Atomic Layer Deposition Process for Barrier Applications of Flexible Packaging Petri Johansson, Kimmo Lahtinen and Jurkka Kuusipalo Tampere University of Technology, Paper Converting and Packaging Technology (TUT/PCT) Tommi Kääriäinen, Philipp Maydannik and David Cameron Lappeenranta University of Technology, Advanced Surface Technology Research Laboratory (LUT/ASTRaL) ABSTRACT Atomic layer deposition (ALD) is a process where thin films of material are deposited in a controlled manner one atomic layer at a time. The main advantages of ALD are the extreme degree of conformality and uniformity which can be obtained regardless of the orientation or shape of the substrate; there are no pinholes in the film. The ability to do roll-to-roll coating would open huge possibilities for the technique, because barrier layers are required to avoid the diffusion of water or oxygen through polymer or paper webs for example in the food packaging industry. According to barrier test results, the aluminum oxide coating provided by the ALD batch process improved the oxygen and water vapor barrier as a function of coating thickness by a large amount. As an oxygen barrier, a thin 10 nm coating is already able to obtain ten times lower transmission levels than the uncoated structure. As a water vapor barrier, the thickness of the polymer layer becomes practically meaningless once the thickness of the ALD– layer increases above 40 nm. With over 100 nm thickness, the water vapor transmission rates of the structures were reduced below the level of 1 g/m 2 /24h (23°C, 50% RH). These results encourage the continuation of investigations towards roll-to-roll solutions of ALD processing. INTRODUCTION The purpose of atomic layer deposition (ALD) process is to produce a thin, gas-tight and stable coating from gaseous precursors. ALD is based on chemical reactions on the surface of a substrate. Precursors are fed to the reaction chamber, including the substrate, one at the time such that the substrate is exposed to only one precursor at a time. The molecules are attached to the substrate as a monolayer via covalent bonding. After the reaction is finished and the surface is saturated with attached precursor molecules, the excess gas and reaction products are removed from the chamber by flushing the space with an inert gas such as nitrogen. A typical ALD cycle consists of four stages. The cycle starts by introducing the first precursor into the chamber which is flushed in the second stage. Then, another precursor is fed in and flushed, completing the four stages. After the complete reaction cycle, one atomic layer of desired coating is chemically bonded to the substrate surface. Figure 1 shows the principles of the ALD reaction cycle. /1,4/ The actual ALD coating consists of several reaction cycles. One reaction cycle is able to achieve about 0.1 nm layer thickness depending on the coating material and process parameters. The thickness of a typical ALD coating is determined by the number of cycles and varies roughly from 1 to 100 nm. Temperature in the chamber can vary from room temperature to several hundreds of degrees Celsius. The role of temperature is to provide activation energy for the ALD process (thermal ALD). The reaction can also be activated using plasma (plasma assisted ALD). Plasma-assisted ALD provides lower cycle periods and process temperatures for the system than thermal ALD. /1- 3/
Transcript
Atomic Layer Deposition Process for Barrier Applications of Flexible Packaging
Petri Johansson, Kimmo Lahtinen and Jurkka KuusipaloTampere University of Technology, Paper Converting and Packaging Technology (TUT/PCT)
Tommi Kääriäinen, Philipp Maydannik and David CameronLappeenranta University of Technology, Advanced Surface Technology Research Laboratory (LUT/ASTRaL)
ABSTRACT
Atomic layer deposition (ALD) is a process where thin films of material are deposited in a controlled manner oneatomic layer at a time. The main advantages of ALD are the extreme degree of conformality and uniformity whichcan be obtained regardless of the orientation or shape of the substrate; there are no pinholes in the film. The abilityto do roll-to-roll coating would open huge possibilities for the technique, because barrier layers are required to avoidthe diffusion of water or oxygen through polymer or paper webs for example in the food packaging industry.
According to barrier test results, the aluminum oxide coating provided by the ALD batch process improved theoxygen and water vapor barrier as a function of coating thickness by a large amount. As an oxygen barrier, a thin 10nm coating is already able to obtain ten times lower transmission levels than the uncoated structure. As a watervapor barrier, the thickness of the polymer layer becomes practically meaningless once the thickness of the ALD–layer increases above 40 nm. With over 100 nm thickness, the water vapor transmission rates of the structures werereduced below the level of 1 g/m2/24h (23°C, 50% RH). These results encourage the continuation of investigationstowards roll-to-roll solutions of ALD processing.
