INTERNATIONAI ISO STANDARD 8226-2 First edition 1990-12-15 Paper and board -- Measurement of hygroexpansivity --- Part 2: Hygroexpansivity up to a maximum relative humidity of 86 % Papiers et cartons -- Détermination de la dilatation a I'humidité Partie 2: Dilatation a I'humidite jusqu'a une humidite relative maximale de 86 % Reference number ISO 8226-2:1990(E) Not for Resale ISO 8226-2:1990(E) Foreword Iso (the International Organization for Standardization) is a worldwide federation of national standards bodies (lsO 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, govern- mental 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. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an Inter- national Standard requires approvai by at least 75 % of the member bodies casting a vote. International Standard IsO 8226-2 was prepared by Technical Committee Iso/TC6,Paper,boardandpulps. IsO 8226 consists of the following parts, under the general title Paper and board -- Measurement of hygroexpansivity: Part 1: Hygroexpansivity up to a maximum relative humidity of 68 % Part 2: Hygroexpansivity up to a maximum relative humidity of 86 % Annex A of this part of isO 8226 is for information only ISO 1990 All rights reserved. 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-1211 Geneve 20 · Switzerland Printed in Switzerland CopyrghtIntenatonalOrganizationforStandardization Not for Resale d without license from IHS ISO 8226-2:1990(E) Introduction The measurement of dimensional changes in paper and board with changes in the ambient humidity is necessary for accurate control of printingand similar Thechange inlength，or processes. swelling or contraction of the fibres by absorption or desorption of wa- ter. The proportion of the two mechanisms effective to produce the environment. midity of 86 % is imposed to accommodate the effects of stress relax- ation on the hygroexpansivity. Is0 8226-1 describes a method for the measurement of hygroexpansivity at 68 %. The relationship between hygroexpansivity and relative humidity above approximately 68 % is non-linear, partiy due to the effects of stress relaxation of the test piece above this humidity. A two-point measure- ment of hygroexpansivity can be used with humidities greater than 68 %, but no attempt should be made to interpolate or correct meas- ranges, by simple arithmetical procedures. ili Not for Resale itted without license from IHS