Choosing effective secondary FR chemical protective garments

Choosing effective secondary FR chemical protective garments

A comprehensive guide for employers and workers

Workers deserve protective garments that don’t compromise chemical protection to provide secondary flame-resistant (FR) protection. Thoroughly assessing both flame resistance (FR) and chemical resistance (CR) needs is imperative when selecting such garments.

Firstly, prioritize evaluating chemical resistance.

Various CR garment technologies and recognized test methods exist to enhance performance. The two most common test methods cited by manufacturers of chemical personal protective equipment (PPE) are ASTM Method F739, the Standard Test Method for Permeation of Liquids and Gases through Protective Clothing Materials under Conditions of Continuous Contact, and ASTM Method F903, the Standard Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Liquids.

While both are official ASTM test methodologies, permeation testing is considered more rigorous as it directly evaluates a fabric's chemical resistance at the molecular level, encompassing absorption, diffusion, and desorption. Conversely, penetration testing examines the bulk passage of chemicals through pores or openings in the material.

To illustrate the disparity between these mechanisms, consider the analogy of a soda bottle. If a sealed bottle of soda loses its fizz over time without any visible damage, it's akin to permeation. Conversely, if an open bottle allows gas to escape through the opening, it mirrors penetration.

Permeation and Penetration Tests

Permeation tests, such as those conducted by DuPont for its chemical protective garments, offer valuable insights into fabric resistance against hazardous liquids and vapours.

Tables 1 and 2 compare the chemical permeation and penetration test results for DuPont? Tychem? 2000 SFR and Pyrolon? CRFR.

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Table 1. Permeation data

Comparison of permeation test (ASTM F739) results

Note: Information on Pyrolon? CRFR is from Lakeland’s U.S. website.?

Table 2. Penetration data

Comparison of penetration test (ASTM F903, Procedure C) results

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Note: ASTM F903 Procedure C=0 psi for 5 min., 2 psi for 1 min. and 0 psi for 54 min. Information on Pyrolon? CRFR is from Lakeland’s U.S. website.

Flame-resistance

It's crucial to differentiate between primary and secondary FR garments.

Primary FR garments, designed as “standalone” protective apparel, are flame-resistant and expected to protect wearers from heat and flame exposures. They offer thermal insulation to prevent burn injuries.

Secondary FR garments, however, are intended to be worn over primary FR garments. They protect the primary FR from contaminants or chemicals and extend their lifespan but do not provide thermal insulation. Secondary FR garments should not be worn alone or worn over everyday garments (i.e., flammable garments) in work areas requiring FR PPE clothing based on a hazard assessment.

A standard test for assessing material response to flame exposure is the ‘vertical flame test,’ usually conducted per ASTM D6413 standards. While this test provides valuable insights, it's essential to consider the garment's overall reaction during flame engulfment scenarios.

The method most used in the USA is ASTM D6413 Standard Test Method for Flame Resistance of Textiles (Vertical Test). This method originated in the 1920s as part of the U.S. government’s Federal Test Method Standard FTMS 191A Federal Standard for Textile Test Methods under Method 5903 Flame Resistance of Cloth; Vertical.

ASTM D6413 is a relatively simple test to run. A 12-inch x 3-inch piece of material is hung vertically in a special chamber. The bottom edge of the long dimension is exposed for 12 seconds to a laboratory flame. After the test flame ceases, the sample is observed to determine if after flaming occurs and if any afterglow is noted. Additionally, observations are made regarding whether the sample exhibited melting or dripping behaviour. After the sample cools, char length is measured. Char length in ASTM D6413 is defined as “the distance from the fabric edge, which is directly exposed to the flame to the furthest point of visible fabric damage after a specified tearing force has been applied.” It is important to note that ASTM D6413 does not impose any pass/fail requirements. It is just a test method, not a performance specification.

Compliance with standards like NFPA 2112 and ASTM F1506 for primary FR garments is paramount to offer adequate protection against short-duration thermal exposures from fire and electric arcs.

In contrast, for secondary FR garments, the focus shifts from charring resistance to the ability to self-extinguish promptly after flame exposure. These garments are not designed to protect wearers from flames but rather to complement primary FR gear. Tychem? 2000 SFR represents a novel approach to secondary FR chemical garment technology, engineered to shrink away from flames without charring, as validated by ASTM D6413 vertical flammability testing.

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Table 3. Performance requirements applied to ASTM D6413 results


Table 4. Tychem? 2000 SFR results, ASTM D6413 testing

MD=machine direction; CD=cross direction

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Figure 1. Test results per ASTM F1930 method with 4-second exposure (average of 3 replicates)

We have not yet validated the effectiveness of Tychem? 2000 SFR in electrical arc flash hazards.

Extensive ASTM F1930 testing further corroborates the superior performance of Tychem? 2000 SFR garments during fire engulfment scenarios. They exhibit lower predicted body burn levels and minimal after-flight compared to competitors like Lakeland Pyrolon? CRFR. Thus, when selecting a secondary FR garment, the garment's performance during fire engulfment should be the primary consideration, as illustrated in Figure 1's comparison of predicted body burn results for Tychem? 2000 SFR and Pyrolon? CRFR garments exposed to a 4.0-second laboratory flashfire.

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*WARNING: This information is based upon technical data that DuPont believes is reliable. It is subject to revision as additional knowledge and experience become available. It is the user’s responsibility to determine the level of toxicity and the proper personal protective equipment needed. This information is intended for use by persons with the technical expertise to evaluate under their specific end-use conditions at their discretion and risk. Anyone planning to use this information should first check that the garment selected is suitable for the intended use. To avoid potential chemical exposure, the end-user should discontinue using the garment if a fabric becomes torn, worn, or punctured. Since conditions of use are beyond our control, DUPONT MAKES NO WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE AND ASSUME NO LIABILITY IN CONNECTION WITH ANY USE OF THIS INFORMATION. This information is not intended as a license to operate under or a recommendation to infringe any patent or technical information of DuPont or other persons covering any material or its use.

? 2024 DuPont. All rights reserved. DuPont?, the DuPont Oval Logo, and all trademarks and service marks denoted with ?, SM, or ? are owned by DuPont de Nemours, Inc. affiliates unless otherwise noted.

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