ASTM_D_756_-_93.pdf

Designation:D 756 93Standard Practice forDetermination of Weight and Shape Changes of PlasticsUnder Accelerated Service Conditions1This standard is issued under the fixed designation D 756;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.This standard has been approved for use by agencies of the Department of Defense to replace Method 6011 of Federal Test MethodStandard 406.Consult the DoD Index of Specifications and Standards for the specific year of issue which has been adopted by theDepartment of Defense.1.Scope1.1 This practice covers the determination of the weight andshape changes occurring in plastics under various conditions ofuse,not where exposure to direct sunlight,weathering,corro-sive atmospheres,or heat alone is involved,but where changesin atmospheric temperature and humidity are encountered.Thisembraces the interior of buildings,and the interior of transportfacilities such as motor vehicles,airplane cargo spaces or winginteriors,holds of ships,and railroad cars.Procedures areprovided for exposing plastics to combinations of extremehumidity and temperature that will accelerate the changestaking place in the materials kept in sheltered spaces butsubject to humidity and temperature variation(see ExplanatoryNote).1.2 Seven test procedures are provided which prescribeconditions for different types of exposure.Six of the proce-dures cover exposures at graduated levels of temperature andextremes of humidity;the seventh prescribes conditions in-volving alternate exposure to high and low temperatures.Insofar as weight and shape changes,embraced under thegeneral term of dimensional stability,are concerned,theseprocedures provide a method of test.Further use of any of theconditions set up in the procedures is suggested,such asconditioning schedules prior to physical testing of the plasticeither to test it at the particular condition involved,or to studychanges resulting from exposure to that condition.1.3 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.4 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.NOTE1There is no similar or comparable ISO standard.2.Referenced Documents2.1 ASTM Standards:D 618 Practice for Conditioning Plastics and ElectricalInsulating Materials for Testing2D 883 Terminology Relating to Plastics23.Terminology3.1 DefinitionsDefinitions of terms applying to this prac-tice appear in Terminology D 883.4.Significance and Use4.1 The test conditions covered in this practice represent astart towards organizing a group of test procedures for deter-mining the effects of specified changes of atmospheric tem-perature and humidity upon plastic articles.These procedureshave been used for testing both thermosetting and thermoplas-tic materials.NOTE2The test procedures covered in this practice have been drawnfrom various tests used in branches of the plastics industry,and bygovernment agencies in procurement of materials.4.2 While several of the testing temperatures are not used inother ASTM standards,they have a background of severalyears experience in portions of the plastics industry.Especiallyin Procedures D and E(Sections 13 and 14)the acceleratingeffect of temperature in prompting changes caused by a rise inhumidity leads to temperatures that are well above thoseencountered in normal service,and they are used simply toaccelerate change.4.3 Procedure A(Section 10)has been found to developwarping,weight change,and exudation in plastic parts.Proce-dure B(Section 11)is designed to reveal poorly cured plasticsby developing cracks in them.Procedures C and D are moresevere measures of the same tendencies developed in Proce-dure A;the conditions of Procedure D will produce noticeablechemical decomposition in many plastics.Procedure E(Sec-tion 14)is especially valuable in testing the behavior of plasticparts with metallic inserts and laminates,for cracking on1This practice is under the jurisdiction of ASTM Committee D-20 on Plasticsand is the direct responsibility of Subcommittee D 20.50 on Permanence Properties.Current edition approved Feb.15,1993.Published April 1993.Originallypublished as D 756 44 T.Last previous edition D 756 78(1983)e1.2Annual Book of ASTM Standards,Vol 08.01.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.NOTICE:This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTMInternational(www.astm.org)for the latest information.exposure to temper