Clays as Inhibitors of Polyurethane Foams’ Flammability

Abstract

Polyurethanes are a very important group of polymers with an extensive range of applications in different branches of industry. In the form of foams, they are mainly used in bedding, furniture, building, construction, and automotive sectors. Due to human safety reasons, these applications require an appropriate level of flame retardance, often required by various law regulations. Nevertheless, without the proper modifications, polyurethane foams are easily ignitable, highly flammable, and generate an enormous amount of smoke during combustion. Therefore, proper modifications or additives should be introduced to reduce their flammability. Except for the most popular phosphorus-, halogen-, or nitrogen-containing flame retardants, promising results were noted for the application of clays. Due to their small particle size and flake-like shape, they induce a “labyrinth effect” inside the foam, resulting in the delay of decomposition onset, reduction of smoke generation, and inhibition of heat, gas, and mass transfer. Moreover, clays can be easily modified with different organic compounds or used along with conventional flame retardants. Such an approach may often result in the synergy effect, which provides the exceptional reduction of foams’ flammability. This paper summarizes the literature reports related to the applications of clays in the reduction of polyurethane foams’ flammability, either by their incorporation as a nanofiller or by preparation of coatings.

Recent Advancements in Flame-Retardant Polyurethane Foams: A Review

“…Literatures also reports the in-situ functionalization of PU foams using FR additives. , Postsynthesis improvements of PU foams for flame retardancy through coating is highly effective, independent of foam type (rigid or flexible), offers better preservation of mechanical properties, and facilitate the use of FRs that are difficult to homogenize with PU foam formulations. Sol–gel, layer-by-layer (LBL), plasma, and in-situ polymerization are some of the coating methods that have been employed to obtain FR PU foams .…”

“…Nanoclays are also known to effectively improve the flame retardancy of polymer–clay nanocomposites, in addition to mechanical properties. , In this sense, PU-nanoclay composite foams showed a decreased rate for both peak heat release and smoke production by offering the thermal insulating effects. FR property of Na-montmorillonite nanoclay modified with diphosphonium (cation exchange capacity, 128 mequiv/100 g) on rigid PU foams has also been investigated .…”

Recent Advances in Development of Waste-Based Polymer Materials: A Review

“…Flizikowski, Wełnowski, and Dudziak [20,21] designed and constructed supersonic aero-kinetic mill and studied the impact of grinding conditions on the size reduction of montmorillonite-nanofiller commonly used in polymer composites, e.g., as flame retardant additive [22].…”

Characterization and Properties of Water-Blown Rigid Polyurethane Foams Reinforced with Silane-Modified Nanosepiolites Functionalized with Graphite

“…Reports on the use of sepiolite as a halogen-free FR of PU foams are scarce [ 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Sepiolite is a natural clay mineral of the structural family known as the 2:1 phyllosilicates, with (Si 12 Mg 8 O 30 )(OH) 4 (OH 2 ) 4 ·8H 2 O as theoretical unit cell formula [ 23 ].…”