1、BSI Standards PublicationBS ISO 11358-2:2014Plastics Thermogravimetry (TG) of polymersPart 2: Determination of activation energyBS ISO 11358-2:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 11358-2:2014. It supersedes BS ISO 11358-2:2005 which is withdraw
2、n.The UK participation in its preparation was entrusted to Technical Committee PRI/21, Testing of plastics.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users
3、are responsible for its correct application. The British Standards Institution 2014.Published by BSI Standards Limited 2014ISBN 978 0 580 84697 7ICS 83.080.01Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of th
4、e Standards Policy and Strategy Committee on 30 June 2014.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dBS ISO 11358-2:2014 ISO 2014Plastics Thermogravimetry (TG) of polymers Part 2: Determination of activation energyPlastiques Thermogravimtrie (TG) des polymres Partie 2:
5、 Dtermination de lnergie dactivationINTERNATIONAL STANDARDISO11358-2Second edition2014-06-15Reference numberISO 11358-2:2014(E)BS ISO 11358-2:2014ISO 11358-2:2014(E)ii ISO 2014 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2014All rights reserved. Unless otherwise specified, no part of this pu
6、blication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the co
7、untry 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 SwitzerlandBS ISO 11358-2:2014ISO 11358-2:2014(E) ISO 2014 All rights reserved iiiContents PageForeword iv1 Scope . 12 Normative r
8、eferences 13 Terms and definitions . 14 Principle 25 Apparatus . 26 Mass and temperature calibration 26.1 Mass calibration . 26.2 Temperature calibration . 27 Test specimens 28 Procedure. 38.1 General . 38.2 Non-oxidative reactions 38.3 Oxidative reactions 39 Expression of results 39.1 Graphical pre
9、sentation . 39.2 Determination of activation energy 310 Precision . 411 Test report . 5Bibliography 6BS ISO 11358-2:2014ISO 11358-2:2014(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparin
10、g International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liai
11、son with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Dire
12、ctives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that s
13、ome of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent decla
14、rations received (see www.iso.org/patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information a
15、bout ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee responsible for this document is ISO/TC 61, Plastics, Subcommittee SC 5, Physical and chemical properties.This second edition cancels and replac
16、es the first edition (ISO 11358-2:2005), of which it constitutes a minor revision. The following are the changes: limitation of the term “activation energy” to gas-phase reactions was deleted; normative references were changed into undated ones; the term “pan” was replaced by “crucible” in the whole
17、 text; in line with 3.2, the term “energy of activation” was replaced with “activation energy” (see 9.2).ISO 11358 consists of the following parts, under the general title Plastics Thermogravimetry (TG) of polymers: Part 1: General principles Part 2: Determination of activation energy Part 3: Determ
18、ination of the activation energy using the Ozawa-Friedman plot and analysis of the reaction kineticsiv ISO 2014 All rights reservedBS ISO 11358-2:2014INTERNATIONAL STANDARD ISO 11358-2:2014(E)Plastics Thermogravimetry (TG) of polymers Part 2: Determination of activation energy1 ScopeThis part of ISO
19、 11358 specifies a method for the determination of the activation energy, Ea, in the Arrhenius formula for the decomposition of polymers using a thermogravimetric technique. The method is applicable only if the reaction proceeds by a single mechanism. It is applicable to multistage reactions if they
20、 consist of clearly separated single-stage steps.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition
21、 of the referenced document (including any amendments) applies.ISO 11358-1, Plastics Thermogravimetry (TG) of polymers Part 1: General principles3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 11358-1 and the following apply.3.1Arrhenius formulaformul
22、a representing the temperature dependence of the rate constant of a reactionNote 1 to entry: The rate constant, k, of a reaction is expressed by the Arrhenius formula, as follows:kAERT=expa(/)whereR is the gas constant (= 8,314 J K1 mol1);T is the absolute temperature, in kelvins (K);A is the pre-ex
23、ponential factor, in reciprocal seconds (s1);Eais the activation energy, in J mol1;k is the rate of reaction (= d/dt), in reciprocal seconds (s1).3.2activation energyEaenergy, above that of the ground state, which must be added to an atomic or a molecular system to allow a particular process to take
24、 placeNote 1 to entry: It is expressed in J mol1. ISO 2014 All rights reserved 1BS ISO 11358-2:2014ISO 11358-2:2014(E)3.3degree of conversionquantity of products present at a particular time and temperature during a reaction compared with the final quantity of the productsNote 1 to entry: It is give
25、n by the formula =()()MM MMit if/ whereMiis the initial quantity, in milligrams;Mtis the quantity at a particular time and temperature, in milligrams;Mfin the final quantity, in milligrams.Note 2 to entry: When multistage reactions occur, the degree of conversion is calculated separately for each st
26、age.Note 3 to entry: The degree of conversion is dimensionless and varies in value from 0 to 1.4 PrincipleTest specimens are heated at several different heating rates and the change in mass measured as a function of temperature. The temperatures corresponding to given degrees of conversion are deter
27、mined for each heating rate. For a given degree of conversion, the logarithm of the heating rate is plotted against the reciprocal of the absolute temperature, and the activation energy is calculated from the slope of the straight line thus obtained.5 ApparatusSee ISO 11358-1.6 Mass and temperature
