1、Designation: F 2256 05Standard Test Method forStrength Properties of Tissue Adhesives in T-Peel byTension Loading1This standard is issued under the fixed designation F 2256; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、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 adhesivesintende
3、d 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 st
4、andard 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 Documents2.1
5、 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 flex
6、ibleas used in this test method, indicates that theadherends shall have such dimensions and physical propertiesas to permit bending them through any angle up to 90 withoutbreaking or cracking.3.2.2 tissue adhesivefor the purposes of this test method,tissue adhesive is defined as a compound or system
7、 intendedfor use in closing wounds (surgical or traumatic) or for sealingagainst leakage of body fluids.3.2.3 tissue sealanta surface coating with adequate adhe-sive strength to prevent leakage of body fluids.3.2.4 T-peel strengththe average load per unit width ofbond line required to produce progre
8、ssive separation of twobonded flexible adherends, under conditions designated in thismethod.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 f
9、rankreplacements for those devices in a wide variety of medicalprocedures. While the 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. There
10、fore, themechanical properties of the materials, and in particular theadhesive properties, 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 contr
11、ol, or as ameans for determining the effects of various surface treatmentson the substrate 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 T-Peel test
12、 arenot suitable for determining allowable design stresses withoutthorough analysis and understanding of the application andadhesive 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 m
13、ust be made with greatcaution since different adhesives may respond differently 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 gr
14、ip.1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved Mar. 1, 2005. Published March 2005. Originallyapproved in 2003. Last previous edi
15、tion approved in 2003 as F 2256 03.2For referenced ASTM standards, visit 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.3Available from the Americ
16、an Association of Tissue Banks (AATB), 1350Beverly Rd., Suite 220-A, McLean, VA 22101.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.1.2 Movable Member, a movable member carrying asecond grip.5.1.3 Grips, for holding the test spec
17、imen between the fixedmember and the movable member of the testing machine canbe either the fixed or self-aligning type.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 tests
18、pecimen is inserted and clamped so that the long axis of thetest specimen 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 al
19、ignment as soon as any load isapplied so that the long axis of the test 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 indu
20、ce slippage or damage to the sample willoccur in the grips; there is a 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 r
21、egulated as specified in 9.3.5.1.5 Load Indicator, a suitable load-indicating 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
22、 an accuracy of 61 % of theindicated value, or better. The accuracy of 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 cont
23、rol is required.Awater bath or environmental chamber capable of maintaining37C 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 beenasepti
24、cally prepared is available commercially and is preferreddue to ease of 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
25、, it should be prepared accordingthe method in Appendix X1.6.2 Application Specific TestingDue to the size of theT-Peel test specimens, many tissues will not be suitable for thistest.6.2.1 The strength of any adhesive is highly dependent onthe test substrate, or adherend. For a specific application,
26、 thepreferred substrate is freshly harvested tissue from the targetorgan of a domestic food animal. Tissue from bovine, porcine,or ovine origin is preferred due to wide availability and the factthat relatively large samples of tissue can be harvested from asingle source. Ideally, the tissue should b
27、e 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 tissue samples should be carried out according tothe guidelines set forth in Standards for Tissue Banking by theAmerican Association of Tissue
28、Banks. The specimens shouldbe brought to the test temperature or other prescribed tempera-ture (such as body temperature) prior to application of theadhesive.6.2.2 Fixed tissue should not be used since it has beendemonstrated that fixatives cause large alterations in themechanical properties of the
29、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 fabrication of test samples as shown in Fig. 1,a tissue of similar origin but larger size should be used. Forexample, if the intended indicati
