1、INTERNATIONALSTANDARDISO22768First edition2006-07-15Reference numberISO 22768:2006(E) ISO 2006Rubber, raw Determination of the glass transition temperature by differential scanning calorimetry (DSC)Caoutchouc brut Dtermination de la temprature de transition vitreuse par analyse calorimtrique diffren
2、tielle (DSC)ISO 22768:2006(E)ii ISO 2006 All rights reservedPDF disclaimerThis PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shallnot be edited unless the typefaces which are embedded are licensed to and installed on the c
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6、t the address below orISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandISO 22768:2006(E) ISO 2006 All rights reserved iiiForewordISO (the Inte
7、rnational Organization for Standardization) is a worldwide federation of national standards bodies(ISO member bodies). The work of preparing International Standards is normally carried out through ISOtechnical committees. Each member body interested in a subject for which a technical committee has b
8、eenestablished has the right to be represented on that committee. International organizations, governmental andnon-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the InternationalElectrotechnical Commission (IEC) on all matters of electrotechnical standa
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10、ing. Publication as anInternational Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patentrights. ISO shall not be held responsible for identifying any or all such p
11、atent rights.ISO 22768 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, SubcommitteeSC 2, Testing and analysis.ivINTERNATIONAL STANDARD ISO 22768:2006(E) ISO 2006 All rights reserved 1Rubber, raw Determination of the glass transition temperature by differential scanning cal
12、orimetry (DSC)WARNING Persons using this International Standard should be familiar with normal laboratorypractice. This standard does not purport to address all of the safety problems, if any, associated with itsuse. It is the responsibility of the user to establish appropriate safety and health pra
13、ctices and toensure compliance with any national regulatory conditions.1ScopeThis International Standard specifies a method using a differential scanning calorimeter to determine the glasstransition temperature of raw rubber.2 Normative referencesThe following referenced documents are indispensable
14、for the application of this document. For datedreferences, only the edition cited applies. For undated references, the latest edition of the referenced document(including any amendments) applies.ISO/TR 9272:2005, Rubber and rubber products Determination of precision for test method standardsISO 1135
15、7-1:1997, Plastics Differential scanning calorimetry (DSC) Part 1: General principlesISO 23529, Rubber General procedures for preparing and conditioning test pieces for physical test methods3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 11357-1, toge
16、ther with the following,apply.3.1 glass transitionreversible change in an amorphous polymer, or in amorphous regions of a partially crystalline polymer, from (orto) a rubbery or viscous condition to (or from) a glassy or hard condition3.2 glass transition temperatureapproximate midpoint of the tempe
17、rature range over which the glass transition takes placeNOTE For the purposes of this International Standard, the glass transition temperature is defined as the point of inflectionof the DSC curve which has been obtained at a heating rate of (see 12.3).4 PrincipleThe change in specific heat capacity
18、 of the rubber as a function of temperature under a specified inertatmosphere is measured using a differential scanning calorimeter (DSC). The glass transition temperature isdetermined from the curve thus produced.Tg20C/minISO 22768:2006(E)2 ISO 2006 All rights reserved5 Apparatus and materials5.1 D
19、ifferential scanning calorimeter, in accordance with ISO 11357-1:1997, 5.1.The calorimeter should be operated in a room held at standard laboratory temperature. It should be protectedfrom draughts, direct sunlight and sudden temperature changes.5.2 Specimen pans, in accordance with ISO 11357-1:1997,
20、 5.2.5.3 Gas supply, analytical grade, usually nitrogen or helium.5.4 Balance, capable of measuring the specimen mass to an accuracy of .6 Test specimenThe test specimen shall be as representative as possible of the sample being examined and shall have a massof between and .7 ConditioningCondition t
