A STUDY OFTHE EFFECTS OF FIN ANDOVERLAP HEAT SEALS
A STUDY OF THE EFFECTS OF FIN AND OVERLAPHEAT SEALS ON THE PERMEABILITY 0FSELECTED PLASTIC FILMSThesis for the Degree of M. S.MICHIGAN STATE UNIVERSITYRICHARD F. WITTE1967
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ABSTRACTA STUDY OF THE EFFECTS OF FINAND OVERLAP HEAT SEALS ON THE PERMEABILITY OF SELEDTED PLASTIC FILMSby Richard F. WitteBecause permeability values of packaging materials may beaffected by physical changes taking place during package fabrication, the author chose to study the effects of fin and overlap heat seals on the permeability of the material utilizedfor a packaging situation.The researcher studied the perme-ability relationships by utilizing a Davis cell and gas chromatographic analysis.Permeability determination was firstcarried out on the material.Fin and overlap heat seals werethen applied to the same material, and permeability valueswere once again determined.Fin, overlap, and sample perme-ability values were compared for the same material.In thismanner, the author not only determined the effects of heatsealing on permeability, but also the relative differencesbetween fin and overlap style heat seals.The major findings of the research pertain to thefollowing materials:2 mil nylon, 2.5 mil polyethylene/nylonlaminant, 2 mil polyethylene/hyIon/polyethylene laminant, 2mil polyethylens/phenoxy/polyethylene laminant, 2 mil polyethylene.All results have shown that no significant changesoccurred in the permeability rates due to fin and overlapheat888.1 8 o
A STUDY OF THE EFFECTS OF FINAND OVERLAP HEAT SEALS ON THE PERMEABILITYOF SELECTED PLASTIC FILMSbyRichard F. WitteA THESISSubmitted toMichigan State Universityin partial fulfillment of the requirementsfor the degree ofMASTER OF SCIENCEDepartment of Forest Products1967
ACKNOWLEDGMENTSWithout the personal and professional support of Dr. H.E.Lockhart and David Pegaz, this work never would have achievedorigin or substance.To these friends and to all who havecontributed, my reSpect and my gratitude.ToSharon and Kristenii.
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TABLE OF CONTENTSPageACKNOWLEDGMENTS .ii.TABLE OF CONTENTS . iii.LIST OF TABLES .LIST OF ILLUSTRATIONS .LIST OF APPENDICES .INTRODUCTION .BACKGROUND .EXPERIMENTAL EQUIPMENT AND PROCEDURES .EXPERIMENTAL RESULTS23.ANALYSIS AND MAJOR FINDINGS .27.DISCUSSION AND CONCLUSIONS .1.33.APPENDICES .36.BIBLIOGRAPHY .“5.iii.
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LIST OF TABLESPage. TableDavis Cell Leakage Rate Tests.19.II.Permeability Values of all Samples .2A.III.MicrOprOJection Measurements Of 000.026.Permeability Values versus Number of HeatSeals on Polyethylene .iv.30.
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LIST OF ILLUSTRATIONSPagemrwmI-IFigurePermeability Testing System .Davis Cell in Open(t0p) and Closed Positions .10.Recorder, Cell System and Gas Partitioner .12.Sentinel Impulse Heat Sealer .13.Scherr MicrOproJector and Device to hold 0.000Davis Cell in Testing Simulation .Cell Gap Distance .Aluminum Blank and Overlap Sample Position .Valve Leakage Determination ApparatusRecorder Trace of Partitioner Output.Leak Test Method of Heat Seal Integrity.114.16.18.18.37.AI.AA.
LIST OF APPENDICESAppendixPageI.Valve Leakage Determination .36.II.Permeability Testing Procedures .38.III.Permeability Value Determination .MO.IV.Leak Test Method of Heat Seal Integrity .143.vi.
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IntroductionAlthough considerable research has been conducted regarding permeability of plastic films, very little work has beencarried out regarding the effects of physical changes thatmay take place during package fabrication procedures.Atypical physical change could be represented by the resultsof a heat sealing operation.Common laboratory proceduresevaluate heat seal strengths, but such values may or may nothave a bearing on the environmental performance of the sealslater on in the total package life cycle.The total package life cycle could be depicted by the‘ following stages:1.Material for package2.Fabrication of material into a package3.Package filling operations4.Distribution of filled packages5.Final purchase of package and productWhen considering the total life cycle of a package, variablesmay occur within each stage resulting in changes in the overall performance of the package.In essence, it could berationalized as moving from a known permeability value in thefirst stage to vague permeability awareness in the last stage.In addition, temperature, relative humidity, and time may allaffect the package and contained product.However, since theproper film or packaging material can be matched against themost extreme conditions of environment in the distribution1.
