ISO-11357-1-1997.pdf
STD*ISO 11357-1-ENGL 1797 4851903 07058V8 488 INTERNATIONAL STANDARD IS0 11 357-1 First edition 1997-04-1 5 Plastics - Differential scanning calorimetry (DSC) - Part 1: General principles Plastiques - Analyse calorimétrique différentielle (DSC) - Partie 1: Principes généraux This material is reproduced from IS0 documents under International Organization for Standardization (EO) Copyright License number IHSIICC11996. Not for resale. No part of these IS0 documents may be reproduced in any form, electronic retrieval system or otherwise, except as allowed in the copyright law of the country of use, or with the prior written consent of IS0 (Case postale 56,1211 Geneva 20, Switzerland, Fax +41 22 734 10 79), IHS or the IS0 Licensor's members. Reference number IS0 1 1357-1 1 1 997(E) - STD-IS0 11357-1-ENGL 1777 4853903 0705849 314 IS0 1 1357-1 : 1997( E) Foreword IS0 (the International Organization for Standardization) is a worldwide federation o f national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 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 liaison with ISO, also take pari in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Drait International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard IS0 11 357 was prepared by Technical Committee ISOTTC 61, Plastics, Subcommittee SC 5, Physical-chemical properties. IS0 11 357 consists of the following paris, under the general title Plastics - Differential scanning calorimetry (DSC): - Part 1: General principles - - Part 2: Determination of glass transition temperature Part 3 : Determination of temperature and enthalpy of melting and crystallization - - Part 4: Determination of specific heat capacity Part 5: Determination of polymerization temperatures and/or times and polymerization kinetics Part 6: Determination of oxidation induction time - - Annexes A, B and C of this pari of IS0 11357 are for information only. Part 7: Determination of crystallization kinetics O IS0 1997 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case postale 56 CH-121 1 Genève 20 Switzerland Internet central9ico.ch X.400 c=ch; ad00net; p=iso; o=icocs; s=central Printed in Switzerland ii STD-IS0 11357-1-ENGL 1777 Li85L703 0705850 03b INTERNATIONAL STANDARD 0 IS0 IS0 1 1 357-1 1997(E) Plastics - Differential scanning calorimetry (DSC) - Part 1: General principles WARNING - The use of this International Standard may involve hazardous materials, operations and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate health and safety practices and to determine the applicability of regulatory limitations prior to use. 1 Scope This International Standard specifies a method for the thermal analysis of polymers such as thermoplastics and thermosetting plastics, including moulding materials and composite materials, using differential scanning calorimetry (DSC). Various determinations can be made on polymers by using differential scanning calorimetty. These determinations are dealt with in parts 2 to 7 of this standard (see the foreword). 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this part of IS0 11357. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this part of IS0 11357 are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 291 :-I), Plastics - Standard atmospheres for conditioning and testing. 3 Definitions For the purposes of this International Standard, the following definitions apply: 3.1 differential scanning calorimetry (DSC): A technique in which the difference between the heat flux (power) into a test specimen and that into a reference specimen is measured as a function of temperature and/or time while the test specimen and the reference specimen are subjected to a controlled temperature programme. It is common practice to record, for each measurement, a curve in which temperature or time is plotted on the x-axis and heat flux difference is plotted on the y-axis. 1) To be published. (Revision of IS0 291:1977) 1 STD-ISO 13357-3-ENGL 1777 4853703 0705853 T72 M IS0 11 357-1 :1997(E) Q IS0 3.2 reference specimen: A known specimen which is usually thermally inactive over the temperature and time range of interest. NOTE - Generally an empty pan identical to the one containing the test specimen is used as the reference specimen. 3.3 standard reference material: A material for which one or more of the thermal properties are sufficiently homogeneous and well established to be used for the calibration of DSC apparatus, for the assessment of a measurement method or for assigning values to materials. 