Flame‐Retardant Properties and Characterization of Nylon/Tannic Acid Electrospun Fibers

Abstract

Incorporating flame‐retardant compounds into polymeric composites is a key area of materials research. Halogenated flame‐retardants are most widely used; however, they are under scrutiny due to health and environmental concerns which increases interest in eco‐friendly alternatives. Tannic acid (TA) is a naturally occurring polyphenol with flame‐retardant properties. To overcome current challenges incorporating TA into polymer composites at high concentrations, nonwoven mats of nylon/TA composite nanofibers are fabricated using electrospinning. TA is incorporated at concentrations up to 50 wt% while maintaining uniform fiber morphology. Thermogravimetric analysis (TGA) shows TA within the nanofibers degrades at 230 °C and nylon degrades at 400 °C, irrespective of the initial TA concentration. Char yield increases with the concentration of TA, resulting in a maximum of 25% for fibers containing 50 wt% TA. Flame resistance is characterized using microscale combustion calorimetry (MCC) which shows composite fibers have reduced heat capacity and total heat release (THR) indicating flame resistance at ≥75 rel. wt%. Finally, ignition tests and condensed phase analysis show that TA acts as an intumescent material when embedded within the polymer matrix which produces an insulating foam‐like char under direct heat that eliminates flaming melt dripping and results in self‐extinguishing nanofibers.

Multifunctional Biobased Polyurethane/Tannic Acid Composites with Controllable Damping, Flame-Retardant, and Ultraviolet-Shielding Performances

“…In particular, the PU/TA15 and PU/TA20 composites formed relatively complete and compact residual char with reduced surface collapse, showing the intumescent behavior of bio-TA within bio-PU matrix . From the schematic illustration for the mechanisms of flame retardancy displayed in Figure f, it can be found that bio-TA embedded within bio-PU matrix acts as an intumescent material and produces an insulating foam-like char, offering adequate barrier protection by impeding heat transfer and isolating oxygen, thereby further inhibiting bio-PU combustion. , …”

“…Additionally, Figure e reveals that after conducting the CCT, the surface of the PU0 elastomer showed almost no residual char. However, the residual char of bio-PU/TA composites significantly increased after the introduction of bio-TA owing to the intumescent char formation from the decarboxylation and subsequent decomposition of bio-TA . In particular, the PU/TA15 and PU/TA20 composites formed relatively complete and compact residual char with reduced surface collapse, showing the intumescent behavior of bio-TA within bio-PU matrix .…”

“…45 From the schematic illustration for the mechanisms of flame retardancy displayed in Figure 4f, it can be found that bio-TA embedded within bio-PU matrix acts as an intumescent material and produces an insulating foam-like char, offering adequate barrier protection by impeding heat transfer and isolating oxygen, thereby further inhibiting bio-PU combustion. 44,46 3.5. Analysis of Multifunctional Performances of Bio-PU/TA Composites.…”