NTC Project S02-CD01 (formerly I02-E01)

Transcription

1 1 Project Title: A Strategic Model for Functional Protective Clothing Project Team: Leader: Gang Sun, Division of Textiles and Clothing, UCD gysun@ucdavis.edu Phone: Members: You-Lo Hsieh Division of Textiles and Clothing, UCD Susan Kaiser Division of Textiles and Clothing, UCD Ning Pan Division of Textiles and Clothing, UCD Peg Rucker Division of Textiles and Clothing, UCD THIRD YEAR OBJECTIVES The third year s focus was to continue evaluation of materials available for firefighters uniforms, which provide multiple protective functions such as radiant heat protective performance, biocidal, antistatic, and physical properties. From these on results, a basic model of the ideal functional protective clothing could be designed for firefighters against fire, heat, biological, and chemical agents. This model could then be tested using simulated weather conditions and other field considerations such as garment storage and laundering practices. INTRODUCTION Environmental health and safety is an important issue in almost every industry, and functional protective clothing is required for many professionals such as firefighters, police officers, emergency medical service responders, military personnel, medical workers, chemical and biological researchers, environmental health workers, pesticide handlers. These protective garments are expected to provide protection for wearers against a variety of environmental hazards, and at the same time, avoid a negative impact on the performance or appearance of the wearers. More specifically, these protective garments should not add discomfort or heat stress to the wearers. The currently employed technologies in manufacturing protective clothing are dominated by barrier materials, and are used in uniforms for firefighters, medical workers, military personnel, and police officers. In those cases, textiles serve as barriers, blocking the transport of heat, fire, biological and chemical agents through the protective layer. These type of textiles are problematic; in addition to causing discomfort among wearers, work performance is hindered due to the bulkiness of the garment and heat stress induced by the lack of moisture transport through the water-resistant material. Moreover, emergency responders are not likely to use barrier materials for all cases of potential exposure because of the tremendous cost and waste incurred when using disposable protective clothing. Concerns arising from September 11 s terrorist attack, coupled with the problems of using currently-available barrier protective clothing, have created a need for development of new functional personal protective gear that can worn by professionals to provide protection against biological and chemical agents in addition to the usual barrier properties. The increased demands on the properties of the clothing bring more questions to textile scientists such as the following: What functions should the protective clothing provide for a specific professional? What are the necessary levels of protection that the clothing should possess? With the protective

2 2 functions included in the clothing, what are the performance and comfort properties that the clothing can maintain? How can dual or multi-protective functions be incorporated in the same clothing system? Which material can provide the best balance between the protective properties and the comfort provided? Many of the properties are negatively associated with each other since increased protection will usually reduce the comfort of the garments. Therefore, a fundamental investigation of the relationships between the performance and comfort of functional protective materials in the areas of physical, physiological, and social responses is not only necessary but critical to the development of novel textile technologies and the competitiveness of the textile industry. DESIGN AND APPROACH With our recent progress in self-decontaminating textile materials, we have identified the newly developed biocidal Nomex fabrics as an ideal material for firefighters uniforms with protective functions against fire, radiant heat, and biological agents. These fabrics are employed as model materials in evaluations of these protective functions according to industry and association standard testing methods. Protection against fire and heat can be quantitatively evaluated by using the 1993 NFPA standard on wildland firefighters protective clothing. Protection against biological agents will be examined by using AATCC test method 100 with gram-positive and gram-negative bacteria. Biocidal protection may also include functions for inactivating viruses, fungus, and spores, in addition to bacteria, since the latest anthrax attacks show the importance of those characteristics. The level of biological protection is the most critical issue here, due to the fact that firefighters, often the first responders to any scene of terrorist attacks or accidents, may face undetectable or unknown hazards at the scene. The research will thoroughly evaluate the impact of heat and UV exposure to biocidal functions of the fabrics, as well as the impact of the additional functions on the mechanical properties of the fabrics. RESULTS AND DISCUSSION Nomex is the most popular fabric material employed in firefighters uniforms. Nomex IIIa poplin (5.5oz), an outer-layer fabric for California wildland firefighters uniforms, was selected and treated with a diluted bleach solution containing varied amounts of active chlorine. The desired properties of the Nomex fabrics were measured according to the following model an ideal firefighters uniform possessing the properties shown in Figure 1. Based on the protective and regular properties that the uniforms should possess, we have evaluated durability of biocidal properties, and biocidal treatments to RPP and antistatic properties, RPP and UV exposures to biocidal and antistatic properties, as well as the multiple functions to physical properties of the fabrics. Some work was also done to fully understand the logistics of translating this technology from lab to field conditions. This includes consideration of laundering practices and protective gear storage procedures.

