be differences in reactivity, color, the ability to move

through barriers, and so on. The underlying reason for

the change in properties is that atomic properties such

as quantum effects and wave-particle duality that do

not have observable effects at larger scales do have

profound impacts on behavior at these tiny sizes.

Furthermore, nanoscale materials have much larger sur-

face areas than similar amounts of larger particles, so

their potential for interaction with surrounding materi-

als is much greater.

Some effects associated with nanoscale structures have

been known for a very long time. Medieval stained glass

windows and ancient pottery get some of their colors from

nanopigments. Gold particles, for example, can impart

an orange color, a red color, or even a greenish color,

depending simply on the size of the particles incorporated.

Other materials that we use have always had ‘‘particles’’

in this size range, so they behave as we’ve expected them

to. For example, antioxidants in plastic ﬁlms, sugar in

water solution, and plasticizers in PVC blisters have

components that are nanoscale in size. The key difference

in the ‘‘nanotechnology’’ that is getting all the attention is

related to materials that we normally use at large scale,

but that have different properties when their particle size

is reduced.

Perhaps in part because of this, some deﬁnitions of

nanotechnology have tried to require more than just size.

A common approach has been to require that to be ‘‘true’’

nanotechnology, the materials have novel properties and

functions because of their small size, and/or that they

involve the ability to control or manipulate materials on

an atomic scale. Of course, one of the problems with such a

deﬁnition is the vagueness of ‘‘novel.’’ Does something

cease being nanotechnology once we become accustomed

to it? Even controlling or manipulating materials on an

atomic scale isn’t really new. All chemical reactions in-

volve such phenomena to some extent.

To further complicate the issue of deﬁnitions, not all

products that use nanotechnology explicitly state that

they do so, and some products claim to use nanotechnology

when they really do not. Furthermore, some products use

nanotechnology in manufacturing, but there are no na-

noscale structures in the ﬁnished product. So, it is under-

standable that there remains a degree of vagueness about

what is and is not nanotechnology, in packaging as well as

in other ﬁelds.

The ofﬁcial U.S. deﬁnition of nanotechnology comes

from the National Nanotechnology Initiative: ‘‘Nanotech-

nology is the understanding and control of matter at

dimensions between approximately 1 and 100 nan-

ometers, where unique phenomena enable novel applica-

tions. Encompassing nanoscale science, engineering, and

technology, nanotechnology involves imaging, measuring,

modeling, and manipulating matter at this length scale.’’

This deﬁnition importantly recognizes that 100 nm is not

a ﬁrm size line between ‘‘nano’’ and ‘‘not-nano.’’ Also, it is

recognized that nanoscale materials and effects are not

limited to synthetic substances, but are also found in

nature. For example, spider silk is naturally reinforced

by nanoscale crystals (1).

NANOTECHNOLOGY IN PACKAGING

Nanotechnology has applications in a vast array of ﬁelds.

Our discussion here will be limited to those applications

that are relevant to packages or packaging materials. By

all accounts, this is a signiﬁcant sector of packaging, and

it is predicted to grow rapidly. A 2005 study by Helmut

Kaiser Consultancy (2) reported that there was $860

million in U.S. sales of nano-related food and beverage

packaging in 2004, with more than 250 nano-packaging

products in the market. Furthermore, the study predicted

that nanotechnology would affect 25% of the food packa-

ging business over the next decade, reaching a value of

$20.4 billion by 2010. Much of this is expected to be for the

NANOTECHNOLOGY AND PACKAGING 813

food products themselves. Packaging applications men-

tioned included improvement in material performance

and extension of product shelf life, along with special

features such as antimicrobial action, tailored permeabil-

ities, and embedded sensors. A 2007 update reported that

the 2005 ‘‘nano-featured food packaging’’ market had a

value of $1.1 billion and was anticipated to reach $3.7

billion in 2010. Furthermore, the prediction was that the

‘‘nano-bio-info convergence’’ would inﬂuence over 40% of

the food industry by 2015 (3).

Similarly, a 2004 report from Pira (4) reported that

beneﬁts of nanotechnology in packaging included (a)

longer shelf life, (b) improved high-temperature perfor-

mance permitting hot ﬁll, (c) thinner ﬂexible packaging

ﬁlms, (d) functionality of various types, including anti-

counterfeit, antitamper, and antimicrobial, (e) various

types of sensors, and (f) integrated power for features

such as self-healing containers and intelligent tags. The

study also mentioned nano barcodes for track and trace

and sensing, use of nanotechnology in the production

process for paper, nanoscale pigments for inks, the use of

nanomaterials to obtain colors without requiring dyes or

conventional pigments, and electronic displays based on

nanomaterials that provide the quality of paper.

