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DIN 53122-1-2001 ENG


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D EUTSCHE NORM

August 2001

Determination of the water vapour transmission rate of plastic film, rubber sheeting, paper, board and

other sheet materials by gravimetry
ICS 59.080.30; 83.140.10; 85.060 Prüfung von Kunststoff-Folien, Elastomerfolien, Papier, Pappe und anderen Fl?chengebilden; Bestimmung der Wasserdampfdurchl?ssigkeit – Teil 1: Gravimetrisches Verfahren

{

53122-1

Supersedes DIN 53122-1, November 1974 edition.

In keeping with current practice in standards published by the International Organization for Standardization (ISO), a comma has been used throughout as the decimal marker.

Foreword
This standard has been prepared by Technical Committee Chemisch- und chemisch technologische Prüfverfahren für Papier, Halbstoff und Chemiezellstoff of the Normenausschuss Materialprüfung (Materials Testing Standards Committee). Although the standard is largely based on International Standard ISO 2528 : 1995, it differs from the latter in that a test dish made of glass without a groove around the rim (cf. figure 3) has been specified as an additional, very widely used design, which has the advantage that a good seal is ensured since the external sealing compound (cf. figure 4) hardly ever becomes detached during cooling. Two points are important in selecting the size of dish, namely preventing the desiccant from becoming saturated during the test, on the one hand, and minimizing the total mass, on the other, to reduce its effect on the accuracy of weighing. Normalization of the water vapour transmission rate to a standard thickness is often required, but is possible only for homogeneous material, not for multilayer or laminated samples, and, of course, only in the case of an unaltered and essentially uniform material matrix. If these conditions are fulfilled, the water vapour transmission rate, WVTR, of similar samples of different thickness is inversely proportional to the thickness, i.e.
WVTR ≈

(WVTR) 1 = Thickness 2 1 or (WVTR) 2 Thickness 1 Thickness

To obtain guideline values for a laminated material (e.g. multi-layer film) from the WVTR values of the components, if the same (above) conditions are fulfilled, the reciprocals of their water vapour transmission rates, 1/ WVTR, shall be added, i.e. the their water vapour transmission rate of the composite will then be:
? ? 1 1 WVTR(1 + 2) ≈ ? ? (WVTR) 1 + (WVTR) 2 ? ? ? ?
?1

This means that, in a laminated material, a layer having a low water vapour transmission rate combined with other highly transmissive layers (i.e. layers having a high water vapour transmission rate) virtually determines the rate of the composite on its own. See DIN 53122-2 for other methods of determining water vapour transmission rates (e.g. if these are very low). Amendments This standard differs from the November 1974 edition as follows. a) The scope of the method has been extended to cover water vapour transmission rates from 1 g/m 2 d to 200 g/m2 d. b) The description of the principle of the method has been amended. c) The specifications for the apparatus and the test procedure have been amended. d) Details of the test report have been changed. e) The standard has been editorially revised. Continued on pages 2 to 7. Translation by DIN-Sprachendienst.
In case of doubt, the German-language original should be consulted as the authoritative text.

? No part of this translation may be reproduced without the prior permission of DIN Deutsches Institut für Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany, has the exclusive right of sale for German Standards (DIN-Normen).

Ref. No. DIN 53122-1 : 2001-08
English price group 07 Sales No. 0107 03.02

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Page 2 DIN 53122-1 : 2001-08 Previous editions DIN 53413: 1940x-11; DIN 53122: 1958-02, 1961-04; DIN 53122-1: 1974-11. All dimensions are in millimetres.

1

Scope

The method specified in this standard serves to determine the water vapour transmission rate, WVTR, of sheet materials by the gravimetric method using a dish sealed with wax and can be applied, for example, to plastic film and rubber sheeting, paper, board or textiles with or without coating. It is especially suitable for determining rates ranging from 1 g/m2 d to 200 g/m2 d. NOTE: Under refined test conditions (e.g. involving air-pressure control, prolonged test duration and constant test atmosphere), the method can also be used down to rates of about 0,5 g/m 2 d.

2

Normative references

This standard incorporates, by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text, and the titles of the publications are listed below. For dated references, subsequent amendments to or revisions of any of these publications apply to this standard only when incorporated in it by amendment or revision. For undated references, the latest edition of the publication referred to applies. DIN 53122-2 DIN DIN DIN DIN 53352 53370 53504 EN 20534 Determination of water vapour transmission rate of plastic film, paper, board and other sheet materials by electrolysis Testing of artificial leather and similar sheet materials – Determination of mass per unit area Determining plastic film and sheeting thickness by the stylus method Determination of tensile stress/strain properties of rubber Paper and board – Determination of thickness and apparent bulk density or apparent sheet density (ISO 534 : 1988) Sheet materials – Determination of water vapour transmission rate – Gravimetric (dish) method Paper and board – Determination of water vapour transmission rate of sheet materials – Dynamic sweep and static gas methods

ISO 2528 : 1995 ISO 9932 : 1990

3

Concept

Water vapour transmission rate For the purposes of this standard, the mass of water vapour that passes, under specified conditions, from an evaporation chamber through the exposed surface of a sample into a test dish per day and per square metre of sample area. NOTE: Since the water vapour transmission rate depends on factors that include the thickness and matrix of the sample material, it is not a material constant. Samples having a thickness greater than 3 mm shall be tested as specified in ISO 9932. Above that thickness and above a water vapour transmission rate of 200 g/m2 d, the accuracy of measurement decreases.