INTRODUCTION
The purpose of atomic layer deposition (ALD) process is to produce a thin, gas-tight and stable coating fromgaseous precursors. ALD is based on chemical reactions on the surface of a substrate. Precursors are fed to thereaction chamber, including the substrate, one at the time such that the substrate is exposed to only one precursor ata time. The molecules are attached to the substrate as a monolayer via covalent bonding. After the reaction isfinished and the surface is saturated with attached precursor molecules, the excess gas and reaction products areremoved from the chamber by flushing the space with an inert gas such as nitrogen. A typical ALD cycle consists offour stages. The cycle starts by introducing the first precursor into the chamber which is flushed in the second stage.Then, another precursor is fed in and flushed, completing the four stages. After the complete reaction cycle, oneatomic layer of desired coating is chemically bonded to the substrate surface. Figure 1 shows the principles of theALD reaction cycle. /1,4/
The actual ALD coating consists of several reaction cycles. One reaction cycle is able to achieve about 0.1 nm layerthickness depending on the coating material and process parameters. The thickness of a typical ALD coating isdetermined by the number of cycles and varies roughly from 1 to 100 nm. Temperature in the chamber can varyfrom room temperature to several hundreds of degrees Celsius. The role of temperature is to provide activationenergy for the ALD process (thermal ALD). The reaction can also be activated using plasma (plasma assisted ALD).Plasma-assisted ALD provides lower cycle periods and process temperatures for the system than thermal ALD. /1-3/
Fig. 1. Principles of ALD reaction cycle /4/.
It is possible to use ALD to deposit a range of different materials. These include e.g. oxides, nitrides and carbides/1/. In addition, it is possible to produce nanolaminates using different materials in atom-thick layers one afteranother. ALD is particularly applicable to substrates with different shapes, even 3D, because thickness variations ofALD coatings are very low since the coating thickness is controlled by a self-limiting reaction at the surface.Because of the chemical bonding the adhesion with the substrate is commonly excellent. The oxide precursors havebeen reported to adhere to most kinds of polymers even if they lack typical chemical functional groups such ashydroxyl (-OH) species. /3,5/
Batch atomic layer deposition process
ALD processing techniques can be divided in two categories regarding substrate handling: batch and continuousprocesses. The batch process is a traditional technique in which the substrate to be coated remains stationary and theprecursors are pulsed in turn onto the surface of the substrate. The actual coating process occurs in a modularchamber, which is filled with substrates. In a chamber, the substrates can be located close to each other because theprecursors are able to penetrate into extremely small holes. The precursors are typically liquids (can be solids aswell) with significant vapor pressures stored in separate containers outside the reactor chamber. They are fed intothe reactor via their own delivery pipes and valves. Because of the low reactor pressure, each precursor evaporatesdue to its own vapor pressure. Figure 2 shows typical equipment used for batch ALD processing. In the figure, thered arrow shows the precursor containers and the blue arrow the reactor chamber.
Fig. 2. A batch ALD reactor (Beneq TFS 500). Red arrow: precursor containers, blue arrow: reactor chamber.
Continuous atomic layer deposition process (CALD)
A new challenge in ALD technology is to develop a continuous process for roll-to-roll materials. This wouldconstitute a new shift of perspective for ALD coating technology. The ability to do roll-to-roll coating would opennew applications for ALD technology e.g. in the packaging industry. Figure 3 shows schematics of a possiblecontinuous ALD process. The substrate moves under the precursor containers that bring the gases onto the substrateone-by-one. The leakage between the chambers is prevented with exhaust pumping (green color). In the system, thepulse times depend only on the chamber length and line speed of the substrate. Thus, gas valves are not needed forcontrolling the pulse times. The assembly shown in Figure 3 is placed in a chamber with low pressure andappropriate temperature.
Fig. 3. Schematics of continuous ALD process.
In the literature, significant barrier properties have been reported for Al2O3 layers deposited on polymer surfaces bythe ALD method /6-8/. According to Groner et al. /6/, WVTR values as low as 1*10-3 g/m2/24h have been achievedfor very thin (10-25 nm) Al2O3 films. The purpose of this study was to investigate the applicability of such ALDlayers for flexible packaging. Batch ALD equipment was used to provide Al2O3 coatings on LDPE, PP, PET andPLA extrusion-coated papers. The WVTRs and O2TRs of the produced materials were tested in order tocharacterize the barrier properties obtained. The results of this study are employed as trend-setters for the futurestudies concerning continuous ALD process.
