1、Designation: D 2578 08Standard Test Method forWetting Tension of Polyethylene and Polypropylene Films1This standard is issued under the fixed designation D 2578; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the measurement of the wettingtension of a polyethylene or polypropylene film surface incontact with d
3、rops of specific test solutions in the presence ofair.1.2 The values stated in SI units are to be regarded asstandard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.3 This standard does not pu
4、rport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific hazardsstatements are given in Sec
5、tion 8.NOTE 1This test method is equivalent to ISO 8296.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:ISO 829633. Summary of Test Method3
6、.1 In this test method drops of a series of mixtures offormamide and ethyl Cellosolve4of gradually increasing sur-face tension are applied to the surface of the polyethylene orpolypropylene film until a mixture is found that just wets thefilm surface. The wetting tension of the polyethylene orpolypr
7、opylene film surface will be approximated by the surfacetension of this particular mixture.4. Significance and Use4.1 When a drop of liquid rests on the surface of a solid, anda gas is in contact with both, the forces acting at the interfacesmust balance. These forces can be represented by surfaceen
8、ergies acting in the direction of the surfaces and it followsthat:gGL cos u5gGS 2gSL (1)where:u = angle of contact of the edge of the drop with thesolid surface,gGL = surface energy of the gas - liquid interface,gGS = surface energy of the gas - solid interface, andgSL = surface energy of the solid
9、- liquid interface.4.1.1 The right side of the above equation (the differencebetween the surface energies of the gas - solid and solid -liquid interfaces) is defined as the wetting tension of the solidsurface. It is not a fundamental property of the surface butdepends on interaction between the soli
10、d and a particularenvironment.4.1.2 When the gas is air saturated with vapors of the liquid,gGL will be the surface tension of the liquid. If the angle ofcontact is 0 the liquid is said to just wet the surface of thesolid, and in this particular case (since cos u = 1) the wettingtension of the solid
11、 will be equal to the surface tension of theliquid.4.2 The ability of polyethylene and polypropylene films toretain inks, coatings, adhesives, etc., is primarily dependentupon the character of their surfaces, and can be improved byone of several surface-treating techniques. These same treatingtechni
12、ques have been found to increase the wetting tension ofa polyethylene or a polypropylene film surface in contact withmixtures of formamide and ethyl Cellosolve in the presence ofair. It is therefore possible to relate the wetting tension of apolyethylene or a polypropylene film surface to its abilit
13、y toaccept and retain inks, coatings, adhesives, etc. The measuredwetting tension of a specific film surface can only be related toacceptable ink, coating, or adhesive retention through experi-ence. Wetting tension in itself is not a completely acceptablemeasure of ink, coating, or adhesive adhesion
14、.NOTE 2A wetting tension of 35 dynes/cm or higher has beengenerally found to reveal a degree of treatment normally regarded asacceptable for tubular film made from Type 1 polyethylene and intendedfor commercial flexographic printing. It is, however, possible that someother level of wetting tension m
15、ay be required to indicate the acceptability1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.19 on Film and Sheeting.Current edition approved Nov. 1, 2008. Published November 2008. Originallyapproved in 1967. Last previ
16、ous edition approved in 2004 as D 2578 - 04a.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from
17、American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Registered trademark of Union Carbide Corp. for ethylene glycol monoethylether.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Har
18、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.of polyethylene films made by other processes, or from other types ofpolyethylene, or intended for other uses.At the present date, insufficient experience has been gained to state agenerally acceptable level of wetting tension f
19、or polypropylene films forcommercial flexographic printing.5. Interferences5.1 Since the wetting tension of a polyethylene or polypro-pylene film in contact with a drop of liquid in the presence ofair is a function of the surface energies of both the air - film andfilm - liquid interfaces, any trace