28、calibration6.1 Mass calibrationSee ISO 11358-1.6.2 Temperature calibrationSee ISO 11358-1.7 Test specimensThe test specimens shall be in the form of powder, pellets, flakes, filaments, or film. The test specimens shall be prepared by cutting the material, as necessary, to a size appropriate for the
29、apparatus (see ISO 11358-1). Particles of small size, i.e. of high surface-area-to-volume ratio, are preferred. Grinding in a liquid-nitrogen mill can be used to decrease the particle size.2 ISO 2014 All rights reservedBS ISO 11358-2:2014ISO 11358-2:2014(E)8 Procedure8.1 GeneralSee ISO 11358-1.Perfo
30、rm the procedure at three or more heating rates, using specimens of identical mass (1 %). The lowest and highest heating rates shall differ by a factor of at least 5.In order to improve the accuracy of the determination, record the mass of an empty crucible subjected to the same test conditions of a
31、tmosphere, gas flow, and heating rate as used in the run with the specimen. If there is a mass change during the run with the empty crucible (which is usually ascribed to buoyancy), subtract the curve obtained with the empty crucible from that obtained with the test specimen to obtain a corrected th
32、ermogravimetric curve for the specimen. This procedure shall be repeated for all heating rates. Corrected curves shall be used for the analysis of the results.NOTE It is preferable to use specimens less than 10 mg in size and heating rates of less than 10 K min1. For specimens greater than 10 mg and
33、 heating rates greater than 10 K min1, the specimen temperature might not follow the required temperature profile.8.2 Non-oxidative reactionsWhen required, an inert-gas atmosphere (e.g. nitrogen) shall be maintained during the determination to prevent oxidation of the specimen. Only purified gas (pu
34、rity at least 99,95 %) shall be used to create the inert atmosphere.8.3 Oxidative reactionsAn oxidative gas atmosphere (oxygen or air) shall be used when testing polymers that undergo oxidation reactions. Details of the type and purity of the gas used shall be included in the test report.9 Expressio
35、n of results9.1 Graphical presentationPresent the thermogravimetry data obtained in the form of a mass change or percentage mass change versus temperature curve. Determine specific temperatures from the TG curve using the procedures described in ISO 11358-1.9.2 Determination of activation energyChec
36、k that the final mass reached at the end of each measurement run is constant, thereby indicating completion of the reaction, and that the percentage change in mass from the start of the run to the end of the run for each of the heating rates is also the same.For a given degree of conversion, , deter
37、mine, from the TG curves, the absolute temperatures for each of the heating rates, . Repeat for other degrees of conversion. Typical curves are shown in Figure 1. ISO 2014 All rights reserved 3BS ISO 11358-2:2014ISO 11358-2:2014(E)Figure 1 Determination of absolute temperature for a given degree of
38、conversion and heating rateThe approximate relationship given by Formula (1) was derived by Ozawa and later by Flynn and Wall (see References 1 and 2 in the Bibliography) and is used to determine the activation energy, Ea.log, / +()=0 4567 ERTaconstant (1)where Eaand R are the activation energy and
39、the gas constant (R = 8,314 J K1 mol1), respectively.For heating rates 1, 2, 3, , and temperatures T1, T2, T3, , Formula (2) is obtained for a given degree of conversion, 1:log, /log ,/log, /112230 45670456704567+()=+()=+ERTERT ERaaaT3()(2)Plotting the logarithm of the heating rate, log, against the
40、 reciprocal of the absolute temperature, T1, for each degree of conversion gives a series of straight-line curves (see Figure 2), and the activation energy, Ea, is calculated from the slope (0,456 7Ea/R) in each case.NOTE 1 This method is not suitable for very high degrees of conversion.NOTE 2 This
41、method is not reliable when the value of Eavaries widely from one degree of conversion to another and/or the log versus T1relationship is not linear.Figure 2 Heating rate versus the reciprocal of the absolute temperature10 PrecisionSee Reference 3 in the Bibliography.4 ISO 2014 All rights reservedBS
42、 ISO 11358-2:2014ISO 11358-2:2014(E)11 Test reportThe test report shall include the following information:a) a reference to this part of ISO 11358, i.e. ISO 11358-2:2014;b) all details necessary for complete identification of the material analysed;c) the form and dimensions (if applicable) of the te
43、st specimen;d) the mass of the test specimen;e) details of the conditioning of the specimen prior to the test;f) the specimen crucible size and material of construction;g) the atmosphere and gas-flow rate used;h) the heating rates used;i) the standard reference material used for temperature calibrat
44、ion;j) the activation energy determined using the formula in Note 1 to entry in 3.1 or Formula (1);k) any observations regarding equipment, test conditions, or test specimen behaviour;l) the date of the determination. ISO 2014 All rights reserved 5BS ISO 11358-2:2014ISO 11358-2:2014(E)Bibliography1
45、Ozawa T. A new method of analyzing thermogravimetric data. Bull. Chem. Soc. Jpn. 1965, 38 p. 18812 Flynn J.H., & Wall L.A. A quick, direct method for the determination of activation energy from thermogravimetric data. J. Polym. Sci. 1966, 4 p. 3233 Anderson H.L., Kemmler A., Hohne G.W.H., Keldt K.,
46、Strey R. Round robin test on the kinetic evaluation of a complex solid state reaction from 13 European laboratories Part 1: Kinetics TG-analysis. Thermochim. Acta. 1999, 332 p. 336 ISO 2014 All rights reservedBS ISO 11358-2:2014BS ISO 11358-2:2014ISO 11358-2:2014(E) ISO 2014 All rights reservedICS 8
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