1、Designation: F 2255 05Standard Test Method forStrength Properties of Tissue Adhesives in Lap-Shear byTension Loading1This standard is issued under the fixed designation F 2255; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar 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 test method is intended to provide a means forcomparison of the adhesive strengths of tissue adhesivesinte
3、nded for use as surgical adhesives or sealants, or both, onsoft tissue. With the appropriate choice of substrate, it may alsobe used for purposes of quality control in the manufacture oftissue adhesive based medical devices.1.2 The values stated in SI units are to be regarded as thestandard.1.3 This
4、 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 Documents
5、2.1 ASTM Standards:2D 907 Terminology of AdhesivesE4 Practices for Force Verification of Testing Machines2.2 American Association of Tissue Banks Standards:3Standards for Tissue Banking3. Terminology3.1 DefinitionsMany terms in this test method are definedin Terminology D 907.3.2 Definitions:3.2.1 t
6、issue adhesivefor the purposes of this test method,tissue adhesive is defined as a compound or system intendedfor use in closing wounds (surgical or traumatic) or for sealingagainst leakage of body fluids.3.2.2 tissue sealanta surface coating with adequate adhe-sive strength to prevent leakage of bo
7、dy fluids.4. Significance and Use4.1 Materials and devices that function at least in part byadhering to living tissues are finding increasing use in surgicalprocedures either as adjuncts to sutures and staples, or as frankreplacements for those devices in a wide variety of medicalprocedures. While t
8、he nature and magnitude of the forcesinvolved varies greatly with indication and with patient specificcircumstances, all uses involve to some extent the ability of thematerial to resist imposed mechanical forces. Therefore, themechanical properties of the materials, and in particular theadhesive pro
9、perties, are important parameters in evaluatingtheir fitness for use. In addition, the mechanical properties of agiven adhesive composition can provide a useful means ofdetermining product consistency for quality control, or as ameans for determining the effects of various surface treatmentson the s
10、ubstrate prior to use of the device.4.2 The complexity and variety of individual applicationsfor tissue adhesive devices, even within a single indicated use(surgical procedure) is such that the results of a single-lap-shear test are not suitable for determining allowable designstresses without thoro
11、ugh analysis and understanding of theapplication and adhesive behaviors.4.3 This test method may be used for comparing adhesivesor bonding processes for susceptibility to fatigue and environ-mental changes, but such comparisons must be made with greatcaution since different adhesives may respond dif
12、ferently tovarying conditions.5. Apparatus5.1 Testing Machine, of the constant-rate-of-crosshead-movement type and comprising essentially the following:5.1.1 Fixed Member, a fixed or essentially stationary mem-ber carrying one grip.5.1.2 Movable Member, a movable member carrying asecond grip.5.1.3 G
13、rips, for holding the test specimen between the fixedmember and the movable member of the testing machine canbe either the fixed or self-aligning type.1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of Su
14、bcommitteeF04.15 on Material Test Methods.Current edition approved Mar. 1, 2005. Published March 2005. Originallyapproved in 2003. Last previous edition approved in 2003 as F 2255 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.
