ASTM_F_2625_-_10.pdf

Designation:F262510Standard Test Method forMeasurement of Enthalpy of Fusion,Percent Crystallinity,and Melting Point of Ultra-High-Molecular WeightPolyethylene by Means of Differential Scanning Calorimetry1This standard is issued under the fixed designation F2625;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 discusses the measurement of the heatof fusion and the melting point of ultra-high-molecular weightpolyethylene(UHMWPE),and the subsequent calculation ofthe percentage of crystallinity.1.2 This test method can be used for UHMWPE in powderform,consolidated form,finished product,or a used product.Itcan also be used for irradiated or chemically-crosslinkedUHMWPE.1.3 This test method does not suggest a desired range ofcrystallinity or melting points for specific applications.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 ASTM Standards:2D3418 Test Method for Transition Temperatures and En-thalpies of Fusion and Crystallization of Polymers byDifferential Scanning CalorimetryE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE793 Test Method for Enthalpies of Fusion and Crystalliza-tion by Differential Scanning CalorimetryE967 Test Method for Temperature Calibration of Differen-tial Scanning Calorimeters and Differential Thermal Ana-lyzersE968 Practice for Heat Flow Calibration of DifferentialScanning CalorimetersE1953 Practice for Description of Thermal Analysis andRheology Apparatus3.Terminology3.1 Symbols:3.1.1 Hf,ntheoretical heat of fusion of 100%crystallinematerial(J/g).3.1.2 Hs,nmass normalized heat of fusion of the testsample(J/g).3.1.3 Tp,nmelting temperature at the peak of the meltingendotherm(C).3.1.4 To,nonset temperature of the melting endotherm(C).3.1.5%X,npercentage of crystallinity of material.4.Summary of Test Method4.1 This test method consists of placing a known mass ofUHMWPE in a sample pan and heating the sample pan at acontrolled temperature while measuring the heat flow to thesample pan and an empty reference pan.The area under themelting endotherm,indicative of the enthalpy of melting,isnormalized with the sample mass.This value is then normal-ized with the theoretical enthalpy of melting of 100%crystal-line polyethylene to determine the percentage of crystallinity inthe test sample.5.Significance and Use5.1 The crystallinity of UHMWPE will influence its me-chanical properties,such as creep and stiffness.The reportedcrystallinity will depend on the integration range used todetermine the heat of fusion,and the theoretical heat of fusionof 100%crystalline polyethylene used to calculate the percentcrystallinity in an unknown specimen.Differential scanningcalorimetry is an effective means of accurately measuring bothheat of fusion and melting temperature.1This test method is under the jurisdiction ofASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved Dec.1,2010.Published December 2010.Originallyapproved in 2007.Last previous edition approved in 2007 as F2625 07.DOI:10.1520/F2625-10.2For 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 5.2 This test method is useful for both process control andresearch.6.Interferences6.1 As machining processes can affect the crystalline struc-ture of UHMWPE,care should be taken to obtain a represen-tative sample away from the surface of a component if bulkmeasurements are desired.6.2 The integration range used to measure the area of themelting endotherm will affect the measured value,as canheating rate.Therefore,the same ranges and test conditionsmust be used to ensure comparative results between laborato-ries.6.3 The sample must not be too tall,as temperature gradi-ents can then be generated in the sample,leading to erroneousresults.It is suggested that the sample height should be lessthan 2 mm.7.Apparatus7.1 Differential scanning calorimeter(DSC),as described inTest Method D3418 and Practice E1953.7.2 Aluminum DSC sample pans,crimpable.Pans withventing holes are opt