Waterborne Intumescent Fire-Retardant Polymer Composite Coatings: A Review

Abstract

Intumescent fire-retardant coatings, which feature thinner layers and good decorative effects while significantly reducing heat transfer and air dispersion capabilities, are highly attractive for fire safety applications due to their effective prevention of material combustion and protection of materials. Particularly, the worldwide demand for improved environmental protection requirements has given rise to the production of waterborne intumescent fire-retardant polymer composite coatings, which are comparable to or provide more advantages than solvent-based intumescent fire-retardant polymer composite coatings in terms of low cost, reduced odor, and minimal environmental and health hazards. However, there is still a lack of a comprehensive and in-depth overview of waterborne intumescent fire-retardant polymer composite coatings. This review aims to systematically and comprehensively discuss the composition, the flame retardant and heat insulation mechanisms, and the practical applications of waterborne intumescent fire-retardant polymer composite coatings. Finally, some key challenges associated with waterborne intumescent fire-retardant polymer composite coatings are highlighted, following which future perspectives and opportunities are proposed.

Keywords: environmental protection; fire retardancy; intumescence; polymer; safety; waterborne coating.

Figure 2

Composition and modification of waterborne acrylic resin: (a) Structure of waterborne acrylic resin and its monomers. (b) Fluorine–silicone modification. (c) Polyisocyanate crosslinking modification. (d) 2-(3,4-Epoxy) ethyltriethoxysilane modification. Adapted with permissions from Refs. [91,96,97,98]. Copyright 2021@American Chemical Society, Copyright 2018@Elsevier Publisher, Copyright 2015@Royal Society of Chemistry, Copyright 2020@Elsevier Publisher.

Figure 3

Enhancement of the flame retardancy of waterborne acrylic resin by combining other materials or adjusting formulations: (a) Preparation of waterborne acrylic-resin-based intumescent flame-retardant coatings using melamine polyphosphate (MPP) as an intumescent flame retardant, graphite nanoplates (GNPs) as a synergistic flame retardant/conductive filler, and acrylic resin as a film-forming agent, showing (b) excellent flame-retardant performance. (c) Improving flame-retardant effects by adjusting the ratio of traditional flame-retardant additives. (d) Mixed carbon materials were applied as fire-retardant filler in the waterborne acrylic-resin-based intumescent flame-retardant coatings. Adapted with permissions from Refs. [99,100,101]. Copyright 2021@Springer, Copyright 2021@Elsevier Publisher, Copyright 2021@Elsevier Publisher.

Figure 1

(a) The IFR systems consist of an acid source, a gas source, and a carbon source. Representative examples: (a) Phytic acid as the acid source, thiourea as the gas source, and pentaerythritol as the carbon source. (b) The sulfonate group works as both the acid and gas sources, while the benzimidazole group acts as the carbon source. (c) Graphene oxide, phosphorus atom, and nitrogen atom/amino functional groups act as the carbon source, acid source, and gas source in the GO/HCPA system, respectively. Adapted with permissions from Refs. [62,63,64]. Copyright 2022@Elsevier Publisher, Copyright 2022@Elsevier Publisher, Copyright 2022@Springer Nature, Copyright 2020@Royal Society of Chemistry, Copyright 2013@American Chemical Society, and Copyright 2021@Elsevier Publisher.

Figure 4

The principal methods for preparing waterborne epoxy dispersions include (a) phase inversion, (b) epoxy chemical modification, (c) ultrasound-assisted supercritical carbon dioxide (scCO₂) technology, and (d) amphiphilic poly(hydroxyaminoethers) emulsifiers. Adapted with permissions from Refs. [106,107,108,109]. Copyright 2019@Elsevier Publisher, Copyright 2024@American Chemical Society, Copyright 2021@Elsevier Publisher, Copyright 2021@Wiley.

Figure 5

Methods to enhance the performance of waterborne epoxy resins: (a) structural design, (b) grafting, (c) blending, and (d) optimization of curing agent content. Adapted with permissions from Refs. [111,112,113,114]. Copyright 2022@Elsevier Publisher, Copyright 2021@Elsevier Publisher, Copyright 2021@Elsevier Publisher, Copyright 2024@MDPI.

Figure 6

(a) The synthesis method of waterborne polyurethane, the required raw materials, and (b) the synthesis route. Adapted with permissions from Refs. [116,117]. Copyright 2015@Elsevier Publisher, Copyright 2022@Springer.

Figure 7

The approaches to modifying waterborne polyurethane: (a–d) incorporating fillers into the polyurethane matrices, and (e–g) modifying the basic building blocks of polyurethane with functional monomers. Adapted with permissions from Refs. [118,119]. Copyright 2019@Elsevier Publisher, Copyright 2019@Elsevier Publisher.

Figure 8

Schematic illustration of silicone emulsion film formation process. Adapted with permissions from Ref. [124]. Copyright 2020@MDPI.

Figure 9

(a) Procedure for preparing waterborne silicone coating; (b) self-cleaning and anti-fouling properties of the coating. Adapted with permissions from Ref. [125]. Copyright 2023@Elsevier Publisher.

Figure 10

Common fillers for enhancing coating performance: (a) inorganic materials, (b–d) two-dimensional materials, (e) organic materials, and (f) organic/inorganic composites. Adapted with permissions from Refs. [112,129,130,131,132,133]. Copyright 2018@Elsevier Publisher, Copyright 2023@MDPI, Copyright 2021@Elsevier Publisher, Copyright 2022@Elsevier Publisher, Copyright 2018@Elsevier Publisher, Copyright 2024@Elsevier Publisher.

Figure 11

The role of additives in intumescent flame-retardant coatings: (a) Sodium alginate as a thickener, and (b) its viscoelasticity. (c) Hexagonal boron nitride nanosheets to improve coating stability. (d) Surfactant-modified coatings. (e) The synergistic effects of defoamers and film-forming additives on coating performance. Adapted with permissions from Refs. [137,138,139,140]. Copyright 2022@Elsevier Publisher, Copyright 2020@MDPI, Copyright 2021@Elsevier Publisher, Copyright 2021@Elsevier Publisher.

Figure 12

Intumescent flame-retardant mechanism: (a) The synergistic flame-retardant mechanism of hollow glass microspheres (HGMs) combined with melamine polyphosphate and starch (M-S system). (b) Phosphorus–nitrogen-containing silicone oil (PNSO) intumescent coating on polyester fabric. (c) Phytic acid sodium salt hydrate combined with N-[3(trimethoxysilyl)propyl]-N,N,N-trimethylammonium chloride as a coating. (d) Flame-retardant chemistry in the pyrolysis zone. Adapted with permissions from Refs. [133,142,143,144]. Copyright 2024@Elsevier Publisher, Copyright 2024@Elsevier Publisher, Copyright 2024@Springer, Copyright 2024@Elsevier Publisher.

Figure 13

Industrial applications of intumescent flame-retardant coatings. Adapted with permissions from Refs. [99,149,150,151,152]. Copyright 2020@Elsevier Publisher, Copyright 2023@American Chemical Society, Copyright 2022@Elsevier Publisher, Copyright 2021@Springer, Copyright 2021@Elsevier Publisher.