1、Designation: F2042 00 (Reapproved 2011)Standard Guide forSilicone Elastomers, Gels, and Foams Used in MedicalApplications Part IICrosslinking and Fabrication1This standard is issued under the fixed designation F2042; the number immediately following the designation indicates the year oforiginal adop
2、tion 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 guide is intended to educate potential users ofsilicone elastomers,
3、 gels and foams relative to their fabricationand processing. It does not provide information relative tosilicone powders, fluids, pressure sensitive adhesives, or othertypes of silicone products.1.2 The information provided is offered to guide users in theselection of appropriate processing conditio
4、ns for specificmedical device applications.1.3 Formulation and selection of appropriate starting mate-rials is covered in the companion document, F2038 Part I. Thismonograph addresses only the curing, post-curing, and pro-cessing of elastomers, gels and foams as well as how theresulting product is e
5、valuated.1.4 Silicone biocompatibility issues can be addressed atseveral levels, but ultimately the device manufacturer mustassess biological suitability relative to intended use. Biocom-patibility testing may be done on cured elastomers prior to finalfabrication, but the most relevant data are thos
6、e obtained on thefinished device. Data on selected lots of material are onlyrepresentative when compounding, and fabrication are per-formed under accepted quality systems such as ISO 9001 andcurrent Good Manufacturing Practice Regulations. Extract-ables analyses may also be of interest for investiga
7、tion ofbiocompatibility, and the procedures for obtaining such datadepend on the goal of the study (see F619, the HIMAMemorandum 7/14/93, and USP 23, for examples of extractionmethods).2. Referenced Documents2.1 ASTM Standards:2D395 Test Methods for Rubber PropertyCompression SetD412 Test Methods fo
8、r Vulcanized Rubber and Thermo-plastic ElastomersTensionD430 Test Methods for Rubber DeteriorationDynamicFatigueD624 Test Method for Tear Strength of Conventional Vul-canized Rubber and Thermoplastic ElastomersD792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by Disp
9、lacementD813 Test Method for Rubber DeteriorationCrackGrowthD814 Test Method for Rubber PropertyVapor Transmis-sion of Volatile LiquidsD926 Test Method for Rubber PropertyPlasticity andRecovery (Parallel Plate Method)D955 Test Method of Measuring Shrinkage from MoldDimensions of ThermoplasticsD1349
10、Practice for RubberStandard Temperatures forTestingD1566 Terminology Relating to RubberD2240 Test Method for Rubber PropertyDurometerHardnessF619 Practice for Extraction of Medical PlasticsF719 Practice for Testing Biomaterials in Rabbits for Pri-mary Skin IrritationF720 Practice for Testing Guinea
11、Pigs for Contact Aller-gens: Guinea Pig Maximization TestF748 Practice for Selecting Generic Biological Test Meth-ods for Materials and DevicesF813 Practice for Direct Contact Cell Culture Evaluation ofMaterials for Medical DevicesF981 Practice for Assessment of Compatibility of Biomate-rials for Su
12、rgical Implants with Respect to Effect ofMaterials on Muscle and BoneF1905 Practice For Selecting Tests for Determining thePropensity of Materials to Cause Immunotoxicity3F1906 Practice for Evaluation of Immune Responses InBiocompatibility Testing Using ELISA Tests, LymphocyteProliferation, and Cell
13、 Migration3F1984 Practice for Testing for Whole Complement Activa-tion in Serum by Solid MaterialsF2038 Guide for Silicone Elastomers, Gels, and Foams1This guide is under the jurisdiction of ASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of Subcommit
14、teeF04.11 on Polymeric Materials.Current edition approved Dec. 1, 2011. Published January 2012. Originallyapproved in 2000. Last previous edition approved in 2005 as F2042 00 (2005).DOI: 10.1520/F2042-00R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer
15、 Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Bo
16、x C700, West Conshohocken, PA 19428-2959, United States.Used in Medical Applications Part IFormulations andUncured Materials2.2 Other Biocompatibility Standards:United States Pharmacopeia, current edition (appropriatemonographs may include: , , , )4FDA Department of Health and Human Services General
17、Program Memorandum #G951, May 1, 1995: Use ofInternational Standard ISO-10993, Biological Evaluationof Medical Devices Part I: Evaluation and Testing5ANSI/AAMI 109931 Biological Evaluation of MedicalDevices, Part I: Guidance on Selection of Tests6HIMA Memorandum Guidance for Manufacturers of Sili-co
18、ne Devices Affected by Withdrawal of Dow CorningSilastic Materials, 7/14/9372.3 Sterilization Standards:ANSI/AAMI ST46 Good Hospital Practice: Steam Steril-ization and Sterility Assurance6ANSI/AAMI ST41 Good Hospital Practice: Ethylene OxideSterilization and Sterility Assurance6ANSI/AAMI ST50 Dry He
