ASTM F2025-2006 Standard Practice for Gravimetric Measurement of Polymeric Components for Wear Assessment《磨损评定用聚合物元件重力测量的标准规程》.pdf

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1、Designation: F 2025 06Standard Practice forGravimetric Measurement of Polymeric Components forWear Assessment1This standard is issued under the fixed designation F 2025; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l

2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes a laboratory method using aweight-loss (that is, mass-loss; see X1.4) technique for evalu-atin

3、g the wear properties of polymeric materials or deviceswhich are being considered for use as bearing surfaces ofhuman joint replacement prostheses, or both. The test speci-mens are evaluated in a device intended to simulate thetribological conditions encountered in the human joint; forexample, use o

4、f a fluid such as bovine serum, or equivalentpseudosynovial fluid shown to simulate similar wear mecha-nisms and debris generation as found in vivo.2. Referenced Documents2.1 ASTM Standards:2D 792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD 1505 Tes

5、t Method for Density of Plastics by the Density-Gradient TechniqueF 732 Test Method for Wear Testing of Polymeric MaterialsUsed in Total Joint ProsthesesF 1714 Guide for Gravimetric Wear Assessment of Pros-thetic Hip-Designs in Simulator Devices2.2 Other Standards:3ISO 142422 Implants for SurgeryWea

6、r of Total Hip-Joint ProsthesesPart 2: Methods of MeasurementISO 142432 Implants for SurgeryWear of Total Knee-Joint ProsthesesPart 2: Methods of Measurement3. Significance and Use3.1 This practice uses a weight-loss method of wear deter-mination for the polymeric components or materials used inhuma

7、n joint prostheses, using serum or demonstrated equiva-lent fluid for lubrication, and running under a load profilerepresentative of the appropriate human joint application(1,2).4The basis for this weight-loss method for wear mea-surement was originally developed (3) for pin-on-disk wearstudies (Pra

8、ctice F 732) and has been extended to total hipreplacements (4, 5, ISO 142422, and Guide F 1714) and tofemoro-tibial knee prostheses (6 and ISO 142432), and tofemoro-patellar knee prostheses (6,7).3.2 While wear results in a change in the physical dimen-sions of the specimen, it is distinct from dim

9、ensional changesdue to creep or plastic deformation, in that wear results in theremoval of material in the form of polymeric debris particles,causing a loss in weight of the specimen.3.3 This practice for measuring wear of the polymericcomponent is suitable for various simulator devices. Thesetechni

10、ques can be used with metal, ceramic, carbon, polymeric,and composite counter faces bearing against a polymericmaterial (for example, polyethylene, polyacetal, and so forth).Thus, this weight-loss method has universal application forwear studies of human joint replacements which featurepolymeric bea

11、rings. This weight-loss method has not beenvalidated for non-polymeric material bearing systems, such asmetal-metal, carbon-carbon, or ceramic-ceramic. Progressivewear of such rigid bearing combinations has generally beenmonitored using a linear, variable-displacement transducers, orby other profilo

12、metric techniques.4. Components and Materials4.1 Hip Prosthesis ComponentsThe hip joint prosthesiscomprises a ball-and-socket configuration in which materialssuch as polymers, composites, metal alloys, ceramics, andcarbon have been used in various combinations and designs.4.1.1 Component Configurati

13、onsThe diameter of theprosthetic ball may vary from 22 to 54 mm or larger. Thedesign may include ball-socket, trunnion, bipolar, or otherconfigurations. If applicable, the normal metal backing for thepolymeric component shall be used provided disassembly andreassembly of these components for the mea

14、surement does nothave an unrepresentative effect on the weight measurements orwear behavior. Otherwise, a modified backing may be used,1This practice is under the jurisdiction ofASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on

15、Arthroplasty.Current edition approved March 1, 2006. Published March 2006. Originallyapproved in 2000. Last previous edition approved in 2000 as F 2025 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM

16、Standards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.1Co

17、pyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.again provided this has no unrepresentative effect on theweight measurements or wear behavior (see X1.5).4.2 Knee Prosthesis ComponentsThe knee joint com-prises femoral, tibial, and patell