15、org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from the American Association of Tissue Banks (AATB), 1350Beverly Rd., Suite 220-A, McLean, VA 22101.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
16、 West Conshohocken, PA 19428-2959, United States.5.1.3.1 Fixed Grips are rigidly attached to the fixed andmovable members of the testing machine. When this type ofgrip is used extreme care should be taken to ensure that the testspecimen is inserted and clamped so that the long axis of thetest specim
17、en coincides with the direction of pull through thecenterline of the grip assembly.5.1.3.2 Self-aligning Grips are attached to the fixed andmovable members of the testing machine in such a manner thatthey will move freely into alignment as soon as any load isapplied so that the long axis of the test
18、 specimen will coincidewith the direction of the applied pull through the center line ofthe grip assembly. The specimens should be aligned as per-fectly as possible with the direction of pull so that no rotarymotion that may induce slippage or damage to the sample willoccur in the grips; there is a
19、limit to the amount of misalign-ment self-aligning grips will accommodate.5.1.4 Drive Mechanism, for imparting to the movable mem-ber a uniform, controlled velocity with respect to the stationarymember, with this velocity to be regulated as specified in 9.3.5.1.5 Load Indicator, a suitable load-indi
20、cating mechanismcapable of showing the total tensile load carried by the testspecimen when held by the grips. This mechanism shall beessentially free of inertia lag at the specified rate of testing andshall indicate the load with an accuracy of 61 % of theindicated value, or better. The accuracy of
21、the testing machineshall be verified in accordance with Practices E4.5.2 Temperature-controlling Equipment, capable of main-taining the test temperature to 62C. If ambient laboratoryconditions are employed the same degree of control is required.Awater bath or environmental chamber capable of maintai
22、ning37C is required for testing on tissue substrates.6. Test Substrate6.1 For comparative testing, either fresh or frozen splitthickness porcine skin graft may be used.6.1.1 Frozen split thickness porcine skin that has beenaseptically prepared is available commercially and is preferreddue to ease of
23、 use and the potential for more consistentproperties. It should be thawed according to the manufacturersinstructions prior to use. Unused graft may be kept at 2 to 8Cfor up to two weeks after thawing.6.1.2 If fresh skin is chosen, it should be prepared accordingthe method in Appendix X1.6.2 Applicat
24、ion Specific Testing:6.2.1 The strength of any adhesive is highly dependent onthe test substrate, or adherend. For a specific application, thepreferred substrate is freshly harvested tissue from the targetorgan of a domestic food animal. Tissue from bovine, porcine,or ovine origin is preferred due t
25、o wide availability and the factthat relatively large samples of tissue can be harvested from asingle source. Ideally, the tissue should be used within 24 h ofharvest, and should be kept between 5 and 10C prior to testingif it cannot be used immediately after harvesting. Storage andhandling of tissu
26、e samples should be carried out according tothe guidelines set forth in Standards for Tissue Banking by theAmerican Association of Tissue Banks. The specimens shouldbe brought to the test temperature or other prescribed tempera-ture (such as body temperature) prior to application of theadhesive.6.2.
27、2 Fixed tissue should not be used since it has beendemonstrated that fixatives cause large alterations in themechanical properties of the tissue and it is probable that theadhesive strength would be affected as well.6.2.3 If the target organ is of a size or geometry, or both, thatdoes not allow fabr
28、ication of test samples as shown in Fig. 1,a tissue of similar origin but larger size should be used. Forexample, if the intended indication is for anastomosis of smallblood vessels, a larger vessel should be substituted.6.2.4 The thickness of the tissue sample should be mini-mized and should not ex
29、ceed 5 mm. Thicker samples will leadto distortion of the substrate and mixed loading (shear andtension). It is also important that the thickness be as uniform aspossible.6.3 Substrates for Quality Control Testing:6.3.1 For testing that is undertaken as part of a qualitycontrol process in the manufac
30、turing of a tissue adhesivedevice, the use of freshly harvested tissue is highly inconve-nient and may also lead to unacceptable variation in the testresults, especially if the failure occurs in the adherend (sub-strate failure). Since the purpose of quality control testing is todemonstrate consiste
31、ncy in the device, substitution of a modelsubstrate is preferred so long as it is demonstrated that theadhesive does bond to the adherand. For devices that requirecontact with tissues to cure, Mediskin XenoGraft should beused for quality control testing as well as comparative testing.7. Test Specime
32、n7.1 Specimens with Soft-tissue Substrates shall conform tothe form shown in Fig. 1. The length of the tissue substrate (L)attached to each specimen holder should be at least 1.5 timesthe length of the overlap area in order to ensure that the failureoccurs at the overlap bond and doesnt pull the tis
