Diana WymanApril 15, 2020 AATCC Newsletter

Impact Penetration Testing for Textiles Part 2

AAMI versus NWSP Blotter Paper

There are slight differences in the tolerances for AAMI PB70 and NWSP 80.3 blotter paper. NWSP 80.3 also has additional parameter specifications. NWSP 80.3.R0 and NWSP 80.3.R1 specify very different mass per unit area.

Table I.

AAMI v. NWSP Blotter Paper

    AAMI PB70: 2012 NWSP 80.3.R1 (19) NWSP 80.3.R0 (15)
Mass per unit area g/m2 139 ± 11 90 ± 4
Density g/cm3 0.24 ± 0.06 0.24 ± 0.05 0.24 ± 0.05
Absorbent Capacity % 480 ± 30 ≥ 480 (NWSP 010.1) ≥ 480 (ISO 9073-6)
Absorbency s < 5 < 5 (ISO 9073-6) < 5 (ISO 9073-6)
Strike-through time s ≤ 3 (NWSP 70.3 w/o sample)

 

AATCC versus NWSP Blotter Paper

NWSP 80.3 includes data and analysis from a study of two types of blotter paper, including the paper used for AATCC TM42. Only the density and manufacturer of the other tested paper were provided; density is the same as currently specified in NWSP 80.3. The conclusion of the study was that “density, absorbency and rate of absorbency are very important factors when selecting a blotter paper.”

According to the note associated with the study results, AATCC blotter paper is less absorbent with a slower absorbent rate and higher test results. The higher results are attributed to paper density (0.53 g/cm3 for AATCC; 0.24 g/cm3 for the other paper.) It is unclear how higher density leads to higher test results (results are the mass increase of the paper due to water passing through the test specimen). In any case, consistently lower results suggest that water passing through the test specimen is being absorbed by the back side of the fabric, or even running off the paper, rather than being absorbed by the blotter paper. For many end uses, this may represent a false pass.

The AATCC blotter paper also had a lower coefficient of variation (CV%), indicating more repeatable and reproducible results. CV% for AATCC blotter paper was 63%; the other paper was 116%.

While the available data suggests that the AATCC blotter paper is better suited to the impact penetration test, it should not be used for AAMI classification unless noted as a modification. Note that blotter paper specifications are not included in AATCC test methods, but a certificate of analysis indicates the properties of each lot.

 

Table II.

AATCC v. NWSP Blotter Paper

    AATCC NWSP 80.3.R1 (19)
Mass per unit area g/m2 369.1
(333.9-406.0)
139 ± 11
Density g/cm3 0.70
(0.60 – 0.80)
0.24 ± 0.05
Absorbent Capacity % 240 (nominal) ≥ 480 (NWSP 010.1)
Absorbency s 5 (0-10.5) < 5 (ISO 9073-6)
Strike-through time s ≤ 3 (NWSP 70.3 w/o sample)

 

AATCC versus NWSP Test Procedure

Although ANSI/AAMI PB70:2012 indicates that “WSP 80.3 is equivalent to and may be substituted for AATCC 42 when the blotter paper specified in 5.2.1.2 is used,” there are additional differences between the current versions of these test methods.

Table III.

AATCC v. NWSP Test Procedure

  AATCC TM42-2017e NWSP 80.3.R1 (19)
Apparatus Type I tester OR

Type II tester

Type II tester
Balance & measurements Accurate to 0.1 g Accurate to 0.01 g
Baffle (to prevent water swirl) Blade fixed to inside of funnel Square plastic baffle inserted
Nozzle holes 0.99 mm 61 drill
Specimens ≥ 3 specimens

178 × 330 mm

10 specimens unless specified

175 × 325 mm

Flow rate Not specified 500 mL/22 ±2 s
Blotter size 152 × 230 mm 150 × 225 mm

 

In most cases, the differences are very minor. Hole, specimen, and blotter size are functionally the same, varying due to conversion and rationalization of units. The integrated blade on the inside of the funnel provided by AATCC serves the same purpose as the additional baffle indicated in NWSP 80.3. If such a blade exists, use of an additional baffle will not affect test results. Some equipment manufacturers may produce impact penetration testers without the integrated blade; in this case, the NWSP baffle or other device should be used to prevent swirling. The requirement to prevent swirling motion as water is poured though the funnel is included in both AATCC and NWSP test methods.

