**Polyurethane Flexible Foam Fire Behavior**

Ahmadreza Gharehbagh and Zahed Ahmadi

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/47965

**1. Introduction** 

100 Polyurethane

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Polyurethanes are a broad range of polymers, which are formed from the reaction between diisocyanates or polyisocyanates with diols or polyols. According to **the types and amounts of, polyols, isocyanate, ingredients** and the overall reaction circumstances, a broad range of products **like flexible foams, rigid foams**, elastomers, coatings and adhesives are produced.

Since the polyurethane products specially foams are playing an indispensable rule in our daily life **because of wide range of applications in automotive, household, refrigerators, insulations,** reducing of the fire risk of such a products are become more vital.

Conventional polyurethane **flexible** foams are easily ignited by a small flame source and burn rapidly with a high rate of heat release and smoke and toxic gases. This high flammability of polyurethane flexible foam is related to its cellular and open cell structure and low density of such foams. Oxygen can easily pass through the cells of the combustible material and in subjecting with an accident, smoldering cigarette or an electrical shock, foam catch fire [1].

Polyurethanes can be resisted against fire by different ways. **Depends on the types and applications of them, fire resisting could be done by the flame retardants using or by changing in** the polymer structure. In the whole picture the polymer ignition can be controlled by the following **factors**.


Different types of the fire retardants could be used according to one of the above mentioned categories. The flame retardants are acting according to one of the following mechanisms.

© 2012 Gharehbagh and Ahmadi, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Gharehbagh and Ahmadi, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1. Reaction with the flame and preventing of the spreading of the fire by the created free radical blocks.

Polyurethane Flexible Foam Fire Behavior 103

**Bonds Decomposition Temperature(ºC)** 

**Table 1.** Heat stability of the diverse products of polyurethanes

**Figure 2.** Fundamental concepts of polyurethane foam Cell Structure (SEM×200)

In recent years the phasing out of some types of halogenated FR (flame retardant) due to persistence at environment and bioaccumulation and toxicity has been more investigated.

**3. Polyurethane flexible foam fire retardants** 

**3.1. Halogenated phosphorous flame retardants** 

Polyurethane morphology plays a vital rule on the fire properties of the polyurethane foam. The porous structure of the foam helps to diffuse the oxygen easily in to the foam and accelerate the ignition process. Fig.2 shows the SEM Picture of the polyurethane flexible foam with no filler inside. As it is clear, the cell structure of the foam includes Cell window,

allophanate 100-200 biuret 115-125 Urea 160-200 Urethane 180-200 Substituted Urea 235-250 carbodiimide 250-280 Isocyanurate 270-300

**2. Polyurethane foam morphology** 

Strut and Strut joint [1].


There are lots of materials which are known as the fire retardants according to the following groups.


**Figure 1.** Condensation reaction of isocyanate to make Carbodiimide


**Table 1.** Heat stability of the diverse products of polyurethanes
