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Nano-layer Effects in Blown Barrier Films (part 2)

Henry G. Schirmer, BBS Corporation, Spartanburg, SC

Tom Schell, Curwood, Inc., Oshkosh, WI

Dr. Mark Pucci, Soarus LLC, Arlington Heights, IL

Dr. Ananda M. Chatterjee, Chatterjee Consulting LLC, Missouri City, TX

Abstract

First heat DSC analysis of blown barrier films containing

EVOH in nano-layer form has shown a lower crystalline

melting point than on reheat indicating subtle changes in

the lamella thickness that are consistent with a lower fold

period. Stretch orienting these nano-layer barrier films

especially containing alternating layers of N6 with EVOH

processed extremely well between the Tg of N6 and

EVOH and 100 C - well below the melting points of both

materials. Since these films were so highly deformable at

these low temperatures there is the implication that they

are also easily thermoformed as well. Barrier property

measurements have been made defining all of these new

films.

Introduction

The newly invented Layer Sequence Repeater (LSR) has

produced coextruded blown films that have internal

structures containing nano-layer bundles within a matrix

of micro-layers. These new films are showing certain

property differences that can’t be obtained from standard

micro-layer coextruded blown films.

This is the third paper in a series given at PO 2009 and PO

2010 (ref. 12 & 13) about the observed effects that nano-

layers have on blown film properties. The first paper

showed that nano-layers consisting of brittle materials

such as EVOH and COC produced films that were less

brittle than the single layer controls. The second paper

showed that nano-layers of EVOH with COC produced

barrier films with no enhanced barrier properties either

wet or dry. In fact the barrier properties appeared to be a

magnitude poorer than expected. This paper continues that

work in order to try to explain these anomalies.

The negative barrier performance anomaly reported in the

second paper was contradicted by a more positive one

reported in the first paper. This showed that Gelbo flexed

nano-layer films containing EVOH actually increased in

barrier performance after this abusive test.

An obvious explanation for the loss of barrier was that

pinhole voids developed within the EVOH nano-layers.

However, pinhole defects did not fit the Gelbo flex test

results. Another thought was that air quenching EVOH

nano-layers might have produced a more amorphous like

crystal. If nano-layers of EVOH were truly quenched to a

less densely packed crystal structure, this could have

reduced the overall degree of tightly packed crystals to a

point where the barrier was poorer. This explanation

would be consistent with the Gelbo flex results where a

more tightly packed crystal pattern may have been formed

by the work input of severe flexing. No one initially

thought that a resin mix-up might be responsible for the

poorer barrier results as was discovered here. This paper

will address these issues by measuring the crystalline

behavior of both test and control films using a Differential

Scanning Calorimeter (DSC) and relating that to barrier

and orientation results.

PAST HISTORY

US Patent 4,064,296 issued in 1978 teaches that EVOH

can be biaxally oriented at 100C or below when it is 2

mils thick and quenched in ice water as part of a 20 mil

thick EVA encapsulated coextruded tubing. This clearly

was the first indication that the crystalline structure was

altered by a rapid quench.

Polymers in a highly packed crystalline state simply

cannot be stretch oriented. Either most of the crystal

structure must be melted or it must be quenched to a more

loosely packed or amorphous state. The low temperature

orientation at 100C ruled out partial melting because the

orientation temperature would have to have been around

185C to melt the crystal structure. Instead, quenching to a

lower ordered crystalline state seems to be the only way to

account for the low orientation temperature of the above

patent. Since the Tg of EVOH is about 60C then any

temperature above this point would be suitable for

orientation if crystalline structure did not impede

stretching.

A polymer need not be totally amorphous for stretching to

be accomplished. However, any residual crystallinity must

be deformable and consistent with a loosely packed crystal

structure. Perhaps an analogy is the comparison of snow to

ice. Snow can be deformed easily while ice cannot.

Discussion

1. Definition of terms:

The Modular Disk Die has produced films containing 25

and more micro-layers independently of the LSR. While it

is generally true that as the number of micro-layers

increases, the individual layer thickness decreases for a

given total film thickness, the thickness of each of the

structural micro-layers are generally all in the same order

of magnitude. This doesn’t preclude that some micro-

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layers may contain the same material to make what would

appear to be fewer and thicker micro-layers. The reason

for doing this might be to simply gain increased output or

to gain some other processing attribute.

The Layer Sequence Repeater (LSR) operates as an

independent unit within a Modular Disk Die and inserts

nano-layer bundles within the matrix of micro-layers.