MATERIALS AND METHODS
The materials to be tested in the study were paper/polymer/Al2O3 –structures in which the polymer layer wasdeposited by extrusion coating and the aluminum oxide in a batch ALD process. The extrusion coating trials wereperformed at the pilot line of TUT/PCT. Four extrusion coating polymers were chosen for the study: LDPE(CA7230, Borealis), PP (WF420HMS, Borealis), PET (Lighter C98, Equipolymers) and PLA (test grade). The aimwas to select polymers with significant scatter in heat resistance, transport and surface properties. The PLA coatingbrought also the aspect of biodegradable polymer into the study. Table 1 shows selected thermal and physicalproperties of the used polymers.
Table 1. Selected thermal and physical properties of the polymers used in the study /9-11/.Tm°C
The LDPE-coated paper samples were produced with three different coating weights: 18, 27 and 36 g/m2. With theother polymers, only one coating weight was performed: 25 g/m2. A one-side mineral-coated paper, Lumiflex 90from Stora Enso, was used as a substrate. The non-pigmented side of the paper was extrusion-coated. Beforehand,the substrate was pre-treated with corona discharge equipment (2 kW) in order to obtain good adhesion with thepolymer.
The batch ALD equipment shown in Figure 2 (Beneq TFS 500 operated by LUT/ASTRaL) was used to producealuminum oxide (Al2O3) coatings on polymer surfaces. The thicknesses of the layers were 10-200 nm measured byspectroscopic ellipsometry from Silicon (100) reference samples placed in the same deposition batch.Trimethylaluminum (TMA) and ozone (O3) were used as precursors for the coatings. All the coatings were producedin thermal ALD processes having different reactor temperatures (65, 100 or 150 C). One deposition cycle consistedof a 250 ms TMA pulse, 6 s purge, 3 s ozone pulse and 6 s purge. The deposition started with 40 s ozone pulse and90 s purge.
The water vapor transmission rate (WVTR) measurements of the study were made according to SCAN P22:68 (cupmethod). In the method, a sample is placed against an aluminum dish containing calcium chloride. The sample isthen covered with a cylindrical template having base area of 50 cm2. Melted wax is poured around the cylinder toseal the sample tightly against the dish. After the wax is cooled, the dish is placed into a conditioning chamberhaving controlled atmosphere. After stabilization, the daily increase in the weight of the dish is measured andconverted to WVTR (g/m2/24h). The conditioning chamber used was Espec PR-1KPH, which is able to carry 60WVTR dishes simultaneously. Two atmospheric conditions were used in the measurements: 23 C, 50% RH and38 C, 90% RH.
The oxygen transmission rate (O2TR) measurements of the study were performed with Mocon Ox-Tran Model 2/21according to a standard ASTM D 3985. In the performed test series, the coated side of the sample was sealed againsta test cell using vacuum grease, thus the paper side was facing oxygen during measurements. The active test areawas 50 cm2. 10% oxygen was used as a test gas. The O2TR measurements were made at 23°C, 0% RH conditions.Both WVTR and O2TR results tabulated in the diagrams of this paper are mean values of two parallelmeasurements.
RESULTS AND DISCUSSION
Al2O3 layers deposited on LDPE- and PP-coated paper
In a preliminary test, thin Al2O3 layers were deposited on the surface of LDPE-coated papers. A low reactortemperature (65°C) was used for the depositions because of the low melting point of LDPE. 120, 350 and 600 cyclesprovided approximately 10, 25 and 40 nm Al2O3 coatings, respectively. With three LDPE coating weights (18, 27and 36 g/m2) and three ALD layer thicknesses, nine different structures were obtained from the depositions. Figures4 and 5 show the WVTR (38°C, 90% RH) and O2TR (23°C, 0% RH) results measured for the structures. The resultsare compared to the reference values measured for the corresponding structures without an Al2O3 layer.
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Fig. 4. WVTR (38°C, 90% RH) results for paper/LDPE/Al2O3 structures having 10-40 nm Al2O3 layer.
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Fig. 5. O2TR (23°C, 0% RH) results for paper/LDPE/Al2O3 structures having 10-40 nm Al2O3 layer.
According to the results, a thin 10 nm ALD coating is already able to obtain considerably improved oxygen barrierproperties for the structure. Concerning water vapor barrier, the decrease of the transmission level is not as dramatic.Polyethylene, being a good moisture barrier itself, provides already an efficient moisture block which is onlymoderately improved by the ALD coating. Nonetheless, the WVTR levels are still considerably decreased and thebarrier effect of the polymer becomes almost meaningless with 40 nm Al2O3 layer.