18、ar configurations in whichmaterials such as metal alloys, ceramics, polymers, and carbonmaterials have been used in various combinations in differentdesigns.4.2.1 Component ConfigurationsThe polymeric compo-nents may be backed by either metal, ceramic, or compositereinforcements. If applicable, the

19、normal metal backing shallbe used provided disassembly and reassembly of these com-ponents for the measurement does not have an unrepresentativeeffect on the weight measurements or wear behavior. Other-wise, a modified backing may be used, again provided this hasno unrepresentative effect on the wei

20、ght measurements or wearbehavior (see X1.5).4.3 Other prosthesis components and test coupons may beused to represent other human joint replacement applications.5. Specimen Preparation5.1 Polymers and CompositesMaterial Condition:5.1.1 A fabrication history shall be obtained for each poly-meric or co

21、mposite component, including information such asgrade, batch number and processing variables, method offorming (extruding, molding, and so forth), temperature, pres-sure and forming time used, and any post-forming treatments,including sterilization method and parameters.5.1.2 Pretest characterizatio

22、n may include measurement ofbulk material properties such as molecular-weight range anddistribution, percent crystallinity, or other. Density is a particu-larly important property because of the conversion of weightmeasurements to volumetric wear (see 7.4). Density measure-ments shall be obtained in

23、 accordance with Test Methods orTest Method D 792 or D 1505. If it can be justified thatprevious density measurements are representative of the mate-rial used in the current wear test, reference to these previousmeasurements and suitable justification shall be provided (seealso X1.6). The surface fi

24、nish of specimens may be character-ized by profilometry, photomicrography, and replication byvarious plastics or other techniques.5.1.3 SterilizationThe components shall be sterilized in amanner typical of that in clinical use for such devices, as thismay affect the wear properties of the materials.

25、 Sterilization ofall test and control components within a specific test groupshould be done simultaneously (in a single container) whenpossible to minimize variation among the specimens. The weartesting procedure makes no attempt to maintain the sterility ofspecimens during the wear test.5.2 Polymer

26、 Specimen Cleaning ProcedurePrior toweighing and wear testing, careful cleaning of the polymerspecimens is important to remove any contaminants that wouldnot normally be present on the actual prosthesis. During thewear test, the components must be re-cleaned and dried beforeeach weighing to remove a

27、ny extraneous material that mightaffect the accuracy of the weighing. The procedure for cleaningand drying of polymeric components is given in Annex A1.With some combinations of materials, wear may result in thetransfer of particulate debris which may then become re-imbedded or otherwise attached to

28、 polymeric, metal, or com-posite surfaces. Such an occurrence will render the weight-lossassessment of wear less reliable.5.3 Polymer Specimen Weighing ProcedureThe poly-meric components shall be weighed on an analytical balancehaving a sensitivity on the order of 10 g. This degree ofsensitivity is

29、necessary to detect the slight loss in weight ofpolymers such as UHMW polyethylene, which may wear 1 mgor less per million cycles. Specimens shall always be weighedin the clean, dry condition (Annex A1). The components shallbe kept in a dust-free container and handled with clean tools toprevent cont

30、amination which might affect the weight measure-ment. Each wear and control component shall be weighed threetimes in rotation to detect random errors in the weighingprocess.5.4 Pre-Soaking of Test Specimens:5.4.1 Polymeric and composite components made frommaterials which absorb fluid initially, but

31、 saturate within a fewweeks, should be presoaked in the test lubricant to reduce theerror due to fluid sorption during the wear run. If the fluidsorption behavior of a particular material is unknown, theinvestigator shall conduct a preliminary study to determinewhether or not the material is exempt

32、from presoaking.5.4.2 Preliminary StudyA minimum of three soak speci-mens (these can be test coupons or actual devices) per materialshall be cleaned and dried in accordance with the procedure inAnnex A1, and then weighed by precisely controlled andrepeatable methods (Annex A1). The specimens shall t

33、hen beplaced in a container of test lubricant and removed, cleaned,dried, and weighed (in accordance with Annex A1) once ortwice a week. The weight change shall be calculated inaccordance with Annex A1. The procedure shall be repeateduntil the specimens have soaked for five weeks. Specimenweight cha

34、nge shall be averaged at each interval and plottedversus time. Data points shall be fit using a second or thirdorder polynomial or hyperbolic function, connecting throughzero. The fit of this curve should have an R2value of 0.8 orgreater. If the slope of this curve at five weeks is ten or moretimes