These are truly an order of magnitude thinner than the

surrounding micro-layers. So this definition of nano-layers

will be used here to differentiate nano-layers from micro-

layers and the difference will become very apparent from

the microphotographs shown in this paper.

2. Proprietary Multi-layer Blown Film Equipment:

MODULAR DISK DIE: Picture 1 shows a 25 micro-

layer barrier film being made from a 2x scale 18” 25-cell

Modular Disk blown film production die. Picture 2 shows

the internal micro-layer structure. In this case the 25

micro-layers were combined to make a “pseudo”-7 layer

PE/adh./N6/EVOH/adh./PE barrier film that is the

standard barrier film structure for the industry and is an

example of creating thicker and fewer micro-layers for the

sake of increased output and lower melt temperature.

Picture 1 - 18” 25 micro-layer Modular Disk Die

functioning to make 25 micro-layer barrier films.

Of course, while this in itself is useful, it is the opposite

end of the micro-layer spectrum. Noteworthy to mention is

that the same material that was used in the above micro-

layers also could be incorporated into nano-layers to make

fewer visible nano-layers. In some cases nano-layers from

one material alone may alter the physical properties from

differential melt shear conditions within the LSR and the

resulting nano-layers having higher melt orientation. So it

should be clear that there are many variations that can be

performed by using so many layers whether they are micro

or nano-layers.

While the “7 layer” micro-layer barrier film shown in

Picture 2 was made from the above 2x scale up of the lab

die, the coextruded nano-layer containing films reported

here were made using only the 1x lab die version. We

have had no reason yet to scale up the yet to be patented

LSR. That may come sometime in the future when the

need may arise.

Picture 2 - Standard Barrier Film thickness front and back

of the bubble at 2.55 mil each

As said earlier, the Layer Sequence Repeater (LSR) is a

separate device inserted within the module of a Modular

Disk Die. These coextruded films show an entirely

different layer structure from the micro-layer films; yet the

appearance of the bubble remains as if they were absent

(See picture 4 containing 75 nano-layers). However, some

more subtle processing differences have been observed.

For example, greater bubble stability has been witnessed

in some cases.

LAYER SEQUENCE REPEATER (LSR): The Layer

Sequence Repeater (LSR) was designed to repeat layers of

different materials in any desired sequence. It

compliments the Modular Disk Die technology and fits

within a module as an integral part or it may be used also

as a separate module. This is a desirable feature when

making rapid changes from say 25 to 75 nano-layers

because the entire module need not be disassembled.

The LSR is also capable of running the same material in

adjacent nano-layers as described above for micro-layers.

So not only can the material sequence be varied but the

FRONT SIDE PE+adhesive Nylon/EVOH/Nylon PE + adhesive PE + adhesive Nylon/EVOH/Nylon PE + adhesive BACK SIDE

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layer thickness can also be varied on the same or different

materials. For example a sequence might be as follows:

C/B/B/B/C/C/B/C/BBBB/C etc.

A typical bundle of 75 nano-layers within a matrix of 8

micro-layers 4 on each side is shown in picture 3. Note

that each of the 3 micro-layers on both sides used the same

polyethylene to make what appears to be a single layer.

Here you see that nano-layers are truly a magnitude

thinner than micro-layers.

Picture 3 - 75 Nano-layers in a matrix of 8 Micro-layers

Sample 12-2 Total Thickness = 3.2 mil

Picture 4 shows that blowing a 75 nano + 8 micro-layer

film in the lab was very similar to blowing single layer

films in production. However, like any other coextruded

film there are a myriad of coextrusion problems that may

be encountered and there were some new ones we

encountered in this work either because of extrusion rate

or materials used. True to its very thin layer nature, nano-

layer melt instability is often seen as very small chevrons.

Because there were no problems scaling up a lab die 2x,

we believe that an LSR can be scaled up with similar

results expected. So we believe that the films made for this

study should be applicable to a production environment.

To sum it up, nano-layer thickness is defined not by actual

thickness but by relative thickness when compared to the

surrounding micro-layer matrix. Further, nano-layers and

micro-layers both can use the same materials but nano-

layers will usually appear as a bundle of thinner layers

within the thicker micro-layer matrix.

Picture 4 - Laboratory 4” Upward Blown Film Line

Used to make Sample 12-2

3. Experimental Procedure:

3a. TEST FILM STRUCTURES

In order to address the possible barrier anomalies and the

ideas of causes, more wet & dry O2 barrier tests as well as

DSC analysis were made on the nano-layer test films.

These included the following test film examples.

