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1 INTERNATIONAL STANDARD ISO First edition Paints and varnishes Determination of curing characteristics using a free damped oscillation method Part 2: Glass transition temperature Peintures et vernis Détermination des caractéristiques de polymérisation par une méthode utilisant un pendule amorti Partie 2: Température de transition vitreuse Reference number ISO :2012(E) ISO 2012

2 COPYRIGHT PROTECTED DOCUMENT ISO 2012 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 either ISO at the address below or ISO s member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel Fax copyright@iso.org Web Published in Switzerland ii ISO 2012 All rights reserved

3 Contents Page Foreword... iv Introduction... v 1 Scope Normative references Terms and definitions Principle Pendulum-damping apparatus Sampling Test panels Substrate Preparation and coating Thickness of coating Procedure Expression of results Precision General Repeatability limit Reproducibility limit Test report... 8 Annex A (informative) Viscoelastic properties... 9 Bibliography...10 ISO 2012 All rights reserved iii

4 Foreword ISO (the International 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 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 liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft 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. Attention is drawn to the possibility that some 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. ISO was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee SC 9, General tests methods for paints and varnishes. ISO consists of the following parts, under the general title Paints and varnishes Determination of curing characteristics using a free damped oscillation method: Part 1: Start temperature of the curing reaction Part 2: Glass transition temperature iv ISO 2012 All rights reserved

5 Introduction When a rigid-body pendulum with a cylindrical edge is placed in contact with a cured coating, the free damped oscillation is measured as, due to heating, the viscoelasticity of the paint film changes. The attenuation of the oscillating rigid pendulum on the coating depends on the viscoelasticity of the paint. When the viscoelasticity of the paint changes, the logarithmic damping ratio of the rigid-body pendulum changes. Various paint film properties can be read from a plot of the logarithmic damping ratio versus temperature (see Annex A). ISO 2012 All rights reserved v

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7 INTERNATIONAL STANDARD ISO :2012(E) Paints and varnishes Determination of curing characteristics using a free damped oscillation method Part 2: Glass transition temperature 1 Scope This part of ISO specifies a free damped oscillation method for determining the glass transition temperature of dried and cured films of paints and varnishes. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 1513, Paints and varnishes Examination and preparation of test samples ISO 1514, Paints and varnishes Standard panels for testing ISO 2808, Paints and varnishes Determination of film thickness ISO 4618, Paints and varnishes Terms and definitions ISO 15528, Paints, varnishes and raw materials for paints and varnishes Sampling 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 4618 and the following apply. 3.1 glass transition reversible change in an amorphous polymer or in amorphous regions of a partially crystalline polymer from (or to) a viscous or rubbery condition to (or from) a hard and relatively brittle one [ISO 472:1999 [1] ] 3.2 glass transition temperature Tg approximate midpoint of the temperature range over which the glass transition takes place [ISO 472:1999 [1] ] NOTE 1 The rotational degrees of freedom of a polymer are excited at the glass transition temperature. NOTE 2 The glass transition temperature varies significantly, depending upon the adhesion to the substrate of the cured coating film, as well as the test method and conditions selected to measure it. ISO 2012 All rights reserved 1

8 3.3 glass transition temperature as determined by the pendulum method T gp glass transition temperature of dried and cured paints and varnishes determined using a f ree damped oscillation method NOTE The damping ratio is determined from the amplitude of oscillation of the pendulum and plotted against the temperature. The peak of the curve thus obtained is taken as the glass transition temperature. 3.4 period absolute value of the time between two oscillations in the same direction of the free damped oscillation 3.5 logarithmic damping ratio Λ logarithm of the ratio between consecutive amplitudes of a free damped oscillation 4 Principle Immediately after a coating material is applied to a test panel, it is dried or cured as specified. The dried or cured test panel is fixed in the apparatus and a rigid-body pendulum with a cylindrical edge (see Figure 1) is lowered on to the film. The heating rate and the amplitude of the first pendulum oscillation are set. The pendulum is released and allowed to oscillate. As the temperature is raised, the amplitude of oscillation of the pendulum becomes progressively smaller. When the temperature becomes greater than T g, the amplitude of oscillation becomes gradually larger again. The damping ratio is determined from measurements of the amplitude of oscillation of the pendulum and plotted against the temperature. The peak of the curve thus obtained is recorded as the glass transition temperature. When the network structure of the dried or cured coatings film on the substrate is heated, it begins to change. When network structure changes, viscosity changes occur. The oscillation of the pendulum is damped by the change in viscosity. After all chemical bonds have been formed, the viscosity decreases due to a rise of the temperature. Therefore a peak is produced. The maximum height of this peak can be read off as T gp. 5 Pendulum-damping apparatus 5.1 General. Figure 1 shows an example of a pendulum-damping apparatus. In addition to the pendulum itself, the apparatus includes an electromagnet with which the required oscillation can be generated, a temperaturecontrolled test block, and a displacement sensor that detects each swing of the pendulum. The amplitude and period of the swings of the pendulum, the time that elapses from the beginning of the first oscillation and the temperature of the sample are monitored by computer. The logarithmic damping ratio and the temperature of the test panel are recorded. 2 ISO 2012 All rights reserved

9 Key 1 displacement sensor 5 dried or cured film on the test panel 2 electromagnet 6 test panel 3 temperature-controlled test block 7 cylindrical edge 4 rigid-body pendulum with cylindrical edge Figure 1 Pendulum-damping apparatus 5.2 Temperature-controlled test block, shown in Figure 2. The dried or cured test panel is mounted on a mounting table (A), the temperature of which is regulated by means of an electric heating current passing through the block from B. ISO 2012 All rights reserved 3