In order to obtain further barrier improvements, thicker A12O3 coatings were produced in the study. By performingmore ALD cycles, coatings with thicknesses between 100 and 200 nm were deposited on LDPE- and PP-coatedpapers. This time, the WVTRs were measured in two atmospheric conditions (23°C, 50% RH and 38°C, 90% RH) inorder to characterize the influence of climatic conditions on the results. The O2TRs were again measured at 23°C,0% RH. The results of the WVTR and O2TR tests are shown in Figures 6 and 7. The thicknesses of the LDPE andPP layers in the structures were approximately 25 g/m2.
LDPE LDPE + 100 nm PP PP + 130 nm
23°C, 50% RH 4,55 0,39 4,24 0,29
38°C, 90% RH 16,74 2,56 10,48 1,94
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Fig. 6. WVTR (23°C, 50% RH and 38°C, 90% RH) results for paper/polymer/Al2O3 structures having 100 nmAl2O3 layer.
LDPE LDPE + 100 nm PP PP + 130 nm
23 °C, 0 % RH 9400 590 4000 230
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Fig. 7. O2TR (23°C, 0% RH) results for paper/polymer/Al2O3 structures having 100 nm Al2O3 layer.
According to the results, more significant barrier improvements were achieved for the structure with thicker Al2O3layers. At 23°C, 50% RH conditions, the WVTR of the structures reduced clearly below the level of 1 g/m2/24hshowing the performance of high moisture barrier coating. Nonetheless, the WVTR levels at tropical conditionswere still rather high comparing to the literature values. The O2TR values decreased also comparing to the thinnerALD coatings, but the values are still quite high.
Influence of reactor temperature on the barrier performance
In general, the thermal ALD process produces more controlled ALD layers when using higher reactor temperature/1/. The influence of reactor temperature on the moisture barrier properties was tested by using two temperatures, 65and 100°C, for the Al2O3 deposition. PP-coated paper was used as a substrate in the test due to the PP’s suitablemelting temperature. The results obtained from the WVTR test are shown in Figure 8.
reference130 nm / 1200cycles, 65 °C,
130 nm / 1660cycles, 65 °C,
80 nm / 1200cycles, 100 °C,
90 nm / 1660cycles, 100 °C,
23 °C, 50 % RH 4,24 0,29 0,22 0,59 0,48
38 °C, 90 % RH 10,48 1,94 2,69 3,54 4,02
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Fig. 8. Influence of reactor temperature and ALD layer thickness on WVTR of PP-coated paper.
According to the results, the use of higher reactor temperature leads to a thinner Al2O3 coating and, thus, higherWVTR value. In other words, the higher deposition speed achieved with low reactor temperature (65°C) producesbetter barrier properties for the structure with an equal number of ALD cycles. This was also observed from theO2TR results. The higher film growth rate at lower deposition temperature is a well known behavior for this type ofALD processes /4,12,13/. The phenomenon can be explained through incomplete chemical reactions during the ALDcycles leading to a higher concentration of compounds formed by hydrocarbons in the film. In result, the lowerreactor temperature used seems to have an advantage over the higher ones regarding the barrier properties of theobtained structure, even if a perfectly controlled ALD process is not achieved in the reactor.
Al2O3 layers deposited on PET- and PLA-coated paper
In addition to LDPE and PP, the ALD coatings were deposited on PET- and PLA-coated paper substrates. The ALDcoatings were again made at 65°C temperature except for the two test points with paper/PET/Al2O3 structure thatwere made at 150°C. Figure 9 shows the WVTR results obtained for the paper/PET/Al2O3 structures made at 65 and150°C temperatures. According to the results, the increased reactor temperature increased also the WVTR of thematerial as was the case with PP. Therefore, the 65°C reactor temperature can be considered as an optimal reactorcondition of the studied conditions. With a PET polymer layer, the obtained moisture barrier properties were the bestones of the study. With paper/PET/Al2O3 structure, the WVTR values below 1 g/m2/24h were also found at tropical(38°C, 90% RH) measuring conditions.
reference120 nm /
1200 cycles65 °C
190 nm /1660 cycles
65 °C
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90 nm / 1660cycles 150 °C
23 °C, 50 % RH 19 0,1 0,6 6 5,1
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Fig. 9. WVTR (23°C, 50% RH and 38°C, 90% RH) results for paper/PET/Al2O3 structures.
reference65 °C, 1200
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Fig. 10. O2TR (23°C, 0% RH) results for paper/PET/Al2O3 structures.