Extruder/layer relationship=

A / D / {C/B/C/…25 nano-layers…B/C/B/C} / D / A

Samples 11/33 & 11-39=

LDPE/adh/{EVOH/COC.... COC/EVOH}/adh/LDPE

25 nano-layers

COC was used above only because it was a completely

amorphous resin and presumably would not hide or alter

crystalline structure of the EVOH during DSC analysis. It

did have very poor adhesion to EVOH and in some new

test structures was replaced with N6.

Samples 11/41, 11/42 & 11/43=

LDPE/adh/{N6/EVOH..… EVOH/N6}/adh/LDPE

25 nano-layers

3b. CONTROL FILM STRUCTURES

The 7 micro-layer control film series 11-29 to 11-32 was

tested for both DSC and O2 permeability. The control film

had a similar structural to the test films pattern but only 2

layers of EVOH on both sides of a COC layer.

Extruder/layer relationship=

A / D /C / B / C / D / A

Samples 11/29 - 11/32 =

LDPE /adh/EVOH/COC/EVOH/adh/LDPE

3 micro-layers PE 1 layer Vistamaxx 75 nano-layers of PP/Vistamaxx 1 Layer Vistamaxx 3 micro-layers PE

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Along with O2 analysis, a study of the crystalline structure

through the use of a DSC was expected to show any

differences related to crystalline behavior. For example, a

DSC 1st heat and 2

nd reheat cycle should give an indication

of the initial melting behavior as well as the annealed

behavior. Any unstable crystalline effects due to possible

quenching should be revealed during the 1st heating cycle

and these could then be compared to the annealed sample

during the 2nd

reheating cycle.

3c. ORIENTATION EFFECTS: Dry quenching of

coextruded EVOH was the key to its orientation below

100C and this implied that changes in crystallinity also

took place. Therefore to avoid water contact and possible

influence on water sensitive EVOH DSC analysis of liquid

N2 quenched thin EVOH samples was also done so that

these could be compared to the DSC curves of the test

nano-layer films. A selected test film was oriented by

stretching longitudinally to determine low temperature

deformation and if stretching would affect the barrier.

3d. EVOH BARRIER THICKNESS: Two methods

were used to determine barrier layer thickness. The first

method was to make a thickness approximation from the

extruder output curves and the second was to determine

the thickness by optical means.

The relative layer thickness values calculated from

extruder output data below were based on the following

expected values: A extruder (1.25”) delivering 10 lbs/hr

PE @ 40 rpm; B&C extruders (0.75”) at 44.65 rpm

delivering @ 3 lbs/hr each of EVOH & COC respectively

and extruder D (0.75”) @ 30 rpm delivering 2 lbs/hr of

adhesive resin.

Both test and control film structures contained identical

micro-layers A & D. Only the C/B/C structural portion

was varied from the 3 micro-layer control films to the 25

nano-layer test films. As the layer thickness estimates

calculated from extruder output show, the total equivalent

EVOH thickness was about .167 mil / mil total thickness

whether this was the sum of 13 EVOH nano-layers or the

sum of 2 EVOH micro-layers. The only EVOH difference

between test and control were the individual layer

thicknesses and the number and not the total equivalent

amount.

TOTAL OUTPUT - LAYER RATIO’S (Basis= 10 mil film)

A= 10 lbs/hr = (10)10/18 = 5.556mil (2 layers)

D= 2 lbs/hr = (10)2/18 = 1.111mil (2 layers)

C= 3 lbs/hr = (10)3/18 = 1.667mil (2 to 13 layers)

B= 3 lbs/hr = (10)3/18 = 1.667mil (1-12 layers)

Lbs/hr=10+2+3+3=18lbs/hr TOTAL = 10.001mil

Calculated barrier/total thickness ratio for test films was

1.667/10 = 0.167mils/mil. Since there were 13 EVOH

nano- layers in the test films, each nano-layer was about

1.67/13 = 0.128mil (3251nm) in a 10 mil film or

0.0128mil (325nm) in a 1 mil film.

In similar fashion, the calculated EVOH thickness of each

micro-layer in the control film was in the order of 1.67/2 =

0.835mil (20,920nm) in a 10 mil film or 0.0835mil

(2,092nm) in a 1 mil film.

The calculated thickness estimates gave support to the

actual optical measurements that were previously made

(ref. 12). Actual optically measured total nano-layer

thickness for each of the EVOH materials used was

averaged and reported in last year’s paper at about

.211mils/mil total thickness. The actual measure could not

be done here because of the difficulty in seeing the

individual layers of COC and EVOH. Both appear to have

similar refractive index and delaminating was common in

trying to get cross-sectioned specimens. Therefore the

slightly larger 0.211 mils/mil barrier figure was again used

here for more accuracy.

