AIMCAL Fall Technical ConferenceOctober 19 – 22
North Myrtle Beach, SC
Over-Treatment of PET: Fact or Fiction.Part I – Corona and Part II Atmospheric Plasma
A study of the following variables: watt density, treatment dwell time, film selection, dyne level and water-soak bond strength
Presented by:Jessica BodineTechnical Sales RepresentativeMica Corporation
Typical Properties of PET*
Tensile Strength = 2,250 kg/cm2
Yield Strength = 1050 kg/cm2
Elongation = 110%Modulus = 42,200 kg/cm2
CoF = .40/.36 (Static/Kenetic)Density = 1.395 g/cm3
Haze (48 ga) = 3%* As provided by Mitsubishi for Hostaphan 2261N
OOC-Ar-COOH + HOCH 2CH2 O
-OOC-Ar-COO-CH2CH2-O- + O3
PET and Corona Treatment
Low Molecular Weight Fragments (LMWF)
C-OHC=OCOOHC-O-CEpoxyEstershydroperoxide
Analytical Techniques
X-ray spectroscopyAtomic Force MicroscopyScanning Force MicroscopyTOF Simms Contact angle measurement (advancing and receding)Standard dyne level testing (dyne solutions)See References 1 – 4 in full published paper
Confirmation of LWMF
Well known and confirmed that higher watt density corona treatment produces more LWMF (References 1-5)Some oxidized species are necessary for adhesionTipping point: Corona no longer beneficial – but detrimental to adhesion = “over-treatment”
Atmospheric Plasma Treatment (APT)
Both corona and APT = ionization of gas at surface of the filmCorona = high voltage for initiationCorona = directional discharge between 2 electrodes, may cause micro re-treatment due to tendency to be attracted to already ionized point(Ref 8)
Advantaged of APT process
Lower initiation voltageCloud-like discharge, more even distributionIn addition to ionization of the air already present at the film surface, chemistries can be introduced by specific selection of gas used
Real World Converting
Instrumental analysis = $$$Is dyne level testing enough?What tests can the average manufacturer run to make understand the “tipping point”What manufacturer controllable variables contribute the most to “over treatment”?
Converting
PrintingCoatingAdhesive LaminationEXTRUSION LAMINATION
Variables
Film selectionWatt density How to achieve watt density? With one electrode or multiple electrodes?APT = gas, ratios and flow rate = 100s of combinations, only 1 was choosen of each and kept constant
Watt Density - Corona
Watt-Density (WD) = power/area/time
Units = W/m2/minute
Calculation:
(KW setting x 1000)/[Line speed (m/min) x width (m)]
Watt Density – Electrode Assemblies
W/m2/minute “W” can be supplied by 1 or more assemblies“W” is additive WD was held constant but was achieved either by treating with 1 electrode assembly or with 2 in sucessionFor example: films treated to 10 WD
1 electrode assembly set at 102 electrode assemblies each set at 5
Watt Density – Atmospheric Plasma
Same units and calculationControllable variables
Power Level (same as corona)Gas chemistries% of gas mixFlow rate
Films and Treatment
Control Film – 48 g unknown polyesterExperimental Film Misubishi Hostaphan 2261N (untreated, uncoated, unfilled PET film)
Watt Densities chosen for experiment:5,10,20,30,40,50,60,70,80 and 100 (one electrode)10,20,40,60,80,100 (two electrodes)
ExperimentalTreatment (Corona) – Compac Universal 2000 manufactured by Enercon, ceramic ground rolls and ceramic electrodes, gap = 0.13 cm, line speed = 61 m/minTreatment (APT) – 60” Wide Enercon Plasma3 supported by a RF power supply at high frequency. Gas Mix = 90% argon, 10% oxygen“Simulated Extrusion Coating” – prime with 0.03 dry grams/meter2, heat seal to polyethylene at 163°C for 3 seconds, 6 mm width, age at least 24 hours
Testing
Dyne Level was tested using ASTM method D2578-79Dyne Solutions ranging from 28 – 64 were employed
Testing
Except for the non-treated samples, all samples (both corona and APT) were found to have destructive, film tear (FT), bonding while dryWater-soak bond strength was used to differential samples 25mm X 6 mm seal areas were immersed into 22°C water for one hour
Bond Strength Unit5 samples of each variable were testedThe average bond strength and the peak bond strength were recorded. The average value was averaged and the peak value was averagedPeelable samples failure analysis – primer did not bond effectively to the PETDespite the stringent test, some samples remained destructive (FT) and the PET tore. The peak value of these samples is a measure of the strength of the 6 mm wide PET, rather than the bond strength Number of FT samples for each variable was recorded as well.