30、on is for anastomosis of smallblood vessels, a larger vessel should be substituted (see 6.2).6.2.4 The thickness of the tissue sample should be mini-mized and should not exceed 5 mm. Thicker samples will leadto distortion of the substrate and mixed loading (shear andtension). It is also important th
31、at 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 manufacturing of a tissue adhesivedevice, the use of freshly harvested tissue is highly inconve-nient and may also lead to unacceptable
32、 variation in the testresults, especially if the failure occurs in the adherend (sub-strate failure). Since the purpose of quality control testing is todemonstrate consistency in the device, substitution of a modelsubstrate is preferred so long as it is demonstrated that theadhesive does bond to the
33、 adherand. Due to the nature of theT-Peel test, the substrate must be flexible and should havesufficient stiffness to minimize substrate distortion during thetest.FIG. 1 T-Peel Sample Configuration (Side View)F22560526.3.2 For devices that require contact with tissues to cure,Mediskin XenoGraft shou
34、ld be used for quality control testingas well as comparative testing.7. Test Specimen7.1 The T-Peel test specimen is shown in Fig. 1.Twosubstrate samples are required for each test.7.1.1 A template of the correct dimensions should be used.A sharp scalpel or similar device should be used to cut thesu
35、bstrate material.7.1.2 Specimen width should be 2.5 6 0.1 cm.7.1.3 Specimen length should be 15 6 0.2 cm (2.5 cmunbonded, 12.5 cm bonded).7.2 Number of Test SpecimensTest at least 10 specimensof each type. Tissue substrates tend to give higher variancesand may require more samples to attain a reason
36、able estimateof the mean strength.8. Sample Preparation8.1 Tissue Preparation:8.1.1 Tissue substrate materials should be kept moist at alltimes with phosphate buffered saline (PBS).8.1.2 The substrate will be cut to the dimensions given inSection 7 using a template and a fresh scalpel blade or a cut
37、terfabricated to the required dimensions.8.1.3 Wrap the tissue with gauze soaked in PBS, place in aplastic bag, and place them in a water bath or environmentalchamber at 37C.8.2 Preparation of the Adhesive Bond:8.2.1 Prepare the test adhesive according to the manufac-turers directions or by other pr
38、escribed 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 adhesive couldrun over the edge of the substrate, causing artificially
39、 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 use a template toprevent overspray. Alternatively, petroleum jelly may
40、 appliedto the portion of the tissue outside of the overlap area toprevent bonding.8.2.4 Place the other non-glued adherend specimen on topof the glued specimen.8.2.5 Apply a force of approximately 5 to 10 N to the bondarea until the adhesive sets. For slow-curing adhesives it maybe necessary to use
41、 a clamping device that can be left in placewhile the fixture is returned to the environmental chamber orwater bath.8.3 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
42、 the constanttemperature environment.9. Test Procedure9.1 Condition the test specimens for definite periods 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-ten
43、ded for internal applications are 37 6 1C in phosphatebuffered saline. For adhesives intended for external 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 condi
44、tioning, it is recommended that all speci-mens be stabilized at the test temperature for 15 min beforetesting 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
45、test conditions should be 23 6 2C and 50 6 5%relative humidity (see Annex A1).9.3 Clamp the unbonded ends of the test specimen in thegrips of the tensile test machine as shown in Fig. 1. Load thespecimen at a constant cross-head speed of 250 mm/min.9.4 Record the load as a function of displacement,
46、and thetype of failure (percentage cohesive, adhesive, or substratefailure) based on observation of the bond area.10. Calculations10.1 For a bonded length of 12.5 cm, the displacement ofthe test grips will be approximately 25 cm. Ignore the load datafor the first 2.5 cm of displacement, and calculat
47、e the averageload between displacements of 2.5 cm and 22.5 cm.10.2 Calculate the average T-Peel strength by dividing theaverage load in Newtons by the width of the specimen incentimetres.10.3 Calculate the average and standard deviation for eachgroup of samples.11. Report11.1 Report the following:11
48、.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.11.1.3 Estimated amount of
49、 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 Average width of the specimen.11.1.7 Conditioning of specimen prior to testing.11.1.8 Maximum, minimum, mean, and standard deviationof the Peel strength for the group of specimens.11.1.9 Number of specimens tested.11.1.10 Type of FailureThis should include estimatedpercentages of cohesive failure in the adhesive, apparentfailure in adhesion, and failure in the adherend (substrate) foreach specimen.11.1.11 Test temperature
