Rigid polyurethane foams with halogen‐free flame retardants: Thermal insulation, mechanical, and flame retardant properties

Abstract

Rigid polyurethane foam (RPUF) composites with triphenyl phosphate (TPhP), aluminum trihydrate (ATH), and zinc borate (ZnB) alone, as well as their binary blends, were prepared via a one-shot process. The amount of flame retardant (FR) or FR blend was varied from 10 to 50% by polyol weight percentage, and the weight fraction of the blends was also fixed at 40%. The effects of additives on thermal insulation, mechanical, and flame retardancy properties of the composites were investigated. Thermal conductivity of the neat foam (RPUF) decreased from 22.53 to 21.04-21.58 mW m −1 K −1 . The compressive strength of foams displayed an increase with increasing the amount of TPhP, ATH, and ZnB till 40% by weight. The limited oxygen index values of all foams increased and the flame spread rates of all foams significantly decreased. It was also observed that the flame was self-extinguished in some cases. The cone calorimeter test results indicated that the FR additives improved the flame retardancy of the RPUF. INDTRODUCTIONRigid polyurethane foams (RPUFs) are one of the most consumed polymeric materials to a great extent. They have wide range applications in insulation, transportation, building construction, domestic appliance, automobile industry, and many others because of their high closed-cell content, low thermal conductivity, high strength with low weight, good shock absorption, and so on. 1-3 Nowadays, humanity is under threat because of limited energy resources in the world. In that case, RPUFs possessing low thermal conductivity values come into prominence because RPUFs are one of the unique materials for thermal insulation. RPUFs predominantly contain closed-cell structures, and in the closed-cell structures of foams, a blowing agent constituting the gas is trapped during production. The thermal conductivity of an RPUF is strongly affected by this blowing agent. The lower thermal conductivity of the blowing agent causes the lower thermal conductivity of RPUF. 4,5 When RPUFs compare with the conventional thermal insulating materials such as brick, concrete, wood, glass fiber, and so on, the conventional materials need to be used at much higher thickness in an attempt to match the insulation performance of 50 mm RPUF, for instance, ranging from 1720 mm for brick, 200 mm for wood, and 80 mm for polystyrene. The excellent thermal insulation property of RPUFs is not the only parameter making RPUFs one of the most used engineering materials but also their high mechanical strength with low weight and their easy processability make it as an interesting material. 6,7 For example, RPUF is one of the most important structural element of the refrigerators' skeleton besides providing high insulation for home refrigerators.However, as in the case of a majority of polymeric materials, RPUF is also easily combustible. As a matter of fact that, it is more combustible than other materials because of its rigid cellular and organic structure, additionally, it contains flammable, explosive gases in its closed cells. During the burnin...

Properties of a novel inherently flame‐retardant rigid polyurethane foam composite bearing imide and oxazolidinone

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Enhanced Fire Safety of Rigid Polyurethane Foam via Synergistic Effect of Phosphorus/Nitrogen Compounds and Expandable Graphite

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