Flame-retardant behaviour

Polyphosphinoboranes are of interest with respect to their potentially useful physical properties such as flame-retardant behaviour and an ability to function as precursors to BP-based ceramics. In addition, the electron-beam sensitivity of some polyphosphinoboranes has been demonstrated. This allows their use as lithographic resists for patterning applications when coated as thin films on substrates such as silicon (Figure 9.11). ... 

Environmentally friendly, bio-based flame retardant epoxy resins have been reported from a di-epoxy fatty compound, 10-[2, 5 -bis(9-oxiranyl-nonayloxy) phenyl]-9,10-dihydro-9-oxa-10-phosphaphenanthrene-l 0-oxide (Rg. 7.5a) and epoxidised 10-undecenoyl triglyceride and epoxidised methyl-3, 4, 5-tris(10-undecenoyloxy)benzoate (Hg. 7.5b and c). The limiting oxygen index (LOI) values of the cured products indicate good flame retardant behaviour owing to the formation of a protective phosphorous-rich layer which slows down degradation and protected the products. 

Periadurai, T., Vijayakumar, C.T., Balasubramanian, M. Thermal decomposition and flame retardant behaviour of Si02-phenolie nanocomposite. J. Anal. Appl. Pyrol. 89, 244-249 (2010)... 

Polyethylene (PE) is one of the most used thermoplastic polymers. PE is versatile, easy to process and has a low cost. It is used in diverse apphcations ranging from construction, vehicles to domestic products, packaging, toys, etc. Some of the limitations of PE are the poor mechanical behaviour under high stress, flame retardant behaviour, low resistance to UV radiation, the permeability to certain gases, and the fact that it is not biodegradable. 

Aromatic and aliphatic bromine compounds play an important role as industrial products, e.g. special products are widely used as flame retardants for polymeric materials (ref. 1). Because there is an increasing interest and concern about the behaviour and fate of anthropogenic compounds in the environment (ref. 2), we have studied the physical behaviour and chemical reactivity of these products which are relevant to the environment. The main object is the study of their thermal behaviour during incineration, as well as photolytic reactions. Of prime concern is... 

Study of the Thermal Behaviour of Bromine Containing Flame Retardants during Incineration... 

The use of copolymers is essentially a new concept free from low-MW additives. However, a random copolymer, which includes additive functions in the chain, usually results in a relatively costly solution yet industrial examples have been reported (Borealis, Union Carbide). Locking a flame-retardant function into the polymer backbone prevents migration. Organophosphorous functionalities have been incorporated in polyamide backbones to modify thermal behaviour [56]. The materials have potential for use as fire-retardant materials and as high-MW fire-retardant additives for commercially available polymers. The current drive for incorporation of FR functionality within a given polymer, either by blending or copolymerisation, reduces the risk of evolution of toxic species within the smoke of burning materials [57]. Also, a UVA moiety has been introduced in the polymer backbone as one of the co-monomers (e.g. 2,4-dihydroxybenzophenone-formaldehyde resin, DHBF). 

Substances applied to or incorporated in a combustible material (e.g. organic polymers, nylon, vinyl and rubber, etc.) to reduce flammability. Act by retarding ignition, control/douse burning, reduce smoke evolution. Slow down or interrupt the self-sustained combustion cycle when the heat-flux is limited. Flame retardants (FRs) improve the combustion behaviour and alter the combustion process (cool, shield, dilute, react) so that decomposition products will differ from nonflame retarded articles. FRs are usually divided into three classes ... 

Covaci A, Harrad S, Abdallah MAE, Ali N, Law RJ, Herzke D, de Wit CA (2011) Novel brominated flame retardants a review of their analysis, environmental fate and behaviour. 

It is nearly 20 years ago that the unacceptable fire behaviour of "modern" upholstered furniture became highlighted in the UK by Fire Brigade reports of domestic fires. This poor performance was blamed on the use of flexible polyurethane (PU) foam upholstery and demands were made to ban PU foam or at least to insist on the use of flame retarded PU foam. 

Fire behaviour of products constitutes a major and permanent preoccupation in multiple areas building and construction, transport, electric and electronic engineering, furniture, etc. This theme possibly involves the largest number of standards, regulations or legislations at national level as well at international level. It is in this context that the use of flame retardants for plastics must be envisaged. Several themes are outlined. 

Polyamide-imides are appreciated for good mechanical and electrical properties high service temperatures (up to 220°C with possible long service times at 260°C) rigidity good creep behaviour fatigue endurance low shrinkage and moisture uptake inherent flame retardancy chemical resistance usability down to -196°C. 

B. Perret and B. Schartel, The effect of different impact modifiers in halogen-free flame retarded polycarbonate blends - ii. fire behaviour, Polym. Degrad. Stab., In Press, Corrected Proof, 2009. 

Price, D., Cunliffe, L. K., Bullett, K. J., Hull, T. R., Milnes, G. J., Ebdon, J. R., Hunt, B. J., and Joseph, R, Thermal behaviour of covalently bonded phosphate and phosphonate flame retardant polystyrene systems, Polym. Degrad. Stab., 2007, 92, 1101-1114. 

