Intumescent organic polymer

As far as we know, only a few papers report on the fire behavior of intumescent inorganic polymers. A possible explanation is that inorganic polymers are inherently FR and are used as is. The particular case of inorganic-organic polymers is either they are already flame retardant or they are used in applications which do not require high level of flame retardancy. The only published work devoted to intumescent inorganic polymer concerns polyphosphazene, and will be discussed below. 

This chapter is organized in four parts. In Sections 6.2 and 6.3, intumescence is briefly reviewed to provide the reader the basic understanding on the mechanisms of action by intumescence and then the main intumescent products available on the market associated with their typical field of application are surveyed. Reaction of intumescent polymers and textiles to fire, i.e., the contribution... 

Use Phosphorus-based catalyst in organic and latex-based fire-retardant intumescent paints, mastics, and polymers. 

Less than 10% of the polyamide produced is made in a flame retardant version. The best system is composed of a combination of red phosphorus and zinc borate (see table above). The only drawback of this system is its color which is restricted to brick red or black. If other colors are required, ammonium polyphosphate is used either in combination with organic flame retardants or with antimony trioxide. It is possible to manufacture a very wide range of colors in the halogen free system. Some systems make use of the addition of novolac or melamine resins. For intumescent applications, ammonium polyphosphate, in combination with other components, is the most frequently used additive. Figure 13.6 shows that fillers such as calcium carbonate and talc (at certain range of concentrations) improve the effectiveness of ammonium polyphosphate. This is both unusual and important. It is unusual because, in most polymers, the addition of fillers has an opposite influence on the efficiency of ammonium polyphosphate and it is important because ammonium polyphosphate must be used in large concentrations (minimum 20%, typical 30%) in order to perform as a flame retardant. 

The presence of phosphorus in the polymer backbone has a veiy practical consequence, quite apart from the structural issues. Phosphorus is one of the most important elements that prevent the combustion of organic materials. The presence of both phosphorus and nitrogen is synergistic. Thus, the phosphorus-nitrogen backbone in polyphosphazenes ensures that many poly(organophosphazenes) are not only nonflammable but also quench combustion of other compounds with which they are in contact. The mechanism of this fire suppression is believed to be both an interruption of the free radical processes that occur in a flame and the formation of an intumescent char that shields the material from the ingress of oxygen. 

The chemistry of flame-retardant additives is highly varied and is optimised not only for specific polymer chemistries, but also to address flammability effects such as flame spread, dripping, smoke release and so on. Flame-retardant chemistry includes classes of compounds such as halogenated organics, char formers, crosslinking compounds, mineral fillers, intumescent packages, phosphorus compounds, nitrogen-based compounds and even certain metal and boron compounds. 

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