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2.channel, it becomes a problem of looking at the original package forming operations and resulting influences on the materials.It is known that package fabrication operationsinfluence the material.The changes may affect the desir-ability of the product within the package.Because stages3, A, and ultimate satisfaction in stage 5 depend on stage 2,it becomes imperative to evaluate the effects of the variablestaking place in stage two.The author chose to study theeffects of fin and overlap heat seals on the permeability ofthe material.Initial experimentation in permeability studies of heatseals on polyethylene indicated that a possibility did existfor an increase in permeability due to application of heatseals.The initial investigation led to a more refined tech-nique for evaluating the effect of heat seals on the permeability of plastic films.The refined technique included thedetermination of leakage rates for fin seal, overlap seal,and material testing procedures as carried out with the DavisCell.The Davis Cell coupled with gas chromatographic analy-sis enabled the author to determine the effects of fin andoverlap heat seals on the permeability of the material.
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BackgroundBrown(1)f in his article, ”Permeability and Shelf Life”,Said that known permeability rates of flexible materials areunreliable guides for predicting the life of products contained within these materials.He concluded that packagestorage tests were the only reliable way of achieving guides.Hu and Nelson(2) in 1953 experimented with water vaporand oxygen transmission through plastic films.At that time,they recognized that the integrity of the completed plasticpackage as in the case of.a pouch could be severely damagedby the variability within the sealing processes.They ex-pressed belief that a need for testing the effectiveness ofthe sealed area was of primary importance.As early as 194“ and possibly earlier, Rabak andDeHority(3) experimented with the effects of heat sealing onthe water vapor permeabilities of coated cellophanes.Theybelieved that even though much work had been conducted on thewater vapor resistance of packaging materials that were heatsealable, virtually no studies had been reported on theeffects of sealing methods or the efficiency of the heatmodified areas of the materials.They thought that the natureof the sealing operation had a direct bearing on the overallefficiency of the packaging material.esis was as follows:Their initial hypoth-If excessive temperature or pressureswere utilized, it was quite possible to change the heat sealedmaterial chemically as well as physically.fNumbers in parentheses identify Bibliography entries.3.
A.A reciprocal heat sealing device was used to controltemperature, pressure, and time of contact.Sealing tempera-ture, pressures, and times of contact were varied.Theeffects of the variables were determined by exposing thesealed samples to a standard dish water-vapor permeabilitytest similar to the General Foods or Tappi Test Methods.Thedish containing the sample was placed in a testing tunnelwith an air velocity of 500 ft./minute, relative humidity at87%, and an average temperature of 89 F.The vapor pressuredifferential between the atmosphere in the tunnel and the in-side of the test dish was calculated to be 28 mm of mercury.Calculation of the water vapor permeability constants wasexpressed as grams of water vapor passing through one squaremeter of surface per 24 hr. /'mm of mercury difference inwater-vapor pressure between the outside and inside of thedish.Two heat seal treatments were used:1) an imprint treat-ment to permit measurement of the effects of temperature andpressure on the lacquers of single thicknesses of cellophaneand, 2) overlap seals were included to ascertain the extentof edge leakages.The following conditions were used forheat sealing purposes:Sealing time—- 1 secondSealing temperature-- 285o - 385 - 450 Pressures-- 10 and 50 p.s.i.The results of the tests indicated definite trends:1.Sealing temperatures of 285 F were not high enoughto create firm bonds.
