SVENSK STANDARD SS-ISO :2011

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SVENSK STANDARD

Fastställd / Approved: 2011-12-28 Publicerad / Published: 2012-01-23 Utgåva / Edition: 1

Språk / Language: engelska / English ICS: 85.060; 85.080.30

SS-ISO 8226-2:2011

Papper och kartong – Mätning av hygroexpansion –

Del 2: Hygroexpansion upp till en relativ fuktighet på maximalt 86 % (ISO 8226‑2:1990, IDT)

Paper and board – Measurement of hygroexpansivity –

Part 2: Hygroexpansivity up to a maximum relative humidity of 86 % (ISO 8226‑2:1990, IDT)

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© Copyright / Upphovsrätten till denna produkt tillhör SIS, Swedish Standards Institute, Stockholm, Sverige. Använd- ningen av denna produkt regleras av slutanvändarlicensen som återfinns i denna produkt, se standardens sista sidor.

© Copyright SIS, Swedish Standards Institute, Stockholm, Sweden. All rights reserved. The use of this product is governed by the end-user licence for this product. You will find the licence in the end of this document.

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Information about the content of the standard is available from the Swedish Standards Institute (SIS), telephone +46 8 555 520 00. Standards may be ordered from SIS Förlag AB, who can also provide general information about Swedish and foreign standards.

Den internationella standarden ISO 8226-2:1990 gäller som svensk standard. Detta dokument innehåller den officiella engelska versionen av ISO 8226-2:1990.

The International Standard ISO 8226-2:1990 has the status of a Swedish Standard. This document contains the official version of ISO 8226-2:1990.

Denna standard är framtagen av kommittén för Massa och papper, SIS / TK 157.

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Fsreword

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. Esch 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 patt 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 approval by at least 75 % of the member bodies casting a vote.

International Standard ISO 8226-2 was prepared by Technical Committee ISO/TC 6, Paper, board and pulps.

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

0 / 0

- Part 2: Hygroexpansivity up to a maximum relative humidity of 86

OO /

Annex A of this part of ISO 8226 is for information only.

ii

SS-ISO 8226-2:2011 (E)This preview is downloaded from www.sis.se. Buy the entire standard via https://www.sis.se/std-82642

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lntroduction

The measurement of dimensional changes in Paper and board with changes in the ambient humidity is necessary for accurate control of printing

and

similar processes. The Change in length or hygroexpansivity, is

due

to stress relaxation of the Paper fibres and swelling or contraction of the fibres by absorption or desorption of wa- ter. The proportion of the two mechanisms effective to produce hygroexpansivity depends upon the upper limit of relative humidity of the environment.

For the purpose of this part of ISO 8226 an upper limit of relative humidity of 86 % is imposed to accommodate the effects of stress relaxation on the hygroexpansivity.

ISO 82264 describes a method for the measurement of hygroexpansivity at 68 %.

The relationship between hygroexpansivity and relative humidity above approximately 68 % is non-linear, partly

due

to the effects of stress relaxation of the test piece above this humidity. A two-Point measurement of hygroexpansivity tan be

used

with humidities greater than 68 %, but no attempt should be

made

to interpolate or correct measurements in the range 33 % r.h. to 84 % r.h. to other relative humidity ranges, by simple arithmetical procedures.

. . . Ill

SS-ISO 8226-2:2011 (E)

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Paper and board - Measurement of hygroexpansivity - Part 2:

Hygroexpansivity up to a maximum relative humiditv of 86 %

1 Scope

This part of ISO 8226 specifres a method for the determination of the hygroexpansivity of Paper and board when subjected to a Change in the relative humidity with which it is in equilibrium from (33 + 2) % to (84 & 2) %. -

The purpose of this part of ISO 8226 is to cover ap- plications of Paper and board intended to be used in high humidity conditions, e.g. as found in tropical countries. lt may also be useful in determining the effect of excessive moisture to which Paper may be subjected for short periods during some printing processes, e.g. offset printing.

This method is applicable to Paper and board gen- erally. lt is not, however, suitable for crepe Papers and

corrugated

fibreboard.

2 Normative references

The following Standards contain provisions which, through reference in this text, constitute provisions of this patt of ISO 8226. At the time of publication, the editions indicated were valid. All Standards are subject to revision, and Parties to agreements

based

on this part of ISO 8226 are encouraged to investi- gate the possibility of applying the most recent editions of the Standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.

ISO 186:1985,, Paper and hoard - Sampling to deter- mine average quality.

ISO 187:1990, Paper, board and pulps -- Standard

atmosphere for conditioning and fesfing and procedure for monitoring the atmosphere and conditioning of samples.