While some of these early studies likely overplayed the

impact and usefulness of nanotechnology in packaging,

there are signiﬁcant applications where nanotechnology

provides real advantages. In this article, we will group

these current and potential applications into three main

categories: barrier, improved mechanical performance, and

communication/sensing, with a fourth category of miscel-

laneous for applications that do not readily ﬁt within these

three. Please note that the discussion that follows is meant

to be illustrative, rather than inclusive, because the num-

ber of applications of nanotechnology in packaging greatly

exceeds the space available for discussion, and new uses,

materials, and systems arise constantly.

Barrier

Use of nanomaterials to improve the barrier of packaging

materials, generally plastics, was one of the earliest

applications to be tagged with the ‘‘nano’’ identiﬁer. It is

also one of the areas where deﬁnitions are fuzzy. Metal-

lized ﬁlm, for example, is not generally labeled as ‘‘nano’’

yet the aluminum thickness is generally 40–50 nm, so it

certainly could be so categorized. The primary function of

the aluminum layer is to improve barrier, often especially

to oxygen.

Similarly, SiO

coatings, such as on ﬁlm or on PET

bottles, generally have a thickness of 40–60 nm. This

glass-like coating, usually inside but sometimes outside

the bottle, also acts to improve barrier. Aluminum oxide

coatings are also used to improve barrier, and they are

applied at nanoscale thickness. Usually, these coatings are

not marketed as nanotechnology.

In contrast, the amorphous carbon systems, also used as

coatings to improve barrier, have been marketed as nano-

technology in some cases. Sidel’s Actist system applies a

layer of 20–200 nm of amorphous carbon to the inside of

PET bottles, Actis Litet provides a thinner layer. Kirin and

Mitsubishi Shoji Plastics implicitly claim nanotechnology

for their ‘‘Plasma Nano Shield’’ system, which provides a 20

to 40-nm-thick layer of amorphous carbon. This system was

previously called ‘‘Diamond-Like-Coating’’ (5).

Most often, nanotechnology for barrier improvement is

associated with the development of nanoclay composite

structures. These are based on various types of layered

clays, most commonly montmorillonite. When properly

formulated and processed, the clay is exfoliated, splitting

into platelets that are typically about 1 nm thick and 70–

2000 nm in length and width. The clay particles are not

mobile in the polymer, and they present a torturous path

for the diffusion of gases, which cannot pass through the

clay platelets. It is reported that 10% clay can cut permea-

tion rates by as much as 75% (6, 7).

There are two major U.S. nanoclay suppliers. One is

Nanocor (8), which produces the Nanomer brand for use

with nylon resins, polyoleﬁns, and other products. The

other is Southern Clay Products (9), which markets under

the Cloisite brand.

Mitsubishi Gas Chemical markets Imperm Nt PET

bottles, ﬁlms, and thermoformed containers that contain

Nanocor nanoclay. The barrier layer is M9t, which is a

nanocomposite with clay platelets in MXD6 nylon (10–12).

Similarly, Honeywell markets Aegis resins for multi-

layer PET bottles. These resins, available with and with-

out oxygen scavenger, are also based on nanoclay from

Nanocor. The clay particles are said to conduct the oxygen

molecules to speciﬁc oxygen-capture sites in the nanocom-

posite (11–13).

Southern Clay Products’ Cloisite nanoclay has been

used to enhance the barrier of ethylene vinyl alcohol

(EVOH) for long-shelf-life packaging, in a joint develop-

ment effort by the U.S. military, NASA, and Triton Sys-

tems, Inc. (11, 12).

Alcoa ﬁled for a patent on coextruded barrier liners for

plastic bottle caps that contain a nylon 6/nanoclay compo-

site, along with oxygen scavengers, to protect oxygen-

sensitive products such as beer or juice. The liners are

reported to be better than other barrier materials at very

high humidities (11).

Other nanominerals can also be used to improve bar-

rier or other performance properties. In 2006, Nanova,

LLC was listed as a supplier of nanotalc and nanocalc,

which consisted of magnesium silicate and calcium carbo-

nate, respectively (14). However, as of late 2008 the

company was evidently no longer in business.

The type of nanomaterial used to improve barrier is not

always identiﬁed. Kuraray (Japan) markets a retort food

packaging ﬁlm, Kuraristert, which is reported to contain

a 1-micron-thick barrier layer on both sides of a PET ﬁlm.

The barrier layer is a composite containing inorganic

nanoparticles. The result is a highly transparent ﬁlm

that can be printed without surface treatment. The coat-

ing is reported to be highly durable, maintaining barrier

properties even if stretched or ﬂexed during processing.