4

Designation Test DIN 53122 – A

Designation of the method for determining the water vapour transmission rate by the gravimetric method as specified in this standard (A):

5

Principle

A dish (see figures 2 to 4) filled with desiccant is covered with the sample using wax as sealant and placed in an enclosure (e.g. a desiccator) with a controlled test atmosphere (see note 2 in subclause 7.5). The amount of water vapour that passes through the test area of the sample surface and is absorbed by the desiccant is determined by weighing the dish at regular intervals and recording the increase in mass.

6
6.1

Samples
Sampling

Samples shall be taken from the product that are representative of the batch delivered. They shall not exhibit any surface inhomogeneities (e.g. specks) or damage (e.g. creases, holes) and shall be free of watermarks or imprints, unless the behaviour of, for example, an imprinted film or a folded paper sample is to be tested.

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Page 3 DIN 53122-1 : 2001-08

6.2

Shape and size

Samples shall be about 90 mm in diameter.

6.3

Preparation

The samples shall be produced, for example, by means of a template or a punch. If the two surfaces of the sample are not the same, the test area, i.e. the surface that is exposed to the moist atmosphere, shall be specified in the test report. If both surfaces of the sample are to be measured, twice the number of samples shall be prepared. If the samples have been prepared using solvents, residues of the latter left in the sample may affect the test results. Details of any treatment of samples to remove the residual solvent shall be included in the test report.

6.4

Number of samples

At least three samples will be required for every surface to be tested. If the water vapour transmission rate is low, the thickness of the samples is large or the samples are very hygroscopic, one or two additional samples shall be prepared.

7
7.1 7.2

Apparatus

The following equipment shall be used. Thickness gauge, as in DIN 53504 for rubber sheeting and rubber-coated textiles, as in DIN 53370 for plastic/rubber sheets and as in DIN EN 20534 for paper and board. Balance, capable of weighing to an accuracy of 0,1 mg.
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7.3 Hygrometer, capable of measuring to an accuracy of 2 % r.h. and having a response sufficient for checking the maximum time to reach steady-state conditions (cf. subclause 7.5) after the evaporation chamber has been closed. 7.4 7.5
Temperature measuring instrument (e.g. a thermometer or electronic instrument), with a limit of error of 0,5 °C. Evaporation chamber, with a controlled atmosphere (i.e. temperature relative humidity). The time required to re-establish the atmosphere after the chamber has been closed should be as short as possible and should not exceed 1 % of the interval between weighings. If this requirement cannot be satisfied because the samples have a high water vapour transmission rate, this shall be recorded in the test report. A desiccator as shown in figure 1, for example, in a controlled-temperature or air-conditioned room may be used as evaporation chamber. NOTE 1: In the case of highly transmissive samples, the number of dishes in the evaporation chamber may be kept low to ensure a constant and uniform distribution of humidity within the tolerances for the test atmosphere concerned (see subclause 8.2).

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Page 4 DIN 53122-1 : 2001-08

Figure 1: Evaporation chamber (without dishes shown in figure 2 or 3) NOTE 2: The relative humidity can be readily established in the desiccator by the solutions containing a large excess of salt specified in table 1.

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Page 5 DIN 53122-1 : 2001-08 Table 1 Relative humidity, as a percentage 75 85 85 90 90 Saturated potassium nitrate solution Salt solution Saturated sodium chloride solution Saturated potassium chloride solution °C 25 20 23 25 38
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7.6

Test dish, (e.g. dish made of oxidized aluminium sheet about 1 mm thick (cf. figure 2) or glass dish as in figure 3, whose mass, including desiccant, sample and a light metal lid, shall not exceed 200 g. The internal depth of the dish should be between 8 mm and 24 mm, but shall preferably be 15 mm. The dish should be shaped so that the test area of the sample is defined to an accuracy of 1 % and the sealing compound between the sample and the rim of the dish prevents the penetration of water vapour.

Figure 2: Aluminium dish

Figure 3: Glass dish

7.7

Desiccant, consisting of calcium chloride or silica gel (blue gel), capable of maintaining a relative humidity in the dish of less than 1 %. The total water absorption of the agent shall not exceed 1,5 g per 25 cm3 during measurement. NOTE: It is advantageous to use material with a particle size of 1,5 mm to 2 mm that passes through a 4 mm sieve, has been freed of any fines using a 1,6 mm sieve, and has been dried in the normal manner. Sealant, consisting of a wax mixture that adheres strongly to both the dish and the sample, is not brittle at the measuring temperature and is neither hygroscopic nor susceptible to oxidation. The mass of a quantity of wax having a surface area of 50 cm2 shall not change by more than 1 mg as a result of absorbing water at a temperature of 38 °C and 90 % relative humidity.

