ASTM_D_1994_-_07_2015.pdf

Designation:D199407(Reapproved 2015)Standard Test Method forDetermination of Acid Numbers of Hot-Melt Adhesives1This standard is issued under the fixed designation D1994;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of acidnumbers of hot-melt adhesives.1.2 This test method is applicable for hot-melt and hot-melt/acid systems that are soluble under the conditions described.The hot melt must also give light-or medium-colored solutionswhen dissolved.If this is not the case another method must beused.1.3 The values stated in SI units are to be regarded as thestandard.The values in parentheses are for information only.1.4 This standard does not purport 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 cautionstatements are given in 7.1 and 7.2.2.Referenced Documents2.1 ASTM Standards:2D907 Terminology of AdhesivesE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 DefinitionsMany of the terms found in this testmethod are defined in Terminology D907.4.Significance and Use4.1 Acidichot-meltadhesivesareusefulinmanyapplications,as the acid functionality can contribute to bettersubstrate wetting and better adhesion to polar,nonporoussurfaces.4.2 Acidic hot-melt adhesives are also quite corrosive toconventional iron and steel adhesive application equipment.The acid number determination will tell an equipment manu-facturer if corrosion-resistant equipment for an applicationshould be recommended.The need for corrosion-resistantequipment will vary depending on the acid number of thehot-melt adhesive and type of metal that will be bonded.5.Reagents5.1 Potassium Hydrogen PhthalatepH standard,dried andpurified(suitable as an acidimetric standard).5.2 Potassium Hydroxide/Methanol Titrant(0.1 N)Dissolve 6 to 7 g of potassium hydroxide(KOH)in methanol,industrial grade,and dilute to 1 L with methanol.This solutionshould be standardized before use(see Section 6).5.3 Phenolphthalein Indicating Solution(2.5 g/L)Dissolve 0.5 g of phenolphthalein in 200 mL of methanol.5.4 TolueneReagent grade.5.5 Deionized Water.6.Calibration and Standardization6.1 Preparation of Standard Acid SolutionDissolve 0.25to 0.35 g of potassium hydrogen phthalate in 100 mL ofdeionized water.6.2 Titration of Standard Acid SolutionAdd 2 mL of thephenolphthalein indicating solution and titrate the entire stan-dard acid solution using the methanolic KOH solution preparedin 5.2.6.3 To calculate the normality of the methanolic KOH,usethe following formula:N KOH 5g of phthalate!31000204.23mL of KOH solution!5g of phthalatemL of KOH solution34.907.Procedure7.1 Dissolve 1.80 to 2.10 g of adhesive in 200 mL oftoluene.(Xylene,reagent grade,may provide a safer alternatesolvent.)Use a thermocouple or thermometer to monitor thetemperature of the solution,and heat the solution(with stirring)to 80 to 90C(176 to 194F)to accelerate dissolution.1This test method is under the jurisdiction of ASTM Committee D10 onPackaging and is the direct responsibility of Subcommittee D10.14 on Tape andLabels.Current edition approved Oct.15,2015.Published October 2015.Originallyapproved in 1991.Last previous edition approved in 2007 as D1994 07.DOI:10.1520/D1994-07R15.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1(WarningToluene boils at 111C(232F),so monitor thesolution temperature closely and do not exceed 90C(194F).)Continue heating and stirring the solution until the sampledissolves in the toluene(15 to 30 min normally).7.2 When the sample is dissolved,turn off the heat andcontinue to stir the solution until it has cooled to 55 to 60C(131 to 140F).(WarningMethanol boils at 65C(149F)sodo not titrate until solution cools to at least 60C(140F).)When the solution has cooled to 55 to 60C titrate immediatelyas in 6.2 until a light pink color remains after 10 s.A whitebackground under the beaker will make the endpoint easier tosee.7.3 If precipitation of the adhesive occurs during thetitration,reheat the flask.8.Calculation8.1 Calculate the acid number of the sample with thefollowing equation:acid numbermilligrams KOH/g of sample!5millilitres of KOH solution!3KOH normality!356.1grams of adhesive8.2 Duplicate analyses should agree within 65%of each