19、at (Heated Air) Sterilizers6ANSI/AAMI ST29 Recommended Practice for Determin-ing Ethylene Oxide in Medical Devices6ANSI/AAMI ST30 Determining Residual Ethylene Chloro-hydrin and Ethylene Glycol in Medical Devices6AAMI 13409251 Sterilization of Health Care ProductsRadiation SterilizationSubstantiatio
20、n of 25kGy as aSterilization Dose for Small or Infrequent ProductionBatches8AAMI TIR8251 Microbiological Methods for Gamma Ir-radiation Sterilization of Medical Devices82.4 Quality Standards:ANSI/ASQC Q9001 Quality SystemsModel for QualityAssurance in Design, Development, Production, Installa-tion a
21、nd Servicing621 CFR 820 Quality System Regulation (current revision)921 CFR 210 Current Good Manufacturing Practice inManufacturing, Processing, Packing or Holding of Drugs:General (current revision)921 CFR 211 Current Good Manufacturing Practice forFinished Pharmaceuticals (current revision)92.5 Ot
22、her Standards:Dow Corning CTM 0155 (Gel-Like Materials With Modi-fied Penetrometer)Dow Corning CTM 0813 (Gel-Like Materials With OneInch Diameter Head Penetrometer)PCB Test Methods such as those used for MRI project No.4473, 1/24/97,10Biological Performance of Materials: J. Black, MarcelDekker, NY 1
23、9923. Terminology3.1 The classification of silicone elastomers is based upon anumber of interrelated factors which include the chemicalsystem used to crosslink the elastomer, the physical character-istics of the uncured elastomer, and the methods used tofabricate the elastomers. Additional pertinent
24、 terms are definedin standard D1566.3.2 Definitions:3.2.1 manufacturethe process which occurs in the suppli-ers facility in which the various components of the elastomerare brought together, allowed to interact, and are packaged toprovide the uncured elastomer for sale.3.2.2 fabricationthe process b
25、y which the uncured elas-tomer is converted into a fully vulcanized elastomer of thedesired size and shape. This process may occur in the samefacility as the manufacture of the uncured elastomer but ismore typically performed at the facility of a customer of thesilicone manufacturer.3.2.2.1 injectio
26、n moldingfabrication of elastomers intoforms defined by molds constructed so that the uncuredelastomer can be transferred by pumping into the closed mold.This method requires venting of the mold in some manner. Theelastomer may be vulcanized by heating the mold after it isfilled but more typically t
27、he molding conditions (temperatureand filling rate) are adjusted so that uncured elastomer can beadded to a pre-heated mold in which it will then cure. The moldis than opened and the part removed and post-cured, ifnecessary.3.2.2.2 compression moldinga process in which the un-cured elastomer is plac
28、ed in an open mold. The mold is closedand pressure applied to the mold to fill the cavity. Heat isapplied to vulcanize the elstomer, the mold is than opened andthe fabricated part is removed.3.2.2.3 fresheningbecause of the interaction that can oc-cur between the fumed silica and silicone polymers,
29、thickuncured high consistency elastomers can become so stiff overtime that they are very difficult to process. To overcome thisproblem, a tworoll mill is used to disrupt this interaction,resulting in a material which is easier to fabricate. This processis called freshening and is typically done imme
30、diately beforecatalyzation.3.2.2.4 transfer moldinga process in which the mixed,uncured elastomer is placed in a compartment connected to themold. The compartment is then closed, pressure is applied totransfer the uncured elastomer to the mold, filling the cavity.Heat and pressure are applied to the
31、 mold to vulcanize theelastomer, the mold is then opened, and the fabricated part isremoved.3.2.2.5 extrusiona continuous process in which themixed, uncured elastomer is forced through an orifice having4Available from U.S. Pharmacopeia (USP), 12601 Twinbrook Pkwy., Rockville,MD 20852-1790, http:/www
32、.usp.org.5Available from Food and Drug Administration (FDA), 10903 New HampshireAve., Silver Spring, MD 20993-0002, http:/www.fda.gov.6Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.7Available from Advanced Medical Techno
33、logy Association, 1200 G St. N.W.Suite 400 Washington, D.C. 200053814, http:/www.advamed.org.8Available from Association for the Advancement of Medical Instrumentation(AAMI), 4301 N. Fairfax Dr., Suite 301, Arlington, VA 22203-1633, http:/www.aami.org.9Available from Standardization Documents Order
34、Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http:/dodssp.daps.dla.mil.10Available from Midwest Research Institute, 425 Volker Blvd., Kansas City,MO 641102299.F2042 00 (2011)2the desired cross-sectional profile. The elastomer is thenvulcanized by passing it through
