ASTM_D_4518_-_91.pdf

Designation:D 4518 91Standard Test Methods forMeasuring Static Friction of Coating Surfaces1This standard is issued under the fixed designation D 4518;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of 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.Scope1.1 These test methods cover the determination of theresistance to sliding on coating surfaces by measuring the staticfriction.1.2 Two test methods are described as follows:SectionsMethod AInclined Plane Test8-13Method BHorizontal Pull Test14-191.3 This standard does not purport to address all of thesafety problems,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.2.Referenced Documents2.1 ASTM Standards:D 823 Test Methods for Producing Films of Uniform Thick-ness of Paint,Varnish,and Related Products on TestPanels23.Terminology3.1 Definition:3.1.1 static frictionthe force required to start the test sledmoving,divided by the mass of the sled.4.Summary of Test Methods4.1 With the inclined plane test(Test MethodA),a weightedsled is placed on a test specimen and the specimen is graduallyinclined from the horizontal until the sled begins to slide.Thetangent of this angle of inclination is reported as the staticfriction.4.2 With the horizontal pull test(Test Method B),aweighted sled is placed on a horizontal test specimen and ispulled across the specimen.The static friction is reported as theforce required to start the sled moving,divided by the mass ofthe sled.5.Significance and Use5.1 The friction characteristics of coating surfaces can beimportant to the use of the coatings.For example,low frictionof exterior can coatings is beneficial to the flow of the cans onproduction lines.Also low friction of interior pipeline coatingsis beneficial to the flow of materials through pipes.On theother hand,low friction of floor coatings can be hazardous tofoot traffic.5.2 Under some conditions,measurement of the staticfriction can be used to evaluate the slip resistance of coatingsunder use conditions.However,results can be extremelydependent on the type of coating surface and the type of slidingunit used.5.3 The tendency for footwear to slip may be influenced byforeign materials or lubricants on the shoe materials or on thewalking surfaces.Also,these test methods do not incorporateall the directional forces involved in the walking process.Consequently,levels of slip resistance as determined by thesetest methods may not predict a persons resistance to slippingwhen walking on various surfaces.5.4 The best precision and sensitivity are obtained whenstainless steel is used as the facing of the sliding unit.In sometests where a leather facing is used,poor precision is obtainedbecause of the inability to control the uniformity of its surfaceduring the test.The use of a hard synthetic rubber facingprovides somewhat better precision.5.5 These test methods provide for static friction measure-ments when the sled facing and the coating surfaces are wetwith water.Results from such tests must be treated withcaution because frequently the static friction values obtainedfor wet,smooth coatings are higher than those obtained for thesame surfaces dry.This is because,when stationary at thebeginning of the test,the sled contact can produce a“suctioncup”effect on a wet surface.Measurements performed on wetcoatings with rough surfaces have been more satisfactory.5.6 A test procedure is offered that eliminates the“suctioncup”effect of wet surfaces.The wet sled is dropped onto thewet coating surface at the start of the test.5.7 Results obtained by these test methods may be ex-tremely sensitive to the age of the test coating because theblooming action of additives or plasticizers is often time-dependent.It may be meaningless to compare slip and fric-tional properties of test coatings applied at different timesunless this effect is being studied.5.8 The measurement of static friction may be influenced bythe length of time that the sled rests on the test specimen beforemotion is initiated.1These test methods are under the jurisdiction ofASTM Committee D-1 on Paintand Related Coatings,Materials,and Applications and are the direct responsibilityof Subcommittee D01.23 on Physical Properties of Applied Paint Films.Current edition approved Sept.15,1991.Published November 1991.Originallypublished as D4518 85.Last previous edition D4518 90.2Annual Book of ASTM Standards,Vol 06.01.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTM5.9 Static friction measurements have been useful in evalu-ating(1)the suitability of coatings for the exterior of cans,(2)the