Permeation basics and their importance for the packaging industry · 2019. 12. 2. · Dr. Adolf Eugen Fick ... From metal can to flexible pouch . ASD Ambalaj Kongresi 2019 Uluslararası

ASD Ambalaj Kongresi 2019

Uluslararası Ambalaj Sanayi Kongresi

Permeation basics and their

importance for the packaging industry

Mr. Gabriele Benedetti, MSc

Area Sales Manager Europe - Permeation Testing Systems

MOCON, Business Unit of AMETEK



MOCON

Market leader for Permeation Testing Analyzers since 1963



Ingress / Egress

Scalping

Shelf Life

Flavor Loss

Oxygen

Water Vapor

WHY IS PERMEATION IMPORTANT?



http://www.mezzogiornoitalia.it/wp-content/uploads/cibo-avariato1.jpg



THE BALANCE BEETWEN FOOD AND PACKAGING WASTE

Minimum environmental impact

Minimum

material

OPTIMUM

PACK DESIGN

Increasing packaging

material weight or volume

Negative

environmental

impact

Overpackaging Underpackaging

Packaging waste

Food waste

Ultimately,

the customer

decides



Micro and macroscopic cracks

(d>1 µm)

Pinholes, pores and

microchannels (2 nm<d<1 µm)

Inter and intra-molecular

spaces

CIN <<< COUT

CAPILLARY FLOWS

ACTIVE DIFFUSION

PERMEATION OR DIFFUSION?



Dr. Adolf Eugen Fick

𝑭 = −𝑫𝝏𝑪

𝝏𝒙

WHAT IS PERMEATION?



Permeation rate

Transmission rate

𝒄𝒎𝟑 ∙ 𝒄𝒎

𝒎𝟐 ∙ 𝒅𝒂𝒚 ∙ 𝒂𝒕𝒎

𝒄𝒎𝟑

𝒎𝟐 ∙ 𝒅𝒂𝒚

PERMEATION BASICS



Steady State

Transient

p2 p1

C1 C2 𝑸 =

𝑨 ∙ 𝒕 ∙ 𝑫 ∙ 𝑪𝟏 − 𝑪𝟐

𝒍

l

𝑸 =𝑨 ∙ 𝒕 ∙ 𝑫 ∙ 𝑺 ∙ 𝒑𝟏 − 𝒑𝟐

𝒍

Q = quantity of permeant transferred

through the material

A = area of the sample

t = time

D = Diffusion coefficient

C = permeant concentration

l = thickness

𝑪 = 𝑺 ∙ 𝒑

S = Solubility coefficient

p = gas partial pressure

SOLUTION-DIFFUSION MECHANISM



0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 2 4 6 8 10 12 14

No

rmal

ize

d F

lux

F/F ∞

1/X = 4Dt/l2

THEORETICAL PERMEATION CURVE



Top of cell

Bottom of

cell

Flush Gas In Flush Gas Out

Test Gas In Test Gas Out

Carrier Gas In Carrier Gas + Test Gas

Out to sensor

Film test sample

O-rings

Flush channel

0

𝑱 = 𝑫𝑪𝟏 − 𝑪𝟐

𝒙



SPERIMENTAL PERMEATION CURVE

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 0,5 1 1,5 2

No

rmal

ize

d F

lux

F/F ∞

1/X = 4Dt/l2

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 0,5 1 1,5 2 2,5 3

No

rmal

ize

d F

lux

F/F ∞

1/X = (4D/l2)t

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5

No

rmal

ize

d F

lux

F/F ∞

1/X = (4D/l2)t

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 1 2 3 4 5 6 7

No

rmal

ize

d F

lux

F/F ∞

1/X = (4D/l2)t

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 1 2 3 4 5 6 7 8 9

No

rmal

ize

d F

lux

F/F ∞

1/X = (4D/l2)t

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 2 4 6 8 10

No

rmal

ize

d F

lux

F/F ∞

1/X = (4D/l2)t

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 2 4 6 8 10 12

No

rmal

ize

d F

lux

F/F ∞

1/X = (4D/l2)t

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 2 4 6 8 10 12 14

No

rmal

ize

d F

lux

F/F ∞

1/X = 4Dt/l2

THEORETICAL PERMEATION CURVE



POLYMER CHARACTERISTICS

Atomic structure, Density, Crystallinity, Molecular

weight, Glass transition, Crosslinking

ENVIROMENTAL CONDITIONS

Relative humidity, Total pressure, Difference of partial

pressure, Temperature, Kind of gas

TECHNOLOGIC FACTORS

Plasticizers, Fillers, Residual solvents, Orientation,

Polymer blend, Copolymers and Composite

structures, Surface, Thickness

FACTORS AFFECTING PERMEATION



PERMEATION IS IMPACTED BY

MATERIAL PROPERTIES



CHEMICAL ADDITIONS TO POLYMER

BACKBONE



CRYSTALLINITY

15 x 15 micron AFM image showing

nucleus and lamellar crystallites.

