Eco-Friendly Flame-Retardant Additives for Polyurethane Foams: A Short Review

Abstract

Polyurethane (PU) materials are extensively used in the construction industry as core material insulation for sandwich panel application, such as wall cladding, structure insulation and roof panel. Demands on PU application have escalated given its significant advantages to reduce energy consumption. Meanwhile, rigid PU (RPU) foams are combustible materials characterized by rapid flame spread, high heat-release rates, and ability to produce large quantities of toxic gases in original form. Thus, flame-retardant (FR) additives are used to improve the thermal properties of PU. However, some commercial additives used today have are hazardous to humans and the environment, and their extensive application is limited by their negative effects on polymer mechanical properties. Accordingly, identifying materials that are environmentally friendly and harmless to humans has become urgent. Some alternative additives that are gaining research interest are clay and fly ash, which are natural and recyclable resources that can enhance the FR properties of other polymers. However, room for improvement is always present as the related technology is continually being developed. This review focuses on studies aiming to enhance the flame retardancy of RPU foam using fly ash and local clay as additives.

Clays as Inhibitors of Polyurethane Foams’ Flammability

“…As mentioned above, the introduction of nanometric aluminosilicate particles into the polymer improves its properties. What is mainly reported, the addition of aluminosilicate can improve the compressive and tensile strength, as well as Young's modulus and elongation at break [131,132]. In addition to mechanical performance, other properties can be significantly improved, including the barrier properties important for thermal stability and flammability of material [133,134].…”

Determining the best flame retardant for rigid polyurethane foam—Tris(2‐chloroisopropyl) phosphate, expandable graphite, or silica aerogel

“…For example, if the cellular polymer has closed-cells, it would be rigid in nature, display excellent dimensional stability, has low water absorption, and be suitable for thermal insulation due to low thermal conductivity, low density, high strength-to-weight ratio, and low moisture permeability. 3 Consequently, rigid polyurethane foams (RPUFs) are widely used in various fields, such as construction, household appliances, automotive, and packaging, because of their exceptional insulation and mechanical properties. 3 In spite of these advantages, a major drawback restricting their application is the high flammability of RPUFs, since the base petrochemical material is highly combustible in its original form.…”

“…3 Consequently, rigid polyurethane foams (RPUFs) are widely used in various fields, such as construction, household appliances, automotive, and packaging, because of their exceptional insulation and mechanical properties. 3 In spite of these advantages, a major drawback restricting their application is the high flammability of RPUFs, since the base petrochemical material is highly combustible in its original form. 3 Thus, flame retardant additives are usually added into the PU blend in order to obtain RPUFs with good flame retardancy.…”

“…3 In spite of these advantages, a major drawback restricting their application is the high flammability of RPUFs, since the base petrochemical material is highly combustible in its original form. 3 Thus, flame retardant additives are usually added into the PU blend in order to obtain RPUFs with good flame retardancy.…”

Effects of the Amount of Fly Ash Modified by Stearic Acid Compound on Mechanical Properties, Flame Retardant Ability, and Structure of the Composites

“…In recent years, the trend has been focusing on the discovery of a new or recyclable material that can be integrated in polymers. e purpose is to replace existing materials that have been prohibited due to environmental and health constraints without compromising mechanical properties but maintaining its characteristic [2].…”