3 3 Ideal Protective Clothing for Firefighters Proper Protections Proper Properties Fire-Protective Radiant heat- Insulation Mechanical properties Transport Properties Bio-Protective Chem-Protective Comfortable Durable Figure 1. A strategic model of multifunctional firefighter s uniform 1. Durable and rechargeable biocidal properties The Nomex fabrics can easily acquire biocidal functions by simple treatment in a diluted chlorine bleach solution. This treatment is implemented in a commercial laundering process, and the function can be easily re-charged using a standard commercial washer. The chlorine bleach solution can convert amide N-H bonds to halamine (N-Cl) structures that provide biocidal functions. Although Nomex and Kevlar are both aromatic polyamide fibers, only Nomex can form stable halamine without compromising any mechanical properties; Kevlar fibers were hydrolyzed during the bleaching process. The treated Nomex fabrics are capable of killing both gram negative (Escherichia coli) and gram positive (Staphylococcus aureus ) bacteria in a contact time of 10 minutes, and the biocidal properties are durable, indicated by no reduction of biocidal power after three months of storage and after five repeated launderings. Figure 2 illustrates active chlorine on the biocidal Nomex fabrics over a storage life of 13 weeks. Chlorine Loss (% 100.0% 90.0% 80.0% 70.0% 60.0% 50.0% 40.0% 30.0% 20.0% 10.0% 0.0% ph -11 ph = 9 ph = Storage Time (week) Figure 2. Storage stability of biocidal Nomex fabrics

4 4 The results shown in Figure 2 prove that the fabrics could be stored for over a month with losing 50% of the original active chlorine, which also represents biocidal power. Furthermore, the biocidal functions are fully rechargeable in a chlorine bleaching process. The biocidal properties on the fabrics can be quantitatively measured by the amount of active chlorine, as shown in Table 3. We normally expect to have over 150 ppm of active chlorine on hydrophobic fabrics such as Nomex to provide biocidal effects in a short contact time. When the active chlorine amount dropped to 113 ppm the fabrics still could provide some reduction, but not a complete kill to all bacteria within a contact time of 10 minutes. When the contact time is prolonged, fabrics with as little an active chlorine content as 32 ppm still provided some kill over time, as seen in Table 1. Thus, in the following tests we used the active chlorine on the fabrics as an indicator of biocidal properties of the fabrics. Table 1. Antibacterial efficiency of selected chlorinated Nomex fabrics * (Bacteria concentration: 10 6 ~ 10 7 CFU/mL Run [Cl] in Sol'n (ppm) [Cl] on Fab. (ppm) Contact Time (minutes) (%) Bacteria Reduction Chlorination conditions for fabrics: Room temperature, ph=11, age=2 days, wash times=2, treatment time=30 minutes, no surfactant The active chlorine concentration on fabric is on fabric is significantly lower in this set of tests since a surfactant was not used. Later tests of samples chlorinated with.05% wt. Triton X-100 non-ionic surfactant solution showed a tremendous increase active chlorine concentration on the fabric. The samples treated with 100 ppm active chlorine in the surfactant solution yielded an average active chlorine content of 150 ppm on the fabric. At this level, antibacterial efficacy is can be considered very effective, as shown in Table Tensile strength of biocidal Nomex fabrics The Nomex fabrics were chlorinated in solutions containing 50 ppm, 150 ppm, and 1500 ppm active chlorine, respectively, before the tensile strength tests. The tenacity of the chlorinated Nomex fabrics was not significantly affected by different chlorine concentrations in bleaching solutions and chlorination time (Figure 3). When the fabrics were bleached with a chlorine concentration of 1500 ppm, the tenacity was almost the same as those bleached at 50 ppm and 150 ppm, respectively. Since 1500 ppm of chlorine bleach will never been employed in practice, the bleaching time of using 1500 ppm was only extended to 30 minutes. Although as the chlorination time increased, a slight decrease of the tenacity was observed, but such a lengthy