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5.2.Sealing temperature of 385 F. created firm bondswith considerable disturbance of the lacquersresulting in permeability increases of 3 to 8times over that of the material.3.Temperatures of “50 F. were very destructive.A.Ten p.s.i. caused considerably less impairmentthan 50 p.s.i.5.The efficiency Of overlap seals appeared to beless affected by variations in sealing pressuresthan the imprint type.Rabak and Stark(A) deveIOped a starch-iodide method thatdemonstrated the porosity of the heat seal area of waxed paper.The method consisted of passing a heat sealed waxed wrapthrough a 1% aqueous iodide solution.Subsequent to this, thewrap was washed in water and dipped in'a 1% starch solution.Deposition of blue-black starch iodide within the heat sealedarea served as an indicator of the porosity of the heat sealedarea.Rabak and Stark(5) also experimented with sealing temperature effects on waxed paper regarding water vapor perme-ability. By varying heat sealing temperatures on various typesOf coatings coupled with the Tappi Dish Determinations Method,they concluded that heat sealing definitely impaired the watervapor resistance of waxed papers.The extent of impairmentincreased with the elevation of sealing temperature.Other seal tests performed by researchers included thoseof Edwards and Strohm(6).Their main concern involved the
6.efficiency of seals on foil packages.They could see littlevalue in utilizing impervious wrapping materials while leav-ing the Joints unsealed in such a manner as to permit readymovement of air in and out of the package.Packets made fromfoil were tested for water vapor permeability by enclosinganhydrous calcium chloride in a heat sealed package.Thepackets were stored in a cabinet at lOO F.and 90 R.H.Ninemonths were then allowed to pass and the increase in weightwas recorded.The efficiency of various closures was investi-gated by tests on cartons and bags fabricated in several waysand sealed by different methods.The results indicated thataluminum foil with applied heat seal proved to be the bestmethod of closure.Past records indicate that substantial research has beenconducted on seal integrity regarding water vapor permeability.The latest trend has been to test the entire package in apouch or similar form.This is the next most logical step tofurther package research.Brickman(7) measured the gas transmission rates of materials in pouch form.He also expressed doubts regardingpermeability values of materials in sheet form due to the nonrepresentative exposure conditions.The method used byBrickman simulated actual package conditions better than othertechniques.His method consisted of a pouch formed over astyrene insert.The insert was utilized to assure a nearlyuniform volume for the pouch.The air was exhausted from thepouch, and nitrogen was introduced at a specified gaugepressure.A rubber patch cemented on the side of the pouch
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7.facilitated syringe samples without distorting the pouch inany manner.Gas samples were drawn off from the pouches andintroduced into a Beckman Gas Analyzer.Pouch conditionsincluded wet and dry interiors exposed to different room andrefrigerated temperatures and relative humidities.Durationof tests for laminated materials of low oxygen permeabilitywas from 20 to 30 days.This was necessary to allow equi-librium or a fairly constant permeation rate.The bulk ofBrickman's work was concerned with cellophane/polyethylene,mylar/polyethylene and other forms of similar laminants.The following is a summary of Brickman's results:1.CelIOphane/polyethylene pouches were affectedmore by changes from dry to wet packs thanother laminants in terms of permeation.2.Pouches formed of laminated materials were notaffected nearly as much by changes in exposureconditions as polyethylene and mylar materials.3.Polyethylene wet packs had higher oxygenpermeation rates than did dry packs exposedto the same conditions.
Experimental Equipment and ProceduresThe permeability testing system is shown by the schematicin Figure I.The system was developed by Lockhart(8).Oxygenand nitrogen were the two gases utilized for all tests.Testswere conducted under ”dry conditions”; consequently, no humiditydevices were required within the system itself.The humiditysensing device was used only for the assurance of dry gasconditions.Dry conditions were represented by 1.5% relativehumidity or less.The relative humidity sensing device wasan Electric Hygrometer Indicator (Catalog no. 4-4902) byAmerican Instrument Company with Aminco-Dunmore sensingelements.A manometer within the system permitted detection of anydifferential pressure in the Davis Cell.gen, and the testgas,The sweep gas, nitro-oxygen, both pass through drying tubesthat contain Drierite Dessicant.Flow measurement was achievedwith rotameters by Brooks and Fisher-Porter and metering valvesby Hoke(8).As mentioned previously, the manometer permittedvisual examination of the pressure differential between thesweep and test gas lines.The differential was zero duringall tests; thus achieving isostatic conditions within theDavis Cell.The Davis Cell is stainless steel, constructed in twosections.(Figure 2).It provides a sample area of 156 square centimetersThe cell is locked in a clamp which appliespressure at three points on the tOp of the cell.The sealbetween the upper portion of the cell and the material to be8.
