1、Designation: F 2042 00 (Reapproved 2005)Standard Guide forSilicone Elastomers, Gels, and Foams Used in MedicalApplications Part IICrosslinking and Fabrication1This standard is issued under the fixed designation F 2042; the number immediately following the designation indicates the year oforiginal ad
2、option 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 guide is intended to educate potential users ofsilicone elastome
3、rs, 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 condi
4、tions for specificmedical device applications.1.3 Formulation and selection of appropriate starting mate-rials is covered in the companion document, F 2038 Part I. Thismonograph addresses only the curing, post-curing, and pro-cessing of elastomers, gels and foams as well as how theresulting product
5、is evaluated.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
6、those 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 inves
7、tigation ofbiocompatibility, and the procedures for obtaining such datadepend on the goal of the study (see F 619, the HIMAMemorandum 7/14/93, and USP 23, for examples of extractionmethods).2. Referenced Documents2.1 ASTM Standards:2D 395 Test Methods for Rubber PropertyCompressionSetD 412 Test Meth
8、ods for Vulcanized Rubber and Thermo-plastic ElastomersTensionD 430 Test Methods for Rubber DeteriorationDynamicFatigueD 624 Test Method for Tear Strength of ConventionalVulcanized Rubber and Thermoplastic ElastomersD 792 Test Methods for Specific Gravity (Relative Density)and Density of Plastics by
9、 DisplacementD 813 Test Method for Rubber DeteriorationCrackGrowthD 814 Test Method for Rubber PropertyVapor Transmis-sion of Volatile LiquidsD 926 Test Method for Rubber PropertyPlasticity andRecovery (Parallel Plate Method)D 955 Test Method of Measuring Shrinkage from MoldDimensions of Thermoplast
10、icsD 1349 Practice for RubberStandard Temperatures forTestingD 1566 Terminology Relating to RubberD 2240 Test Method for Rubber PropertyDurometerHardnessF 619 Practice for Extraction of Medical PlasticsF 719 Practice for Testing Biomaterials in Rabbits forPrimary Skin IrritationF 720 Practice for Te
11、sting Guinea Pigs for ContactAllergensGuinea Pig Maximization TestF 748 Practice for Selecting Generic Biological Test Meth-ods for Materials and DevicesF 813 Practice for Direct Contact Cell Culture Evaluation ofMaterials for Medical DevicesF 981 Practice for Assessment of Compatibility of Bioma-te
12、rials for Surgical Implantation With Respect to Effect ofMaterials on Muscle and BoneF 1905 Practice for Selecting Tests for Determining thePropensity of Materials to Cause ImmunotoxicityF 1906 Practice for Evaluation of Immunological Re-sponses in Biocompatibility Testing Using ELISA Tests,Lymphocy
13、te Proliferation, and Cell MigrationF 1984 Practice for Testing Whole Complement Activationin Serum by Solid MaterialsF 2038 Guide for Silicone Elastomers, Gels,and FoamsUsed in Medical Applications Part IFormulations andUncured Materials1This guide is under the jurisdiction of ASTM Committee F04 on
14、 Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF4.11 on Polymeric Materials.Current edition approved Mar. 1, 2005. Published March 2005. Originallyapproved in 2000. Last previous edition approved in 2000 as F 2042 00e1.2For referenced ASTM standards, visit
15、 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-295
16、9, United States.2.2 Other Biocompatibility Standards:United States Pharmacopeia, current edition (appropriatemonographs may include: , , , )3FDA Department of Health and Human Services GeneralProgram Memorandum #G951, May 1, 1995: Use ofInternational Standard ISO-10993, Biological Evaluationof Medi
17、cal Devices Part I: Evaluation and Testing4ANSI/AAMI 109931 Biological Evaluation of MedicalDevices, Part I: Guidance on Selection of Tests5HIMA Memorandum Guidance for Manufacturers of Sili-cone Devices Affected by Withdrawal of Dow CorningSilastic Materials, 7/14/9362.3 Sterilization Standards:ANS
18、I/AAMI ST46 Good Hospital Practice: Steam Steril-ization and Sterility Assurance5ANSI/AAMI ST41 Good Hospital Practice: Ethylene OxideSterilization and Sterility Assurance5ANSI/AAMI ST50 Dry Heat (Heated Air) Sterilizers5ANSI/AAMI ST29 Recommended Practice for Determin-ing Ethylene Oxide in Medical
19、Devices5ANSI/AAMI ST30 Determining Residual Ethylene Chloro-hydrin and Ethylene Glycol in Medical Devices5AAMI 13409251 Sterilization of Health Care ProductsRadiation SterilizationSubstantiation of 25kGy as aSterilization Dose for Small or Infrequent ProductionBatches7AAMI TIR8251 Microbiological Me
20、thods for Gamma Ir-radiation Sterilization of Medical Devices72.4 Quality Standards:ANSI/ASQC Q9001 Quality SystemsModel for QualityAssurance in Design, Development, Production, Installa-tion and Servicing521 CFR 820 Quality System Regulation (current revision)821 CFR 210 Current Good Manufacturing