Gao, F., Tong, L., and Fang, Z. 2006. Effect of a novel phosphorous-nitrogen containing intumescent flame retardant on the fire retardancy and the thermal behaviour of poly(butylene terephthalate). Polym. Deg. Stab. 91 1295-1299. 

Horrocks A.R. and Davies, P.J. 2000. Char formation in flame-retarded wool fibres. Part 1. Effect of intumescent on thermogravimetric behaviour. Fire Mater. 24 151-157. 

S. Padbury, B.K. Kandola, and A.R. Horrocks, The effect of phosphorus-containing flame retardants and nanoclay on the burning behaviour of PA 6 and PA 6.6, Proceedings of the 14th BCC Conference on Flame Retardancy, M. Lewin (Ed.), Business Communications Co Editions, Norwalk, CT, 2003. 

Schartel B, Balabanovich AI, Braun U, Knoll U, Artner J, Ciesielski M, Doring M, Perez P, Sandler JKW, Altstadt V, Hoffmann T, Pospiech D. Pyrolysis of epoxy resins and fire behaviour of epoxy resin composites flame-retarded with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide additives. J. Appl. Polym. Sci. 2007 104 2260-2269. 

Kandola, B. K., Horrocks, A. R., and Rashid, M. R. Effect of reinforcing element on burning behaviour of fibre—Reinforced epoxy composites, Proceedings of 17th Annual BCC Conference on Flame Retardancy, Stamford, CT, May 22-24, 2006. 

Modesti, M. Lorenzetti, A. Simioni, F. Checchin, M. Influence of different flame retardant on fire behaviour of modified PIR/PUR polymers. Polym. Degr. Stab. 2001, 74, 475-479. 

Schartel, B. Braun, U. Balabanovich, A.I. et al. Influence of the oxidation state of phosphorus on the decomposition and fire behaviour of flame-retarded epoxy resin composites. Polymer 2006, 47, 8495-508. 

Modesti, M. Lorenzetti, A. Besco, S. Hrelja, D. Semenzato, S. Bertani, R. Michelin, R.A.. Synergism between flame retardant and modified layered silicate on thermal stability and fire behaviour of polyurethane nanocomposite foams. Polym. Degrad. Stab. 2008, 93, 2166-2171. 

Modesti, M. Lorenzetti, A. Improvement on fire behaviour of water blown PIR-PUR foams Use of an halogen-free flame retardant. Eur. Polym. J. 2003, 2, 263-268. 

Wang, Z., Shen, X., Fan, W., Hu, Y., Qu, B., andZou, G., Effects of poly(ethylene-co-propylene) elastomer on mechanical properties and combustion behaviour of flame retarded polyethylene/magnesium hydroxide composites, Polym. Int., 2002, 51(7), 653-657. 

Watanabe, I., Sakai, S. (2003) Environmental release and behaviour of brominated flame retardants. Environ. Int., 29 665-682. 

This chapter discusses the dynamic mechanical properties of polystyrene, styrene copolymers, rubber-modified polystyrene and rubber-modified styrene copolymers. In polystyrene, the experimental relaxation spectrum and its probable molecular origins are reviewed further the effects on the relaxations caused by polymer structure (e.g. tacticity, molecular weight, substituents and crosslinking) and additives (e.g. plasticizers, antioxidants, UV stabilizers, flame retardants and colorants) are assessed. The main relaxation behaviour of styrene copolymers is presented and some of the effects of random copolymerization on secondary mechanical relaxation processes are illustrated on styrene-co-acrylonitrile and styrene-co-methacrylic acid. Finally, in rubber-modified polystyrene and styrene copolymers, it is shown how dynamic mechanical spectroscopy can help in the characterization of rubber phase morphology through the analysis of its main relaxation loss peak. 

Polyester fabrics when burned exhibit a melt-drip behaviour. Since the fabric melts away from the flame, some polyester fabric constructions can actually pass vertical flame tests without any flame-retardant treatment. The waiving of melt-drip specifications for children s sleepwear has allowed untreated polyester garments to be sold into that market. 

Providing flame retardancy for fibre blends has proved to be a difficult task. Fibre blends, especially blends of natural fibres with synthetic fibres, usually exhibit a flammability that is worse than that of either component alone. Natural fibres develop a great deal of char during pyrolysis, whereas synthetic fibres often melt and drip when heated. This combination of thermal properties in a fabric made from a fibre blend results in a situation where the melted synthetic material is held in the contact with the heat source by the charred natural fibre. The natural fibre char acts as a candle wick for the molten synthetic material, allowing it to bum readily. This can be demonstrated by the LOl values of cotton (18-19), polyester (20-21) and a 50/50 blend of both (LOl 18), indicating ahigher flammability of the blend as described later (Section 8.11). But a rare case of the opposite behaviour is also known (modacrylic fibres with LOl 33 and cotton in blends from 40-60 % can raise the LOl to 35). 

---