Flammability of polymers

Flammability of polymers can be determined by their reactivity with oxygen. The limiting oxygen index (LOI), defined as the minimum amount of oxygen required to sustain combustion under specified conditions, is a quantitative measure of the tendency of materials to burn (Table 17.1). In a flame-retarded system, the study ofthe LOI can provide information on the effectiveness of flame-retardant materials [29]. 

Depending on the polymer and the applicable fire retardance standards, flame retardants are chosen to interfere with one or more stages ofthe combustion process heating, decomposition, ignition, flame spread, and smoke density. Fire retardants have to inhibit or even suppress the combustion process. 

Fire retardants can be divided into halogen containing and nonhalogen containing. This is a useful categorization as it leads into an explanation of their different modes of actions. Chief among the nonhalogen fire retardants are aluminum trihydrate 

Plastics and the Environment, Edited by Anthony L. Andiady. ISBN 0-471-09520-6 2003 John Wiley Sons, Inc. 

Polymers are formulated to satisfy specific end-use requirements for the lifetime of the products  

This chapter deals with the subject of flammability of polymers where thermal, oxidative, and radiative degradations all play very significant roles. Flanunability of polymers is a complex subject and has been discussed in other books and review articles by various authors [12-22], 

According to Webster s New World Dictionary Thesaurus the word flammable means easily set on fire that will bum readily or quickly term now preferred to INFLAMMABLE in commerce and industry. Easily set on fire refers to the ignition behavior, bum readily refers to the combustion behavior, and bum quickly refers to the fire propagation behavior of a material. Thus, flammability and fire behavior of materials are used synonymously when describing the ignition, combustion, and fire propagation behaviors of materials separately or in combination. 

The ignition, combustion, and fire propagation behaviors of polymer are examined in various flammability test standards, where polymers are intentionally degraded, and the degradation products are ignited and burned under controlled exposure and environmental conditions. Various countries and agencies promulgate these types of flammability test standards  

---

The tables were taken from A. Tewarson, Flammability of Polymers, Chapter 11 in Plastics and the Environment, A. L. Andrady (editor), John Wiley and Sons, Inc. Hoboken, N.J. 2003. 

R.N. Walters and R.E. Lyon, Flammability of polymer composites, SAMPE 2007, Baltimore, MD, June 3-7, 2007. 

As another example, Kashiwagi et al.7 have investigated the flammability of polymer/single wall carbon nanotube (SWNT) nanocomposites. It has been observed that in the case where the nanotubes were relatively well-dispersed, a nanotube containing network structured layer was formed without any major cracks or openings during the burning tests and covered the entire... 

Tewarson A. Flammability of polymers. In Plastics and the Environment. Andrady AL, Ed. John Wiley Sons Hoboken, NJ, 2003 chap. 11. 

Most of the previous studies on flame retardation of polymer nanocomposites are focused on the relationship between macroscopic morphologies of chars and the flammability properties. Fang et al. studied the relationship between evolution of the microstructure, viscoelasticity and graphitization degree of chars and the flammability of polymers during combustion (68). The flame retar-dancy of ABS/clay /MWNTs nanocomposites was strongly affected by the formation of a network structure. Flammability properties... 

This paper is concerned with the flammability of polymer materials. It is an attempt to review the state of the art in the field of ignition and combustion of these materials. Attention is paid to the establishment of fundamental relationships between chemical structure and flammability of polymers. The existing theories for the action mechanisms of various flame retardants are critically analyzed. 

Van Krevelen noted that the flammability of polymers containing C, H, N, O, and halogens, depends on a composition parameter CP ... 

Also the thermo-oxidative stability of the deactivated polymer is excellent. At the present time, hydroxides and partially dehydrated hydroxides of amphoteric metals, especially of aluminium, are applied as additives suppressing the flammability of polymers. 

Flame Retardation. Polymer combustion, a highly complex process, is composed of a vapor phase, in which the reactions responsible for the formation and propagation of the flame take place, and a condensed phase, in which fuel for the gas reactions is produced. Flame retardancy, therefore, can be improved by appropriately. pa modifying either one or both of these phases ( ). The approaches aimed at reducing the flammability of polymer systems can be grouped into the following three categories ... 

Much literature discusses the flame retardation of various polymeric materials (10-15). The techniques of reducing the flammability of polymers, in principle, are based on one or more of the three fundamental approaches described earlier. This section deals with the concept of synergism and its application in reducing flammability, selection of fire-retardant additives, and flame retarding some specific polymer systems. 

In 1910, the Celluloid Company patented use of triphenyl phosphate in combination with cellulose acetate to circumvent the inherent flammability danger of cellulose nitrate (5). Since then, use of phosphate plasticizers to reduce flammability of polymer compounds has become widespread. Other plasticizer types have become standards for their effect on other specific properties. 

Improvements in the reduction of flammability of polymers with low clay contents and better processability have been reported, in addition to reductions in the concentration of toxic vapors produced in the combustion stage [116-120]. In connection to their flame-retardant properties, exfoliated nanocomposites based on PP [121, 122, 115, 123], PS [115, 123, 124], poly(ethylene-vinyl acetate) [125, 126], styrene-butadiene rubber [127], PMMA [128], polyesters... 

Masarik, J. and Ryska, M. Inflammation of plastics and composition of their combustion products. Proc. Zrd Conf. on Non-Flammability of Polymer Materials, Wood and Textiles, Dom Techniky SVTS, Bratislava, 1974... 

Hirschler, M. M. Thermal analysis and flammability of polymers. Effect of halogen-metal additive systems. Europ. Polym. J., 19, 121 (1983)... 

Typenreihe Apyral. Prepr. 1th Conf, Non Flammability of Polymer Materials, Dom Techniky SVTS, Bratislava, 1983... 

Table 2.6 shows the PCFC results as well as some TGA results, from which we can see that different bridging groups in the bisphenols also have a large influence on the flammability of polymers. 

---