The barrier is also not much affected by moisture. A nylon-

based ﬁlm, Kuraristert N, is also available and offers

improved retention of mechanical properties after retort-

ing, compared to conventional nylons. The materials are

being marketed as an alternative to foil laminates in

814 NANOTECHNOLOGY AND PACKAGING

pouches for retorted foods, as well as for medical packa-

ging and lidding ﬁlm. Their microwaveability and the

ability to use metal detectors on the packaging line are

mentioned as two signiﬁcant advantages (15).

Combustion chemical vapor deposition (CCVD) is used

to produce 30 to 60-nm-thick barrier coatings on PET

bottles in the nGimat system (formerly MicroCoating

Technologies). The company also produces nanopowders

and devices. The company’s catalog in late 2008 listed 7

single-oxide nanopowders, 15 bi-metal oxides, 9 multi-

metal oxides, 2 phosphates, 2 hydroxyapatites, and 7

metal and metal-alloy nanopowders, along with the po-

tential for special orders for others not listed. Barrier

coatings for packaging are targeted at improving carbon

dioxide and oxygen barrier in PET containers and PET/

polyoleﬁn ﬁlms. The coatings are applied using nGimat’s

proprietary Nanomiser t device. The resultant barrier

layers are 30–60 nm in thickness and are transparent.

Barrier performance is reported to be comparable to

metalized ﬁlm. The company claims that the shelf life of

20 oz PET bottles for carbonated beverages can be ex-

tended from the 10 weeks common for uncoated bottles to

30 weeks (16).

Researchers have even hypothesized the use of nano-

technology to control the permeability of a packaging

system by using a molecular ‘‘switch’’ such as a change in

pH to open or close pores in a nanoporous ﬁlm layer (17).

Improved Mechanical Performance

Addition of nanoclay also increases the stiffness and

strength of polymer materials. While most applications

speciﬁcally targeting improved mechanical performance

are in products, rather than packages, PolyOne was

reported in 2004 to be nearing commercialization of their

nanoclay-reinforced PP, Maxxam LSTt, in pallets and

dunnage (9). The 2008 information from the company

indicates that two grades of nanoclay-reinforced PP, now

called Nanoblendt LST, are currently available (18).

Addition of nanoscale nucleating agents in foams re-

sults in smaller cell size and higher cell density, along with

improving the performance of the foam (11). Researchers

have also investigated the use of nanotechnology to pro-

duce foams that can be tuned to protect the contents from

speciﬁc frequencies (17).

Nanoscale silica and alumina particles have been found

to increase the scratch and abrasion resistance of coatings,

while not interfering with transparency (17).

Conductive polymers can be made by using carbon

nanotubes as a reinforcing ﬁller. The carbon nanotubes

also offer signiﬁcantly improved tensile strength and

greater thermal conductivity. Other carbon-based nano-

materials can provide similar improvement. Pyrograf

Products produces vapor-grown carbon nanoﬁbers that

are reported to cost signiﬁcantly less than carbon nano-

tubes, while providing similar beneﬁts (11). Fiber dia-

meters are 70–200 nm, and lengths are 50–100 microns.

The company does not currently list packaging applica-

tions as typical uses, but they do have potential (19).

Potentially even less expensive but with similar perfor-

mance are graphite nanoplatelets (11).

Addition of nanoscale inorganic alumina platelets to

plastics is reported to provide sizeable improvements in

rigidity, strength, and thermal stability. Some researchers

are currently working on development of synthetic alu-

mina platelets. Others are developing large organic mole-

cules in the form of rigid disks, with the idea that the

chemical properties can be adjusted by attaching func-

tional groups to the uniformly shaped disks (20).

Communication/Sensing

The communication category includes RFID tags incorpor-

ated into or onto packaging materials. While the tags

themselves are not nano-sized, nanotechnology is used

in manufacture of the embedded computer chips, and

RFID tags have been the target of groups outraged at

what they see as potential invasion of privacy (21). The

potential advantages of RFID for inventory control, track-

and-trace functionality, and so on, have led to a steady

increase in its use.

Other communication functions related to nanotechnol-

ogy include embedded sensors, to detect and/or record

changes in temperature, pressure, concentrations of che-

mical substances, shocks, vibration, and so on (17, 22).

One example is ‘‘nano ink’’ for detection of oxygen as an

indication of faulty packaging or product tampering.