Dyne Level Results (Control Film)
Plamsa Treatment - Dyne Levels of Control Film 1 and 2 Assemblies
0
10
20
30
40
50
60
70
0 20 40 60 80 100Watt Density
Dyn
e Le
vel
Plasma - Control Film 1 AssemblyPlasma Control film 2 Assembly
Dyne Level Results (2261 Film)Plasma Treatment Dyne Levels 2261 Film 1 and 2 Electrode Assemblies
0
10
20
30
40
50
60
70
0 20 40 60 80 100Watt Density
Dyn
e Le
vel
Plasma Treament - 2261 Film 1 AssemblyPlasma 2261 Film - 2 assembly
Maximum Dyne Level
Maximum dyne level achieve at lower WDMaximum level = 60 (even though tested for levels as high as 64)“Saturation Phenomena” well documented (ref. 5)Do all film with a 60 dyne level behave the same? BOND TESTING!
Corona: Control Film - Bond Strength Data (g/6mm)
WattDensity
# of electrodes
Avg / avg # of FT Weightedavg. avg.
Avg. peak
0 0 0 0 0
.5 1 179.25 3 254.25 439.5
1 1 221 4 321 398.2
2 1 203.8 1 228.8 379.4
3 1 165 3 240 410.2
4 1 153.8 1 178.8 341.8
5 1 111.2 2 161.2 351.8
6 1 55 55 152.4
8 1 95.5 95.5 185.5
10 1 91.25 91.25 187.5
Corona: Control Film – Bond Strength Data (g/6mm)
WattDensity
# of electrodes
Avg / avg # of FT
Weightedavg. avg.
Avg. peak
1 2 225.2 2 275.2 382.6
2 2 343.6 5 468.6 586.2
4 2 67.2 1 92.2 194.4
6 2 131 1 156 263.2
8 2 8.8 8.8 51.2
10 2 69.25 69.25 201.5
Corona: 2261 Film – Bond Strength Data (g/6mm)
Watt Density
# ofElectrodes
Avg. avg # of FT Weighted Avg. avg.
Avg peak
0 00 0 0
.5 1206.5 206.5 468
1 141.25 41.25 144
2 1 137.2 1 162.2 309.8
6 170.8 70.8 136.8
8 1139.2 139.2 293.4
10 1 192.2 2 242.2 355.4
Corona: 2261 Film – Bond Strength Data (g/6mm)
Watt Density
# ofElectrodes Avg. avg
# of FT
Weighted Avg. avg. Avg peak
1 2102.2 3 177.2 422.6
2 2218 3 293 428.2
4 2206.2 4 306.2 436.4
6 2135 135 273.6
8 2201.6 2 251.6 389.4
10 2124.8 124.8 281.8
Corona Treated Films Watt density vs. weight Avg.
0
50
100
150
200
250
300
350
400
450
500
0 10 20 30 40 50 60 70 80 90 100WD
g/.5
inch
WD (1) weigthed avg controlWD (2) weighted avg controlWD (1) weighted avg 2261WD (2) weighted avg 2261
Corona treatment:Control Film - Watt density vs. weight avg
0
50
100
150
200
250
300
350
400
450
500
0 10 20 30 40 50 60 70 80 90 100
WD
g/.5
inch WD (1) weigthed avg control
WD (2) weighted avg control
2661 Film - Watt density vs. weight avg
0
50
100
150
200
250
300
350
400
450
500
0 10 20 30 40 50 60 70 80 90 100
WD
g/.5
inch WD (1) weighted avg mit
WD (2) weighted avg mit
Corona Conclusions
Dyne level testing does not tell the whole storyWhen using a primer, water soak bonds may help determine over-treatment Film selection is biggest variableUsing multiple electrode assemblies may produce more consistent results (confirmation of micro re-treatment theory?)