21、Practice inManufacturing, Processing, Packing or Holding of Drugs:General (current revision)821 CFR 211 Current Good Manufacturing Practice forFinished Pharmaceuticals (current revision)82.5 Other Standards:Dow Corning CTM 0155 (Gel-Like Materials With Modi-fied Penetrometer)Dow Corning CTM 0813 (Ge
22、l-Like Materials With OneInch Diameter Head Penetrometer)PCB Test Methods such as those used for MRI project No.4473, 1/24/97,9Biological Performance of Materials: J. Black, Marcel De-kker, NY 19923. Terminology3.1 The classification of silicone elastomers is based upon anumber of interrelated facto
23、rs 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 terms are definedin standard D 1566.3.2 Definitions:3.2.1 manufacturethe process which occurs in the supp
24、li-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 by which the uncured elas-tomer is converted into a fully vulcanized elastomer of thedesired size and shap
25、e. 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 injection moldingfabrication of elastomers intoforms defined by molds constructed so that the uncuredelastomer ca
26、n 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 the molding conditions (temperatureand filling rate) are adjusted so that uncured elastomer can beadded to
27、 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 placed in an open mold. The mold is closedand pressure applied to the mold to fill the cavity. Heat isapplied
28、 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, thickuncured high consistency elastomers can become so stiff overtime that they are very difficult to pro
29、cess. 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 immediately beforecatalyzation.3.2.2.4 transfer moldinga process in which the mixed,uncured elastomer is plac
30、ed 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 mold to vulcanize theelastomer, the mold is then opened, and the fabricated part isremoved.3.2.2.5 extru
31、siona continuous process in which themixed, uncured elastomer is forced through an orifice havingthe desired cross-sectional profile. The elastomer is thenvulcanized by passing it through either a hot air or radiant heatoven. The most common application of extrusion processing isthe fabrication of t
32、ubing but it can be used to produce otheritems as well.3Available from U.S. Pharmacopeia (USP), 12601 Twinbrook Pkwy., Rockville,MD 20852.4Available from Food and Drug Administration (FDA), 5600 Fishers Ln.,Rockville, MD 20857.5Available from American National Standards Institute (ANSI), 25 W. 43rd
33、St.,4th Floor, New York, NY 10036.6Available from Advanced Medical Technology Association, 1200 G St. N.W.Suite 400 Washington, D.C. 200053814.7Available from Association for the Advancement of Medical Devices, 1110North Glebe Rd., Suite 220, Arlington, VA 222014795.8Available from Standardization D
34、ocuments Order Desk, Bldg. 4 Section D, 700Robins Ave., Philadelphia PA 191115094, Attn: NPODS.9Available from Midwest Research Institute, 425 Volker Blvd., Kansas City, MO641102299.F 2042 00 (2005)23.2.2.6 post-curethe process of subjecting a vulcanizedelastomer to elevated temperature, usually in
35、a hot-air oven,after its initial 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
36、 attemptto accelerate molding process, 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 m
37、aterial andis usually done to allow 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 elas
38、tomer, to preventpreferential settling 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
39、elastomeran elastomer supplied 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 t
40、ypically used in injection molding 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
41、molded. They are typically used 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
42、dependent upon diffusion ofwater 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
43、 platinum catalyzed addition cure 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 m
44、ay also be used to provide protection 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 usually
45、two-part formulations utilizing 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 w
46、eightbasis, they are highly crosslinked 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 guida
47、nce relative totesting that might 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 customerse
48、ither directly or through the US 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 genera
49、tion 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 platinumcomplex. The catalyst will be present at a level such that theconcentration of platinum is in the range of 5 to 20 ppm but ismore typically present at a level of about 7.5 ppm. Whenmultiple silylhydrides are present in the same molecule, forexample, in a crosslinker mole
