Different materials for use in the production of personal protective equipment (PPE), such as protective garments or suits, are known. The properties of such materials are often evaluated with reference to different standards, such as according to the European harmonised standards that are used to determine compliance with the PPE directive 89/686/EEC for CE marking (e.g. EN 943-1 and EN 943-2) as well as the American standards set by NFPA (the National Fire Protection Association), NFPA 1991, for vapour protective clothing, which is the higher level of chemical protection, and NFPA 1992, for liquid-splash protective clothing, which consequently is considered to be a lower level of chemical protection. An example of such an important property is resistance against chemical permeation, which e.g. is evaluated with tests performed according to EN 374-3 and ASTM F 739, where the breakthrough time in minutes is determined for different chemicals. Other important properties are the actual material properties, such as abrasion resistance, flex cracking resistance, tear resistance, tensile strength, burst strength, puncture resistance, seam strength (of a suit), resistance to ignition and flammability resistance. All of these material properties are also evaluated according to specific standardised methods.
Below, NFPA 1991 will be discussed in more detail. Much of the information has been extracted from three different references, namely 1) “Understanding NFPA 1991” (Jeffrey O. Stull, International Personnel Protection, Inc.), 2) “Differences in Certified NFPA 1991 chemical protective suits” (Jeffrey O. Stull, International Personnel Protection, Inc.), and 3) the article “NFPA 1991 and 1992 synopsis” from the homepage of Trelleborg Protective Products.
NFPA 1991 imposes a difficult set of performance criteria for materials, namely chemical resistance against a broad range of chemicals (permeation resistance), physical hazard resistance/durability, and flame resistance. For e.g. the Environmental Protection Agency's Level A entries where hazards can be extreme or unknown, it is a further requirement that the chemical protective suits be able to offer protection against several types of exposures. Suits must not only prevent the permeation of chemicals or chemical mixtures, they must also resist rough physical environments, and not create additional hazards to the wearer. According to NFPA 1991, the suit should e.g. resist ignition and if it does ignite, self extinguish when removed from the flame or heat source. Accordingly, NFPA 1991 sets minimum criteria that have to be met, such as e.g. with reference to permeation resistance, but also states additional criteria, such as e.g. flash fire escape protection.
The only way to recognize a chemical protective suit that has been certified to NFPA 1991 is to examine the product label. Certified suits must have a product label that states that the suit meets the requirements and is certified to NFPA 1991. In addition to provide product information (e.g. the manufacturer identification and the model number), the label must include the mark of the third-party certification organization. To be certified, chemical protective suits must be certified by a independent certification organization, such as the Safety Equipment Institute or the Underwriter Laboratory. The certification organization's mark on the label is an indication that the product has been certified to the respective edition of the NFPA standard. The manufacturer is also required to state on the product label all items or parts (e.g., overcovers) that are required to provide a fully-compliant chemical protective ensemble.
Below, NFPA 1991 is explained in general terms. Some of the important tests performed according to NFPA 1991 are also summarised.
NFPA 1991 Standard on Vapor-Protective Ensembles for Hazardous Materials Emergencies (2005 Edition)
NFPA 1991 defines an ensemble consisting of a suit with attached gloves that totally encapsulates the wearer and his or her breathing apparatus. Ensembles are frequently configured with an overcover, outer gloves, and outer boots in order to meet the requirements of the standard. However, some products can achieve these requirements without these extra layers.
NFPA 1991 establishes some design requirements. Ensembles must be provided in a minimum of four sizes and must have protective, inverted pockets over exhaust valves. Gloves and footwear are subject to minimum length and height requirements, respectively.
Performance requirements include:                Inflation of ensembles to determine integrity against gas penetration and a “shower-like” test for demonstrating integrity of clothing against liquid penetration.        Permeation testing of suit, visor, glove, and footwear materials and their seams against a battery of 21 industrial chemicals to demonstrate resistance against a broad range of industrial chemicals, where the battery contains gases and liquids representing different classes of chemicals. These chemicals are presented below.        Burst strength, puncture/tear resistance, low temperature performance, abrasion resistance, and flex fatigue testing of suit, glove, and footwear materials.        Breaking strength testing for seams and closures.        Leakage and mounting strength testing of exhaust valves.        Tests for evaluating the functional use of the ensemble and dexterity of gloves.        
NFPA 1991 also includes optional criteria for liquefied gas protection and flash fire escape protection. Additional criteria are provided for each of the certification options. Product labels must clearly indicate which options apply to the specific ensemble. The primary purpose of NFPA 1991 is to define requirements that isolate the wearer from a surrounding hazardous chemical environment.
Below, some of the important tests for NFPA 1991 certification are given.
Flame Resistance
The test involves suspending a folded edge of the material over a methane flame in a two-part exposure. The first exposure is for 3 seconds and is intended to represent incidental flame contact. During this exposure that material cannot ignite. If it does, the material fails the test. The same material specimen is then exposed for an additional 12 seconds. While ignition is permitted, the material can burn no more than 10 seconds and the burn distance cannot exceed 4 inches (10 centimeters). The second exposure is intended to demonstrate the self-extinguishing characteristics of the material. In addition, NFPA 1991 does not permit the material to melt as evidenced by dripping.
