STANDARD PROCEDURE: NWSP 070.3.R0 (15)
Nonwoven Coverstock Liquid Strike-Through Time Using Simulated Urine
1.
Scope
This test method measures the strike-through time, i.e. the time taken for a known volume
of liquid (simulated urine) applied to the surface of a test portion of nonwoven coverstock,
which is in contact with an underlying standard absorbent pad, to pass through the
nonwoven. This test method is only designed to compare strike-through time of nonwoven
coverstock. It is not intended to simulate in-use conditions for finished products.
SI values are regarded as the official standard system of measurement for this standard
procedure. If other systems of measurement are used in place of SI units (including inchpound) their values must be reported independently. Systems of measurement must not be
combined in any way, but shall be regarded and reported separately.
NOTE 1 SAFETY
This standard does not claim to address all of the safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate safety and health practices and determine
the applicability of regulatory limitations prior to use. It is expected that the person performing this test has
been fully trained in all aspects of this procedure.
2.
References
The following referenced documents are useful for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document applies.
2.1
International standards
a)
ISO 9073-8 Textiles – Test method for nonwovens – Part 8: Determination of
liquid strike-through time (simulated urine)
b)
ISO 9073-6 Textiles -- Test methods for nonwovens -- Part 6: Absorption.
c)
ISO 5636-5 Paper and board -- Determination of air permeance (medium
range)— Part 5: Gurley method
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2.2
NWSP
a) NWSP 001.0 Standard Terminology Relating to the Nonwoven Industry, EDANA’s
and INDA’s Standard Procedures
3. Terms and Definitions
The following referenced terms are of utility for the application of this document:
3.1 Sample
For testing purposes a product or a portion of a product taken from a production lot. The
sample shall be identifiable and traceable back to the origin.
3.2 Simulated urine
A testing liquid consisting of a 9 g/l solution of sodium chloride in distilled water with a
surface tension of (70 ± 2) mN/m.
3.3 Specimen
A specific portion of the identified sample upon which a test is performed. Many
specimens may be tested from the same sample, using different locations.
4. Principle
A specified quantity of simulated urine is discharged at a prescribed rate under specified
conditions onto a test specimen of nonwoven, which is superimposed on a reference
absorbent pad. The time taken for the entire liquid dose to penetrate the nonwoven is
measured electronically.
5. Reagents and Materials
Use only reagents of recognized analytical grade, unless otherwise specified.
5.1 Standard Absorbent Pad (Blotter Paper)
Reference absorbent pad, consisting of 3 - 4 layers of reference blotter paper (100 mm x
100 mm) with the test side uppermost and having a mean strike-through time, in 10
determinations without using any coverstock nonwoven material, of 3 seconds or less.
a) Must have an absorbent rate of (3 ± 0.5) s or less (ISO 9073-6)
b) The Liquid Absorption Capacity, of the paper, as determined by standard NWSP
010.1, must at least 480 %.
c) The mass per unit area of paper must be (90 ± 4) g/m² and the air flow resistance,
as determined by ISO 5636, must be (1.9 ± 0.3) kPa.
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NOTE 2 Information concerning suitable blotter paper may be obtained from the nonwovens industry
associations:
EDANA, Avenue Herrmann Debroux, 46 B-1160 Brussels, Belgium Phone +32 2 734 93 10 Fax +32 2 733 35
18, info@edana.org Please check the EDANA website for updated information on blotter paper.
INDA, 1100 Crescent Green Suite 115, Cary NC 27518 Phone +1 919 233 1210, Fax +1 919 233 1282,,
Info@Inda.org
5.2 Simulated urine
Consisting of a 9 g/l solution of sodium chloride in distilled water with a surface tension of
(70 ± 2) mN/m. This surface tension should be checked before each series of tests, as
surface can alter tension during storage.
NOTE 3 The surface tension of adult human urine is published as 69 to 70 mN/m. There is a suggestion that
some babies’ urine could have a lower surface tension (e.g. 45 mN/m). The surface tension of the simulated
urine can be adjusted by the addition of a surfactant. In this case it should be reported as a deviation from
standard procedure and the surface tension should be stated in the test report.
6.
Apparatus
6.1 Burette
This has a 50 ml capacity and is attached to a supporting stand.
6.2 Funnel
Fitted with a magnetic valve, giving a rate of discharge of 25 ml in (3.5 ± 0.25) s.
6.3 Ring stand
To support the funnel
6.4 Strike-through plate (see figures 1 and 2)
Constructed of 25 mm thick transparent acrylic sheet, of total mass (500 ± 5) g, fitted with
corrosion-resistant electrodes consisting of 1.6 mm diameter platinum or stainless steel
wire set in grooves of cross-section 4.0 mm x 7.0 mm cut in the base of the plate and
fixed with quick-setting epoxy resin. The electrodes shall be positioned as shown in
figures 1 and 2.
6.5 Baseplate
Made of transparent acrylic sheet, approximately 125 mm x 125 mm square and 5 mm
thick.
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6.6 Electronic timer
Which can be read to the nearest 0.01 s.
NOTE 4 The sensitivity of the timing mechanism is such that different apparatus could give results slightly
lower or higher than the specification for the standard absorbent pad alone.
NOTE 5 Users of the method are therefore advised to validate their equipment against results provided by the
producer of the blotter paper.
NOTE 6 This complete machine can be purchased from: W. Fritz Mezger, Inc.,155 Hall St.