3.4 heat flux; thermal power: The amount of heat transferred per unit time (dQ/dr). NOTE - The total quantity of heat transferred Q corresponds to the time integral of the heat flux Q=j-di dQ dt where Q is expressed in joules or in joules per unit mass (J.kg-1 or J.g-1). 3.5 change in enthalpy, AH: The quantity of heat absorbed (AH positive) or released (AH negative) by a test specimen undergoing a chemical or physical change, and/or a temperature change, at constant pressure. AH is expressed in joules or in joules per unit mass (J.kg-1 or J.g-1): T2 dH A H = -dT dT Ti 3.6 specific heat capacity at constant pressure, cp: The quantity of heat necessary to raise the temperature of unit mass of material by 1 “C at constant pressure, with all other intensive parameters constant: c =-x(%) 1 P ' r n where aQ is the quantity of heat, expressed in joules, necessary to raise the temperature of material of mass m by aT degrees Celsius at constant pressure; cp is expressed in joules per kilogram degree Celsius J/(kg.“C) or joules per gram degree Celsius J/(g.“C). When analysing polymers, care must be taken to ensure that the measured specific heat capacity does not include any heat change due to a chemical reaction or a physical transition. 3.7 baseline: The part of the recorded curve outside, but adjacent to, the reaction or transition zone. In this part of the recorded curve, the heat flux difference is approximately constant. 3 . 8 virtual baseline: An imaginary line drawn through a reaction and/or transition zone assuming that the heat of reaction and/or transition is zero. It is commonly drawn by interpolating or extrapolating the recorded baseline. It is normally indicated on the DSC curve for convenience (see figure 1). 3.9 peak: The part of the DSC curve which departs from the baseline, reaches a maximum, and subsequently returns to the baseline. NOTE - The start of the peak corresponds to the start of the reaction or transition. 3.9.1 endothermic peak: A peak in which the energy supplied to the test specimen is greater than the energy corresponding to the virtual baseline. 3.9.2 exothermic peak: A peak in which the energy supplied to the test specimen is less than the energy corresponding to the virtual baseline. 2 STD.IS0 31357-3-ENGL 1777 4853703 0705852 709 Q IS0 IS0 1 1357-1 : 1997(E) NOTE- In accordance with the accepted conventions of thermodynamics, the enthalpy change is negative when the reaction or transition is exothermic and positive when the reaction or transition is endothermic. The direction corresponding to exothermic or endothermic is normally indicated on the DSC curve. 3 . 9 . 3 peak height: The distance between the virtual baseline and the point of maximum height of a peak. The height is expressed in milliwatts. The height is not proportional to the mass of the test specimen. 3 . 1 O characteristic temperatures: The following are the Characteristic temperature on a DSC curve: - onset temperature Ti - extrapolated onset temperature Tei - peak temperature TP - extrapolated end temperature Tef - end temperature T r Teig 1 Teig m = melting g = glass transition c = crystallization ! Temperature, ' I : Figure 1 - Typical DSC curve 4 Principle The difference between the heat flux into a test specimen and that into a reference specimen is measured as a function of temperature and/or time, while the test specimen and the reference specimen are subjected to a controlled temperature programme under a specified atmosphere. NOTE - Two types of DSC, power-compensation DSC and heat-flux DSC, may be carried out. They are distinguished by the design of instrumentation used for measurement, as follows: a) Power-compensation DSC: The difference between the heat flux into the test specimen and that into the reference specimen is measured as a function of temperature or time while varying the temperature of the specimens in accordance with a controlled programme, keeping the temperature of both specimens equal. Heat-flux DSC: The difference in heat flux derived from the temperature difference between a test specimen and a reference specimen is measured as a function of temperature or time while varying the temperature of the specimens in accordance with a controlled programme. In this type of measurement, the difference in temperature between the test specimen and reference specimen is proportional to the difference in heat flux. b) 3 STD-IS0 11357-1-ENGL 1977 Li851703 0705853 845 IS0 1 1357-1 : 1997( E) Q IS0 5 Apparatus and materials Differential scanning calorimeter, the main features of which are as follows: the capability to generate constant heating and