In conjunction with the Combat Capabilities Development (CCDC) Command Soldier Center, Warwick Mills has completed a preliminary evaluation on the toxicity of Fire Resistant (FR) candidates used in shelter laminates. Several chemistries were examined as alternatives to the halogenated FR chemistries used in legacy laminate systems. Some candidates with promising features for FR performance, low leaching, and flame toxicity characteristics were developed. This work is in line with Environmental Protection Agency programs and initiatives for environmentally friendly materials and sustainability, such as Executive Order 13693 and Sustainability Materials Management.
This study focused on a number of non-halogenated FR candidates of various configurations, with various particle sizes and chemistries. FR candidate coupons size 12 inch x 12 inch were tested in accordance with vertical flame testing, breaking strength, and gelbo flex durability testing as a pre-qualification test. Candidate samples that passed this set of basic fabric testing requirements were sent for toxicity characteristic leaching procedure and Toxicity Test Screening. All candidates showed promising results below toxicity limits.
In addition, current legacy general purpose laminate MIL-PRF-44103D Green and Tan samples were tested for comparison for toxicity, along with Warwick’s current General Purpose uncoated base laminate with no FR. Of note from the many toxic materials screened, are results that showed Hydrochloric Acid was detected for MIL-PRF-44103D Camouflage Green and Desert Tan at the 500 parts per million limit, but not for the Warwick base laminate, and MIL-PRF-44103D Camouflage Green showed detection of the metal lead but others did not.
Based on preliminary research, three viable Warwick FR candidates for general purpose laminates were downselected, which will be exposed to further testing by CCDC Soldier Center. A following effort will be required to provide more in depth conditioning, weathering, and environmentals in accordance with MIL-PRF-44103D. Additional toxicity testing is recommended, such as flammability using microscale combustion calorimetry; oxygen depletion calorimetry; pyrolysis unit with gas chromatograph/mass spectrophotometer; transition temperatures and enthalpies of fusion and crystallization of polymers, compositional analysis by thermogravimetry; simultaneous differential scanning calorimetry and thermogravimetry, oxygen index, and heat and visible smoke release rates.