Figure 10 shows the O2TR results for the paper/PET/Al2O3 structures. Remarkable oxygen barrier improvementswere found for the structures when using 65°C reactor temperature. The O2TR values found were significantly lowerthan the ones achieved with the other polymers. However, with the 150°C ALD process the oxygen barrier of thestructure was greatly deteriorated. All the four O2TR results obtained from the test were over the range ofmeasurement. It was suggested that the heating of the PET film to 150°C followed by slow cooling caused shrinkingand brittleness for PET via re-crystallization. This resulted in non-uniform ALD and polymer layers providing easierroutes for oxygen molecules to transport through the structure.
Figures 11 and 12 show the WVTR and O2TR results caught for the paper/PLA/Al2O3 structures. In this case, theAl2O3 layer also improved the water vapor and oxygen barrier properties but the WVTR level found was not as lowas with the other substrates. The water vapor barrier of the structure was approximately at the same level as those ofPP- and LDPE-coated papers at mild measuring conditions but poorer at tropical conditions.
reference 65 nm / 600 cycles110 nm / 1200
cycles
23 °C, 50 % RH 72 3,9 4,1
38 °C, 90 % RH 290 55 53
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Fig. 11. WVTR (23°C, 50% RH and 38°C, 90% RH) results for paper/PLA/Al2O3 structures.
reference65 nm / 600
cycles110 nm / 1200
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23 °C, 0 % RH 660 94 53 12
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Fig. 12. O2TR (23°C, 0% RH) results for paper/PLA/Al2O3 structures.
CONCLUSIONS
As a summary, Figures 13 and 14 compare the WVTR and O2TR levels achieved with all the tested structures.According to the figures, the most significant barrier improvement of the study was found for PET extrusion-coatedpaper. In such case, both the water vapor and oxygen barrier properties were at the level of high barrier coatingsafter the ALD layer was introduced into the structure. In the case of LDPE- and PP-coated papers, the water vaporbarrier achieved was excellent but the oxygen barrier properties of the structure remained at modest level. For PLA-coated paper, good oxygen barrier properties were found but the water vapor barrier of the structure was modest.The interpretation of the results is currently ongoing. Nonetheless, the obtained results prove the potential of ALDmethod and guide the future investigations towards real life roll-to-roll applications in flexible packaging.
LDPE ref PP ref PET ref PLA ref LDPE + ALD PP + ALD PET + ALD PLA + ALD
23 °C, 50 % RH 4,6 4,2 19 72 0,4 0,3 0,1 4,1
38 °C, 90 % RH 17 10 69 290 2,6 1,9 0,8 53
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Fig. 13. Comparison between the WVTR results.
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PLA +ALD
23 °C, 0 % RH 9400 4000 150 660 590 230 2 53
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Fig. 14. Comparison between the O2TR results.
ACKNOWLEDGEMENTS
The financial supports of the Finnish Funding Agency of Technology and Innovation (TEKES), Stora Enso Oyj,UPM-Kymmene Oyj and Savcor Face Group Oy are gratefully acknowledged.
REFERENCE
1. Ritala M and Leskelä M. “Atomic Layer Deposition”. In: Nalwa (ed) Handbook of thin film material, Vol. 1.Deposition and processing of thin films. Stanford Scientific Corporation. USA, 2002.
2. Sneck S. “High Capacity Atomic Layer Deposition for Industrial Coating Applications”. SVC – 50th AnnualTechnical Conference Proceedings. April 28- May 3, 2007. Louisville, KY.
3. Groner M, Fabreguette F, Elam J and George S. “Low-Temperature Al2O3 Atomic Layer Deposition”. Chemistryof Materials 16, 4 (2004).
4. Puurunen R. “Surface chemistry of atomic layer deposition: A case study for the trimethylaluminum/waterprocess”. Journal of Applied Physics 97, 12 (2005).
5. Ferguson J, Weimer A and George S. “Atomic Layer Deposition of Al2O3 on Polyethylene Particles”. Chemistryof Materials 16, 26 (2004).
6. Groner M, George S, McLean R and Carcia P. “Gas diffusion barriers on polymers using Al2O3 atomic layerdeposition”. Applied Physics Letters 88, 051907 (2006).
7. Carcia P, McLean R, Reilly M, Groner M and George S. “Ca test of Al2O3 gas diffusion barriers grown by atomiclayer deposition on polymers”. Applied Physics Letters 89, 031915 (2006).
