Polyurethanes (PUs) are versatile and widespread, particularly as flexible and rigid foams. To avoid isocyanates and other toxic reagents required for synthesis, such as phosgene, alternative synthetic routes have been utilized to produce non-isocyanate polyurethanes (NIPUs). A thermally and flame-resistant rigid NIPU was produced from environmentally benign and bio-sourced ingredients, requiring no catalyst or solvents. A foamed structure was obtained by the addition of glutaraldehyde and four different carboxylic acids: malic acid, maleic acid, citric acid, and aconitic acid. The resulting morphology, thermal degradation, and flame resistance of each foam were compared. The properties vary with each carboxylic acid used, but in each case, peak thermal degradation and peak heat release are postponed by >100 °C compared to commercial rigid PU foam. Furthermore, in a butane torch test, NIPU foams exhibit an 80% higher remaining mass and a 75% reduction in afterburn time, compared to commercial polyurethane. This bio-based polyurethane eliminates the hazards of traditional PUs, while imparting inherent thermal stability and flame resistance uncharacteristic of conventional foams.

Chitosan is one of the most abundant biopolymers on earth. It is used as a nontoxic alternative in a wide range of medicines, packaging, adhesives, and flame retardants. Chitosan is poorly soluble in neutral or alkaline solutions, but it dissolves in solutions of weak acids, such as acetic acid or citric acid, both of which occur naturally. As a replacement for formaldehyde-containing resins in engineered wood, a chitosan-acid mixture acts as a low-cost, nontoxic adhesive for natural wood that also offers fire protection by forming a char barrier. Pentaerythritol was studied as an additive due to its similarity to glycerol (a common plasticizer for chitosan) and its potential flame retardant benefit. The properties of chitosan adhesives produced with acetic acid and citric acid are compared, and moderate thermal treatment is applied to facilitate covalent bonding (e.g., Maillard reaction) that improves water resistance. Tensile shear strengths of >1 MPa are obtained on lap joints. The unique combination of fire protection and adhesion for wood makes these low cost, biobased systems very appealing.

The soft nap and deep pile that impart comfort and warmth to cotton fleece also amplify its flammability. Using ambient aqueous processing, an environmentally benign polyelectrolyte complex (PEC), consisting of poly(allylamine hydrochloride) and sodium hexametaphosphate, was deposited on cotton fleece. This treatment adds only 12.5% weight, reduces peak heat release by 68% and total heat release by 74%, and protects from fire via intumescence. Without treatment, fleece burns aggressively with long afterburn and afterglow times, leaving no residue. With the applied PEC, the fabric self‐extinguishes within a few seconds and exhibits no afterglow. In addition, it withstands at least five simulated laundering cycles in alkaline detergent, maintaining a 57% reduction in fire growth capacity afterward. The original soft surface can be restored to the fleece by manual brushing. This simple and environmentally benign treatment provides an opportunity to effectively protect highly flammable textured cellulosic textiles in a safe way.

Over 60 million tons of polyethylene terephthalate (PET) fibers are produced annually for clothing, upholstery, linens, and carpeting. Despite its widespread use, the versatility of PET is constrained by its flammability, which poses a particular fire hazard to homes with synthetic furnishings. To mitigate this fire risk, a polyelectrolyte complex (PEC) solution composed of polyallylamine hydrochloride and poly(sodium phosphate) is deposited onto the surface of 100% polyester fabric to render it self-extinguishing and eliminate melt dripping. A buffered solution of acetic acid, citric acid, or formic acid is used to initiate ionic complexation, rendering the PEC water resistant. Buffer identity affects deposition, but does not significantly influence the intumescent mechanism. This rapidly deposited aqueous coating primarily operates by facilitating production of an insulating char layer that limits the heat release and degradation of polyester into volatile byproducts.