1、Designation: D 5946 04Standard Test Method forCorona-Treated Polymer Films Using Water Contact AngleMeasurements1This standard is issued under the fixed designation D 5946; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers measurement of the contactangle of water droplets on corona-treated polymer film sur-faces
3、.NOTE 1There is no similar or equivalent ISO standard.1.2 The values stated in SI units are to be regarded as thestandard. The values given in brackets are for information only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsi
4、bility 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.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 724 Test Method for Surface Wettability o
5、f Paper (Angle-of-Contact Method)E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 static contact angle, u (degrees), nthe angle be-tween the substrate surface and the tangent line d
6、rawn to thedroplet surface at the three-phase point, when a liquid drop isresting on a plane solid surface.3.1.1.1 DiscussionContact angle values can be deter-mined as follows: (1) by analyzing an image of a droplet usingvarious projection or reflective devices and measuring thecontact angle directl
7、y with a protractor by using tangentialalignment of a cursor line or the use of reference alignmentprocedures (Test Method D 724); or (2) by analyzing an imageof a droplet using various projection or reflective devices andmeasuring the height and width on the substrate surface tocalculate the contac
8、t angle as follows:u52 arc tan H/R! (1)where:u = contact angle,H = height of a droplets image, andR = half its width.3.1.1.2 DiscussionInstrumentation is also available thatutilizes an image and directly determines the contact anglebased on the calculation shown for Method (2) of U.S. PatentNo. 5,26
9、8,733.3.1.1.3 DiscussionMethod (1) may be biased due to thesubjective nature of visually finding a tangent to the dropletimage at the three-phase point; if Method (1) is to be used, thebias of each operators measurements shall be determined.Because Method (2) utilizes measured dimensions of thedropl
10、et, it would be expected to have less bias. Comparativeanalyses using these various procedures have not been con-ducted. Therefore, caution is recommended when comparingdata obtained from these different methods.3.1.1.4 DiscussionMethod (2) may not be applicable inspecial cases in which the contact
11、angle is greater than 901This 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 February 1, 2004. Published March 2004. Originallypublished as D 5946 96. Last previous edition D
12、 5946 01.2For 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.1*A Summary of Changes section appears at the end of
13、 this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Test Method4.1 In this test method, drops of water are placed on thesurface of a film sample, and the contact angle values aremeasured and then averaged.5. S
14、ignificance and Use5.1 The ability of polymer films to retain inks, coatings,adhesives, etc. is primarily dependent on the character of theirsurfaces and can be improved by one of several surface-treating techniques. The electrical discharge treatment, such ascorona treatment, has been found to incr
15、ease the wettingtension of a polymer film. The stronger the treatment, the moreactively the surface reacts with different polar interfaces. It istherefore possible to relate the contact angle of a polymer filmsurface to its ability to accept and retain inks, coatings,adhesives, etc., if the ink, coa
16、ting, or adhesive contains thepolar functionalities. Contact angle in itself is not a completelyacceptable measure of ink, coating, or adhesive adhesion.5.2 The wetting tension of a polymer film belongs to agroup of physical parameters for which no standard of accu-racy exists. The wetting tension o
17、f a polymer cannot bemeasured directly because solids do not change shape measur-ably in reaction to surface energy. Many indirect methods havebeen proposed.3Different test methods tend to produce differ-ent results on identical samples. Practical determination of asolids surface energy uses this in
18、teraction of the solid with testliquids.5.3 Although the level of surface treatment of polymer filmshas been traditionally defined in the industry in terms ofdynes/cm (mN/m), these values are derived from a subjectiveinterpretation of the observed test liquid behavior.5.4 The following ranges of wat
19、er contact angle values canbe used as a guide for defining the level of surface treatment ofpolyolefins and many other polymer films with initial lowsurface energies:Marginal or no treatment 90Low treatment 85 to 90Medium treatment 78 to 84High treatment 71 to 77Very high treatment 715.4.1 The suita