Abrasion Resistance Test
In the abrasion test, an 80-grit sandpaper is placed on a curved drum. The material sample is clamped in a holder under tension and pressure on top of the drum and the drum oscillates back and forth to abrade the specimen. In NFPA 1991, a total of 25 cycles of abrasion are used. Separate specimens are then cut from the centre of the abraded area and tested for chemical permeation resistance against each of the 21 industrial chemicals in the prescribed chemical battery. The material cannot show permeation to any of the chemicals within a 1-hour period.
Permeation Test
The permeation tests for NFPA 1991 are performed according to ASTM F 739 with a breakthrough criterion of 0.1 μg/cm2*min. The different 21 industrial chemicals tested in accordance with NFPA 1991 are listed below.
AcetoneDiethylamineMethyl Chloride(gas)AcetonitrileDimethylformamideNitrobenzeneAmmonia, anhydrousEthyl AcetateSodium Hydroxide(gas)1,3-ButadieneEthylene OxideSulfuric Acid(gas)(gas)Carbon DisulfideHexaneTetrachloroethyleneChlorineHydrogen ChlorideTetrahydrofuran(gas)(gas)DichloromethaneMethanolToluene
When tested in accordance to the European standard EN 943-2, the tests are performed according to EN 374-3 with a breakthrough criterion of 1.0 μg/cm2*min. In the European standard, hepane is tested instead of hexane.
Many of the materials used today for protective garments are built up by different layers in a matrix. By combining different material layers in a matrix it is possible to achieve different important properties, e.g. a protection against specific chemicals at the same time as a abrasion resistance and puncture resistance. Layers comprising polymers or rubbers in such matrices are often used for their material properties as well as their permeation resistance against some chemicals.
One example of a multilayer chemical barrier material is disclosed in the international patent application WO 89/10840. The multilayer chemical barrier material is a composite multilayer material comprising a base sheet of material having internal open spaces, a first multilayer film sheet laminated to one face thereof and a second multilayer film sheet laminated to its opposite face, wherein said first multilayer film sheet comprises a film of ethylene vinyl alcohol, a film layer of nylon laminated to each face thereof, and an outer film of heat-sealable polyethylene, and wherein said second multilayer film sheet comprises a film of polyvinylidine chloride having a film of ethylene vinyl acetate laminated to the inner face thereof and a film of heat-sealable polyethylene laminated to its outer face. To adhere the first and second multilayer films to the base sheet, layers of adhesive are provided in between these layers. The material is said to show resistance to breakthrough to at least eight hours for the chemicals listed on the ASTM F1001, which is a list used according to NFPA 1991 for evaluation of chemical breakthrough resistance according to the method ASTM F 739. An evaluation of a type example of a suit which could be made of a material according to WO 89/10840 is shown in Table 1 below, where this suit is stated as the generic level A suit.
As mentioned however, to evaluate materials for use in PPE, such as protective garments or suits, today, the American standard NFPA 1991 is to be used for American certification. If a suit which e.g. comprises a composite multilayer material according to WO 89/10840, that is the generic level A suit, would be tested according to the tests specified for NFPA 1991, this suit would neither meet the basic requirements, such as for e.g. flex cracking resistance, abrasion resistance, and flammability resistance, nor the optional requirements, such as for e.g. flash fire escape protection. Another problem for such a suit is the limited use thereof. This suit should normally be disposed after one single exposure, rendering an expensive solution for users having to use such a suit more than once.
Moreover, to meet even the basic requirements for suits like the generic level A suit according to Table 1 below, an overcover suit has to be worn outside of these suits. This is a complicated solution for the end user due to the simple fact that they have to use two different suits in the right way at the same time. Another problem is the fact that some users may believe that the overcover or outer cover suit is optional for specific situations, while it in fact should be seen as an integral part of the suit system to meet even the minimum requirements of NFPA 1991. The problem with price in relation to number of uses is great for these 2 suits-systems as they normally are disposed in full after one single exposure.
There exists other chemical protective suit types, additionally to the generic level A suit according to Table 1 below, which are aiming at meeting the requirements according to NFPA 1991. One example of a material for such another suit is a 3 layer composite with 2 barrier films, wherein the composite is made of non-woven aramid fibers and polytetrafluoroethylene (PTFE). The PTFE is applied as a cast film providing a protective layer. One problem with this type of material and a suit made of such a material, when tested, is the poor mechanical strength, such as e.g. the low burst strength and low seam breaking strength. The poor mechanical strength properties of a suit made of such a material makes it prone to e.g. seam leakage and other mechanical damage. In such exposure events there is an evident risk for permeation of chemicals when reusing such a suit in a contaminated area and hence a suit made of such a material may and sometimes should be disposed after one single exposure. These disadvantages can be seen in Table 1 below for the alternative concept suit, which is one type of such a suit.
In other words, there is a need for materials for PPE, such as for suits and garments, which meet all of the requirements today, such as according to NFPA 1991, both in terms of the minimum basic requirements and the optional requirements, as well as according to the European harmonised standards that are used to determine compliance with the PPE directive 89/686/EEC for CE marking (e.g. EN 943-1 and EN 943-2). These materials should preferably at the same time have high values with reference to mechanical strength and durability amongst others. As an example, there is a need for a material for PPE which has a high protection against permeation of chemicals, i.e. the chemicals usually tested in standard tests for materials intended for protective garments, and which at the same time yields a high protection against flash fire escape and heat and flame as well as provides desired material properties, such as e.g. a high abrasion resistance, burst strength and puncture resistance. As another example, there is a specific need for protective suits made of such a preferred material as stated above and which are reusable.
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