20、 of surface-active impurities inthe liquid reagents or on the film may affect the results. It is,therefore, important that the portion of the film surface to betested not be touched or rubbed, that all equipment bescrupulously clean, and that reagent purity be carefullyguarded. Glass apparatus in pa
21、rticular is likely to be contami-nated with detergents having very strong surface tensionreducing ability unless specific precautions are taken to ensuretheir absence such as cleaning with chromic-sulfuric acid andrinsing with distilled water.6. Apparatus6.1 Cotton-Tipped Wooden Applicators, approxi
22、mately 150mm (6 in.) in length.6.2 Burets, two, 50-mL.6.3 Bottles, 100-mL, with caps and labels.7. Reagents and Materials7.1 Prepare mixtures of reagent grade formamide(HCONH2) and reagent grade ethyl Cellosolve(CH3CH2OCH2CH2OH) in the proportions shown in Table 1for the integral values of wetting t
23、ension in the range overwhich measurements are to be made. For extremely precisework, mixtures for determining fractional values of wettingtension may be made up by interpolating between the concen-trations shown in Table 1.NOTE 3Although the mixtures of ethyl Cellosolve and formamideused in this te
24、st method are relatively stable, exposure to extremes oftemperature or humidity should be avoided.7.2 If desired, add to each of the formamide ethyl Cello-solve mixtures a very small amount of dye of high tinctorialvalue. The dye used should be of such color as to make dropsor thin films of the solu
25、tions clearly visible on the surface ofpolyethylene or polypropylene film and must be of suchchemical composition that it will not measurably affect thewetting tension of the solutions in the concentration used.57.3 Fully prepared mixtures of these reagents in varyingconcentrations are available fro
26、m a number of commercialsources. Pens containing these mixtures are also commerciallyavailable. However, correlations between these options andfreshly prepared solutions have not been established.NOTE 4Care must be taken when handling pens. Prolonged exposureto the atmosphere, temperature or humidit
27、y extremes, exposure tocontaminants, or use beyond the stated expiration date will change theircharacteristics creating a potential for erroneous results.8. Hazards8.1 Formamide may cause skin irritation and is particularlydangerous in direct contact with the eyes. Safety gogglesshould be worn when
28、making up new test mixtures.8.2 Ethyl Cellosolve is a highly flammable solvent.8.3 Both ethyl Cellosolve and formamide are toxic and poseexposure risks. Consult the applicable MSDS before use andensure that the appropriate Personal Protective Equipment(PPE) is used, especially when preparing new sol
29、utions.8.4 All tests should be performed with adequate ventilation.9. Sampling9.1 The minimum amount of film required for this testdepends upon the skill of the operator. This usually amounts toone sample across the entire width of a roll in order to obtaina representative value.9.2 Extreme care mus
30、t be taken to prevent the surface of thefilm sample from being touched or handled in the areas uponwhich the test is to be made.9.3 Usually it will be adequate to make one determination ateach location14 ,12 ,34 of the way across the width of thefilm, to arrive at an average value for the sample or
31、todetermine when treatment is uneven.10. Conditioning10.1 ConditioningCondition the test specimens at 23 62C (73.4 6 3.6F) and 50 6 10 % relative humidity for notless than 40 h prior to test in accordance with Procedure A ofPractice D 618 unless otherwise specified by agreement or therelevant ASTM m
32、aterial specification. In cases of disagree-ment, the tolerances shall be 61C (61.8F) and 65%relative humidity.5“DuPont Victoria Pure Blue BO” at a maximum concentration of 0.03 % hasbeen found satisfactory.TABLE 1 Concentration of Ethyl CellosolveFormamideMixtures Used in Measuring Wetting Tension
33、ofPolyethylene and Polypropylene FilmsFormamide,Volume %Ethyl Cellosolve,A%Wetting Tension,Bdynes/cm0 100.0 302.5 97.5 3110.5 89.5 3219.0 81.0 3326.5 73.5 3435.0 65.0 3542.5 57.5 3648.5 51.5 3754.0 46.0 3859.0 41.0 3963.5 36.5 4067.5 32.5 4171.5 28.5 4274.7 25.3 4378.0 22.0 4480.3 19.7 4583.0 17.0 4
34、687.0 13.0 4890.7 9.3 5093.7 6.3 5296.5 3.5 5499.0 1.0 56ACellosolve is the registered trademark of Union Carbide Corp. for ethyleneglycol monoethyl ether.BMeasured under conditions of 23 6 2C and 50 6 5 % relative humidity.D257808210.2 Test ConditionsConduct the tests at 23 6 2C (73.46 3.6F) and 50
35、 6 10 % relative humidity unless otherwisespecified by agreement or the relevant ASTM material speci-fication. In cases of disagreement, the tolerances shall be 61C(61.8F) and 65 % relative humidity.NOTE 5In specific cases, such as control testing, where the condition-ing requirements cannot be met