8. Langereis E, Creatore M, Heil S, van de Sanden M and Kessels W. “Plasma-assisted atomic layer deposition ofAl2O3 moisture permeation barriers on polymers”. Applied Physics Letters 89, 081915 (2006).
9. Borealis. “Polyolefins for Extrusion Coating, 2nd Ed.” Austria, 2008.
10. Equipolymers. “Lighter C98”. Product Data Sheet. July 2004.
11. Callister Jr, W. Chapter 16 in: Materials Science and Engineering, An Introduction, 5th Ed. John Wiley & Sons,Inc. New York, NY, 2000.
12. Matero R, Rahtu A, Ritala M, Leskelä M and Sajavaara T. ”Effect of water dose on the atomic layer depositionrate of oxide thin films”. Thin Solid Films 368, 1 (2000).
13. Elliot S, Scarel C, Wiemer C, Fanciulli M and Pavia G. “Ozone-Based Atomic Layer Deposition of Aluminafrom TMA: Growth, Morphology, and Reaction Mechanisms”. Chemistry of Materials 18, 16 (2006).
Atomic Layer Deposition Process for Barrier Applications of
Flexible Packaging
Presented by:Petri JohanssonTampere University of Technology
IntroductionIntroductionThe purpose of atomic layer deposition (ALD) process is to produce a thin, tight and stable coating from gaseous precursors.
The main advantage of ALD is the conformality and uniformity which can be obtained regardless of the orientation or shape of the substrate. I.e., there are no pinholes in the film.
IntroductionIntroductionIn ALD process, thin films of material are deposited one atomic layer at a time.
.
IntroductionIntroduction
exhaust pump
precursor A precursor B
movement gas leakage web
purge purge
L
One possible solution of continuous ALD
Roll-to-roll ALD would open huge possibilities. It would allow all the flexibility and surface control capabilities of ALD to a large scale production.
IntroductionIntroductionThe ALD coating consists of several reaction cycles. One reaction cycle is able to achieve about 0.1 nm layer depending on the coating material and process parameters. Thickness of a typical ALD layer can vary from 1 to over 100 nm.The role of temperature in the ALD process is to provide activation energy. The reactor temperature can vary from room temperature to several hundreds of degrees Celsius.
MaterialsMaterials and methodsand methodsThe materials tested in the study were paper/polymer/Al2O3 –structures.
Polymer layer via extrusion coatingAl2O3 layer in a batch ALD process
4 extrusion coating polymers were used in the study: LDPE, PP PET and PLA.
MaterialsMaterials and methodsand methodsTrimethylaluminum (TMA) and ozone (O3) were used as precursors for the Al2O3 -coatings.All the coatings were produced in thermal ALD processes having different reactor temperatures of 65, 100 or 150 °C.One deposition cycle consisted of a 250 ms TMA pulse, 6 s purge, 3 s ozone pulse and 6 s purge. The deposition started with 40 s ozone pulse and 90 s purge.
MaterialsMaterials and methodsand methodsThe barrier properties against water vapor and oxygen were measured for the obtained materials.The water vapor transmission rate (WVTR) measurements were made according to SCAN P22:68 (cup method).2 atmospheric conditions (normal and tropical) were used in the WVTR -measurements:23 °C, 50 % RH and 38 °C, 90 % RH.
MaterialsMaterials and methodsand methodsThe oxygen transmission rate (O2TR) measurements were made according to a standard ASTM D 3985.The active test area was 50 cm2 ,10 % oxygen was used as a test gas and the measurements were made at 23 °C, 0 % RH conditions.Each WVTR and O2TR result shown in the diagrams is a mean value of two replicates.
ResultsResults and discussionand discussion
Al2O3 layers deposited on LDPE-coated paper
ResultsResults and discussionand discussion
Al2O3 layers deposited on LDPE-coated paper
ResultsResults and discussionand discussion
Al2O3 layers deposited on LDPE- and PP-coated paper
ResultsResults and discussionand discussion
The influence of reactor temperature
ResultsResults and discussionand discussion
Al2O3 layers deposited on PET-coated paper
ResultsResults and discussionand discussion
Al2O3 layers deposited on PET-coated paper
ResultsResults and discussionand discussion
Al2O3 layers deposited on PLA-coated paper
ResultsResults and discussionand discussion
Al2O3 layers deposited on PLA-coated paper
ConclusionsConclusions
Comparison between the WVTR results
ConclusionsConclusions
Comparison between the O2TR results
AcknowledgementsAcknowledgements
We wish to thank:
TEKES, Stora Enso, UPM-Kymmene and Savcor for financial support.
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