The ink contains light-sensitive nanoparticles that are

‘‘switched on’’ with ultraviolet light. The UV light changes

the ink color to white, but it changes back to blue under

normal room light if oxygen is present. The dye is en-

capsulated in polymer, allowing it to be coated only on

surfaces. Coupled with MAP packaging, it will change

color if oxygen is present in the package but remain

colorless if oxygen remains absent (23).

Strathclyde University has developed a ﬁlm, based on

nanocrystalline semiconductor technology, that changes

color with oxidation of food inside the package. The color

and sensitivity can be changed, and the sensor is printable

on paper, plastic, or metal (12).

Some sensors are designed to detect substances other

than oxygen, such as ethylene, which is associated with

ripeness in many fruits. Sensors for fresh pears are

already marketed (24). Dublin University is developing

printable oxygen and carbon dioxide sensors. Sensors can

also be targeted at detection of microbial contamination or

toxins, resulting either from contamination or spoilage or

from terrorism. While not all of these sensors involve

nanotechnology

, many do

(22).

Detection of counterfeiting is the target of another

nanomarking system. IDGlobal has a forensic marking

technology in which packaging materials, including inks,

adhesives, and varnish coating, are tagged with nanomo-

lecular markers. Hand-held scanners then use spectro-

metry to read the chemical signatures imparted by the

nanomarkers. The information from the bar codes or RFID

tags is matched to the product signature in the marker.

Any disagreement may mean counterfeiting. Further-

more, the markers cannot be detected visually, and the

cost per label is less than one cent (25).

Similarly, Microtrace produces taggants that act as

‘‘ﬁngerprints’’ for product identiﬁcation and authentication.

NANOTECHNOLOGY AND PACKAGING 815

While the particles themselves are larger than nano, at 20

microns or larger, the structures within the particles are

often nanoscale. In fact, each encoded particle may contain

multiple nanotaggant technologies. Packaging applications

of the taggants include holographic and laminate ﬁlms and

shrink sleeves, among others (26).

5In 2001, researchers at Pennsylvania State University

reported the development of a method to form nano-sized

rods that could be used to produce nanoscale bar codes , which

could have use as covert anticounterfeit measures (17).

Another potential packaging application of nanotech-

nology is in printed electronics, which might be used, for

example, to provide displays on packages themselves (17,

27). In 2006, Pliant and NovaCentrix announced an alli-

ance to develop ‘‘unique ﬁlm and packaging solutions’’ by

combining Pliant’s ﬁlm expertise with NovaCentrix’s ex-

pertise in nanoparticle based inks and coatings (27). While

no recent reference to this alliance was found, NovaCen-

trix continues to develop printed electronics with potential

applications to advanced packaging systems (28).

Similarly, Siemens in 2005 developed color displays

that can be printed on paper or foil, suggesting that the

displays could be printed on packages to show information

about products or to show operating instructions. They

were even working on the ability to show moving pictures,

suggesting that it would be possible even to have small

computer games printed on packages, powered by printa-

ble batteries (29). It was anticipated that the ﬁrst displays

would become available in 2007, but no current reference

to them was found. However, the potential remains.

Other

Nanoclays are also being used to act as ﬂame retardants in

plastic materials. The nanoclay acts to form a char coating

that delays the polymer degradation and reduces the heat

output. It also increases the heat-distortion temperature

(11, 12).

Nanomaterials can also be used to provide antimicrobial

properties, for either packages or products. One common

system uses silver, either incorporated into zeolites or, in

the case of nGimat, deposited as a layer of ‘‘adherent silver

nanodots’’ which have antimicrobial activity against fungi

and bacteria in the presence of moisture (30). Other

systems use tethered bioactive compounds on surfaces,

such as peptides linked to amines that in turn were

attached to polyethylene (31). While these are not usually

tagged with the ‘‘nano’’ label, they are nanoscale in size.

Organic/inorganic nanocomposite coatings were devel-

oped as part of the EU Solplas project, which began in

2002, for antimicrobial activity as well as for barrier

improvement. This process uses aerosol-assisted atmo-

spheric plasma (AAAP) coating, in which the ﬁlm precur-

sor is introduced into a plasma adjacent to the substrate as

aerosol droplets. In the nano-alternative, an electrospray

process is used to decrease the size of the aerosol droplets

to the nanoscale, making the process more effective (31).

Nanopigments can be used to provide colors for packa-

ging materials without the use of conventional dyes or

pigments. The color is created by dispersion of uniformly

sized nanoparticles. Such nanopigments can also be used

in inks. A different type of nanomaterial, hyperbranched

polymers, can also be used to allow the same ink formula-

tion to be used to print on both polar and nonpolar

surfaces. BASF reportedly estimated that 10% of its ink

sales already involve nanotechnology (32).