Experimental Work

In order to make the best possible comparison between the

test and control films, only the module that defined the

film structure was exchanged. One module was

constructed with 7 cells to make the 7 layer control films.

The other module contained 4 micro-layer cells and a LSR

to make the 25 nano-layer + 4 micro-layer test structures.

Both modules were exactly the same size and used the

same die. The LSR only occupied the space of 3 normal

cells.

Picture 5 – 2” Test Line used to make both 7 micro-layer

and 25 nano + 4 Micro-layer test films

Downward Blown Film Test Line: The test line used to

manufacture all films used in this study is shown in picture

5. It blew film downward into a portable converging frame

winder. To the left of the die was an independently

variable speed 0.75-inch extruder D that delivered the 2

micro-layers of adhesive adjacent to both sides of the 25

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nano-layer test barrier structure or the 3 micro-layer

barrier structure of the control film. To the right was a

triplex extruder that delivered 2 melts from 2 - 0.75-inch

extruders B and C to the LSR. These 2 extruders were

commonly driven at a 20/60/20 ratio from a 1.25-inch

extruder that delivered low-density polyethylene to the

inside and outside of the bubble. The triplex extruder was

run at 40 rpm while the opposing .075-inch extruder D

was run at 30 rpm for the duration of each run to make

both control and test films.

Test Films 11-18 to 22 vs. Control Films 11-29 to 32

The sample 11-18-test film series that were made earlier

was still very clear and had been drawn thinner and

thinner until sample 11-22 at 0.7 mil was made at the

maximum winder speed. The quality and clarity of all of

the films was excellent but there was no adhesion of COC

to EVOH. Picture 6 shows the dual problems of

delaminating layers and difficulty in seeing layers that

were not delaminated. The materials used were as follows:

25 nano-layers

PE/adh/{L-171EVOH/COC8007/L-171EVOH}/adh/PE

Picture 6a - Sample 11-18 Optical Micro-photo (1.6 mil)

Picture 6a had less layer definition because of

backlighting very thin slivers of cross-sectioned film.

Pictures 6b had better definition because of surface

lighting.

The sample 11-29 7-micro-layer control film series now

extruded was also very clear and it too was drawn thinner

and thinner until the maximum take away speed was

attained with sample 11-32 at 0.7 mil. Again there was no

adhesion between COC and EVOH. Picture 7 shows a rare

cross section of sample 11-29 without delaminating layers.

Both the above sample series were then submitted for wet

and dry barrier testing in spite of the lack of adhesion. The

results supported the barrier tests from the 2010 paper

(Ref 13) but in more detail.

Picture 6 b Sample 11-18

Picture 7 Sample 11-29 (1.7 mil)

Table 1 below summarizes the equivalent thickness of the

barrier layers from both 25 nano-layer test and 7 micro-

layer control films that were selected for barrier tests. Of

course, these measurements have some margin of error

and that should be considered in reporting the results of

testing.

25 nano-layer section some delaminating

layers during cross sectioning

PE/ Admer

EVOH/COC/EVOH

PE/ Admer

Sample Equivalent Thickness

ID Total EVOH COC

11-18 & 11-29 1.6mil 0.338mil 0.338mil

11-19 & 11-30 1.2mil 0.253mil 0.253mil

11-20 & 11-31 1.0mil 0.211mil 0.211mil

11-22 & 11-32 0.7mil 0.148mil 0.148mil

Basis for Equivalent Thickness (optical as in ref. 14)

COC & EVOH = 0.211mils/mil total thickness

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Table 1 EVOH and COC equivalent thickness

The equivalent thickness of EVOH within each of the test

and control films was within the range used in most

industrial barrier films. So the barrier results obtained on

each of these films and shown in table 2 would represent

values that would be present in most packaging films

being used today.

Barrier Performance Tests - Samples 11-29-32 in table 2

below were the 7-micro-layer control films. Two 27mol %

EVOH (L-171) micro-layers were present within the

single micro-layer barrier matrix of (EVOH/COC/EVOH).

3-micro-layers

PE/adh/{L-171EVOH/COC/L-171EVOH}/adh/PE

Samples 11-18b-22b were the 25 nano-layer test films

with a similar structure but having much thinner repeat

units of EVOH and COC. These samples contained 13

nano-layers of EVOH and 12 layers of COC at the same

total amount of material or equivalent EVOH thickness as

the above control films.

