Silicon-based flame retardant

Q Recent Developments in Silicon-Based Flame Retardants... 

Kashiwagi, T. and Gilman, J.W., Silicon-based flame retardants, in Fire Retardancy of Polymeric Materials, Grand, A.F. and Wilkie, C.A., Eds., Marcel Dekker, New York, 2000, Chap. 10, p. 353. 

A silicone-based flame-retardant with the trade name SFR 100 has recently been developed by the General Electric Co., Silicone Products Division. 

A silicon-based flame-retardant, SFR 100 of Silicon Product Division, General Electric Co., is recommended for producing polyolefins rated V-0 or even 5V (UL 94). SFR 100 is always combined with magnesium stearate. A suggested composition is... 

Kashiwagi, T. Oilman, J.W. Silicon-based flame retardants, in S. Al-Malaika, A. Golovoy, and C.A. Wilkie, Eds., Specialty Polymer Additives Principles and Applications. Blackwell Science, Oxford, England, 2001, pp. 353-389. 

Weil, E.D. Levchik, S.V. Ravey, M. Zhu, W.M. A survey of recent progress in phosphorus-based flame retardants and some mode of action studies. Phosphorus, Sulfur Silicon Relat. Elem. 1999, 144, 17-20. 

Dow has produced a polycarbonate grade for liquid crystal display monitors, incorporating a silicone flame retardant. Formulations containing the silicone additive are said to have better impact strength and temperature resistance than those protected by phosphorus based flame retardants, and better heat and light stability than those containing brominated FRs. 

This paper reports the results of a molecular-level investigation of the effects of flame retardant additives on the thermal dedompositlon of thermoset molding compounds used for encapsulation of IC devices, and their implications to the reliability of devices in molded plastic packages. In particular, semiconductor grade novolac epoxy and silicone-epoxy based resins and an electrical grade novolac epoxy formulation are compared. This work is an extension of a previous study of an epoxy encapsulant to flame retarded and non-flame retarded sample pairs of novolac epoxy and silicone-epoxy compounds. The results of this work are correlated with separate studies on device aglng2>3, where appropriate. 

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). ... 

At an optimum addition level of only 1.5 w t %, nano-size magnesium-aluminum LDHs have been shown to enhance char formation and fire-resisting properties in flame-retarding coatings, based on an intumescent formulation of ammonium polyphosphate, pentaerythritol, and melamine.89 The coating material comprised a mixture of acrylate resin, melamine formaldehyde resin, and silicone resin with titanium dioxide and solvent. It was reported that the nano-LDH could catalyze the esterification reaction between ammonium polyphosphate and pentaerythritol greatly increasing carbon content and char cross-link density. 

This chapter has provided a concise account of an important type of flame retardants based on silicon. This class of flame retardants may provide an opportunity to develop systems for fire retardancy that are environmentally friendly. It seems that there is a growing interest in this type of flame retardant, and this trend most likely will continue, given the increasing concern over the release of the halogenated species into the environment. 

A mixture of ammonium chloride and borax was one of the treatments of cellulosic fabrics reported by Gay-Lussac in 1821. Due to its low dehydration temperature and water solubility, sodium borates are only used as flame retardants in cellulose insulation (ground-up newspaper— see Sections 9.2.1.2 and 9.2.2.1), wood timber, textiles, urethane foam, and coatings. For example, a mixture of urethane (100 parts), borax (100 phr), and perlite (30phr) was claimed to provide flame-retardant urethane foam.8 Borax in conjunction with boric oxide, silica, ammonium chloride, and APB as ceramizing additives and volume builders, are claimed in a fire-protection coating based on polybutadiene and silicone microemulsion.9 Using a modified DIN 4102 test, the chipboard with the coating showed a loss of mass less than 1% and there was no pyrolysis of the wood sample. 

Permanent antistatic fmishes, based on crosshnked polyamines and polyglycols, need an alkaline catalyst. Therefore the one-bath combination with finishes, which need acid catalysis, is difficult but not impossible. Examples of acid-catalysed fmishes are the easy-care and durable press fmishes, durable hydrophylic silicone softeners and elastomeric finishes, also fluorocarbon-based repellency and some flame-retardant finishes. High finish effects result from a two-bath application with of the easy-care finish first followed by the surface-related antistatic finish. 

In the case of flame retardant silicone elastomer, many ingredients such as silica, platinum, and other flame retardant agents are incorporated into the base siloxane polymer. But there is no need to use the halogenated flame retardant agent, for example, bromine or chlorine compounds. This difference is an advantage of silicones compared with other synthetic polymers in terms of health and safety. 

NEC has a target to phase out the use of all halogenated flame retardants by 2011. In 1999 the company launched a polycarbonate containing a silicone flame retardant that it claims to be far superior to conventional flame retardants and is neither phosphorus nor halogen based and can be recycled up to five times for the same purpose. 

Liquid immersed types use various forms of oil and special synthetic liquids. The chlorinated liquids, e.g. polychlorinated-biphenyl, have been banned in most countries because they are very strong pollutants and are almost impossible to destroy, except by intensive burning in a special furnace. Modern liquids are synthetic compounds typically silicone based, and are usually specified to be flame retardant. 1EC60296, 60836, and 60944 describe suitable liquids. These transformers are the type normally used in oil and gas plants. Resin insulated transformers are very suitable for indoor locations and off-shore plants because they contain no flammable liquid, produce no spillage and require minimal maintenance. They are usually more expensive than conventional liquid immersed transformers. 

Cotton fibers have been coated with silicone dioxide-based layers using atmospheric pressure plasma (APP) technique. SiO network armor was obtained through hydrolysis and condensation of the precursor TEOS and has been cross linked on the surface of cotton fibers. Because of the protective effects of the SiO network armor, the modified cellulosic fibers exhibit improved flame retardancy. SiO -APP coated textiles may have in the future numerous applications in the development of upholstered furniture, clothing, and military (Totolin et al., 2010). 

Antimony trioxide-brominated PC [30], silicones [46, 47] and hydroxyapatite [48] have all been studied as flame-retardants for PC. Figure 6.1 shows the perceived flame retardancy mechanism occurring during the thermal decomposition of PC containing trifunctional phenyl silicone based additives [47]. This process involves the formation of a p-cumylphenoxy end-structure. 

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