35、less than the slope of the curve at zero (see X1.7), thenthis material must be subjected to presoaking before weartesting (if gravimetric wear measurement is to be used).Otherwise, it is exempt.NOTE 1Even if presoaking is not required, one to three soak controlcomponents are still necessary per mate

36、rial condition to account for fluidsorption by the wear components during the wear test.5.4.3 Pre-soaking Procedure (if Required)After fabrica-tion and characterization, the wear components and one tothree soak-control components of each test material shall becleaned in accordance with the procedure

37、 in Annex A1. Thewear components and soak control(s) shall then be placed in acontainer of test lubricant for a minimum of five weeks (35days).6. Measurement Procedure6.1 After fabrication, characterization, and the completionof the presoak period (if required), the wear components andsoak control(s

38、) should be cleaned, dried, and weighed byprecisely controlled and repeatable methods (Annex A1).These weights shall be recorded as the initial weights of theF2025062specimens for purposes of calculating the progressive weightloss during the wear test. The soak control specimen(s) shall beplaced in

39、holders in a soak chamber of test lubricant, such thatthe total surface area exposed to the lubricant is equal to that ofthe wear components when mounted in the test chamber. Thesoak chamber temperature shall be maintained at the sametemperature as the bulk lubricant in the wear test, or specifiedif

40、 different. It is recommended that the soak chamber beattached to the test machine or otherwise agitated in the samemanner as the actual wear chambers. In addition, it may beadvantageous to apply a cyclic load to the soak controlspecimen(s) (without tangential motion) comparable to thatapplied to th

41、e wear specimens, since this can also affect the rateof fluid sorption.6.2 The wear and soak component(s) shall be removed atspecified intervals, washed, rinsed, and dried concurrently, inaccordance with the procedure inAnnexA1. It is important thatboth the wear and soak component(s) be treated iden

42、tically toensure that they have the same exposure to the wash, rinse, anddrying fluids.This will provide the most accurate correction forfluid sorption by the wear specimens.6.3 After rinsing and drying, the wear components and soakcontrols shall be weighed on an analytical balance in accor-dance wi

43、th 5.3.6.4 The wear chambers and component surfaces shall bethoroughly rinsed with distilled or deionized water.6.5 The bearing surfaces of the components shall be in-spected, and the characteristics of the wear process noted.Visual, microscopic, profilometric, replication, or other inspec-tion tech

44、niques can be used. However, care must be taken thatthe surfaces do not become contaminated or damaged by anysubstance or technique which might affect the subsequent wearproperties. If contamination occurs, the specimens shall bethoroughly re-cleaned prior to restarting the wear test.6.6 The wear co

45、mponents and soak control(s) shall bereplaced in fresh lubricant and wear cycling continued.7. Determination of Wear Rates7.1 Test LengthThe accuracy of the test method dependson the relative magnitudes of wear and fluid sorption. This isespecially true when the fluctuations in the weight due tovari

46、ation in the amount of surface drying are large in compari-son to the incremental weight-loss due to wear. For high-wearlow-sorption materials, the wear rate may be clearly estab-lished in as few as 50 000 wear cycles. With comparativelylow-wearing materials, such as UHMWPE, several millioncycles or

47、 more may be required to clearly establish thelong-term wear properties.7.2 Number of Measurements per TestWhen specimenscan be removed for intermediate weight measurement, at leastthree measurements per test series shall be made.7.3 Correcting for Fluid SorptionThe average gain (orloss) of the soak

48、 control component(s) shall be added to (orsubtracted from) the measured weight loss of each wearcomponent (Annex A2.6); this procedure corrects both forsystematic sorption as well as random differences in theamount of surface drying (of the entire set of test and controlspecimens) and balance fluct

49、uations due to environmental orother variables at each interval of weighing.7.4 Conversion to Volumetric WearIn tests where thewear rates of materials with different densities are evaluated, itmay be preferable to compare these on the basis of volumetricwear, rather than weight loss. The volumetric wear rate may beobtained by dividing the weight loss data by the density of thematerial, in appropriate units. The accuracy of this calculationis dependent on the material being reasonably homogeneous(that is, having a constant density with wear depth). Thedensity va