36、and the data are of direct assistance to theoperation, other conditioning procedures can be used and recorded in thereport.11. Procedure11.1 Wet the very tip of a cotton applicator with one of themixtures. Use only a minimum amount of liquid as an excessof reagent can affect the end point of the tes
37、t.11.2 Spread the liquid lightly over an area of approximately6.5 cm2(1 in.2) of the test specimen. Do not try to cover alarger area lest there be insufficient liquid to give completecoverage.11.3 Note the time required for the continuous film of liquidformed in 11.2 to break up into droplets. If th
38、e continuous filmholds for2sormore, proceed to the next higher surfacetension mixture, but if the continuous film breaks into dropletsin less than 2 s, proceed to the next lower surface mixture. Aclean, new cotton applicator must be used each time to avoidcontamination of the solutions (even for suc
39、cessive dips intothe same solution).NOTE 6The solution is considered as wetting the test specimen whenit remains intact as a continuous film of liquid for at least 2 s. The“reading” of the liquid film behavior should be made in the center of theliquid film. Shrinking of the liquid film about its per
40、iphery does notindicate lack of wetting. Breaking of the liquid film into droplets within 2s indicates lack of wetting. Severe peripheral shrinkage may be caused bytoo much liquid being placed upon the film surface. Experience with thetest will give excellent insight into “reading” the liquid film b
41、ehavior.11.4 Proceeding in the direction indicated by the results of11.3, continue repeating 11.1 through 11.3 until it is possible toselect the ethyl Cellosolve-formamide mixture that comesnearest to wetting the film surface for exactly 2 s. The surfacetension of this mixture in dynes per centimetr
42、e is called thewetting tension of the polyethylene or polypropylene filmspecimen.NOTE 7Since the surface tension of the formamide/ethyl cellosolvesolutions can change, for example, through evaporation of one or bothcomponents, or through contamination, and is dependent upon tempera-ture, the actual
43、surface tension of the solution that wet the film for exactly2 s should be measured. This can be accomplished very simply with asurface tensiometer.611.5 Experience with this test has shown that on occasionerroneous wetting tension results can be obtained when thefinal wetting tension is determined
44、by working progressively tolower surface tension mixtures when practicing 11.1-11.4.Itisrecommended that the test analyst should check the reportedwetting tension of the film by working progressively to highersurface tension mixtures.12. Report12.1 Report the average value of the wetting tension of
45、eachsample to the nearest 0.5 dynes/cm.12.2 If the polyethylene or polypropylene film has beenunevenly treated, it may not be possible to arrive at a singlevalue of wetting tension. In this case, report the individualvalues whenever the largest value exceeds the smallest by morethan 1 dyne/cm.13. Pr
46、ecision and Bias713.1 Precision:13.1.1 Table 2 is based on an interlaboratory study con-ducted in 1995 in accordance with Practice E 691 involvingthree materials and thirteen laboratories. Each test result wasthe average of three individual determinations. Each laboratoryobtained three test results
47、for each material on two days.13.1.2 The values of the repeatability standard deviation Sr,reproducibility standard deviation SR, the 95 % repeatabilityand reproducibility limits on the difference between two testresults, r and R, respectively, for different treatment levels havebeen determined and
48、are shown in Table 2. The resultsdemonstrate that the precision of the results depends on thetreatment level (wetting tension) of the film, the higher thetreatment level, the higher the variability between single testresults obtained in different laboratories, or the lower theprecision.13.1.3 Defini
49、tions:WarningThe following explanations of r and R are onlyintended to present a meaningful way of considering theapproximate precision of this test method. The data in Table 1should not be rigorously applied to the acceptance or rejectionof material, as those data are specific to the interlaboratorystudy and may not be representative of other lots, conditions,materials, or laboratories. Users of this test method shouldapply the principles outlined in Practice E 691 to generate dataspecific to their laboratory and materials, or between specificlaboratories. The
