Calculation 12. Procedure

I Calculate the compression set expressed

¶12.1 Original Thickness Measurementas a percentage of the original deflection as fol- Measure the original thickness of the specimen lows: to the nearest 0.02 mm (0.001 in.). Place the specimen on the anvil of the dial micrometer so CB = [(lo - I , ) k - l.)] x loo (2) that the presser foot will indicate the thickness at where: the central portion of the top and bottom faces. C. = compression set (Method B) expressed as

¶12.2 Application of CompressiveForce-Place percentage of the original deflection, the test specimen between the plates of the com- r, = original thickness of specimen (12. I), pression device with the spacers on each side, I, = final thickness of specimen (12.3, and allowing sufficient clearance for the bulging of

= thickness of the spacer bar used. the rubber when compressed (Fig. 3). Where a lubricant is applied, it shall consist of a thin NOTE 5-Lubrication of the operating surfaces of coating of a lubricant having substantially no the compression device is optional while giving more action on the rubber. For most purposes, a silicon reproducible results, lubrication may somewhat alter the compression set values. or fluorosilicon fluid is suitable. Tighten the bolts so that the plates are drawn together uniformly until they are in contact with the spacers. The 14. Report amount of compression employed shall be a p 14.1 The report shall include the following: proximately 25 %. A suitable mechanical or hy- 14. I. I Original dimensions of the test speci- draulic device may be used to facilitate assem- men including the original thickness, fo, bling and disassembling the test fixture. 14.1.2 Percentage compression of the speci12.3 Test Time and Temperature-Choose a men actually employed, suitable temperature and time for the compres- 14.1.3 Thickness of the test specimen 30 min sion set, depending upon the conditions of the after removal from the clamp, ti, expected service. In comparative tests, use iden- 14. I .4 Type of test specimen used, together tical temperature and test periods. It is suggested with the time and temperature of test, that the test temperature be chosen from those 14. I .5 Whether or not the surfaces ofthe com- listed in Recommended Practice D 1349. Sug- pression device are lubricated. If they are, what gested test periods are 22 h and 70 h. The test type lubrication was used, specimen shall be at room temperature when 14. I .6 Compression set, expressed as a per- inserted i n the compression device. Place the centage of the original deflection, assembled compression device in the oven within 14. I .7 Method used (Method B), and

¶D 395

¶14.1.8 Ntinlth.. :pecimens tested. A testing, therefore the precision for Method A 15. Precision' and b. is derived from four laboratories.

¶15.4 The precision results are given in Tables

¶15.1 These precision ,,atements have been I and 2. prepared in accordance with Practice D 3040-8I. 15.5 Bias-In test method statistical termi- Please refer to this practice for terminology and nology, bias is the difference between an average other testing and statistical concepts. test value and the reference or true test property

¶15.2 Prepared test specimens of two rubbers, value. Reference values do not exist for this test Methods A and B, were supplied to five labora- method since the value or level of the test p r o p tones. These were tested in duplicate each day erty is exclusively defined by the test method. on two separate testing days. A test result, there- Bias, therefore, cannot be determined. fore, is the average of two test specimens, for both Methods A and B. 'Supporting data arc available fmm ASTM H e a d q m r s .

¶15.3 One laboratory did not run the Method RequestRRD-11-1138.

TABLE I LQC Pmisioa Data Comprearion Set-Method A Within Laboratories Among Laboralones

¶Material Mean Level -

S cv S CV A 1.73(I) 0.0500 0.0277 0.190 0.1096 B 26.1 0.898 0.0336 2.37 0.0908 Avcrage or Pooled 0.636 0.0308 I .68I 0.1006 Values Repcatabilily Reproducibility Standard Deviation, (9" 0.636 1.743 Callicient or Variation. ( C V ) 0.0308 0.103 Least Significant Di!Terena. (LSD)*' 8.8 I 29.1 I

¶A An averagc value. the value of S varies with mean level.

¶.LSD based on 95 Iconfidence level: two results are considered significantly different If their difference. expressed as a percentage ortheir avcragc. exceeds the stated p e m n l value.

¶CThe LSD values are relative percent. that is, a percent of the 'percent" values used to measure the tested PmWrtY.

TABLE 2 LQC Precision D.¹¹ For the purpose of this report, a procedure is a formal set of instructions designed to guide and assist in the performance of a technical or management function. g8 mid., July 24, 1986, p. 11. 1 9 9 Ibid., June 25, 1986, p. 52. . Colnprrssh Set-Melhod 6 Within Laboratories Among laboratones

¶Material Mean Level

S cv S cv A 13.7 (A) 0.591 0.0420 1.543 0.113 B 52.8 0.567 0.01 10 5.924 0.112

Average or Pooled 0.579 0.OM7 4.329 0.1124 valuei Repeatability Repmducibilily Standard Deviation. (W 0.579 4.348 Coetlicient or Variation. ( C V ) 0.0307 0.1 14 Lean Significant Difference. (LSD)*E 8.7 Sb 32.4 I

¶An average value, the value oTS varies with mean level.

¶LSO b a d on 95 A oonfdence level: two results are considered significantly different if lhetr dimerence. expresvd a sa percentage oftheir average, exceeds the stated percent value.

¶The LSD values are relative percent. that is. a percent of the 'percent" values used to measure the tested property.

¶D 395

FIG. I Device for Compreash Sef Test, Usins Chlibnted Spring lmdinll, Method A

FIG. 3 Device for C o m p ~ i u a sct Test Under Consmat DellectioqMC(M B

¶The American Societyfor Testingand Materials rakes no position respfrring the v d i d i y orany pamu ri&s asserted in connection with any irem mentionedin this standard. Users ojrhis srandard are expressly advised thru dormninruion dthe volidiry oJany such patent rights. and the risk of infiingement of such rights. are entirely their own tesfmnsibiliry.

¶This standard is subject to revision at any rime by the responsible technical committee and musr be r e v i d everyjve ypan and if nor revised, eirher reapproved or wirhdrawn. Your commenrs are invited either far revision ofthis sran&rd o r for additional standards and should be addressed to ASTM Headquarters. Your comments will receive c a r & / cansideration a r a meering d t h e responsible technical committee. which you may attend. Uyou/eel that your comments have nm received a b i r hearing you should make your views known to the ASTM Committee on Standards, I916 Race SI.. Philadeldria. Pa. 19/03.

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