APT: Control Film - Bond Strength Data (g/6mm)Sample ID Watt
Density# of electrodes
Avg / avg # of FT Avg. peak
PA1 0 0 0 0PB1 5 1 91 274.2PC1 10 1 181.2 2 403.4PD1 20 1 7.6 38PE1 30 1 120.6 1 287PF1 40 1 36.6 153.8PG1 50 1 9 48.6PH1 60 1 21.8 134.6PI1 70 1 15.2 72PJ1 80 1 46.6 72.4PK1 100 1 56.8 155.8
APT: Control Film - Bond Strength Data (g/6mm)
Sample ID WattDensity
# of electrodes
Avg / avg # of FT Avg. peak
PB2 10 2 96.8 1 243.4PC2 20 2 20.2 93PD2 40 2 13.4 68PE2 60 2 27.5 109.5PF2 80 2 10.4 53PG2 100 2 10.3 71.6
APT: 2261 Film - Bond Strength Data (g/6mm)
Sample ID
WattDensity
# of electrodes
Avg / avg # of FT Avg. peak
PA1 0 0 0 0PB1 5 1 45.4 171.6PC1 10 1 23.2 127.4PD1 20 1 71 285.2PF1 40 1 4.2 29.4PH1 60 1 5.5 31.5PJ1 80 1 4.8 25.4PK1 100 1 5.6 19.2
APT: 2261 Film - Bond Strength Data (g/6mm)
Sample ID WattDensity
# of electrodes Avg / avg
# of FT Avg. peak
PB2 10 2 110.75 1 356.5PC2 20 2
61.75 136PD2 40 2
3.2 12.2PE2 60 2
5 21.2PF2 80 2
5.5 18PG2 100 2
6.6 45.2
APT - Wt. avg bonds vs. WD
0
50
100
150
200
250
300
350
400
450
500
0 10 20 30 40 50 60 70 80 90 100
wd
g/in
ch
control 1 assemblycontrol 2 assembly2261 1 assembly2261 2 assembly
Comparisons:
Corona – concluded that 2261 film and 2 electrode assembly highest bonds across wides range of watt densityAPT – much smaller difference between films and # of assembliesAPT - control film with 1 assembly might be slightly better
Plasms vs. Corona 2261 film
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
watt density
bond
str
egth
Corona 2 assembly 2261Plasma 2 assembly 2261
Plasam vs. Corona - Control film
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
watt density
bond
str
engt
h
Corona control 1 assemblyPlasma control 1 assembly
Highest bond Values of Corona vs. APT
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
Watt Density
Bon
d St
reng
th (g
/6m
m)
Corona 2261 2 assemblyplasma control film 1 assembly
Discussion
Dyne leve testing does not indicate over-treatmentUsing a primer allows for all conditions to be destructive for dry bondsWater-soak data may differentiate over-treatment
Discussion
Corona treatment + primer = advantage in water soak bond strengths as compared to APT under these specific conditions (90% argon, 10% oxygen)APT = little differentiation between films or # of electrode assemblies (confirmation of better uniformity?)Clear point of over treatment
More work needs to be done…
Although, water-soak bond data is higher for corona in these experiments, a process that is less dependent on film selection and electrode assemblies may be useful to the converterCan the poor water-soak bond strength be over-come?Are other gas chemistries better at water-soak tests?
PART III: More APT variable
Use first two studies to narrow processing conditionsLook at other APT variables
Gas chemistryGas ratiosAir flw
STAY TUNED…Part III – Available in November, e-mail contact information to author!
Acknowledgement
Thank you
Rory Wolf and Dave Mandel, Enercon Industries
Jeff Toke, Mitsubishi Films
Thank YouPRESENTED BY
Jessica BodineMica Corporation9 Mountain View DriveShelton, CT 06484(203) [email protected]
