ISO 5636-4:2013

INTERNATIONAL ISO
STANDARD 5636-4
Third edition
2013-11-01
Paper and board — Determination of
air permeance (medium range) —
Part 4:
Sheffield method
Papier et carton — Détermination de la perméance à l’air (valeur
moyenne) —
Partie 4: Méthode Sheffield
Reference number
©
ISO 2013
© ISO 2013
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ii © ISO 2013 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Sampling . 3
7 Conditioning . 3
8 Preparation of test pieces . 3
9 Calibration . 4
9.1 Variable-area flow-measuring device . 4
9.2 Electronic flow-measuring device . 4
10 Procedure. 4
11 Expression of results . 4
11.1 Calculation of air permeance . 4
11.2 Reporting the results . 5
11.3 Standard deviation and coefficient of variation . 5
12 Test report . 5
Annex A (normative) Calibration of flowmeters . 6
Annex B (informative) Conversion of Sheffield units (SU) to SI units .10
Annex C (informative) Precision data .11
Bibliography .13
Foreword
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described in the ISO/IEC Directives, 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
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to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 6, Paper, board and pulps, Subcommittee SC 2,
Test methods and quality specifications for paper and board.
This third edition cancels and replaces the second edition (ISO 5636-4:2005), which has been technically
revised. In this third edition mainly editorial changes have been made and also precision data has been
added as informative Annex C.
ISO 5636 consists of the following parts, under the general title Paper and board — Determination of air
permeance (medium range):
— Part 3: Bendtsen method
— Part 4: Sheffield method
— Part 5: Gurley method
— Part 6: Oken method
NOTE 1 Part 1: General method will be withdrawn after the third editions of Parts 3, 4 and 5 have been
published, as it was considered redundant.
NOTE 2 Part 2: Schopper method was withdrawn in 2006 as it was considered obsolete.
NOTE 3 Part 6: Oken method is being prepared.
iv © ISO 2013 – All rights reserved

INTERNATIONAL STANDARD ISO 5636-4:2013(E)
Paper and board — Determination of air permeance
(medium range) —
Part 4:
Sheffield method
1 Scope
This part of ISO 5636 specifies the Sheffield method for determining the air permeance of paper and
board using the Sheffield apparatus.
It is applicable to papers and boards which have air permeances between 0,02 µm/(Pa·s) and 25 µm/
(Pa·s) when tested with the Sheffield apparatus.
It is unsuitable for rough-surfaced materials, which cannot be securely clamped to avoid leakage.
2 Normative references
The 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 of the referenced document (including any amendments) applies.
ISO 186, Paper and board — Sampling to determine average quality
ISO 187, Paper, board and pulps — Standard atmosphere for conditioning and testing and procedure for
monitoring the atmosphere and conditioning of samples
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
air permeance
mean air flow rate through unit area under unit pressure difference in unit time, under specified conditions
Note 1 to entry: Air permeance is expressed in micrometres per pascal second [1 ml/(m ⋅Pa⋅s) = 1 μm/(Pa⋅s)].
Note 2 to entry: This property is called air permeance, and not air permeability, because it is reported as a sheet
property and is not standardized with respect to thickness to give a material property per unit thickness.
Note 3 to entry: The Sheffield unit is not defined, since it has been shown that the scale units (Sheffield units) on
different types of Sheffield instruments can correspond to different air flows, and there is no precise physical
definition. This part of ISO 5636 requires that the flowmeters be calibrated to give a flow rate in millilitres per minute.
4 Principle
A test piece is clamped between two rubber orifice plates of known dimensions. The absolute air
pressure on one side of the test piece is equivalent to atmospheric pressure and the difference in pressure
between the two sides of the piece is maintained at a small, substantially constant, value. The air flow
rate through the test area is determined and the air permeance is calculated.
5 Apparatus
The Sheffield apparatus, see Figure 1 for an example of one type of instrument, shall consist of an air
supply (see 5.1), an air-pressure regulating device (see 5.2), a pressure manometer (see 5.3), an air-flow-
measuring device (see 5.4) and a test assembly (see 5.5) which houses a measuring head in which the
test piece can be securely clamped.
23 4 5
Key
1 air supply
2 pressure regulator
3 air-flow-measuring device
4 flow impedance
5 shut-off valve
6 measurement air
7 clamping air pressure
8 orifice plates
9 test piece
Figure 1 — Principles of operation of one type of apparatus
5.1 Air supply, free from water, oil and other contaminants, at a pressure of 420 kPa to 950 kPa. A small
compressor using laboratory air is preferred to external compressed air.
5.2 Air-pressure regulating device, to reduce the pressure to the nominal pressure at the measuring
head of 10,3 kPa (variable-area flow-measuring devices, see 5.4.1) or 9,85 kPa (electronic flow-measuring
devices, see 5.4.2).
5.3 Pressure manometer, with a suitable range to enable the air pressure at the measuring head to be
set to the specified pressure within 2 % of the nominal value.
5.4 Air-flow-measuring device, of either a variable-area (5.4.1) or an electronic type (5.4.2), for
measuring the air flow rate to the measuring head. The air flow rate shall be measurable to an accuracy of
± 5 % of the measured value.
5.4.1 Variable-area flow-measuring device, consisting of three variable-area flowmeters each having
a tapered glass column containing a metering float suspended by the air flow in the column. The three
columns shall be chosen with dimensions such that they enable measurements to be made on a continuous
scale of flow rate from 10 ml/min to 3 000 ml/min, with some overlap of scales between columns. Each
2 © ISO 2013 – All rights reserved