25 nano-layers

PE/adh/{EVOH/COC/EVOH}/adh/PE

However, the EVOH in 11-18b was most likely 44 mol%

ethylene not 27 mol% due to a resin mix-up. This was

discovered when DSC analysis was run on 11-18b and 11-

29. Graphs 1a & b show the difference in melting peaks

between the test film 11-18b and the control film 11-29.

The DSC data were obtained from 2 different laboratories

and the implication was clear that the EVOH identity in

sample 11-18b was in question. 44mol% ethylene EVOH

has a melting point of 164C and this is very close to that

melting point value observed by DSC for test film 11-18b.

The unfortunate resin mix up clearly was responsible for

the higher 02 permeation values we observed. This data

was preserved to show the difference in permeability

between test films containing 25 nano-layers of

EVOH/COC where the mol% ethylene is higher.

Test Films 11-33c, 39b, 41c, 42b, & 43b

DSC ANALYSIS (1st & 2

nd Tm differences) – The

above DSC analysis identified the resin mix-up between

“44mol%” and 27mol% ethylene EVOH. The DSC

analysis was then continued further to identify any

differences in EVOH melting points between the

quenched and annealed states. Another run repeated the

above work using both Soarnol DT 2904, a 29mol %

ethylene EVOH and Eval L-171, a 27mol% ethylene

EVOH. These 2 grades are known to be equivalent in

barrier properties under all humidity conditions, and

therefore can be compared to one another. The film

structures were as follows and were used primarily for

DSC studies to identify ∆Tm values.

Sample 11/33 = 27mol% ethylene EVOH/ COC

(1.5mil)LDPE 5563/Admer498/{EVOH/ COC..25 nano..

COC/ EVOH}/Admer498/ LDPE 5563

Sample 11/39 = 29 mol % ethylene EVOH/ COC (1.5mil)

LDPE 5563/Admer498/{EVOH DT2904/ COC8007..25

nano.. COC 8007/EVOH DT2904}/Ad. 498/LDPE 5563

Surprisingly the DSC results on the above films showed a

significant difference between the 1st heat Tm and the 2

nd

heat Tm. This is shown in the example below (graph 2)

and is typically indicative of changes in the lamella

thickness that are consistent with a lower fold period.

Graph 1a

Sample 11-18b

2nd

MP = 161C

Graph 1b

Sample 11-29

2nd

MP = 185C

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Graph 2 DSC 1

st and 2

nd heat curves for 11-33C

Both of the above samples gave similar ∆Tm results from

two Soarus Labs: one in the USA and the other in Japan.

These are summarized in table 2.

Table 2 ∆Tm of 29mol% & 27mol% EVOH in nano-

layers

DSC analysis was repeated on pressed samples of the

29mol% EVOH resin that were quenched in liquid N2 or

air-cooled. These results are shown in table 3.

Table 3 ∆Tm of N2 quenched vs. Air for 29mol% EVOH

Clearly there was the same quench effect with the pressed

samples of EVOH but to a lesser degree (∆Tm = 1.2C).

The N2 quench while very rapid on the sample surface

was probably slowed down in the interior of these thicker

(11-12mil) specimens due to the poor thermal conductivity

of EVOH.

The “quenched” lower melting point indicated that the

crystals were smaller in thickness (lower lamella fold

period) and the surface energy became more and more a

factor. Thermodynamics are such that since the crystal

had more "energy" associated with it, it would undergo the

transition to the liquid state at a lower temperature.

The Japan laboratory also concurred that the ∆Tm could

explain a difference in deformability. They felt that an

amorphous chain in a polymer crystal having a lower

melting point could deform the crystal more easily

because the connection between them would be reduced in

strength slightly due to smaller crystal size.

Following the above DSC tests another replacement 11-

18b series was run as 11-45D through 11-48 and again

tested for wet and dry barrier. This time the EVOH was L-

171 from an unopened labeled bag. Identification of the

new nano-layer series is as follows:

PE/adh/{EVOH/COC..25nano..COC/EVOH}/adh/PE

11/45A-D (nominal 1.6 mil) = 5563/A498/{ L-171/8007…25nano…8007/L-171}/A498/5563 11/46 (nominal 1.2 mil) = 5563/A498/{ L-171/8007…25nano…8007/L-171}/A498/5563 11/47 (nominal 1.0 mil) = 5563/A498/{ L-171/8007…25nano…8007/L-171}/A498/5563 11/48 (nominal 0.7 mil) = 5563/A498/{ L-171/8007…25nano…8007/L-171}/A498/5563

Because of the poor adhesion to EVOH, again COC was

used in the nano-layer structures above only because of its

amorphous nature and transparency in DSC work.