The partial crystallization of the material modifies both the free

volume (i.e. Solubility S0) and the frequency of the molecular

motions (i.e. Diffusion Coefficient D) and therefore also the

permeability coefficient P



• The degree of packing, crystallinity, and orientation of the molecular

chains affect barrier properties

• Close packing and/or high crystallinity results in low free volume

and better barrier.

• Orientation results in better barrier by creating a more tortuous

diffusion path.

POLYMER MORPHOLOGY O2

PERMEATION* COMMENTS

PET (poly(ethylene terephlate)) 10% crystalline 10.0

PET 50% crystalline 5.0 Higher crystallinity reduces the available sites for permeation

PET 50% crystalline and oriented

3.0

Crystallinity and orientation produces more tortuous path for permeation

* cm3∙mil/(100 in2∙day∙atm)

CRYSTALLINITY



AGING

Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)

Variation of the

oxygen permeation

with the aging time



Effect of permeant size: diffusion rate decreases

as permeant size increases.

Molecule Diameter (nm) Molecule Diameter (nm)

𝑯𝒆 0.26 𝑪𝟐𝑯𝟒 0.39

𝑯𝟐 0.289 𝑿𝒆 0.396

𝑵𝑶 0.317 𝑪𝟑𝑯𝟖 0.43

𝑪𝑶𝟐 0.33 𝒏 − 𝑪𝟒𝑯𝟏𝟎 0.43

𝑨𝒓 0.34 𝑪𝑭𝟐𝑪𝒍𝟐 0.44

𝑶𝟐 0.346 𝑪𝟑𝑯𝟔 0.45

𝑵𝟐 0.364 𝑪𝑭𝟒 0.47

𝑪𝑶 0.376 𝒊 − 𝑪𝟒𝑯𝟏𝟎 0.50

𝑪𝑯𝟒 0.38

GAS SELECTIVITY




ENVIRONMENTAL CONDITIONS



ENVIRONMENTAL EXPOSURE



TEMPERATURE

LDPE d=50 µm

Time (sec)

Perm

eab

ilit

y (

cm

3/(

m2∙d

ay∙b

ar)

TRANSIENT

STEADY STATE



TEMPERATURE

0

100

200

300

400

500

600

0 50 100 150 200

WV

TR

(m

g/(

m2∙d

ay)

Time (h)

WVTR at different temperatures

85°C

50°C

23°C



TEMPERATURE

• Permeation rates typically change 5-7% per degree C

• For every 10°C increase in temperature, Transmission Rate doubles

• Crucial errors can occur when testing at elevated temperatures close to Tg.

• Package testing is of special concern due to temperature variations in ovens.

Gas T

ran

sm

issio

n R

ate

Temperature



EFFECTS OF HUMIDITY ON OTR

Polymer 0%RH 100%RH

*K. Cooksey, IMPORTANT FACTORS FOR SELECTING FOOD PACKAGING MATERIALS BASED ON PERMEABILITY

(10∙1011 ml∙cm/(cm2∙sec∙cmHg ) analyzed at 25°C

Nylon 6 0.06 0.3

PVA 3.3 9.0

ABS 0.06 0.06

HDPE 6.6 6.6

LDPE 28.8 28.8

PVOH 0.0006 1.5

Uncoated Cellophane

0.0078 12.0



EFFECTS OF HUMIDITY ON OTR

0,001

0,01

0,1

1

10

0 20 40 60 80 100

O2 P

erm

ea

tio

n

(cm

3∙m

il/(

100

in2∙d

ay∙a

tm)

RH (%)

NYLON 6 @ 23°C

SELAR® PA @ 23°C

NYLON MXD6 @ 23°C

44% EVOH @ 20°C

30% EVOH @ 20°C

SELAR® OH PLUS @ 23°C

*Web Coating & Handling Conference 2014 Europe, 10 June 2014




TECHNOLOGIC FACTORS



ADDITIVES

PVC Poly (vinyl chloride)

Material state Pure, rigid

PVC Plasticized,

soft PVC O2 Permeation rate (cm3∙mil)/(100in2∙day∙atm)

8 150

• Additives used in manufacturing or in modifying the

polymer can affect permeation.