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Shut offNitrogenDrying Tubes//wanometer9ASeptum,AA9%E-\B DeviceSensingHumidityIDavis CellIIIRotameters -Hoke Valve82Toggle Valve@«Metering ValveSamplingPermeability Testing SystemFigure 1e z - orRegulatorand PressureOxygen8-Needle Valve
10.Figure 2Davis Cell in Open(t0p) and Closed Positions
11.tested is provided by the material and the stainless steelcell itself.The seal between the lower half of the cell andthe material is provided by a neOprene O-ring bearing againstthe material.Gas samples were analyzed with a Fisher Gas Partitioner,Model 25V.The column system is designed for an 80 ml/minutecarrier flow.The instrument used to record the output of thepartitioner was a Sargent Model SR Laboratory Recorder.Out-put of the partitioner was recorded at four inches per minute.Figure 3 shows the recorder, cell system, and gas partitioner.The heat sealing device was a Sentinel Pacemaker ThermalImpulse, Model 12-TP with glass cloth covering the heat sealingbands on both Jaws (Figure A).Jaw pressures were controlledby an air pressure valve connected to a pressurized line withinthe sealer.Total impulse range covered 1.20 seconds in grad-uatiOns of 0.10 seconds.Heat sealed cross sections were observed with a ScherrMicroprojector.observations.A 100 magnification lens was used for allThe samples were held in a device so as tofacilitate exposure of the edge of the heat seals to the lightand lens.Seals were viewed on a screen upon which the imageof the heat seal was reflected.A steel machinist's scalein l/lOO inch increments and a small hand lens of ten magnification were used to measure the thickness of the heat sealsand adjacent material.The microprojector and the device forholding the samples are shown in Figure 5.
Recorder, Cell System and Gas PartitionerFigure 3-12-
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1U.Figure 5Scherr Mi croprojector and Device to hold H eat Seals
15.Earlier tests had indicated an excessive leakage rate forthe Davis Cell.It, therefore, became necessary to examinethe valves on the lower half of the cell to determine thesource of the leak.The original valves were identified asthe source of the leak, and new valves were installed.leakage determination is explained in Appendix I.ValveThe follow-ing description of testing procedures helps to explain whyvarious components of the cell system were leak rated.Thefilm sample to be tested was placed in the cell with a stainlesssteel-sample seal on the top half and an O-ring-sample seal onthe bottom half of the cell.After the film sample was placedin the cell, a 100 ml/min. oxygen and nitrogen flow was imposed on each side of the cell.flow for one-half hour.Both sides were allowed toAfter this period of time, the bottomhalf of the cell was isolated by means of the two Hoke valves.The cell system would then be as shown in Figure 6.The permeation rate of oxygen into the lower half of thecell was determined by taking samples from the lower half witha syringe and septum device.All samples were drawn from thelower half of the cell; consequently,the leakage rate betweenthe film sample and the O-ring had to be determined for finalcalculation of permeability rates.After the leakage rate determination of the new valves,the valves were installed on the lower half of the Davis Cell.Subsequent to this, a leakage rate determination was carriedout for the cell system.The lower half cell-valve system wasleak tested as shown in Figure 6 with aluminum foil serving asa blank.This test gave a true indication of the leakage rate
16.'11 Hoke Valve (closed)o— Sampling Septum100 ml/min. Oxygen FlowIUpper Half of CellLower Half of Cell(NitrOgen)-];L; ,as}Vertical Arrows Simulate Jig PressureFigure 6Davis Cell in Testing Simulation
17.between the O-ring on the bottom half and the aluminum blank.Due to the physical differences of fin and overlap seals, itwas necessary to leak test both heat seal styles.It was alsonecessary to study the gap distance between cell faces ifconstant leakage rates were to be established.Earlierexperimentation of leak testing fin and overlap seals withouta known gap distance had introduced a problem of Obstructionof oxygen and nitrogen flows.The force applied in closingthe cell could be such that the interior clearance between tOpand bottom of the cell was reduced to zero or nearly so.Atthat minimum point, gas flows across the surfaces of the filmwith fin or overlap seals were obstructed.The problem in-volved minimizing the leakage rates for fin and overlap sealswhile arriving at a maximum gap distance for proper gas flows.Figure 7 shows the gap distance (x) arrived at by a trial anderror method.The trial and error method established leakagerates at decreasing gap distances using aluminum blanks(Tab1e ILAfter test number 8 (Table I) had been performed, an overlapseal-aluminum blank combination was tested in the configurationshown in Figure 8.At this time, it was discovered that a0.010 inch gap distance was the minimum distance that could beused for proper gas flows.Once the correct gap distance wasestablished, only fin seal-aluminum blank combinations remainedto be leak rated.All heat seals were perpendicular to theflow of the test gas.This was true for leakage rate determin-ation and actual material testing procedures.All materialtesting was done with a 0.010 inch gap distance.