Substituting N6 was the practical end use goal as was

done with the preceding samples.

NYLON 6 / EVOH STRUCTURES

Replacing nylon 6 for COC resulted in the following

samples that progressed from thinner to thicker films as

indicated below:

Sample 11/41, 42, & 43b = 29mol% ethylene EVOH/ N6

LDPE 5563/PX3227/ {N6 3411/ EVOH DT2904/..25

nano../ EVOH DT2904/ N6 3411}/ PX3227/ LDPE 5563

(STRETCHED & UNSTRETCHED)

The preceding N6/EVOH structures were found to

coextrude very well and certainly were equal to the

COC/DT2904 film quality. Since N6 adhered very well to

EVOH, this was an ideal combination to continue this

study further into orientation work on the above thicker

sample 11/43b. The coextrusion quality was excellent and

a micro-photo of it is shown in picture 8 that follows.

ORIENTATION STUDY

As mentioned above, the ultimate aim in doing this work

was to obtain a more functional film that used N6 instead

of COC. N6 would adhere to EVOH and help impart more

toughness as well. Sample films, 11-41c and 11-42b, were

made thinner for barrier comparison purposes. The

thickest, 11-43b, was then oriented 2:1 and 3:1

longitudinally at between 160 –200F. The orientation was

very stable as if the film were rapidly quenched in cold

Sample 11-33C

1st MP=185.20C

2nd

MP=187.20C

∆Tm = 2.00C

Quench 1st heat 2

nd heat ∆Tm Thickness

N2 185.7C 186.9C 1.2C 11-12mil

Air 186.0C 186.9C 0.9C 11-12mil

Sample 1st heat 2

nd heat ∆Tm Lab

11-39b 181.4C 184.7C 3.3C USA

11-39b 183.5C 185.7C 2,2C Japan

(Average)…………………… (2.8C)

11-33c 185.2C 187.2C 2.0C USA

11-33c 181.7C 186.5C 4.8C Japan

(Average)……………………. (3.4C)

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water rather than air-cooled. Since sample 11-43b had a

new crystalline form of EVOH as indicated by the above

DSC work, that crystalline form must have been easily

deformable in order to stretch orient below 100C.

Picture 8 Sample 11- 43A (25 nano-layers of N6/EVOH)

The tubular orientation is shown in picture 9. Samples 11-

43b1 and 11-43b2 were oriented in this manner with

progressively higher stretch ratios. There was a distinct

tendency of the material to biaxially orient. But the

starting material at 2.5 mil was too thin to make a useful

film. Nano-layers of N6/EVOH certainly proved to assist

in orientation both biaxially and monaxially.

Picture 9 - Sample 11-43b being stretched 2:1@160-200F

POLYBUTENE-1 ANALOGY – Isotactic PB-1 resin

and its 2 crystal forms is another example of a quenched

form and an annealed or aged form of crystal. The

quenched form II also must be deformable because it

could also be oriented below 100C. The orientation work

for isotactic polybutene–1 is described in US patent

“Oriented Blends of Polypropylene and Polybutene-1”

(ref. 14).

When isotactic polybutene-1 is crystallized from the melt,

initially a soft metastable tetragonal crystal form II is

produced. Over storage time of about 1 week at 21oC the

form II crystals are transformed spontaneously and

irreversibly into the thermodynamically more stable

hexagonal form I (ref. 15).

The glass transition temperature (Tg) of polybutene-1 is -

21 degrees C so at room temperature the form II crystals

are not frozen in place like those in EVOH (Tg=60C) and

are therefore free to transform to the more stable state at

room temperature.

After stretching or under hydrostatic pressure the form II

crystals are transformed into form I in the solid state. The

transformation is also affected by temperature, molecular

weight of PB-1, tacticity, comonomers, additives,

impurities, sample thickness and gamma radiation (ref 15).

Form II has melting temperature about 115C; form I

(stable) at about 127C. So ∆Tm for these crystal form

differences is about 12C when compared to the lesser

∆Tm of 2-4 C for the nano-layer EVOH.

BARRIER TESTING

Samples 11-41c (1.8mil) and 11-42b (2.2mil) were made

thinner than 11-43b (2.5mil) and were also included in

table 4 for barrier measurement and comparison both wet

and dry. Please note that O2 transmission is shown using 2

common measures, one bases area on 100in2 and the other

(meter)2. Also note the equivalent EVOH is shown based

on .211mil/mil total thickness.