cooling rates between 0,5 “C/min and 20 “C/min; the capability to maintain the test temperature constant to within Ir 0,5 O C for at least 60 min; the capability to carry out step heating or any other heating mode; a gas-flow rate in the range 10 ml/min to 50 ml/min, controllable to f 10 %; temperature signals with 0,l O C resolution and noise below 0,5 OC; facilities for calibration and use with a minimum test specimen mass of 1 mg (or with smaller quantities if required by specific applications); a recording device which is capable of automatically recording the DSC curve, and of integrating the area between the curve and the virtual baseline with an error of less than 2 %; a specimen holder assembly which has one or more holders for pans. Pans, for test specimens and reference specimens, all made of the same material and of equal mass. The pans shall be physically and chemically inert under the measurement conditions to both the test specimen and the atmosphere. The pans should preferably be made of a material with a high thermal conductivity. They shall be able to be fitted with lids and sealed so that they can withstand the overpressure which can arise during measurement. 5.3 Balance, capable of measuring the specimen mass with an accuracy of Ir 0,Ol mg. 5.4 Standard reference materials (see annex A). 5.5 Gas supply, analytical grade. 6 Test specimen The test specimen may be in the liquid or solid state. If in the solid state, it may be in the form of a powder, pellets or granules, or may be cut from sample pieces. The test specimen shall be representative of the sample being examined and shall be prepared and handled with care. If the specimen is taken from sample pieces by cutting, care shall be taken to prevent heating, polymer reorientation or any other effect that may alter the properties. Operations such as grinding that could cause heating or reorientation and could therefore change the thermal history of the sample shall be avoided. When aggregates or powders are involved, two or more specimens shall be taken. The method of sampling and test specimen preparation shall be stated in the test report. NOTE - Incorrect specimen preparation can affect the properties of the polymers examined. For further information, see annex B. 7 Test conditions and specimen conditioning 7.1 Test conditions Prior to any testing, switch the equipment on for at least one hour to allow the electronics to temperature-equilibrate. Maintain and operate the instrument in an atmosphere as specified in IS0 291. NOTE- It is advisable to protect the instrument from air draughts, exposure to direct sunlight and/or sharp changes in temperature, pressure or electric supply during measurements. 4 Q IS0 STD=ISO lL357-L-ENGL 1977 q853903 070585'4 781 IS0 1 1 357-1 : 1 997( E) 7 . 2 Conditioning of test specimens Condition test specimens before measurements as specified in the relevant material standard or by a method agreed between the interested parties. NOTES 1 Unless other conditions are specified, it is recommended that test specimens are conditioned in accordance with IS0 291. 2 Results obtained by DSC can be greatly affected by conditioning. 8 Calibration 8.1 General Calibrate the energy and temperature measurement devices of the calorimeter at least in accordance with the instrument manufacturer's recommendations. NOTES 1 The calibration function K(T) (see 8.3) cannot be expressed as a simple proportionality factor since it varies with temperature. It is essential therefore to carry out calibration with at least two standard reference materials for each parameter, ¡.e. temperature and energy. Most recommended standard reference materials, as given in annex A, can be used for both temperature and energy calibrations. 2 Calibration is affected by: - the type of calorimeter used; - the gas used and its flow rate; - the type of specimen pan used, its dimensions and its position in the specimen holder; - the mass of the test specimen; - the heating and cooling rates; - the type of cooling system used. It is therefore advisable to define the conditions of the actual determination as precisely as possible and carry out the calibration using the same conditions. Computer systems associated with DSC instruments may automatically correct some of the parameters. 3 It is advisable to carry out calibrations regularly. It is considered good practice to check the temperature and energy measurement devices using standard reference materials which have melting points close to the temperature range used for the material being analysed. 8.2 Temperature ca