35、 either a hot air or radiant heatoven. The most common application of extrusion processing isthe fabrication of tubing but it can be used to produce otheritems as well.3.2.2.6 post-curethe process of subjecting a vulcanizedelastomer to elevated temperature, usually in a hot-air oven,after its initia
36、l fabrication. This process step is done tocomplete cross-linking of the object, remove peroxide by-products, and eliminate changes in its physical properties.Post-cure is often necessary when the component is onlypartially cross-liked by molding; it is performed in an attemptto accelerate molding p
37、rocess, and increase its output.3.2.2.7 calendaringthe process of forming an uncured,mixed elastomer into a thin sheet or film by passing it betweentwo rolls.3.2.2.8 dispersionthe process of placing an uncured elas-tomer in a solvent. This lowers the viscosity of the material andis usually done to a
38、llow the fabrication of thinner films that canbe obtained by calendaring or to form coatings. Followingdispersion use, the solvent must be removed either before orduring the vulcanization process. Care must be taken to assurethat the solvent is compatible with the elastomer, to preventpreferential s
39、ettling of the components of the formulation byexcessive dilution of the elastomer.3.2.3 one-part elastomeran elastomer supplied in theuncured form in one package containing all of the formulationcomponents. It does not require mixing before fabrication.3.2.4 two-part elastomeran elastomer supplied
40、in twopackages which must be mixed in specified proportions beforefabrication.3.2.5 liquid silicone rubber or low consistency siliconerubber (LSR)an elastomer having a viscosity such that it canbe moved or transferred by readily available pumping equip-ment. LSRs are typically used in injection mold
41、ing operations.3.2.6 high consistency rubber (HCR)an elastomer havinga viscosity such that it cannot be moved or transferred byreadily available pumping equipment. These elastomers arefabricated using high shear equipment such as a two-roll milland cannot be injection molded. They are typically used
42、 incompression or transfer molding and extrusion processes.3.2.7 RTV (room temperature vulcanization)a one-partelastomer which cures in the presence of atmospheric moisture.Little, if any, acceleration of cure rate is realized by increasingtemperature. Because cure is dependent upon diffusion ofwate
43、r into the elastomer, cure in depths of greater than 0.64 cmis not recommended.3.2.8 gela lightly crosslinked material having no or rela-tively low levels of reinforcement beyond that provided by thecrosslinked polymer. Gels are usually two-part formulationsutilizing a platinum catalyzed addition cu
44、re system. Thehardness of the gel can be adjusted within wide limits. Thematerial is not usually designed to bear a heavy load but ratherto conform to an irregular surface providing intimate contact.As a result, loads are distributed over a wider area. Thesematerials may also be used to provide prot
45、ection from envi-ronmental contaminants.3.2.9 foama crosslinked material which has a componentadded to it which generates a volatile gas as the material isbeing vulcanized. This vulcanization process results in amaterial with a relatively low density. Foams are usuallytwo-part formulations utilizing
46、 a platinum catalyzed additioncure system. They conform as they expand to irregular surfacesjust as gels do to provide intimate contact and protection fromthe environment but are more rigid and provide more strengththan gels. Since foams are expanded elastomers, on a weightbasis, they are highly cro
47、sslinked relative to gels. Most cureconditions will result in a closed cell foam.4. Significance and Use4.1 This guide is intended to provide guidance for thespecification and selection of fabrication methods for siliconesused in medical devices. It also provides guidance relative totesting that mig
48、ht be done to qualify lots of acceptablematerial, based on desired performance properties.4.2 Silicone manufacturers supplying material to the medi-cal device industry should readily provide information regard-ing non-proprietary product formulation to their customerseither directly or through the U
49、S FDA Master File program.5. Crosslinking Chemistry5.1 Silicone elastomers used in medical applications aretypically crosslinked by one of three commonly used curesystems. These involve the platinum catalyzed addition of asilylhydride to an unsaturated site, the generation of freeradicals by a peroxide or the reaction of an easily hydrolyzablegroup of silicon.5.1.1 addition curethis cure system utilizes the additionof a silylhydride to a site of unsaturation, usually a vinyl group.As shown in Fig. 1, this reaction is catalyzed by a platin
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