ISO 8226.1:1985, Paper and board - Measurement of hygroexpansivity - Part 1: Hygroexpansivity up to a maximum relative humidity of 68 %.

3 Definition

For the purposes of this part of ISO 8226, the following definition applies.

hygroexpansivity: The increase in length relative to the initial length that occurs when the relative humidity with which the test piece of Paper or board is in equilibrium is raised from a specified lower relative humidity to a specified higher relative humidity.

NOTE 1 A contraction of the test piece is regarded as negative hygroexpansivity.

4 Principle

To ensure that all test pieces being tested are brought to the initial relative humidity, from an im- mediate similar moisture level, this method includes a preliminary conditioning Step, at a very low relative humidity.

Preliminary conditioning of test pieces at a specified temperature (preferably 23 OC + 1 “C), under Zero load and a relative humidity of (22 + 3) % and then at relative humidities of (33 &- 2) %<nd (84 + 2) %.

Measurement of the Change in length between the latter two relative humidities under a load appropriate to the grammage of the test pieces.

SS-ISO 8226-2:2011 (E)

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5 Apparatus

5.1 Cabinet, with air circulation, capable of being maintained at one of the temperatures specified in ISO 187, preferably 23 OC & 1 OC. lt shall be possible to attain uniform relative humidities of (22 $- 3) %, (33 + 2) %, (50 & 5) % and (84 $- 2) O/o within the whok cabinet and within a short time, for example, 30 min.

Any method which will provide the specified relative humidities within the tolerantes indicated may be used, for example, the saturated salt solutions given in annex A.

5.2 Clamps, or other means for suspending the test pieces vertically in the cabinet (5.1) and provided with some means of ensuring the unloaded test pieces are free from tension.

5.3 Loading weights, for application to the test pieces during measurement (see table 1).

Table 1 - Test loads Test piece

grammage, eA

g/m2

Total load (including

clamps) Nlm

Equivalent mass

g/15 mm

eA < 125 15+ - 1 23 + - 1,5 125<e,G200 30 + - 1 46 + - 1,5 200 < eA < 275 50 + 1 - 76 + - 1,5 275 < eA 80 + 1 - 122 + - 1,5

5.4 Means for measuring the relative humidity of the air in the cabinet (5.1) with a precision of + 1 % - (maximum error of reading) and an accuracy of + 2 % (maximum departure from true relative humidity).

5.5 Means for measuring the temperature in the cabinet (5.1).

5.6 Device for measuring the increase in Iength of the test pieces to the nearest 0,Ol mm. This device

may be mechanical or electronie.

6 Sampling and preparation of test pieces

6.1 Where possible, Sample in accordance with ISO 186.

6.2 From undamaged specimens free from watermarks, folds

and

wrinkles, tut five test pieces in the machine direction and/or five in the Cross direction as required. Esch test piece shall be at least 20 mm longer than the nominal free span between the clamps, and the minimum free span shall be 100 mm. The width of the test piece shall be at least 15 mm. For the determination sf hygroexpansivity in the machine direction or in the Cross direction, tut the test pieces with the longer side parallel to the relevant direction.

7 Procedure

7.1 Initial length (Io)

Set the clamps (5.2) inside the cabinet (5.1) to a span of at least 100 mm (known to within 1 mm). Clamp, then condition the unloaded test pieces for at least 30 min at the selected temperature (see 5.1) and at a relative humidity of (50 + 5) %. Gently apply the appropriate load in accordance with table 1 and note the readings on the length-measuring devices (5.6) to the nearest 0,Ol mm. Record this length as I,.

7.2 Preliminary conditioning of test pieces Condition the unloaded test pieces for at least 30 min at a relative humidity of (22 + 3) %. Gently apply the appropriate load in accordance with table 1 and note the readings on the length- measuring

devices.

Remove the load and repeat the conditioning and measurement until the length un-

der

load changes by no more than 0,02 % between measurements.

NOTE 2 These readings are not used in the calculation.

7.3 Measurement of hygroexpansivity

Change the conditioning atmosphere to one of (33 + 2) %, and record the relative humidity value obtained. Condition the unloaded test pieces for at least 30 min at a relative humidity of (33 $I 2) %.

Gently apply the appropriate load in accordance with table 1 and note the readings on the length- measuring devices. Remove the load and repeat the conditioning and measurement until the length under

load

changes by no more than 0,Ol mm. Record these to the nearest 0,Ol mm (l&).

Condition the test pieces in the Same way for a minimum of 18 h in an atmosphere having a relative humidity of (84 + 2) %. Note the relative humidity value obtained. Record the new readings (284) of the test pieces to the nearest 0,Ol mm.

NOTE 3 Shorter conditioning times at a relative humidity of 84 O/o may be used by agreement, but this fact should be noted in the test report.

,