posted on 2023-11-09, 08:07authored byNatalie
A. Vest, Miguel O. Convento, Danixa Rodriguez-Melendez, Dallin L. Smith, Jaime R. Ayala, Jazmine Aiya D. Marquez, Maya D. Montemayor, Yufeng Quan, Andrea O. Afonso, Ethan T. Iverson, Sarbajit Banerjee, Qingsheng Wang, Jaime C. Grunlan
The flammability of cotton fabric
poses a risk of injury and death,
specifically in aerospace applications, where oxygen concentrations
are higher than typical atmospheric conditions. In an effort to reduce
its flammability in high-oxygen environments, cotton was treated with
a 12-bilayer coating consisting of poly(allylamine hydrochloride)
(PAH), poly(sodium phosphate) (PSP), and ammonium pentaborate tetrahydrate
(APB). With a formulation of 6.5% PAH/8% PSP+5% APB, cotton is rendered
self-extinguishing, exhibiting a reduction in peak heat release and
fire growth capacity of 72 and 88%, respectively. Moreover, cotton
remains self-extinguishing in highly oxygenated environments, having
a limiting oxygen index of 35.5%. This layer-by-layer assembled coating
operates via an intumescent mechanism that is aided by the formation
of borate esters cross-linking the char structure, resulting in reduced
gas diffusion and increased thermal stability. This unique, scalable
treatment is especially promising for space exploration and could
potentially be used in other polymeric materials.