Fire retardant polymers

The assessment of the contribution of a product to the fire severity and the resulting hazard to people and property combines appropriate product flammabihty data, descriptions of the building and occupants, and computer software that includes the dynamics and chemistry of fires. This type of assessment offers benefits not available from stand-alone test methods quantitative appraisal of the incremental impact on fire safety of changes in a product appraisal of the use of a given material in a number of products and appraisal of the differing impacts of a product in different buildings and occupancies. One method, HAZARD I (11), has been used to determine that several commonly used fire-retardant—polymer systems reduced the overall fire hazard compared to similar nonfire retarded formulations (12). 

The history of polymer fire retardance is reviewed from its inception with the early Egyptians to the most recent developments in intumescent fire retardants and inherently fire retardant polymers. 

FIRE RETARDANT FILLERS. The next major fire retardant development resulted from the need for an acceptable fire retardant system for such new thermoplastics as polyethylene, polypropylene and nylon. The plasticizer approach of CP or the use of a reactive monomer were not applicable to these polymers because the crystallinity upon which their desirable properties were dependent were reduced or destroyed in the process of adding the fire retardant. Additionally, most halogen additives, such as CP, were thermally unstable at the high molding temperatures required. The introduction of inert fire retardant fillers in 1965 defined two novel approaches to fire retardant polymers. 

A fire retardant polymer that is easily impregnated into wood to petrify the material, making it stronger and nonflammable. 

S. Bourbigot and S. Duquesne, Fire retardant polymers Recent developments and opportunities. J. Mater. Chem., 17, 2283-2300 (2007). 

Typically a brominated or chlorinated organic compound is added to the polymer or, in suitable cases, halogenated structures are introduced into the polymer chain by copolymerization to prepare fire-retardant polymer materials. Metal compounds, such as antimony trioxide, which do... 

Levchik, S. V., Levchik, G. F., Balanovich, A. I., Camino, G., and Costa, L., Mechanistic study of combustion performance and thermal decomposition behaviour of Nylon 6 with added halogen-free fire retardants, Polym. Degrad. Stab., 1996, 54, 217-222. 

Camino, G., Costa, L., and Trossarelli, L. 1985. Study of the mechanism of intumescence in fire retardant polymers Part V—Mechanism of formation of gaseous products in the thermal degradation of ammonium polyphosphate. Polym. Deg. Stab. 12 203-211. 

Chigwada, G., Jash, P., Jiang D.D., and Wilkie, C.A. 2005. Fire retardancy of vinyl ester nanocomposites Synergy with phosphorus-based fire retardants. Polym. Deg. Stab. 89 85-100. 

There has been a great recent market demand for halogen-free fire-retardant polymers. Zinc borates are also multifunctional fire retardants in halogen-free polymers. They can promote char formation, reduce the Rate of Heat Release, smoke evolution, carbon monoxide generation, and afterglow combustion. When used in conjunction with metal hydroxides, they can also display synergy in fire test performance. 

The market demand for halogen-free fire-retardant polymers has been increasing steadily in applications such as electrical/electronics, transportation, and construction products. In wire and cable, the high loadings of ATH or MDH are required (60-70 wt.%). Recent developmental efforts... 

Shen, K.K. 2000. Zinc borates—30 years of successful development as multifunctional fire retardants. Polym. Mater. Sci. Eng., 83, 64—67. 

E. Kandare, G. Chigwada, D. Wang, C.A. Wilkie, and J.M. Hossenlopp, Probing synergism, antagonism, and additive effects in poly(vinyl ester)(PVE) composites with fire retardants, Polym. Degrad. Stabil., 2006,91 1209-1218. 

B. Schartel, U. Knoll, A. Hartwig, and D. Ptttz, Phosphonium-modified layered silicate epoxy resins nanocomposites and their combinations with ATH and organo-phosphorus fire retardants, Polym. Adv. Technol., 2006, 17 281-293. 

Apart from some specific areas such as fuel tanks or intumescent coatings, the performance in a fire test simulating a fully developed fire is often not of real interest with respect to the development of fire-retarded polymers, since common flame-retarded polymeric materials are used in applications... 

Camino G, Costa L, Trossarelli L. Study on the mechanism of intumescence in fire retardant polymers. 1. Thermal-degradation of ammonium polyphosphate pentaerythritol mixtures. Polym. Degrad. Stab. 1984 6 243-252. 

Figure 19.9a-d shows that both the phosphinate FR and the nanoparticles change the structure of char compared with pure PBT. In contrast to the pure polymer, which leaves a char consisting of oligomeric components of PBT, the fire-retarded polymer (by phosphinate or nanoparticles) leaves a char consisting of polycyclic aromatic hydrocarbons (PAHs). The PAH structure of the char is expected to make the char stronger and capable to withstand erosion in full-scale fire tests. This observation is verified from the strength analysis of the char residue in intermediate scale... 

Ferrocene has been reported to be very effective as a soot reducing agent in combustion [42 — 44]. Thus, when ferrocene compounds are incorporated in a fire retardant polymer, such as a phenolphthalein-based polymer and poly(phosphate ester)s, they have shown added advantages in that they promote extinction and reduce smoke formation by accelerated char reduction [45, 46]. The synthesis of such ferrocene-containing poly(phosphate ester)s was achieved by interfacial polycondensation using a phase transfer catalyst [47]. Accordingly, l,l -bis(p-hydroxy-phenylamido)ferrocene and l,l -bis(p-hydroxyphenylcarbonyl)ferrocene underwent condensation with various aryl phosphoroic acid dichlorides to yield two series of ferrocene-containing polymers, i.e., poly (amide-phosphate ester)s 38a and poly(ester-phosphate ester)s 38b respectively, as shown in Scheme 10-17. 

Visakh P. M. (MSc, MPhil) is a Research FeUow at the School of Chemical Science Mahatma Gandhi University. He edited 2 books with Sabu Thomas from Wiley and more than 8 books in press, (from Wiley, Springer, American Chemical Society and Royal Society of Chemistry and Elsevier) He has been invited as a visiting student in Italy (2009, 2012), Argentina (2010) Sweden (2010, 2011, 2012), Switzerland (2010), Spain (2011, 2012), Slovenia (2011), France (2011), Belgium (2012), and Austria (2012) for his research work and he published more than 5 publications and more than 5 book chapters. He has attended and presented more than 25 conferences. His research interests include polymer nanocomposites, bio-nanocomposites, mbber based nanocomposites, fire retardant polymers and liquid crystalline polymers. 

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