1、Designation: F 1634 95 (Reapproved 2000)Standard Practice forIn-Vitro Environmental Conditioning of Polymer MatrixComposite Materials and Implant Devices1This standard is issued under the fixed designation F 1634; the number immediately following the designation indicates the year oforiginal adoptio
2、n 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.1. Scope1.1 This practice covers two procedures for conditioningnon-absorbable polymer
3、 matrix composite (PMC) materialsand implant devices in a liquid environment to obtain a state ofsaturation.1.2 The purpose of this practice is to standardize methodsand reporting procedures for conditioning PMC materials andimplant devices (PMC specimens) in a user selected liquidenvironment prior
4、to conducting subsequent tests. It is not thepurpose of this practice to determine the diffusion coefficientsor actual saturation levels of a given liquid into the materialsand devices. For these determinations, other procedures, suchas Test Method D 5229, may be followed.1.3 Diffusion of liquid int
5、o a solid material is a slowprocess. While the time necessary to achieve saturation at 37Cmay be sufficiently short for thin specimens, such as fracturefixation plates, it may be prohibitively long in thick sections,such as femoral components for hip arthroplasty. However, thediffusion process may b
6、e accelerated at an elevated tempera-ture. Consequently, two separate procedures (Procedures A andB) are presented in this practice. Procedure A covers exposingthe specimen to the desired conditioning environment at 37C.Procedure B prescribes a method to accelerate the diffusionprocess by conditioni
7、ng the specimen at a selected elevatedtemperature.1.4 This practice does not specify the test environment to beused for conditioning. However, the pH value of immersionliquid shall be maintained at 7.4 6 0.2 to simulate the in vivoenvironment.1.5 This standard does not purport to address all of thes
8、afety 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:D 618 Practice for Conditionin
9、g Plastics and ElectricalInsulation Materials for Testing2D 756 Practice for Determination of Weight and ShapeChanges of Plastics Under Accelerated Service Condi-tions2D 3878 Terminology of High-Modulus Reinforcing Fibersand Their Composites3D 5229/D 5229M Test Method for Moisture AbsorptionProperti
10、es and Equilibrium Conditioning of Polymer Ma-trix Composite Materials33. Terminology3.1 Definitions:3.1.1 cumulative moisture content, Mt(%), nthe amountof absorbed moisture in a material at a given time t, expressedas a percentage of the weight of absorbed moisture divided bythe initial specimen w
11、eight, as follows:Mt,%5Wi2 WbWb3 100 (1)where:Wt= current specimen weight, g, andWb= initial (baseline) specimen weight at t = 0 and stan-dard laboratory atmosphere, g.3.1.2 liquid, nwater, saline solution, calf serum, or anyother liquid solution that is used to condition PMC specimens.3.1.3 nominal
12、 saturated moisture content, Ms(%)an ap-proximation of the amount of moisture absorbed by a specimenat saturation, expressed as a percentage of the weight ofabsorbed moisture at approximate saturation divided by theinitial specimen weight, as follows:Ms,%5Ws2 WbWb3 100 (2)where:Ws= specimen weight a
13、t approximate saturation, g, andWb= initial (baseline) specimen weight at t = 0 and stan-dard laboratory atmosphere, g.3.1.4 standard laboratory atmosphere, n a laboratoryatmosphere having a temperature of 23 6 2C and a relativehumidity of 50 6 10 %.4. Summary of Test Method4.1 In Procedure A, a spe
14、cimen is immersed in a liquid bathat 37 6 1C with a pH value of 7.4 6 0.2.1This practice is under the jurisdiction of ASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.14 on Composite Materials.Current edition approved Nov. 10, 1995.