Please note that the more recently measured values for

permeability to O2 on nano-layer films showed no higher

values than on the micro-layer control films. Samples 11-

45 to 11-48 are in the same order of magnitude as the

control film samples 11-29 to 11-32.

While nano-layer film showed no difference in barrier

properties, the new and more deformable EVOH crystal

form within the nano-layers certainly contributed to the

usefulness of the film in its ability to be oriented. Because

of the ease in orienting these films at a temperature below

100C, we also must imply that thermoforming within these

parameters would also be an attribute of nano-layer films.

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Table 4 - O2 Barrier Measurements (Lab 1 Data)

Sample

OTR @ CC/100 IN2 /CC/M2 (0% RH, 23C)

OTR @ CC/100IN2 CC/M2 (85% RH, 23C)

Mils total Mils EVOH

11--29 0.015/.233 0.158/2.45 1.8 / .38 11--30 0.023/.357 0.240/3.72 1.2 / .25 11--31 0.026/.403 0.256/3.97 1.0 / .21 11--32 0.042/.651 0.471/7.30 0.7 / .15 11--18b 0.471/7.30 0.881/13.66 1.4 / .30 11--19 0.491/7.61 0.930/14.42 1.2 / .25 11--20 0.630/9.77 1.152/23.56 1.0 / .21 11--22b 1.029/15.90 1.810/28.06 0.7 / .15 11—41c 0.0365/.5645 0.2670/4.14 1.99 / .42 11—42b 0.0240/.3715 0.2195/3.40 2.10 / .44 11--43b 0.0295/.4510 0.1040/1.61 2.33 / .49 11--43b1 0.0385/.6005 0.2695/4.18 1.56 / .33 11--43b2 0.0350/.5456 0.2880/4.47 1.24 / .26 11--33b 0.046/0.72 0.149/2.30 1.57 / .33 11--39 0.060/0.92 0.130/1.98 1.93 / .41 11—45d 0.043/0.66 0.320/4.93 1.67 / .35 11--46 0.058/0.90 0.070/1.05 1.06 / .22 11--47 0.072/1.11 0.360/5.47 1.08 / .23 11--48 0.116/1.80 0.560/8.75 0.73 / .15

The data contained in table 4 was then put into a single

graph in order to show the differences in barrier both in

the dry and wet states. Graph 3 is very clear in showing

that the 13 nano-layers of “44mol %” EVOH produced a

film that was a poorer barrier than the 2-micro-layers of

27mol% EVOH.

The encircled areas of graph 3 capture the wet and dry

barrier data. This data shows that the barrier of 25 nano-

layer films is in the same range as the 7 micro-layer

control and that the barrier does not change if nylon is part

of the structure or not. Further, both 27mol% and 29mol%

EVOH appeared to be very similar in barrier values.

Comparing all of the encircled values to the much steeper

slope of the 25 nano-layer “44mol %”EVOH test films,

samples 11-18 to 22 shows that the higher mol% films

deteriorate in barrier far more as the film thickness

decreases. The higher “44mol %” EVOH was clearly

responsible for the poorer barrier observed in the earlier

2010 paper (ref. 13).

Nano-layer N6/29mol % EVOH samples 11-41 through

43 whether blown or oriented also compared favorably

with the barrier values of the 7 micro-layer control film.

Please note specifically that because the 25-nano-layer

samples 11-41c, 42b and 43b, 43b1 & 43b2 used 29mol %

ethylene EVOH and were still in the same order of

magnitude as the 7 micro-layer control film. From this

data nano-layers did not appear to enhance barrier

properties of EVOH but at the same time neither did the

barrier diminish as was earlier reported in error due to the

resin mix up.

Some of the earlier anomalies reported may have been

partially due to orientation effects. Certainly we know now

that there are crystallinity differences that take place,

particularly with EVOH in nano-layer form as it is cooled.

These differences do not appear to increase or decrease

the overall barrier properties but certainly make it easier to

deform as in orientation and thermoforming.

Graph 3 - Barrier performance of 2 micro-

layer EVOH vs. 13 Nano-layer EVOH films

SUMMARY OF BARRIER TESTS

3 Micro-layers = 25 Nano-layers in barrier

27mol% = 29mol% EVOH in barrier

N6/EVOH = COC/EVOH in barrier

“44mol%” 25 nano-layers

27 & 29mol% EVOH wet

27 & 29mol%

EVOH dry

10

SUMMARY & CONCLUSIONS

1. Quenching 11-12mil thick samples of EVOH into

liquid N2 produced a lower melting point crystal

structure (∆Tm=1.2C) than air-cooled (∆Tm=0.9C) or

annealed EVOH as measured by DSC.