5 5 bleaching duration (over 60 minutes) is not realistic in practice. The chlorine resistance of Nomex polymer showed in this study is indeed interesting since Kevlar is very vulnerable to chlorine solution. A similar treatment of Kevlar fabrics severely damaged the tensile strength of the fabrics. The cause of such a difference is still under investigation Tensile Loss (%) ppm 300 ppm Chlorination Time (min) Figure 3. Tensile loss of Nomex fabrics after chlorination 3. Firefighter Considerations The biocidal treatment of Nomex must be simple enough for firefighters to apply in station. Structural firefighters at the Sacramento Metropolitan Fire District were interviewed about their protective gear use and laundering practices. Turnouts, the uniforms used for fighting fires, are only worn during the actual fire. Otherwise, emergency personnel and firefighters at the station use station-wear, a more comfortable protective gear option made of Nomex IIIa. Station-wear is also worn during non-fire emergency calls, such as car accidents and medical house calls. Although the threat of fire is not applicable in these situations, firefighters reported high incidences of uniform soiling by unknown chemicals and bodily fluids. Each emergency call presents a number of unpredictable threats to a responder, and often calls occur continuously throughout a day. In such situations, firefighters and other emergency personnel reported that they were unable to change their contaminated gear as frequently as desired. The soiled garments often remained in contact with the body for several hours. Station-wear, unlike traditional turnout gear, is washed by the firefighters in station. Therefore, a simple modification of the washing protocol to allow for chlorination, and thus chemical and biological protection, would be possible. CONCLUSIONS A strategic model of protective clothing for firefighters was established, and several key properties of the Nomex fabric have been further evaluated in the third year of this research. Treatment of Nomex by a chlorinating agent in a surfactant solution gives the fabric powerful and rechargeable biocidal properties without foregoing other valuable functions. With the addition of the biocidal properties, the radiant heat protective performance, mechanical properties, antistatic properties, and durability of the fabrics were unaffected. Treated but un-

6 6 used fabric has a long storage life, and fabric that has been used can be re-charged via simple chlorination processes to restore biocidal properties. Radiant heat could damage the biocidal functions, but if the exposure is limited, most of the lost biocidal functions can be recharged. UV irradiation did not show any impact to the biocidal properties, but affected antistatic properties of the fabrics. Because stationwear used by both firefighters and emergency personnel is cleaned using on-site commercial washing machines, it is relatively to integrate this technology into the current laundering protocol. FUTURE WORK We will continue the evaluation of overall performance of the multi-functional Nomex fabrics in the categories of thermal protection, comfort performance, mechanical properties, and biological/chemical protective functions. Due to technical difficulties, a series of tests using both a launder-ometer and weather-ometer remains to be conducted within the next few months, which will provide us information on the durability of the special properties under any potentially severe environment of applications. With these results, we will be able to finalize a model of textile materials that can both provide necessary protection against several hazardous factors but still maintaining good comfort performance. In addition, we hope to further integrate psychological and sociological evaluations from the firefighters interviewed to ensure the relevance of our model to their needs in the field. OUTREACH TO INDUSTRY: With a model developed from a comprehensive study of performance and protections against specific working environment hazards, the textile industry can have a convenient manual for optimizing materials and chemical treatments on the fabrics used for firefighters protective clothing. The results of the study may stimulate production and development of innovative textile materials for the special protective clothing. As a result, people may have increased safety in the work environment. Companies such as Southern Mills, Springs Industry Inc. may get the direct benefits. In addition, this research is highly relevant to protection of first responders and fits the research priorities of the Department of Homeland Security. It is also related to emergency responder needs as identified and described by RAND institute research in conjunction with NIOSH objectives. URL: