ASTM_D_957_-_21.pdf

Designation:D95721Standard Practice forDetermining Surface Temperature of Molds for Plastics1This standard is issued under the fixed designation D957;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.Scope*1.1 This practice is intended for determining the tempera-ture at a specified point or points on the surface of the cavityand base of a mold for plastics.By determining the temperatureat as many points as deemed necessary,the overall temperaturecondition of the surface can be determined.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.NOTE1There is no known ISO equivalent to this standard.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Summary of Practice2.1 With the use of a calibrated surface or radiation(infra-red)non-contact pyrometer,the overall temperature conditionof a mold for plastics can be determined by taking readings ata specified point or many points on the mold surface.3.Significance and Use3.1 The properties of molded parts and the ease of produc-ing satisfactory specimens are influenced by the temperature ofthe mold.It is desirable to know the actual mold temperature,which can differ from the mold temperature control medium.3.2 The user needs to be aware of temperature differencesacross the mold/thermocouple interface and at leads,and takeappropriate precautions to minimize such differences.4.Apparatus4.1 Surface PyrometerA calibrated temperature devicedesigned to measure surface temperatures that is traceable tothe international system of units(SI)through a nationalmetrology institute(NMI)2accurate to within 61.5C shall beused.4.2 Non-Contact PyrometerA Radiation(infrared)Ther-mometer that is traceable to the international system of units(SI)through a national metrology institute(NMI)2accurate towithin 61.5C shall be used.Radiation Thermometers withselectable emissivity shall be set to the estimated emissivity ofthe surface to be measured.An emissivity correction shall bemade when using Radiation Thermometers with a presetemissivity.4.3 Calibration and Emissivity Corrections of PyrometersFollow manufacturers recommendations for calibration of andmaking emissivity corrections to pyrometers.5.Procedure5.1 The size,shape,and contours of a mold determine thelocation and number of points at which temperature readingsare observed.Take temperature readings at as many points asdeemed necessary to determine the temperature condition ofthe mold surface.At a minimum,it is suggested that tempera-tures be measured at the mold center,near the edge,and at leasttwo different but intermediate points between the center andedge.5.2 Place the thermocouple of the pyrometer at any speci-fied point on the surface of the cavity and base of the mold,making certain that good contact is maintained between thetwo(see Note 2).Maintain contact until the scale reachesequilibrium.Record the temperature reading on the scale at thispoint.NOTE2Wax,or any suitable material with a low melting temperature,can be used to ensure intimate contact between the mold surface and thethermocouple of the pyrometer.This is accomplished by allowing a smallportion of the material to melt at the point where the temperature readingis to be taken.The thermocouple is then placed in the puddle of moltenmaterial.1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.09 on Specimen Preparation.Current edition approved Jan.1,2021.Published January 2021.Originallyapproved in 1948.Last previous edition approved in 2012 as D957-12.DOI:10.1520/D0957-21.2NMI includes such organizations as the National Institute of Standards andTechnology.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Com