Layer-by-Layer-Coated Cellulose Fibers Enable the Production of Porous, Flame-Retardant, and Lightweight Materials

Abstract

New sustainable materials produced by green processing routes are required in order to meet the concepts of circular economy. The replacement of insulating materials comprising flammable synthetic polymers by bio-based materials represents a potential opportunity to achieve this task. In this paper, low-density and flame-retardant (FR) porous fiber networks are prepared by assembling Layer-by-Layer (LbL)-functionalized cellulose fibers by means of freeze-drying. The LbL coating, encompassing chitosan and sodium hexametaphosphate, enables the formation of a self-sustained porous structure by enhancing fiber−fiber interactions during the freeze-drying process. Fiber networks prepared from 3 Bi-Layer (BL)-coated fibers contain 80% wt of cellulose and can easily self-extinguish the flame during flammability tests in vertical configuration while displaying extremely low combustion rates in forced combustion tests. Smoke release is 1 order of magnitude lower than that of commercially available polyurethane foams. Such high FR efficiency is ascribed to the homogeneity of the deposited assembly, which produces a protective exoskeleton at the air/cellulose interface. The results reported in this paper represent an excellent opportunity for the development of fire-safe materials, encompassing natural components where sustainability and performance are maximized.

Layer-over-Layer Electrostatic Self-Assembly of Bioresourced Compounds in Thermoreversible Polylactide Gels as an Effective Approach to Enhance the Flame Retardancy of Aerogels

“…The schematic in Figure c illustrates the possible flame retardant mechanism of the PLLA@SA@CS@PA aerogel. When exposed to fire, PA in the outer layer of the aerogel can decompose to produce phosphoric or polyphosphoric acid, which can promote the dehydration of CS and the formation of the carbonized layer. , Similar to CS, SA also acts as a charring agent with its polysaccharide rings and enormous hydroxyl groups and can further enhance the intensity of the carbonized layer Figure S2 shows the Raman spectrum of the char residue obtained after the burning of PLLA@SA@CS@PA aerogel.…”

Cellulose Nanocrystals/Melamine/Phytic Acid Nanocomposites as Thermally Insulating and Flame-Retardant Structural Materials

“…However, the usage of traditional halogenated FRs is limited due to considerable toxic and hazardous carcinogenic byproducts during a fire. − Therefore, developing environmentally friendly FRs that are efficient and low in toxicity is crucial. Recently, renewable, biobased FRs such as nucleic acids, chitosan, and lignin have been extensively used to solve this issue and replace the fossil-fuel-based materials, but their insulating and fire-retardant performances are still big challenges, especially their performance in maximum degradation temperatures, as presented in Table S1, − although solid heat conduction was substantially reduced by forming a dense-phase carbon barrier.…”