Nanoscale additives have found use in papermaking.

Colloidal silica sols and cationic polymers have been used

in papermaking for many years, without being labeled

as ‘‘nano,’’ to aid in ﬁber retention and drainage

systems. Newer technologies use highly structured

nanoparticles for this purpose. Inorganic/organic hybrid

materials, mineral-based coatings, and polymer-encapsu-

lated nanoclay hybrids have all been used as paper coat-

ings (32).

One company is now marketing a nano-dispersed bio-

polymer that is intended to be a substitute for wax

emulsions for manufacturing water-resistant paper and

paperboard. TopChim claims its technology maintains the

water barrier of wax emulsions while improving repulp-

ability and recyclability. The biopolymer contains a

‘‘monodisperse distribution of nanoparticles with a regu-

lar shape’’ (33).

Similarly, the SustainPack project in the EU has a

goal of reducing the environmental impact of packaging

materials. One target is to increase the strength, including

wet strength, of ﬁber-based packaging materials through

the use of nanotechnology. Researchers are using nano-

clays modiﬁed with chitosan derived from crustacean

shells (34).

Greenbox Systems claims nanotechnology is the basis

of their Thermal-Lokt panels that provide ‘‘unparalleled

resistance to heat transfer’’ and permit the Greenbox

containers, with appropriate phase-change materials, to

provide temperature stability for extended periods for

sensitive products such as pharmaceuticals, blood, and

biologics. Details of the technology are proprietary, other

than it uses a carbon-silica material in a nanotechnology-

based process that results in an insulating capacity ten

times greater than typical foams (35).

Hybrid organic–inorganic nanocomposites based on

titania siloxane have been developed for glass bottles in

both Japan and Europe. The coatings provide a wide

variety of colors while improving the mechanical proper-

ties of the bottles. Furthermore, the bottles can be easily

recycled as uncolored glass (12).

Nanotechnology can also be used to release desired

substances. In 2003, researchers in the Netherlands were

working on use of nanotechnology to develop intelligent

packaging

in which a

bioswitch would send a command to

the package to release a preservative if the food within

began to spoil (17).

Researchers at the University of Leeds have worked on

incorporation of oils and oil-soluble sensors for fragrance

release, color change, and anticounterfeiting applications.

NaturalNano reported in March 2008 that the company

won an award for innovation from a Fortune 500 company

for its work in extended release capability. The desired

components are loaded into nanotubes, which release

the material slowly over time (36). While it appears that

the current target is consumer products, applications to

packaging are obvious.

816 NANOTECHNOLOGY AND PACKAGING

Nanotechnology can also play a role in something as

simple as starch-based adhesives. In 2004, EcoSynthetix

Inc. developed a nanostarch powder adhesive that has

advantages over conventional starch adhesives used for

manufacture of corrugated board. The 50 to 100-nm starch

particles in the EcoSphere adhesive could be used at lower

water content than conventional starch adhesives, mean-

ing that less energy and shorter times were needed for

drying, allowing ovens to run at lower temperatures (37).

Evidently the higher cost proved prohibitive, at least for

now, since the company no longer lists this adhesive as a

product. However, they do market a binder coating for

paper and paperboard, EcoSpheret 2202, that reportedly

consists of crosslinked biopolymer nanoparticles. The

company also manufactures a variety of pressure-

sensitive adhesives; it is not clear whether these also

involve nanotechnology (38).

On a more high-tech level, researchers at the Polymer

Centre at Shefﬁeld University have used nanotechnology

to develop an adhesive that can be turned on and off,

which they termed ‘‘molecular velcro’’ (17).

Regulations and Public Concern

Regulations for nanotechnology are still developing. Reg-

ulatory systems in place for ‘‘ordinary’’ materials are not

always appropriate for nanoscale versions of those mate-

rials. For example, for materials that are categorized as

GRAS (generally recognized as safe), the differences in

behavior that appear when size is reduced to the nanos-

cale may result in differences in toxicity. On the other

hand, if the migration or other safety testing was done

with materials already dispersed at the nanoscale, simply

applying the ‘‘nano’’ tag to the product or system obviously

does not change its properties.

An additional concern is that we are still early in

learning how nanoscale materials behave. We do not yet

have a full understanding of how variations in particle

size within the nanoscale, the presence of contaminants,

dispersal into the environment after use, and so on, affect

the behavior of the materials. In 2008, the Woodrow

Wilson International Center for Scholars Project on Emer-

ging Nanotechnologies, in collaboration with the GMA,

published an analysis of key regulatory issues for use of

nanomaterials in food packaging (39).

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