33、sue substrateoff of the specimen holder. For very strong adhesives, L mayneed to be 2 to 3 times the overlap length. The tissue can bebonded to the specimen holder with any suitable adhesive.Gel-type cyanoacrylate adhesives have been found to beconvenient for this purpose since they adhere well to m
34、oisttissues and cure quickly.7.2 Specimens with Polymer or Metal Substrates shallconform to the form and dimensions shown in Fig. 2.7.3 Number of Test SpecimensTest at least 10 specimensof each type. Discard results if failure occurs between the testfixture and the tissue sample and test additional
35、samples toobtain a total of 10 valid tests. Tissue substrates tend to givehigher variances and may require more samples to attain areasonable estimate of the mean strength.8. Sample Preparation8.1 Tissue Preparation:8.1.1 Tissue substrate materials should be kept moist at alltimes with phosphate buf
36、fered saline (PBS).8.1.2 The substrate will be cut to the dimensions shown inFig. 1 using a template and a fresh scalpel blade or a cutterfabricated to the required dimensions. Alternatively, a slightlyoversized piece of tissue can be glued to the test fixture, andtrimmed to size using the fixture a
37、s a template.8.1.3 The back-side of the tissue sample will be glued to thetest fixture using a suitable adhesive. Gel-type cyanoacrylateF2255052adhesives have been found to be useful for this purpose sincethey set quickly and adhere to most materials. Care must betaken to ensure that the substrate i
38、s aligned square with thesides of the test fixtures and does not extend past the end of thefixture.8.1.4 Wrap the tissue with gauze soaked in PBS, place thefixtures in a plastic bag, and place them in a water bath orenvironmental chamber at 37C.8.2 Preparation of the Adhesive Bond:8.2.1 Prepare the
39、test adhesive according to the manufac-turers directions or by other prescribed procedure.8.2.2 Remove the test fixtures from the plastic bag and patthe surface of the tissue dry with fresh gauze.8.2.3 Apply sufficient adhesive to uniformly coat the over-lap area without significant overflow. Excess
40、 adhesive couldrun over the edge of the substrate, causing artificially high testvalues. The amount required will have to be determinedexperimentally. For adhesives that are delivered with a spraydevice, controlling the amount and distribution of the materialwill be difficult. It may be necessary to
41、 use a template toprevent overspray. Alternatively, petroleum jelly may appliedto the portion of the tissue outside of the overlap area toprevent bonding.8.2.4 Bond the two sides of the test fixture together, takingcare to keep the fixtures aligned and to maintain the prescribedoverlap.8.2.5 Apply a
42、 force of approximately 1 to2Ntothebondarea until the adhesive sets. For slow-curing adhesives it maybe necessary to use a clamping device that can be left in placewhile the fixture is returned to the environmental chamber orwater bath.FIG. 1 Soft Tissue FixtureFIG. 2 Metal/Polymer Substrate Specime
43、nF22550538.3 Measure and record the width and length of the adhesivebond to within 0.05 cm.8.4 Re-cover the tissue with gauze soaked in PBS, replacethe sample in a plastic bag, and return it to the constanttemperature environment.9. Test Procedure9.1 Condition the test specimens for definite periods
44、 of timeunder specified, controlled conditions before testing if desired.For comparative testing, the conditioning time should be 1 h 615 min. Recommended conditions for Tissue adhesives in-tended for internal applications are 37 6 1C in phosphatebuffered saline. For adhesives intended for external
45、topical use,recommended conditions are 30 6 1C and 50 6 5 % relativehumidity. For quality control testing, the recommended condi-tions are 23 6 2C and 50 6 5 % relative humidity.9.2 After conditioning, it is recommended that all speci-mens be stabilized at the test temperature for 15 min beforetesti
46、ng if the test temperature is different from the conditioningtemperature. Tissue samples must be kept moist throughout theprocess to prevent shrinkage due to drying. For comparativetesting the test conditions should be 23 6 2C and 50 6 5%relative humidity (see Annex A1).9.3 Place the test specimens
47、in the grips of the testingmachine so that the applied load coincides with the long axis ofthe specimen. Load the specimen to failure at a constantcross-head speed of 5 mm/min.9.4 Record the load at failure (maximum load sustained)and the type of failure (percentage cohesive, adhesive, orsubstrate f
48、ailure based on observation of the bond area).10. Calculations10.1 Calculate the bond area to the nearest 0.05 cm2.Calculate the apparent shear strength as the maximum loaddivided by the bond area in mega-Pascals (MPa).10.2 Calculate the average and standard deviation for eachgroup of samples.11. Re
49、port11.1 Report the following:11.1.1 Complete identification of the adhesive tested, in-cluding type, source, date manufactured, manufacturers codenumber, and lot number.11.1.2 Complete identification of the substrate used, itsthickness, and any method used to clean or prepare the surfaceprior to bonding. Also report the method used to adhere tissueto the specimen holder.11.1.3 Estimated amount of adhesive applied.11.1.4 Method of adhesive application.11.1.5 Ambient conditions at time of bonding (temperature,humidity, and so forth).11.1.6 Length and width of overlap.
