Recent patent and technical works indicate a growing interest in halogen-free solutions with the predominance of the literature focusing on phosphorus-based flame retardants. Patents published on the flame retardancy of polycarbonate and its blends significantly exceed the number of patents on flame retardancy of any other polymer. Bridged aromatic diphenyl phosphates, especially resorcinol bis(diphenyl phosphate) and bisphenol A bis(diphenyl phosphate) have found broad application because of their good thermal stability, high efficiency, and low volatility. Another actively reported group of compounds are the metal salts of dialkylphosphonic acid as well as calcium hypophosphite, which have recently been found to be particularly effective in poly(butylene terephthalate) and polycarbonate. These products are synergistic with a number of phosphorus and nitrogen-containing compounds, such as melamine salts, which seem to be very efficient and commercially useful in nylons. Printed wiring boards comprise the largest market for flame-retardant polymeric materials. Recently, there has been a strong interest in halogen free solutions in East Asia and Europe. A recent halogen-free introduction is the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, which can be reacted into epoxies. Another reactive product with some processing and property advantages is poly(m-phenylene methylphosphonate). Because of the banning of pentabromodiphenyl ether in Europe and voluntary withdrawal of this product from the market in the US, the polyurethane (PU) industry is searching for a more environmentally acceptable low-scorch alternative. Both halogenated and halogen-free solutions are being considered but the PU industry seems to have a preference for the halogen-free products, generally containing phosphorus.

An overview of the recent literature on combustion and flame‐retardancy of epoxy resins is presented. A brief overview of the structures of cured epoxy resins is also presented as a background for better understanding of the thermal decomposition and combustion phenomena. The literature sources were mostly taken from the publications of 1995 and later; however, for basic descriptions of the structural and thermal decomposition principles, older publications are also cited. New developments in flame‐retardant additives, epoxy monomers and curing agents are described. It is shown that the main attention in recent years has been focused on phosphorus‐containing epoxy monomers and epoxy resins. Silicon‐containing or nitrogen‐containing products and inorganic additives remain of great interest as supplementary materials to phosphorus flame‐retardants. Copyright © 2004 Society of Chemical Industry

An overview of the literature together with selected authors' data on thermal and thermo‐oxidative decomposition of commercial aliphatic nylons (nylon 6, nylon 7, nylon 11, nylon 12, nylon 6.6, nylon 6.10, nylon 6.12) is presented. Despite the high level of research activity and the large number of publications in the field, there is no generally accepted mechanism for the thermal decomposition of aliphatic nylons. Polylactams (nylon 6, nylon 11 and nylon 12) tend to re‐equilibrate to monomeric or oligomeric cyclic products. Diacid–diamine type nylons (nylon 6.6, nylon 6.10 and nylon 6.12) produce mostly linear or cyclic oligomeric fragments and monomeric units. Because of the tendency of adipic acid to fragment with elimination of CO and H2O and to undergo cyclization, significant amounts of secondary products from nylon 6.6 are reported in some papers.  Many authors have shown that the primary polyamide chain scission occurs either at the peptide C(O)NH or at adjacent bonds, most probably at the alkyl–amide NHCH2 bond which is relatively the weakest in the aliphatic chain. Hydrolysis, homolytic scission, intramolecular CH transfer and cis‐elimination (a particular case of CH transfer) are all suggested as possible primary chain‐scission mechanisms. There are no convincing results reported which tend to generally support one of these mechanisms relative to the others; rather, it seems that the contribution of each mechanism depends on experimental conditions. This conclusion is also supported by the wide spread of kinetic parameters measured under the different experimental conditions.  More uniform results are observed in the literature regarding the mechanism of thermo‐oxidative decomposition of aliphatic nylons. Most authors agree that oxygen first attacks the N‐vicinal methylene group, which is followed by the scission of alkyl–amide NC or vicinal CC bond. Alternatively, it is suggested that any methylene group which is β‐positioned to the amide group methylene can be initially oxidized. There are few mechanisms in the literature which explain discoloration (yellowing) of nylons. UV/visible active chromophores are attributed either to pyrrole type structures, to conjugated acylamides or to conjugated azomethines.  Some secondary reactions occurring during the thermal or thermo‐oxidative decomposition lead to crosslinking of nylons. Nylon 6.6 crosslinks relatively easily, especially in the presence of air, whereas nylon 11 and nylon 12 crosslink very little. Strong mineral acids, strong bases, and some oxides or salts of transition metals catalyse the thermal decomposition of nylons, but minimize crosslinking. In contrast, many fire retardant additives promote secondary reactions, crosslinking and charring of aliphatic nylons. © 1999 Society of Chemical Industry

An overview is presented of the literature on thermal decomposition, combustion and fireretardancy of polyurethane (PU) elastomers, PU-based coatings, rigid and flexible PU foams. A brief overview of the structure of PU polymeric networks is helpful for a better understanding of the thermal decomposition and combustion phenomena. Literature sources were mostly taken from the publications of 1995 and later; however, for a basic description of the structural and thermal decomposition principles, older publication have also been cited. New developments in the efficient halogen-containing additives and reactive copolymers are described. However, major progress in the area of flame-retardant PUs in recent years is found in the field of phosphorus-or silicon-containing products, especially reactive ones. Inorganic additives remain of great interest, especially in PU-based intumescent coatings.

This paper presents an overview of the recent literature on flame retardancy of polycarbonate (PC) and polycarbonate-based resins. A brief survey of the major mechanisms of thermal decomposition of PC is also presented because it gives insight in the mechanisms of flame retardant action. Mostly industrial laboratories are involved in the development of new flame retardants for PC and, to a much lesser extent, academic laboratories are doing research on the mechanistic aspects of flame retardancy. The number of patents published annually on the flame retardancy of PC and its blends significantly exceeds the number of patents on flame retardancy of any other polymer. Because PC is a naturally high charring polymer, the condensed phase active flame retardants, in particular phosphorus-based ones, are widely used in PC-based blends. Plain PC can pass stringent flame retardant tests with very low additions of some sulfur-or silicone-based flame retardants.

An overview is presented of the literature on the flame retardancy of thermoplastic polyesters, especially poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT). The main focus is on publications of the last fifteen years; however, some earlier work of major importance is discussed as well. Because PET and PBT almost totally convert to volatile fragments upon exposure to heat, providing fuel to the flame, it is a challenging task to flame‐retard these polymers. Although many of the commercially available systems for flame retardancy of PET and PBT consist of a halogen‐containing additive and a synergist, more recent publications and patents emphasize halogen‐free, particularly phosphorus‐based systems. Several phosphorus‐based additive or reactive systems are well‐established for use in PET textiles, and phosphorus‐based additives have recently been introduced for PBT. Copyright © 2004 Society of Chemical Industry

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An overview is presented of the literature on the thermal decomposition and combustion of thermoplastic polyesters, especially commercially important poly(ethylene terephthalate) (PET) and poly(1,4‐butylene terephthalate) (PBT). Although the literature is not clear as to whether heterolytic or homolytic scission of aliphatic fragments is the first step in the thermal decomposition of polyesters, in any case volatilization of light aliphatic fragments make polyesters easily ignitable polymers. Despite the presence of benzene groups in the main polymer chain, thermoplastic polyesters show very limited tendency to char, but instead, aromatic‐containing polymer fragments volatilize and feed the flame. Fire retardant additives, although they usually facilitate decomposition of the polyesters at lower temperature, also usually promote charring and therefore suppress combustion. Copyright © 2004 John Wiley & Sons, Ltd.