20、bility of the test for specification acceptance,manufacturing control, and end use of polymer films will haveto be established through capability studies for each particularfilm and treatment.5.5 Almost all materials have variations in contact angle asone moves from point to point. Nonuniform treatm
21、ent of filmwith corona treaters may also add variability to the results.Therefore, multiple measurements are necessary to reflectvariation in treatment and surface roughness.6. Interferences6.1 The wetting tension of a polymer film in contact with adrop of liquid in the presence of air is a function
22、 of the surfaceenergies of both the air-film and film-liquid interfaces; anytrace of surface-active impurities in the test liquid or on thefilm may affect the results. It is therefore important that theportion of the film surface to be tested not be touched orrubbed, that all equipment be scrupulous
23、ly clean, and thatwater purity be guarded carefully. Glass apparatus, in particu-lar, is likely to be contaminated with detergents having verylow surface tension, unless specific precautions are taken toensure their absence, such as cleaning with chromic sulfuricacid and rinsing with distilled water
24、.6.2 The presence of slip, antistatic, or antiblocking andother additives can change the surface of the film since theseadditives leach out to the surface with time.6.3 Finely embossed films add more variability to themeasurements.6.4 Polymer films often generate static charges when theyare processe
25、d. Corona treatment usually exacerbates the prob-lems. The film sample for surface measurement may carry thestatic charge generated in processing or may acquire a chargeby friction when sliding over the specimen holder surface.6.4.1 The static charges may cause errors in contact anglemeasurements. T
26、hese errors occur as the electrostatic fieldgenerated by the charged sample pulls the water droplet to thefilm surface stronger than it would be in the absence of charges.6.4.2 To prevent measurement errors, the film sample shallbe kept free of static buildup before and during measurementsby placing
27、 an air ionizer, also known as a static eliminator, inthe vicinity of the specimen holder. These devices produce airions of positive and negative polarity. The charged object in thevicinity of the ionizer will attract ions of the opposite polarityand will be neutralized.6.5 The transfer of a droplet
28、 onto the measured surface shallbe accomplished following the procedure described in Section11. An improper transfer technique increases the variability ofmeasurements.6.6 The contact angle measuring method using tangentialalignment of the cursor line of a protractor, as described in3.1.1.1 (1), is
29、biased due to the subjective nature of finding atangent to the droplet image at the three-phase point. Thesmaller the measured contact angle, the larger the error. Thebias of each operators measurements shall be determined ifthis method is to be used.7. Apparatus7.1 Contact Angle Meter, or Goniomete
30、rThe apparatusfor measuring contact angles shall contain the following: (1)aliquid dispenser capable of suspending a precise droplet of thespecified volume from the tip of the dispenser, (2) a sampleholder that can stretch a film sample flat without wrinkles anddistortions, (3) provisions for bringi
31、ng the sample toward thesuspended droplet in a controlled manner to accomplish droplettransfer onto the measured surface, and (4) means for project-ing a “silhouette” image of the drop with minimal distortions.The apparatus shall have means for direct angle measurements,such as a protractor, or dire
32、ct measurements of the dropletsdimensions, such as a grid or scale, or both, or a suitable chargecoupled device sensor and analysis hardware and softwareappropriate for subsequent analysis.3Wu, S., Polymer Interface and Adhesion, Marcel Dekker, Inc., New York, NY,1982.D59460428. Reagents and Materia
33、ls8.1 Purity of WaterDeionized ultra filtered water shouldbe used for testing purposes. The test liquid shall be kept inscrupulously clean containers.9. Sampling9.1 The minimum amount of film required for this test is anapproximately 25-mm wide and 300-mm long sample strip. Ifa sample is taken from
34、a roll, the direction of the samplerelative to the machine direction of the web shall be noted.9.2 Extreme care shall 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 The number of measurements per film sample can bedet