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/V18.Top part of cellJr///”Fi 1 mLBottom part of cellFigure 7Cell Gap DistanceL1xygen y/O flowTop part of cellr'A:LB1ank .‘IBottom.part of celle[/- Figure 8Aluminum Blank and Overlap Sample PositionOverlapsample
19.Table I.Test No.Davis Cell Leakage Rate TestsType of TestGapDistanceLeakage Ratg(ml/214 hr.-2.5 mil aluminum blankUnknown22.5 mil aluminum blankUnknown2Installed new aluminumblankUnknownAluminum blank with 1mil nylon overlap heatseal under the blankUnknownSame as no. A - newsamples installedUnknownAluminum blank with 1mil nylon overlap heatseal under the blankAluminum blank0.016810.013800.010Aluminum blank with 1mil nylon overlap heatseal under the blank100.010Aluminum blank with 2mil nylon overlap heatseal under the blank0.01011Aluminum blank0.0101312Aluminum blank0.010100.0101213Aluminum blank with 2mil poly/phenoxy/polyfin heat seal under theblankI“Aluminum blank with 2mil nylon fin heat sealunder the blank0.010)
20.The highest leakage rate was 13 ml/24 hr.-m2;rate was 2 ml/24 hr.-m2 (Table I).the lowestOverlap and fin sealsprobably did not contribute to a much higher rate.The leak-age rate proved to be very low regardless of the conditions.The author chose to use an average of all leakage values intests 8-1“.Tests 1-5 were not included due to the unknowngap distances.Tests 6-7 were excluded because of the obvi-ously incorrect gap distances.The calculated average leakagerate was 7 ml/2N hr.-m2.Leakage rate studies indicated that the number of samplesextracted from the cell had a direct bearing on the apparentpermeability.It was also discovered that errors would beintroduced when intervals between samples were one hour orless.It was decided not to take more than Six to seven samplesat intervals of 1 1/2 to 2 hours.The sampling intervals weredependent on the material being tested;only 2 mil polyethylenewith its high permeability rate required sample intervals ofless than one hour.Tests conducted overnight were based onthree to four samples.Syringe samples were 0.20 ml.Totalvolume extracted from the cell was 1.20 to 1.40 ml. per test.This represented approximately 6% of the cell volume from whichthe samples were drawn.The materials used for permeability testing were:1.2 mil nylon 6-Capran, type 7702.2.5 mil polyethylene/nylon laminationa.1.5 mil Capranb.1.0 mil polyethylene
21.3.2 mil polyethylene/hylon/polyethylene laminationa.1.0 mil nylonb.2 - 0.5 mil polyethyleneA.2 mil polyethylene/phenoxy/polyethylene lamination5.2 mil polyethylene - Dow Poly Film, type 114 t-lThe permeability of a chosen material was first established byconducting two tests on two different samples.In all cases,agreement between the two samples proved to be very satisfactory.After establishing the permeability of the material, heat sealedsamples were exposed to the same conditions to determine theeffect of the heat seal.Refer to Appendix II for the perme-ability testing procedure and Appendix III for permeabilityvalue calculations.A suitable heat sealing combination was difficult toestablish for 2 mil nylon material.seemed to be the main problem.Pinholes in the heat sealIt was decided to avoid wasting"cell time" by fabricating sealed samples of the material forheat seal integrity testing prior to installation of anotherlike sample for permeability testing.The heat seal integritytest was very simple, took little time, and required no addi-tional equipment.It was performed as shown in Appendix IV.Overlap heat sealed samples of 2 mil nylon material werepressure tested over the following impulse-pressuresettings:Impulse times were varied from 0.10 seconds to 1.20 secondsin 0.10 second intervals.Pressure was maintained at 15 p.s.i.All results indicated "leakers".binations were attempted.Higher impulse-pressure com-A successful combination of 0.80
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22.sec.-60 p.s.i. produced suitable seals.Heat seal combinationsfor the remaining four materials were much simpler to establish.Adoption of the heat seal integrity test enabled the author toinitiate permeability testing as close as possible to the heatseal leakage boundaries of the last four materials.The heatseal leakage boundary of a particular material-impulse-pressurecombination was approached as follows:Pressure was held con-stant; impulse times were varied in even increments from lowto high settings.Each successive heat seal was subjected tothe heat seal integrity test.If it passed the test, anotherheat seal was fabricated with a higher impulse setting.Even-tually a point (boundary) was reached where the materialimpulse-pressure combination produced heat seals that failedthe seal integrity test.Permeability testing was conductedon the heat sealing combination that immediately preceeded thecombination that failed.Possible distortion factors couldchange the characteristics of the material while undergoingthe seal integrity test.In no cases were one and the samesample subjected to the seal integrity and permeability test.Standardizing all techniques associated with the experimental equipment and procedures made it possible to produceprecise and valid results.The reported values for leakageand material testing represent results that were achieved bycareful consideration of the variables that were treated asconstants after study.
