Aluminum hydroxide multilayer assembly capable of extinguishing flame on polyurethane foam

Abstract

Polyurethane foam found in household furnishings and bedding creates a severe fire hazard, resulting in loss of life and property each year. In an effort to reduce the flammability of polyurethane foam, a polyelectrolyte multilayer (PEM) coating, comprised of polyethylenimine and polyacrylic acid-stabilized aluminum hydroxide (ATH), was deposited onto foam using layer-by-layer (LbL) assembly. PEM coatings with and without incorporation of ATH were deposited and compared to assess the effectiveness of ATH on flame suppression. All recipes resulted in conformal coatings, maintaining the open cellular structure of the foam. Only three bilayers of PEI/ PAA-ATH retained the shape of foam after exposure to a butane torch flame for 10 s. With six bilayers, the flame was extinguished, which prevented flashover. Cone calorimetry revealed that this 6 BL coated foam exhibited a 64 % reduction in peak heat release rate and a 44 % reduction in maximum average rate of heat emission. This work demonstrates an extraordinarily effective flame-retardant nanocoating that uses environmentally benign chemistry and relatively few deposition steps, prepared using LbL assembly.

Combination Intumescent and Kaolin‐Filled Multilayer Nanocoatings that Reduce Polyurethane Flammability

“…[20] Despite all its advantages, the main drawback of the LbL assembly technique is the need to build a thick enough film to achieve sufficient fire resistance, which increases processing time and cost. [21] Kaolin (KAO), with a chemical formula of Al 2 Si 2 O 5 (OH) 4 , is attractive as a composite filler due to its abundancy, low cost, and shielding effect in polymers. [22] It has an asymmetric plate structure with the superposition of the tetrahedral and…”

“…In general, phosphorus‐containing coatings exhibit a condensed phase flame retardant mechanism, forming a solid char barrier to interrupt the polymer combustion process of fuel generation and heat feedback from burning polymer decomposition products . Despite all its advantages, the main drawback of the LbL assembly technique is the need to build a thick enough film to achieve sufficient fire resistance, which increases processing time and cost …”

Mechanical properties, thermal stability, sound absorption, and flame retardancy of rigid PU foam composites containing a fire‐retarding agent: Effect of magnesium hydroxide and aluminum hydroxide

“…1,2 As a result, there are strict safety guidelines for home furnishings in order to reduce the threat to human life and economic losses. 3 An additional concern is that selected halogen-containing flame retardants have been banned because they have poor environmental profiles, along with some human health and toxicity effects. 4,5 Therefore, people are concerned about the development of effective halogen-free flame retardants.…”

“…Alumina trihydrate (Al (OH) 3 ) and magnesium hydroxide (Mg (OH) 2 ) that account for greater than 50% by weight have been popular fire retardants worldwide. 12 The most common route to produce aluminum hydroxide (Al (OH) 3 ) is known as Bayer process, and bauxite (composed mainly of Al (OH) 3 ) and impurities such as SiO 2 , Fe 2 O 3 , and TiO 2 are its main raw materials. 13,14 Initially, bauxite is dissolved in a hot (70-90°C) NaOH solution for the formation of sodium aluminate, according to the general expression:…”

“…After filtration steps for the removal of undissolved impurities, the clarified sodium aluminate solution is cooled down to precipitate Al (OH) 3 :…”