ASTM_D_3896_-_07_2011.pdf

Designation:D389607(Reapproved 2011)Standard Practice forRubber From Synthetic SourcesSampling1This standard is issued under the fixed designation D3896;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 practice,intended for referee purposes,covers auniform procedure for sampling lots of solid synthetic rubbers.Raw synthetic rubber generally is marketed in bales or pack-ages of various sizes.1.2 A procedure for determining the acceptability of lots ofsynthetic rubber is given.This procedure is based on avariables sampling plan.1.3 The sample size is based on the assumption of a visuallyhomogeneous material.If obvious heterogeneity exists,thenumber of samples shall be increased.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 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.2.Referenced Documents2.1 ANSI Standard:Z1.9 Sampling Procedures and Tables for Inspection byVariables for Percent Defective23.Significance and Use3.1 The sampling plan is intended for referee purposes onlyin establishing the properties or quality of a lot or shipment ofsynthetic rubber.4.Sampling4.1 Number of SamplesThe number of samples to beselected to represent the lot shall be determined by the size ofthe lot as indicated in Table 1.A sample bale or package isselected randomly from the lot for each sample required.NOTE1The sampling plan is more efficient for large lots.The risk forthe producer and consumer decreases as the sample size increases.4.2 Removal of Test Portions:4.2.1 BalesFrom each sample bale selected,cut one 600to 1500-g test portion of rubber,depending on the tests to bemade.Each test portion is tested separately.Cut the test portionthrough the entire bale,normal to the bale surfaces of thelargest area without the use of lubricant.Remove polyethylenefilm,paper,talc,or other extraneous surface material prior totesting.Unless the test portion is to be tested immediately,place it in an airtight container of not more than twice thevolume of the test portion,or wrap it tightly in two layers ofaluminum foil until tested.4.2.2 PackagesFrom each sample package selected,re-move between 600 and 1500 g of rubber depending on the teststo be made.The rubber should be selected randomly from thepackage and should be as free of surface material as practical.Unless the sample is to be tested immediately,place it in anairtight container.5.Lot Acceptability5.1 Each property of the lot is evaluated separately.Therequirements of these tests are of two types:(1)those having asingle limit such as a minimum or maximum and(2)thosehaving double limits,that is,a minimum and a maximum.Aquality index is calculated for each property tested,and fromthis index,an estimate is made of the percent of the lot that isdefective.If this percentage does not exceed the allowablevalues shown in Table 1,the lot is considered acceptable.5.2 Quality Index Calculations:5.2.1 For a requirement having a maximum limit,calculatethe quality index as follows:Q 5U 2 X!/S(1)where:Q=quality index,U=maximum value permitted by the specification,X=mean of values obtained for the test portion,andS=standard deviation of the samples.5.2.2 For a requirement having a minimum limit,calculatethe quality index as follows:Q 5X2 L!/S(2)1This practice is under the jurisdiction ofASTM Committee D11 on Rubber andis the direct responsibility of Subcommittee D11.23 on Synthetic Rubbers.Current edition approved Nov.1,2011.Published January 2012.Originallyapproved in 1980.Last previous edition approved in 2007 as D3896 07.DOI:10.1520/D3896-07R11.2Available from the American National Standards Institute,25 W.43rd St.,4thFloor,New York,NY 10036.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 where:Q,X,and S=same as those for maximum value,andL=minimumvaluepermittedbythespecification.5.3 Acceptability:5.3.1 For a quality characteristic having a single specifica-tion limit,a lot is acceptable if the quality index equals orexceeds the minimum quality index shown in Table 1 for theapplicable lot and sample size.5.3.2 For a quality characteristic having both an upper andlower specification limit,estimate the percentages of the lotabove the upper limit and below the lower limit from Table 2using the appropriate sample size and quality index valuescalculated in 5.2.A lot is acceptable if the sum of the twopercentages does not exceed the maximum allowable percentdefective shown in Table