• Depending on the upon the chemical nature, as well

as the manner which the additive is blended, the

barrier can be either enhanced or reduced.



SURFACE EFFECT

• The nature of the surface can determine the permeability as much as the polymer bulk.

• An example is hydrocarbon permeation through polyethylene:

– Polyethylene polymer is very nonpolar and thus a very poor barrier to nonpolar permeants such as hydrocarbon liquids.

– By treating the surface with fluorine gas, the fluorine adds on to the chains at or near the surface and by virtue of its bulk and polarity prevents hydrocarbon liquids from entering the polymer



MATERIAL THICKNESS

Thinner samples = higher transmission

rates

When thickness is doubled, it takes 4X

longer to reach equilibrium

𝑮𝑻𝑹 ∝𝟏

𝒍

𝒕 = 𝒍𝟐

𝟔𝑫



IMPORTANCE OF TESTING WHOLE

PACKAGE



TESTING THE WHOLE PACKAGE



TESTING THE WHOLE PACKAGE

[O2](g) 20.9% (room air) 100%

OTR

Equilibrium Time

[O2](g) 20.9% (room air) 100%

OTR 0.0012 cm3/(pkg∙day) 0.0052 cm3/(pkg∙day)

Equilibrium Time

[O2](g) 20.9% (room air) 100%

OTR 0.0012 cm3/(pkg∙day) 0.0052 cm3/(pkg∙day)

Equilibrium Time 4 days 4 days

𝑭 = −𝑫𝝏𝑪

𝝏𝒙



CASE STUDIES



COOKIE PACKAGE CASE STUDY

Ship to Film A

(Excellent)

Film B

(Good)

Film C

(Fair)

Testing

Conditions

Northern

Europe PASS PASS PASS

15°C

30% RH

South

Korea PASS PASS FAIL

23°C

50%RH

Vietnam PASS FAIL FAIL 30°C

85%RH

Apply average destination environmental conditions to test

conditions



FAILED HAM PACKAGE CASE STUDY

• Ready-to-eat ham

• Packed in clear film pouch

• Ham spoiled before anticipated shelf life

• Packaging film delaminated



Ham product

• Measured 75% RH in headspace

Packaging Material

• PE/Nylon/sealing layer

OTR

• Vendor tested: 0.05 cm3/(pkg·24h) at 4°C and 0%RH

• MOCON tested: 0.4 cm3/(pkg·24h) at 4°C and 75% RH

FAILED HAM PACKAGE CASE STUDY



HEALTH SUPPLEMENT PACKAGING

CASE STUDY



Sample WVTR (g/(pkg·day))

W-1 0.0070

W-2 0.0089

W-3 0.0099

W-4 0.0042

W-5 0.0107

W-6

(no cap) 0.003

0

0,002

0,004

0,006

0,008

0,01

0,012

W-1 W-2 W-3 W-4 W-5 W-6 (no cap)

WV

TR

(g

/(p

kg

·da

y))

Different liner in W-1 to W-5

Bottle WVTR results

HEALTH SUPPLEMENT PACKAGING

CASE STUDY



INFANT FORMULA CASE STUDY

From metal can to flexible pouch



INFANT FORMULA CASE STUDY

ID WVTR Film

g/(m2·day)

A <0.005

B <0.005

C <0.005

D <0.005

E <0.005

WVTR Package

g/(pkg·day)

0.0021 (met)

0.0010 (foil)

0.0022 (met)

0.0034 (met)

0.0015 (foil)

Pouch test results (23°C, 100%RH)



TARGET SHELF LIFE (BALANCE)

• Target shelf life

of 300 days

• Product fails at

0.7 total grams

of moisture

ID WVTR Package

g/(pkg·day)

Total Days

Shelf Life

B 0.0010 700 days

A 0.0021 333 days

D 0.0034 205 days

Over

Packaging

700 days

Under

Packaging

205 days

Target

Packaging

333 days



Please, after the conference, send your possible

questions to [email protected]

Documents

Permeation basics and their importance for the packaging industry · 2019. 12. 2. · Dr. Adolf Eugen Fick ... From metal can to flexible pouch . ASD Ambalaj Kongresi 2019 Uluslararası