21、he sample to be examined and the test specimen according to ISO 23529.8CalibrationCalibrate the calorimeter according to the manufacturers instructions.The use of suitable analytical grade substances is recommended to check the accuracy of the temperaturescale. Ideally substances whose melting point
22、s bracket the temperature range of interest should be chosen.n-Octane and cyclohexane have been found to be useful. Indium should be used if a higher temperaturecalibrant is required.9 Procedure9.1 Gas flow rateThe same inert gas flow rate, with a tolerance of , shall be used throughout the procedur
23、e. Flow ratesbetween and have been found to be suitable.9.2 Loading the test specimenDetermine the mass of the test specimen to an accuracy of . The same nominal mass shall be usedfor all determinations. If possible, the specimen shall have a flat surface so as to give good thermal contact withthe b
24、ottom of the pan.NOTE Intimate thermal contact between the test specimen and the bottom of the pan is essential for good repeatability.Place the specimen in the pan, using tweezers, and seal with a lid. Place the sealed pan in the calorimeter usingtweezers.Do not handle the test specimen or the pan
25、with bare hands.0,000 1 g0,01 g 0,02 g10 %10 ml/min 100 ml/min0,001 gISO 22768:2006(E) ISO 2006 All rights reserved 39.3 Temperature scan9.3.1 Cool the test specimen to a temperature of approximately at a rate of and hold atthis temperature for .NOTE A starting temperature of is required for the det
26、ermination of rubbers with very low glass transitiontemperatures, e.g. high-cis polybutadiene. For rubbers with higher glass transitions, this temperature is not necessary.A starting temperature should be chosen so that a stable base line is achieved before the glass transitionregion, e.g. about to
27、below the expected glass transition temperature.If the apparatus is not capable of maintaining the specified cooling rate, it should be adjusted to give a rate asclose as possible to that specified.9.3.2 Perform the temperature scan at a heating rate of , heating until a temperature about above the
28、upper limit of the glass transition range is reached.NOTE Most instruments can be programmed to carry out the required thermal cycle automatically.10 Expression of resultsDetermine the glass transition temperature as the inflection point of the transition curve using the instrumentsoftware.NOTE If t
29、he glass transition temperature has to be determined directly from the curve, a better indication of the position ofthe inflection point is given by studying the derivative of the curve.11 Test reportThe test report shall include the following:a) a reference to this International Standard;b) identif
30、ication of the sample;c) the mass of the specimen, in grams;d) the type of DSC instrument used;e) the type of inert gas and the flow rate;f) the calibrants used;g) the thermal cycle used;h) the value in degrees Celsius, together with the DSC curve;i) the date of the test.12 Precision12.1 General12.1
31、.1 The interlaboratory test programme (ITP) for precision evaluation for was conducted in 2004, usingthe precision procedures and guidelines as described in ISO/TR 9272:2005 (this revised precision standardwas under ballot review at the time of this ITP). Refer to this revised edition for other deta
32、ils and terminology onprecision evaluation.12.1.2 The ITP was conducted using four rubbers, NdBR (neodymium-catalysed high-cis BR), SBR 1502,SBR 1721 and OESSBR. These represent a range of values from about to . Thirtylaboratories participated in the ITP and a Type 1 precision was evaluated. A test
33、result represents a singledetermination or measurement of using the DSC procedure as specified in this International Standard. Two140C 10C/min1 min140C30C 40C20C/min 30CTgTgTg100C 20CTgISO 22768:2006(E)4 ISO 2006 All rights reservedmeasurements of were conducted on two test days, one week apart. Mea
34、surements were conducted at bothand at on each test day. For precision analysis, all values were converted to Kelvin.This avoids negative values in the calculation algorithms and, more importantly, it provides mean values (for )that are not near zero and thus permits relative precision (in percent)
35、to be more meaningful for all materials; i.e.it avoids large percent values.12.1.3 The precision results as determined by this ITP may not be applied to acceptance or rejection testingfor any group of materials or products without documentation that the results of this precision evaluation actuallya