column shall be provided with a means of adjusting the flow rate (float-position knob) and a means of
span calibration (calibration knob). This type of instrument shall operate at a supply pressure of 10,3 kPa.
At air flow rates greater than 1 200 ml/min, the pressure drop in the Sheffield system is substantial.
To ensure reproducibility of results, it is necessary that the tubing used to connect the flowmeter to
the measuring head be carefully controlled with a length of (1,50 ± 0,01) m and an internal diameter of
(6,25 ± 0,25) mm. For the same reason, openings in valves and other fittings on the instrument shall not
be changed from those provided by the instrument manufacturer.
5.4.2 Electronic flow-measuring device, for measuring the air flow to the measuring head. The inlet
pressure to the measurement device shall be controlled at 9,85 kPa.
NOTE The 9,85 kPa pressure is the typical pressure measured downstream of variable-area flow tubes that
have been calibrated using the air bleeds (zero and span-adjustment) to the atmosphere.
5.5 Test piece clamping device (test assembly), incorporating a detachable measuring head with a set
of rubber orifice plates to provide a test area of 283,5 mm (19 mm diameter), constructed so that a test
piece can be clamped between the orifice plates.
NOTE Additional sets of orifice plates may be available for the following four optional test areas:
—  71 mm (9,5 mm diameter);
—  1 135 mm (38 mm diameter);
—  2 550 mm (57 mm diameter);
—  4 540 mm (76 mm diameter);
but the use of these test areas is not in accordance with this part of ISO 5636. Doubling the test area does not
necessarily double the air flow, since the specific design of the instrument means that the pressure difference is
affected by the test area.
5.6 Flat non-porous plate, of approximate dimensions 100 mm x 100 mm, which can be clamped
between the rubber orifice plates to check the zero reading.
5.7 Calibration plate device, to enable the test assembly to be connected to an external calibration
system (see Clause 9 and Annex A).
6 Sampling
If the mean quality of a lot is to be determined, sampling shall be in accordance with ISO 186. If the
tests are made on another type of sample, make sure that the test pieces taken are representative of the
sample received.
7 Conditioning
Condition the sample in accordance with ISO 187.
8 Preparation of test pieces
Prepare the test pieces in the same atmospheric conditions as were used to condition the sample.
Cut not less than 10 test pieces, each at least 15 mm larger in both dimensions than the diameter of the
circular orifice of the rubber plate to be used, and identify their two sides, for example side 1 and side 2.
The test area shall be free from folds, wrinkles, holes, watermarks or defects not inherent in the sample.
Do not handle the part of the test piece which will become the test area.
If the air permeances measured on the two sides differ significantly and if this difference is required to
be shown in the test report, 10 tests are required for each side.
9 Calibration
9.1 Variable-area flow-measuring device
Calibrate the instrument against an external flow-measuring device as described in A.1, and prepare a
calibration graph or chart as described in A.2.
Calibrate the instrume
...