Fig. 2

The Type II tester was developed for use with nonwoven fabrics. Its sturdier construction limits vibration that may cause additional liquid to pass through a test specimen (see Fig. 2). The Type II tester also includes an integrated drip tray that is moved under the nozzle immediately after the water has run through the funnel to prevent any residual drops from falling on the test specimen. It is possible for samples that fail or perform poorly on a Type I tester to achieve better results on a Type II tester. In general, a fabric that performs well on a Type I tester is unlikely to have worse results on a Type II tester.

The NWSP method calls for greater accuracy than the AATCC method. Mass is measured and recorded to 0.01 g rather than 0.1 g. As noted in the previous section, NWSP blotter paper results in much lower values, so the increased accuracy may be relevant for comparing similar products. Most pass/fail decisions can be determined using measurements with 0.1 g accuracy, regardless of the blotter paper used.

Other Test Procedures

ISO 18695:2007 is based on AATCC TM42 and has the same specifications. ISO 9073-17:2008 is equivalent to NWSP 80.3 (corresponding version is unknown).

AATCC TM42 Blotter Paper History

1945-2006

AATCC TM42 is first published. The test method references AATCC Textile Blotting Paper but does not include detailed specifications for the paper. AATCC TM35 and AATCC TM70 are published in 1947 and 1952, respectively, with similar references to blotter paper. The official blotter paper is sold by AATCC; properties are defined by internal quality control procedures and reported to customers on certificates of conformity.

January 2006

The manufacturer of AATCC blotting paper could no longer provide the specified material. AATCC contacted several other potential manufacturers.

Based on manufacturer specifications, a close alternate paper was proposed for further study.

July-August 2006

Three labs evaluated the established and proposed blotter papers. Results were compared for AATCC TM35, TM42, and TM70.

September 2006

The AATCC RA63 chair sent a letter to committee members informing them that the proposed blotter paper provides “statistically comparable data and is therefore considered an approved replacement.”

February 2007

Remaining stock of the “old” blotter paper was depleted and replaced by “new” paper.

AAMI PB70 Blotter Paper History

2003

First edition of ANSI/AAMI PB70, Liquid barrier performance and classification of protective apparel and drapes intended for use in health care facilities, was published.

2012

ANSI/AAMI PB70 was revised. According to the annex, “The most significant revision to PB70 involves two water-impact resistance tests: AATCC 42 and the newer WSP 80.3, which has more stringent specifications for blotter paper and equipment calibration.”

Alternate blotter paper is specified for use with AATCC TM42:

  • It should exhibit no distortions when wet.
  • It should have an absorbent rate of < 5 seconds.
  • It should have an absorbent capacity of 480% ± 30%.
  • It should have a sheet density of 0.24 g/cc ± 0.06 g/cc.
  • It should exhibit uniform sheet formation.
  • It should be traceable to the production lot.
  • It should be weighed to the neared 0.01 grams.

NWSP 80.3 Blotter Paper History

2005

WSP 80.3 was first published.

2015

Revised NWSP 80.3.R0 (15) was published.

There were no significant technical changes in the revision. Standard designation was changed from WSP (Worldwide Strategic Partners) to NWSP (Nonwovens Standard Procedures). Note 3, regarding source of blotter paper was also updated.

2019

Revised NWSP 80.3.R1 (19), Evaluation of Water Penetration (Spray Impact Test) of Nonwoven Fabrics, was published.

The blotter paper specification was updated in this revision. Mass per unit area was significantly increased (from 90 g/m² to 139 g/m²).

  • No visible distortion in the paper when wetting while testing
  • The mass per unit area of the paper is (139 ± 11) g/m².
  • The liquid absorption capacity, of the paper, as determined by NWSP 010.1 is at
  • least of 480 %
  • The mean strike-through time is 3 seconds or less, using test procedure NWSP 70.3, but without a test sample.
  • An absorbent rate of 5 seconds or less (ISO 9073-6)
  • Exhibits uniform sheet formation
  • Traceable back to production lot
  • A sheet density of 24 ± 0.05g/cc

EDANA published an online note dated August 9, 2018 indicating that changes were intended to resolve ambiguities concerning the use of blotter paper; however, the online summary does not match the blotter paper specifications in the standard. The specifications in NWSP 80.3.R1 are also slightly different from those published in ANSI/AAMI PB70:2012.

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