35、ermined using published tables for sampling plans. Com-plete tables can be found in most books on quality control.4The recommended number of readings per sample is ten.9.4 For the purpose of determining the contact angle profileacross the width of the roll, one contact angle measurement canbe taken
36、every 25 mm 1 in. across the sample.10. Conditioning10.1 Conditioning is not generally required for routinequality assurance (QA) or process control measurements sinceconditioning may affect the measured value and misrepresentthe actual conditions.10.2 Conditioning is required for interlaboratory me
37、asure-ments intended to compare the results. Condition the testspecimens at 23 6 2C 73.4 6 3.6F and 50 6 5 % relativehumidity for not less than 40 h prior to testing in accordancewith Procedure A of Practice D 618, for those tests in whichconditioning is required. In cases of disagreement, the toler
38、-ances shall be 61C 61.8F and 62 % relative humidity.10.3 Test ConditionsSpecial test conditions are not gen-erally required for routine QA or process control measure-ments.10.4 Test Conditions for Interlaboratory StudiesWhenever possible, conduct tests in the standard laboratoryatmosphere of 23 6 2
39、C 73.4 6 3.6F and 50 6 5 % relativehumidity, unless otherwise specified in the test methods or inthis test method. In cases of disagreement, the tolerances shallbe 6 1C 61.8F and 62 % relative humidity.11. Procedure11.1 Place a sample strip onto the specimen holder of theinstrument. Make sure the fi
40、lm sample is lying flat withoutwrinkles and distortions.11.2 Suspenda5to8-L droplet at the end of a syringeneedle. Bring the surface with the mounted sample upwarduntil it touches the pendant drop. Then lower the surface withthe sample to complete the droplet transfer. Do not drop orsquirt droplets
41、on the surface. See Fig. 1.11.3 Follow the instrument manufacturers instructions for amaximum time between dropping of the water droplet andmeasurement. Use the measurement techniques listed in3.1.1.1.11.4 Advance the sample to place the next droplet onto apreviously untouched area.11.5 Take ten con
42、tact angle measurements on the sample.12. Calculation12.1 Calculation:12.1.1 Calculate the average of the ten measurements.12.1.2 Calculate the standard deviation of the measure-ments.12.1.3 Example:(1) 66 (6) 72(2) 72 (7) 72(3) 66 (8) 72(4) 72 (9) 69(5) 73 (10) 69Average contact angle: 70. This res
43、ult corresponds to thelower end of the very high treatment level. Standard deviation:2.4.13. Report13.1 Report the instrument used, number of readings, aver-age value of the contact angle measurements and standarddeviation, method used for determination of contact angle,temperature, humidity, and an
44、y comments and observations.14. Precision and Bias14.1 Precision:14.1.1 Instrument error depends on the instrument used. Theinstrument error can be assessed by measuring a uniformsurface such as solidified paraffin wax and calculating thestandard deviation of the measurements.14.1.2 Precision of the
45、 TestTable 1 is based on aninterlaboratory study conducted in 1995 in accordance withPractice E 691 involving four materials and eight laboratories.Each test result was the average of ten individual determina-tions. Each laboratory obtained three test results for eachmaterial on two days. The result
46、s demonstrate that the preci-sion of the results is generally independent of the treatmentlevel (wetting tension) of the film. (WarningThe followingexplanations of r and R are only intended to present ameaningful way of considering the approximate precision ofthis test method. The data in Table 1 sh
47、ould not be appliedrigorously to the acceptance or rejection of material, as thosedata are specific to the interlaboratory study and may not berepresentative of other lots, conditions, materials, or laborato-ries. Users of this test method should apply the principlesoutlined in Practice E 691 to gen
48、erate data specific to their4Duncan, J. A., Quality Control and Industrial Statistics, 3d Ed., Irwin,Homewood, IL, 1965.FIG. 1 Water Droplet Transfer TechniqueD5946043laboratory and materials, or between specific laboratories. Theprinciples of 14.1.3-14.2 would then be valid for such data.)14.1.3 Co
49、ncept of r and RIf Srand SRhave been calcu-lated from a large enough body of data, and for test results thatwere averages of ten test determinations:14.1.3.1 Repeatability, r (Single Operator)The two testresults should be judged not equivalent if they differ by morethan the r contact angle degrees for that treatment level.14.1.3.2 Reproducibility, R (Multilaboratory)The two testresults should be judged not equivalent if they differ by morethan the R contact angle degrees for that treatment level.14.1.3.3 Any judgment per