15、Published January 1996.2Annual Book of ASTM Standards, Vol 08.01.3Annual Book of ASTM Standards, Vol 15.03.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.4.2 In Procedure B, conditioning occurs in a liquid bath at aselected elevated temperature.4.3 Weight cha
16、nge is monitored over time until specimensreach the nominal moisture saturation content.4.4 Keep specimens in the conditioning bath for storageprior to subsequent tests.5. Significance and Use5.1 The conditioning procedures covered in this practiceprovide methods for saturating PMC specimens in a li
17、quidenvironment prior to conducting other tests for propertyevaluation.5.2 The conditioning may affect geometric and dimensionalchanges in specimens. In some severe cases, chemical changesmay occur in the fiber, polymer and fiber-polymer interphaseand interface.5.3 Caution must be taken if Procedure
18、 B (10.2, ProcedureBAccelerated Moisture Saturation at Elevated Temperature)is followed to condition PMC specimens at an elevatedtemperature. Physical and chemical reactions in materials arenormally temperature dependent. An increase in experimentaltemperature may accelerate a desirable moisture dif
19、fusionprocess. However, elevated temperatures above 37C may alsocause undesirable reactions that do not represent appropriateresponses of materials at 37C. Consequently, a pilot study isrecommended in Procedure B to determine if a selectedelevated temperature can be used for accelerated conditioning
20、.If the properties of materials are determined to be irreversiblyaffected by this pilot study at the selected elevated temperature,then either an appropriate lower elevated temperature shouldbe determined by repeating the pilot study, or Procedure Bshould not be used.6. Apparatus6.1 BalanceAn analyt
21、ical balance capable of measuringweight of specimens to within a resolution of at least 0.005 %of the total specimen weight.6.2 Conditioning BathA temperature-controlled liquidbath shall be capable of maintaining the required temperatureto within 61C. The bath shall be monitored either on anautomate
22、d continuous basis or on a manual basis at regularintervals.6.3 Specimen Bag A sealable, flexible, moisture-proofbag made of material suitable for exposure to specimens thathave been removed from the conditioning bath for coolingprior to weighing. Bags that meet the requirement of MIL-B-131 have bee
23、n found to be satisfactory for use in suchapplications.6.4 Absorbent Cloth Clean, non-linting absorbent clothfor use in wiping excess liquid from surface of specimens.6.5 GlovesClean, non-linting gloves for use when han-dling specimens.6.6 pH Measurement SystemAn analytical system capableof measurin
24、g pH to within 60.1.6.7 Differential Scanning CalorimeterAn analytical sys-tem capable of heating a specimen at a controlled rate whilemeasuring heat input and temperature.7. Sampling and Test Specimens7.1 Preparation Precaution shall be taken to avoid theentrapment of moisture in uneven surfaces, o
25、r delaminationdue to inappropriate machining and manufacturing processes.7.2 LabelingLabel the specimen so as to be distinct fromeach other in a manner that will both be unaffected by the testand not influence the test and, furthermore, will not be removedduring conditioning.8. Measurements of Test
26、Specimens8.1 The following measurements shall be made on speci-mens prior to immersion, after conditioning at the end of a testprocedure, and at any intermediate stage as prescribed in thetest procedures:8.1.1 WeightThe weight within 0.005 % of specimenweight.8.1.2 Characteristic dimensions of speci
27、mens may be mea-sured as a function of immersion time to determine the amountof swelling induced by moisture absorption.9. Visual Examination9.1 Noticeable qualitative changes in surfaces, outline, andgeneral appearance of the test specimen shall be recorded aftereach stage of the testing procedure.
28、 These changes includecolor, surface irregularities, odor, surface voids, delaminationand cracking. The immersion liquid should also be observedfor evidence of material that has leached from specimens orholders, and evidence of bacterial or fungal contamination. Ifbacterial or fungal contamination i
29、s found, specimens shouldbe removed from the solution, washed with detergent andwater, rinsed, and placed in fresh solution. If contamination isa recurring problem, antibacterial or antifungal agents must beadded to the solution; minimal amounts should be used as theymay affect specimen properties.1
30、0. Procedures10.1 Procedure AMoisture Saturation Determination at37C:10.1.1 Specimen PreconditioningBring the test specimensto a uniform 23 6 2C after manufacturing process.10.1.2 Moisture Absorption:10.1.2.1 Record the initial (baseline) weight, Wb.10.1.2.2 Place the specimen in the conditioning ba
31、th, whichhas previously reached the specified temperature 37 6 1C.The pH value of immersion liquid used shall be maintained at7.4 6 0.2 throughout the conditioning process and monitoredat least once a week. If the solution pH falls outside thedesignated range, the solution should be changed. The pHs
32、hould not be maintained by repeatedly adding buffer to thesame solution. This will change solution composition and mayaffect specimen properties. Evaporation losses should be madeup with sterile deionized water if saline, serum, plasma, orother hydrous medium is used as the conditioning environ-ment