2. Nano-layers of EVOH in blown film produced an even

lower melting point crystal structure (∆Tm=2-4.8C)

than the N2 quenched samples probably because the

significantly higher surface area and lower mass may

have actually cooled the material faster internally.

3. The lower melting point crystal structure is consistent

with a lower density thinner crystal showing changes in

the lamella thickness having a lower fold period. The

lower density crystal may also have an amorphous

chain going through it aiding in the ability to deform.

4. The nano-layer EVOH/N6 films were oriented

longitudinally at 2 & 3:1 stretch ratios at a temperature

between Tg and 100C, well below the melting point of

both materials. This confirmed the ability of the lower

melting EVOH crystals to deform. Similar crystal

deformation also seems to be present in the N6 as well.

5. The oriented films kept their barrier properties

compared to the micro-layer controls even though they

were thinner as a result of stretching.

6. EVOH in nano-layer form had barrier properties

similar to EVOH in micro-layer form. However, the

new lower density thinner crystalline form being more

deformable aids in orientation around Tg and by

implication easier thermoforming as well.

ACKNOWLEDGEMENTS:

1. Ken Toyosu at the Soarus Lab for his help with

DSC studies.

2. The people at Nippon Gohsei in the Japan Lab

for their corroboration of DSC analysis.

3. The people at the Curwood lab for their initial

DSC work and extensive barrier testing.

REFERENCES

1. Comparison of Irreversible Deformation &

Yielding in Micro-layers of PC with PMMA

& Poly (styrene-co-acrylonitrile) Kerns,

Hsieh, Hiltner, Baer - J. of Applied Science

Vol.77, 1545-1557 (2000)

2. The Modular Disk Coextrusion Die –

Schirmer Polyolefins 2000

3. New Compositions of Matter from The

Modular Disk Coextrusion Die - Schirmer,

Love, Schelling, Loschialpo - ANTEC 2000

4. Breathable Polymer Films Produced by the

Micro-layer Coextrusion Process Mueller,

Topolkaraev, Soerens, Hiltner, Baer - J.

Applied Science Vol. 78, 816-828 (2000)

5. Micro-layer Coextrusion Technology Baer,

Jarus, Hiltner - ANTEC 1999

6. Modular Disk Coextrusion: Production Rate

Tests with the 9” flex-Lip Die Schirmer -

Future-Pak 1999

7. Oxygen Barrier Enhancement of PET

Through Physical Modification Sekelik,

Nazarenko, Stepanov, Hiltner, Baer -

ANTEC 1998

8. Novel Structures by Layer Multiplier

Coextrusion - Nazarenko, Snyder, Ebeling,

Schuman, Hiltner, Baer - ANTEC 1996

9. 25 Micro-layer Blown Film Coextrusion Die

– Schirmer - Polyolefins 2008

10. Exploratory Experiments on Solid-State

Foaming of PLA films and COC/LDPE

Multi-layered Films - Lu, Kumar, Schirmer -

ANTEC 2009

11. Improved Flexible Packaging Film

Performance via Layer Multiplication- Sam

Iuliano – Polyolefins 2009

12. Nano-layers in Blown film – Schirmer,

Jester, Medlock – Polyolefins 2009

13. Nano-layers in Blown Barrier Films –

Schirmer, Jester, Medlock, Schell – PO 2010

14. Oriented Blends of Polybutene –1 and

Polypropylene –Schirmer–US Pat. 3,808,304

15. A.M. Chatterjee, “Butene Polymers”,

Encyclopedia of Polymer Science and

Engineering, Vol 2, 2nd

. Ed, 590 (1985)

11

AUTHOR CONTACTS

Henry G. Schirmer

BBS Corporation

2066 Pecan Drive

Spartanburg, SC 29307

Tel: (864) 579-3058

E-Mail: hschirmer@att.net

Tom Schell

Curwood, Inc.

2200 Badger Avenue

Oshkosh, WI 54904

E-Mail: TASchell@bemis.com

Dr. Mark Pucci

Soarus LLC

3930 Ventura Drive, Suite 440

Arlington Heights, IL 60004

E-Mail: mpucci@soarus.com

Dr. Ananda M. Chatterjee

Chatterjee Consulting, LLC

Missouri City, TX 77459

E-Mail: am_chatterjee@yahoo.com