Spartanburg, SC 29302
7.
Sampling
7.1 Lot Size
A lot should be established based on a logical break in the process or as prescribed by a
regulation or traceability requirements.
7.2 Sampling
If provided in the customer specification, take random sample as directed. If no
requirements are provided, ISO 2859-1 (Sampling procedures for inspection by attributes)
or ISO 3951-1 (Sampling procedures for inspection by variables) can be used. In and of
themselves, these are not valid sampling plans by default. An agreement between the
purchaser and supplier requires taking into account process stability, producer’s risk,
consumer’s risk, acceptable quality level and also the cost needs to be established.
In general, if the test characteristic can be considered normally distributed, the sampling
procedures for inspection by variables will require fewer samples. However, small
samples may not reflect that normal distribution and the estimated percent defective can
therefore be over or under estimated. In this case, as well as for attribute data, the
sampling procedures for inspection by attributes should be used.
In the absence of any sampling size requirement, the following tables can be used.
Switching rules are required to maintain the AQL protection.
Attributes (1.0 AQL, General Inspection Level II)
Number of units in the lot inclusive
1 to 150
151 to 280
281 to 500
501 to 1200
Number of units that comprise the lot sample
13
32
50
80
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Variables (“s” method, General Inspection Level II)
Number of units in the lot inclusive
1 to 15
16 to 25
26 to 50
51 to 90
91 to 150
151 to 280
281 to 500
501 to 1200
Number of units that comprise the lot sample
3
4
6
9
13
18
25
35
NOTE 7 Results obtained on small hand samples can only be considered as representative of that sample
and cannot be assumed to be representative of the material portion from which the small hand sample was
taken.
NOTE 8 An adequate specification or other agreement between the purchaser and supplier requires taking
into account the variability between rolls of nonwoven fabric and between specimens from a swatch from a roll
of material to provide a sampling plan with meaningful producer’s risk, consumer’s risk, acceptable quality
level, and limiting quality level.
8.
Conditioning
For Conditioned Testing
Bring test samples and blotter paper both to moisture equilibrium in the standard
atmosphere for testing nonwovens as directed in ISO 139. Equilibrium is considered to
have been reached when the increase in mass of the specimen in successive weighings
made at intervals of not less than 2 hours does not exceed 0.25 % of the mass of the
specimen.
NOTE 9 While conditioning for a fixed time cannot be accepted in cases of dispute, it may be sufficient in
routine testing to expose the material to the standard atmosphere for testing textiles for a reasonable period of
time before the specimens are tested.
9.
Procedure
9.1 Set up the ring stand
By positioning the burette with the tip inside the funnel.
9.2 Cut the required number of specimens of Nonwoven
125 mm x 125 mm, test specimens being selected in accordance with NWSP 005.0, if
applicable.
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9.3 Place one nonwoven test specimen
On top of one set of 3-4 reference blotter papers on the base plate. Place the nonwoven
on the blotter paper in such a way that the side of the nonwoven, which is intended to be
in contact with the user’s skin, is uppermost. Ensure that the electrodes in the strikethrough plate are clean. Place the strike-through plate on top of the nonwoven with the
center of the plate over the center of the test specimen. Center the burette and the funnel
over the plate.
9.4 Adjust the height of the funnel
So that the funnel is (5 ± 0.5) mm above the top of the cavity in the plate (i.e. 30 mm
above the test specimen).
9.5 Ensure the electrodes are connected to the timer
Activate the timer and set the clock to zero.
9.6 Fill the burette with simulated urine
Keep the discharge valve of the funnel closed and run 5.0 ml of liquid from the burette into
the funnel.
9.7 Open the magnetic discharge valve
Of the funnel to discharge 5.0 ml of liquid. The initial flow of liquid will complete the
electrical circuit and start the timer. It will stop when the liquid has penetrated into the
nonwoven and fallen below the level of the electrodes in the strike-through plate.
9.8 Record the time
Indicated on the electronic timer.
10. Calculation
Calculate average time for n repeats
11. Report
In addition to the precise test results, the report shall include the following information:
a) Reference the test method used
b) Complete identification of all materials tested and method of sampling
c) Name and address of testing institution
d) Make and model of testing equipment
e) Laboratory testing conditions
f) Number of specimens tested and note CD and/or MD if significant
g) For computer processed data, identify the software used and version.
h) Deviation from the standard test procedure, if any
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i)
j)
k)
l)
m)
n)
When calculated, the standard deviation or the coefficient of variation
Whether or not samples were conditioned prior to testing and, if so, for how long
Anything unusual noted during the testing
When photos are used as the standard, attach copies
Individual strike-through times, in seconds
Average strike-through times, in seconds
12. Precision
The precision for this method is yet to be determined.
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Dimensions in
millimetres
Optional weighting strips
Ø 58
Strike-through plate
(Transparent acrylic
Electrodes Ø 1,6 mm (see subclause
6.4)
Figure 1
Strike-through plate
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Wire electrodes Ø 1.6 mm
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ANNEX A
Modification Track Sheet
History starting with WSP 2005 or later edition
Present document version
number (name)
Previous version (s)
NWSP 070.3.R0 (15)
(Nonwoven Coverstock
Liquid Strike-Through Time
Using Simulated Urine)
Originally published
as WSP 70.3 (2005)
Changes made
•
•
NWSP numbering
Modification track
sheet
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NWSP 070.3.R0 (15)