33、.10.1.2.3 Monitor the weight gain of specimens over time. Asuggested schedule is to weigh each specimen every 24 h forthe first 120 h, then every 96 h.10.1.2.4 At the end of each time interval, remove thespecimens from the conditioning bath and place them in thespecimen bag. Seal the bag and allow t
34、he specimens to come tolaboratory standard temperature. Remove the specimens fromF 16342the bag and wipe the specimens free of surface moisture withan absorbent lint-free cloth. Wait for 10 min and measure theweight of specimens to the required precision, and Wt, alongwith the corresponding total el
35、apsed time and the time intervalsince the previous measurement.10.1.2.5 Return the specimens to the conditioning bath. Thespecimens shall not be out of the conditioning bath for morethan 30 min and shall not be out of the specimen bag for morethan 15 min.10.1.2.6 Calculate cumulative moisture conten
36、t, Mt(%),using Eq 1 at each time interval and plot versus time.10.1.2.7 The minimum time, tmin, required to reach nominalsaturated moisture content, Ms, is the time at which the changein cumulative moisture content from the prior measurement isless than 0.010 % of specimen weight for three consecuti
37、veweighings with no less than 96 h of elapsed time between eachconsecutive weighing.10.1.2.8 Following moisture saturation within the specifiedtolerance range, the specimen should be stored in a bath of thesame fluid which is to be used for post-conditioning testinguntil the time the post-conditioni
38、ng testing is conducted.10.2 Procedure BAccelerated Moisture Saturation at El-evated Temperature:10.2.1 Determination of Accelerated Temperature (Ta)Level:10.2.1.1 Specimens should be first saturated in the condi-tioning environment at 37C and then evaluated by differentialscanning calorimeter (DSC)
39、 evaluation over a temperaturerange of 37 to 120C. The purpose of this is to determine if amaterial transition temperature (that is, glass transition ormelting temperature), or a degradation temperature (such as anoxidation or thermal decomposition temperature), occurswithin this temperature range.
40、If the material is stable withinthis range, then accelerated conditioning may be conducted atTa= 95C in a conditioning environment containing water. If atransition or degradation temperature is found between 37 and120C, then the maximum acceleration temperature to be usedshould be at least 25C below
41、 the lowest transition or decom-position temperature. If nonhydrous solutions are used as theconditioning environment (that is, pure lipid), then a similarprocedure can be followed except the temperature would nowbe governed by the boiling or decomposition temperature ofthe given environment and spe
42、cimen combination.10.2.2 Effect of Accelerated Temperature Conditioning:10.2.2.1 Once Tais determined from 10.2.1.1, at least fivesamples representative of the specimen being evaluated shouldbe conditioning at both Taand 37C and then tested to checkfor conditioning temperature induced differences. B
43、ecauseconditioning may influence different material properties ofPMC specimens in different ways, the test implemented tocheck for differences between Taand 37C should closelymatch the intended post-conditioning test that the PMC speci-men will be conditioned for. If Tainfluences the properties inqu
44、estion, then a lower conditioning temperature must beidentified by repeating this procedure at selected lower tem-peratures in which the property is not influenced by condition-ing. If the property is determined to be not influenced by Ta,then Tacan be used to accelerate the conditioning process for
45、subsequent specimens.10.2.3 Accelerated Conditioning:10.2.3.1 Follow the procedures outlined in 10.1.2 with theexception that the conditioning bath will be maintained at Ta61.0C. The same time-measurement sequence as described in10.1.2 should be used to determine the minimum time, tmin,when saturati
46、on is reached. The bath should be adequatelysealed to minimize evaporation loss and periodically monitoredto ensure adequate bath depth is maintained for completeimmersion of samples. If the bath is physically sealed, a safemechanism of pressure relief (that is, pressure relief valve orreleasable li
47、d seal) must be provided to prevent pressurebuild-up if the oven is accidentally overheated. Evaporationlosses should be made up with sterile deionized water if saline,serum, plasma, or other hydrous medium is used as theconditioning environment.10.2.3.2 Following moisture saturation within the spec
48、ifiedtolerance range, the specimen should be stored in a bath of thesame fluid which is to be used for post-conditioning testinguntil the time the post-conditioning testing is conducted.11. Selection of Conditioning Procedure11.1 The choice between procedures should preferably bebased on the one tha
49、t gives the most reproducible results.12. Report12.1 Report the following information:12.1.1 Description of the specimen or device being consid-ered (that is, material name, dimensions, part number, modelnumber, size designation).12.1.2 The date of issue of this practice and the procedureused.12.1.3 The date(s) and location(s) of the test.12.1.4 The name(s) of the test operator(s).12.1.5 Any variations to this practice, anomalies noticedduring testing or equipment problems occurring during testing.12.1.6 Description of the materials and fabrication metho