7.8

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Page 6 DIN 53122-1 : 2001-08 Standard sealants are: a) a mixture containing 80 % (m/m) of paraffin wax melting at temperature of 50 °C to 52 °C and 20 % (m/m) of polyisobutylene having a fairly low degree of polymerization; b) a mixture containing 60 % (m/m) of a microcrystalline wax and 40 % (m/m) of fully refined crystalline paraffin wax. NOTE 1: It is advantageous to use a light metal lid that covers the dish when it is removed from the test atmosphere and weighed so that the sample releases as little water as possible to the surrounding air during weighing. This, however, is generally unnecessary in the case of non-hygroscopic film or sheets or of those having low water vapour transmission rates. NOTE 2: Cover templates of the type shown in figure 4 facilitate the sealing operation.

Figure 4: Details of sealing samples

8
8.1 8.2

Procedure

Determine the mean thickness from five measurements on each sample. In the case of products having an outer layer, determine the mass per unit area as described in DIN 53352. Use one of the following atmospheres in the evaporation chamber: a) atmosphere A: (25 t 1) °C and (90 t 2) % relative humidity; b) atmosphere B: (38 t 1) °C and (90 t 2) % relative humidity; c) atmosphere C: (25 t 1) °C and (75 t 2) % relative humidity; d) atmosphere D: (23 t 1) °C and (85 t 2) % relative humidity; e) atmosphere E: (20 t 1) °C and (85 t 2) % relative humidity. Use atmosphere B for rubber sheets, atmosphere D for plastic film and laminated paper, and atmospheres D and E for paper and board.

8.3

To carry out a series of tests, fill the dried dishes, which have been thoroughly cleaned, with the same mass of the chosen desiccant, ensuring that the latter will be 3 mm to 4 mm below the former. Then cover the dishes with the samples and firmly seal them to the dish wall, ensuring that the temperature of the sealant (and any annular template used) does not bring about any alteration in the sample. If the wax is spread out on the rims with the aid of a hot spatula, check that the seal is still intact after the sealant has cooled. Weigh the dish and sample (and the lid if fitted) to an accuracy of 0,1 mg, then place it in the evaporation chamber and remove the lid.

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Page 7 DIN 53122-1 : 2001-08

8.4

Carry out weighings preferably at intervals of less than 24 hours, 24 hours, 48 hours, 72 hours and 96 hours, depending on the water vapour transmission rate of the sample, and plot the results as a mass/time curve until at least three consecutive points lie on a straight line, i.e. the difference between two consecutive weighings is constant to within 5 % for one and the same interval. Check that the increase in mass between two consecutive weighings is at least 5 mg. In blank tests, examine samples having low permeation rate and large thickness (e.g. paper laminated with polymers, plastic film or aluminium foils, cardboard or board, plastics or rubber, and hygroscopic samples) in parallel with the blank samples. Make such blank samples in the same way and subject them to the same conditions, but without desiccant in the dishes. Subtract the blank values from the values measured for the sample dishes having undergone the same treatment.

8.5

9

Evaluation
Dm . 104 A

Calculate the water vapour transmission rate, WVTR, in g/m2 d, using the following equation:

WVTR =

(1)

where D m is the difference in mass between the last two consecutive weighings, in g; A is the test area of the sample, in cm2. This equation applies if the interval between consecutive weighings is 24 hours (see subclause 8.4). For other time intervals:

WVTR =

24 Dm . . 104 t A

(2)

where t is the interval between two weighings used to determine Dm, in hours; D m is the difference in mass between the last two consecutive weighings, in g; A is the test area of the sample, in cm2. Take the arithmetic mean of the individual values and report it to three significant places, but not to more than one decimal place. NOTE: Variations in the measurements that are so large that three consecutive values do not lie approximately on a straight line in the mass/time diagram may occur if the sample material absorbs moisture itself. The same phenomenon will be observed if the humidity of the test atmosphere varies considerably during weighing. It may also be due to sample defects and to differences in water vapour transmission rates in the case of samples with single-side or even double-side lamination. If the mass/time curve is parallel to the time axis, this indicates exhaustion of the absorption capacity of the dish concerned. This can be remedied, for example, by increasing the mass of desiccant and repeating the test.

10

Test report

The test report shall refer to this standard and include the following details: a) type and description of the sample material, including whether it is laminated on one side or both, and the type of laminating material; b) mass per unit area of sample material in the as delivered condition (single values and mean); c) thickness of samples, to two significant places; d) sample side(s) tested; e) size and type of dish, test surface area (in cm2), clearance between dish bottom and sample and distance between desiccant surface and sample; f) type of desiccant and initial mass; g) test conditions (e.g. atmosphere chosen, test time, number of dishes, number of test runs (if not all the dishes were tested at the same time)); h) water vapour transmission rate (single values and mean) for each side tested, to three significant places, but not to more than one decimal place. If the maximum difference between single values exceeds 10 % of the mean, report only the former; i) date of testing; j) any deviation from this standard that may have affected the result.

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