36、pply to the products or materials tested.12.2 Precision results12.2.1 Precision results are given in Table 1 for each of the four materials for both and .The precision results were obtained using the outlier deletion procedures as described in ISO/TR 9272:2005.Table 1 lists the number of laboratorie
37、s remaining in the database for the precision evaluation after the deletionof laboratories that had outlier values. General statements for the use of the precision results are cited in 12.2.2.These are given in terms of both the absolute precision, or , and also for relative precision and .12.2.2 Re
38、peatability and reproducibility statements are as follows.a) Repeatability: The repeatability, or local domain precision, for each of the materials (rubbers) has beenestablished by the values found in Table 1, for each of the materials as listed in the table. Two single testresults (obtained by the
39、proper use of the method of this International Standard) that differ by more than thetabulated values for in measurement units, and in percent, shall be considered as suspect, i.e. to havecome from different populations. Such a decision suggests that some appropriate investigative action betaken.b)
40、Reproducibility: The reproducibility, or global domain precision, for each of the materials has beenestablished by the values found in Table 1, for each of the materials as listed in the table. Two single testresults obtained in different laboratories (by the proper use of the method of this Interna
41、tional Standard) thatdiffer by more than the tabulated values for in measurement units, and in percent, shall be consideredas suspect, i.e. to have come from different populations. Such a decision suggests that some appropriateinvestigative action be taken.12.2.3 Additional analysis comments: The la
42、st column of Table 1 (the number of laboratories that wereincluded in the database used for the final calculations for precision) indicates that a substantial number oflaboratory data values were deleted as outliers. The final number of laboratories for NdBR is low becauseseveral laboratories did no
43、t submit data. There was some variation in precision improvement among thematerials with outlier deletion but, on an overall basis (mean for all four materials), the repeatability limit, , wasreduced by a reduction factor ( ) of 0,56 for and 0,46 for , after all repeatabilityoutlier data were delete
44、d. On the same overall basis, the reproducibility limit, , was reduced by a reductionfactor of 0,71 for both and procedures, after all reproducibility data outliers were deleted.Individual laboratories may show poor agreement in repeatability or poor agreement in reproducibility, or both.There does
45、not appear to be any substantial overall difference in the precision for vs. . Therepeatability for is greater than for , while the reproducibility for is less than for .The final precision, as expressed in Table 1, represents the precision for the majority of laboratories in the ITP;these may be co
46、nsidered as a core group of high quality testing laboratories that constitute a benchmark levelof performance for this particular property measurement.12.2.4 Bias is the difference between a measured average test result and a reference or true value for themeasurement in question. Reference values d
47、o not exist for this test method and therefore bias cannot beevaluated.Tg10C/min 20C/min TgTg10C/min 20C/minr R (r) (R)r (r)R (R)rrfinal/rorig10C/min 20C/minR10C/min 20C/min10C/min 20C/minr 10C/min 9% 20C/min R 10C/min 3%20C/minISO 22768:2006(E) ISO 2006 All rights reserved 512.3 ConclusionsThe glas
48、s transition temperature determined at a heating rate of is about higher than with aheating rate of . The heating rate of or makes no significant difference to theprecision. Therefore, in the interests of convenience, the faster rate has been chosen.Table 1 Precision data for glass transition temper
49、atureMaterialMean level Within laboratories Between laboratoriesNo. of labsaKMeasurements at 1 NdBR 166,7 0,379 1,06 0,64 1,531 4,29 2,57 202 SBR 1502 218,5 0,382 1,07 0,49 1,160 3,25 1,49 253 SBR 1721 238,7 0,408 1,14 0,48 1,417 3,97 1,66 244 OESSBR 248,7 0,245 0,69 0,28 1,449 4,06 1,63 23Pooled or average valueb0,354 0,990 0,473 1,39 3,89 1,84Measurements at 1 NdBR 168,2 0,273 0,76 0,45 1,418 3,97 2,36 192 SBR 1502 220,3 0,462 1,29 0,59 1,431 4,01 1,82 273 SBR 1721 240,8 0,372 1,04 0,43 1,164
