Protective Materials

Spore bio-terror agents such as anthrax are the most menacing bio-terror species to guard against.  They are very tenacious and adhere strongly to materials such as fabric and filter medium. Anthrax spores are very hardy and can survive superheated steam for two hours.  They can survive for an extended period of time under dry conditions.  Anthrax can be destroyed under certain conditions.  They are killed in air on exposure to ultraviolet light. Other methods include incineration, steam autoclaving, exposure to formaldehyde, glutaraldehyde, hydrogen peroxide, household bleach, ethylene oxide, beta-propiolactone and peracitic acid.  Such processes are conducted as decontamination processes.  Until now, there were no biocides or antimicrobials deemed effective for anthrax preventative measures.  The presented research has demonstrated such an antimicrobial (HM 4100). The antimicrobial has been incorporated into collective and personal protective materials including nonwovens and is capable of destroying anthrax in-situ.  Such a material has wide ranging bio-defense, homeland defense and commercial implications.

Cellulose fibers containing polymeric D-(+)-Trehalose and ß-cyclodextrins were prepared by cross-coupling with appropriate alkyl spacers. These functionalized cellulose fibers were chemically inert and robust enough to endure extended exposure to stressful conditions. They were demonstrated to absorb organic pollutants such as methyl parathion (MPT) and p-nitrophenol (pNP) in aqueous medium. Upon exposure to methanol, these compounds were released out into the organic medium for safe disposal and thereby the functionalized cellulose fibers were recovered for cycled use. The functionalized cellulose fibers were employed as physical supports of organophosphorous hydrolase (OPH), organophosphorous acid anhydrolase (OPAA), and haloalkane dehalogenase (HD) enzyme which rapidly degrade chemical agents upon counter. These enzyme friendly trehalose/OPH-OPAA-HD/polyelectrolytes bearing cellulose fibers could serve as an efficient platform for destroying biological and chemical threat agents.

The concept of using heavy weight nonwoven wipes to instantaneously absorb/wick away liquid toxins and then hold the toxin is relatively new. This dual mechanism is important to decontaminate human skin and military equipment. Earlier presentations in public domain have focused mainly on chemical warfare simulants and toxic industrial chemicals such as Pinacolyl methylphosphonate and toluene. In order to validate and verify earlier results with above mentioned simulants, it is important to have results with real chemical warfare agents or neat agents. This task is extremely difficult as only certain Government laboratories and Defense Contractor laboratories have the access and permission to work with nerve agents. Recent collaborative study by Texas Tech University with a Government laboratory has for the first time experimented with a real agent on multilayered sorbent nonwoven composites.

As this is a highly sensitive result, further details of the experiments are not currently provided. However, clearance to release data will be obtained by April 2007. The study is extremely new and has been not reported in any nonwoven and textile industry related outlets.

The presentation at the INTC 2007 will feature results on the decontamination/wiping capability of real chemical warfare agent by nonwoven wipe and will definitely open up new ideas and opportunities for nonwoven sector to eye on military opportunities. The presentation will only feature scientific/technical results involving chemical agent.

Polypropylene fibers are widely employed as biological and chemical barrier materials in healthcare protective clothing.  Incorporation of biocidal functions onto the materials will significantly improve the protection to the professional.  Halamine structures can provide rechargeable biocidal and chemical detoxification functions on many materials and have been applied to woven fabrics by wet chemical finishing. However, the chemical treatment cannot work on polypropylene fibers.  In this research, a novel radical reaction was attempted during fiber extrusion process to chemically graft halamine precursors onto polypropylene fibers.  This process can easily graft allyl or vinyl halamine precursor to polypropylene fibers.  The thus produced ,fibers can be easily converted to halamine structures by chlorine bleaching, and the chlorinated polypropylene fibers demonstrated powerful biocidal functions against both gram negative and gram positive bacteria.  The reaction conditions and parameters of the extrusion process, as well as the impact on graft polymerization reaction, will be discussed in the presentation.  This process can be employed in producing meltblown nonwoven fabrics for biological protective clothing and filters. 

Transport mechanism of gases through microporous membranes were investigated and used in the construction of chemically protective materials. Experiments were conducted to evaluate the permeation of air and mimics of harmful gases such as mustard, sarin, etc through nylon and polypropylene microporous membranes at different temperatures and pressure differences. A mathematical model was constructed based on membrane spatial properties and permeate characteristics and compared to experimental data. Acceptable correlations were observed.