Experimental ResultsRegardless of the material, all heat seal cooling timeswere maintained at 6.0 seconds.No mention of cooling timesare made in the remaining text.All impulse and Jaw pressurevariables are shown as seconds - p.s.i.Two mil nylon material was used for initial permeabilitytesting.After establishing the permeability rate of thematerial, overlap and fin style heat seals were applied tothe material with a 0.80 sec. - 60 p.s.i. combination.Thepermeability values of the unsealed material were comparedto the values of the heat sealed material (Table II).As theresults indicate, no apparent significant differences exist.The first laminated material selected for study was 2.5mil polyethylene/nylon.Two mil nylon had not shown variabil-ity in permeability with applied heat seals; therefore, it wasdecided to study the permeability of the approximate identicalmaterial in laminant form.The purpose was to reduce thepressure or impulse and contain the entire depth of the heatseal within the polyethylene coating.Two mil polyethylene/hylon/polyethylene and 2 mil polyethylene/phenoxy/polyethylene were the last laminated materialstested.All values are shown in Table II.Preliminary experimentation with overlap heat seals onpolyethylene had indicated a possible increase in permeability.The data in Table II for 2 mil polyethylene seemed to substantiate the preliminary experimentation.To assure prOperanalysis, data of a different nature was gathered.23.Heat seal
Table II,MaterialAggregate Perm.Rate 2(ml/2A hr.-m )2 milnnylonn2.5 mil poly/nylonm.1:Permeability Values of all SamplesLeakage Rate2hr.-m )(ml/2M23212O777Actual Perm.Av. Perm. RateRate 2 (polyethylene)(ml/2A hr.-m ) (ml/2A hr.-m2)Heat Seal StyleIm 2? N p§§ 33351285115 3.232331111112218 ) T8881 331132?N ' Of T85”TSeaII0.800.8060601l.000AA82.87Average of 2Average of 773131OverlapF10@0750,75202011.OOOAA82.871Average 0f 751456Average of 21OyerlapElm0.350 35151511.0004482.871Average of 2.0004A8.OOOAAB2.872.87Average of 212 mialOIy/hylon/polynn32 milnpoly/phenoxy/poly”nAverage of ;.1 000,25202011l97191film910002011Average of 2Average of 2‘42 mil polyethylene229372286\\: 33373235072236/8” 7 2261aye/1% p*231.0030722379\\ O 607 a“ verlapH1.00307.0029137233618.61Finn1.003012343 0*Indicates the spread for two tests based on the larger value1
25.thickness measurements (Table III) provided the additionalinformation.Two mil nylon had not shown significant perme-ability value differences.Because of this, the researcherwanted to compare heat seal thickness measurements for nylonand polyethylene material.Final analysis would then dependa;on the comparison of the data in Table II and III.
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yethylenemil polyethylenemil polyethylenemil polyethylene0.80-600.4400.480mil nylon0.46093.20.80-600.4200.450mil nylonmil 73.371.791.794.40.80-600.4250.45090.9mil nylon0.80-60(Sec.-p.s.i.)(4)Column 2Column 10.400(inches)(3)Imp.-Pres.(2)Seal Thicknessat Center0.440(inches)Dbl. Thicknessof Material(100 Magnification)MicroproJection Measurements of Polyethylene and Nylon Heat Sealsmil nylonMaterialTable III(5)73.692.9(%)TheAverage26.010101010]
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Analysis and Major FindingsExt
effects of fin and overlap heat seals on the permeability of the material. Initial experimentation in permeability studies of heat seals on polyethylene indicated that a possibility did exist for an increase in permeability due to application of heat seals. The initial investigation led to a more refined tech-
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Government ofthe Russian Federation prior to taking any such measure. Ifprior and prompt consultations are not possible because ofan emergency situation, the Government ofthe United States shall consult with the Government ofthe Russian Federation as soon as possible after taking the measure. Article 7: Amendments.
