Thermosets flame retardation

C2HgNg H4O2P2 (60). The pyrophosphate is reported to be only soluble to the extent of 0.09 g/100 mL water, whereas melamine orthophosphate is soluble to 0.35 g/mL. The pyrophosphate is the most thermally stable. Melamine orthophosphate is converted to the pyrophosphate with loss of water on heating. AH three are available as finely divided soflds. AH are used commercially in flame-retardant coatings (qv) and from patents also appear to have utihty in a wide variety of thermoplastics and thermosets. A detaHed study of the thermal decomposition of the these compounds has been pubHshed (61). 

Usage of phosphoms-based flame retardants for 1994 in the United States has been projected to be 150 million (168). The largest volume use maybe in plasticized vinyl. Other use areas for phosphoms flame retardants are flexible urethane foams, polyester resins and other thermoset resins, adhesives, textiles, polycarbonate—ABS blends, and some other thermoplastics. Development efforts are well advanced to find appHcations for phosphoms flame retardants, especially ammonium polyphosphate combinations, in polyolefins, and red phosphoms in nylons. Interest is strong in finding phosphoms-based alternatives to those halogen-containing systems which have encountered environmental opposition, especially in Europe. 

E. Termine and K. G. Taylor, "A New Intumescent Flame Retardant Additive for Thermoplastics and Thermosets," n Additive Approaches to PolymerModification, SPE RETEC Conference Papers, Toronto, Ontario, Canada, Sept. 1989. 

MixedPhosphona.te Esters. Unsaturated, mixed phosphonate esters have been prepared from monoesters of 1,4-cyclohexanedimethanol and unsaturated dicarboxyhc acids. Eor example, maleic anhydride reacts with this diol to form the maleate, which is treated with benzenephosphonic acid to yield an unsaturated product. These esters have been used as flame-retardant additives for thermoplastic and thermosetting resias (97). 

Ethylene vinyl acetate (EVA) polymers are used in thermoplastic and thermosetting jacketing compounds for apphcations that require flame retardancy combined with low smoke emission during the fire as well as the absence of halogen in the composition. 

The binder system of a plastic encapsulant consists of an epoxy resin, a hardener or curing agent, and an accelerating catalyst system. The conversion of epoxies from the Hquid (thermoplastic) state to tough, hard, thermoset soHds is accompHshed by the addition of chemically active compounds known as curing agents. Flame retardants (qv), usually in the form of halogens, are added to the epoxy resin backbone because epoxy resins are inherently flammable. 

Thermosetting unsaturated polyester resins constitute the most common fiber-reinforced composite matrix today. According to the Committee on Resin Statistics of the Society of Plastics Industry (SPl), 454,000 t of unsaturated polyester were used in fiber-reinforced plastics in 1990. These materials are popular because of thek low price, ease of use, and excellent mechanical and chemical resistance properties. Over 227 t of phenoHc resins were used in fiber-reinforced plastics in 1990 (1 3). PhenoHc resins (qv) are used when thek inherent flame retardance, high temperature resistance, or low cost overcome the problems of processing difficulties and lower mechanical properties. 

PP-g-MA) silicate nanocomposites and intercalated thermoset silicate nanocomposites for flame-retardant applications were characterised by XRD and TEM [333], XRD, TEM and FTIR were also used in the study of ID CdS nanoparticle-poly(vinyl acetate) nanorod composites prepared by hydrothermal polymerisation and simultaneous sulfidation [334], The CdS nanoparticles were well dispersed in the polymer nanorods. The intercalation of polyaniline (PANI)-DDBSA (dodecylbenzene-sulfonate) into the galleries of organo-montmorillonite (MMT) was confirmed by XRD, and significantly large 4-spacing expansions (13.3-29.6A) were observed for the nanocomposites [335],... 

Metal phosphinates have found applications as coatings and lubricants [76], as flame retardant additives in thermosetting compositions [77], and as pigments [78]. The possibility to introduce specific properties by the organic groups has not been exploited yet. 

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. 

Flame retardant fillers have been used for many years in thermosets, but have only recently begun to make an impression in the thermoplastics area due to the need to develop products sufficiently stable to withstand the higher processing temperatures involved. 

A composition is prepared by dissolving the MMBS modified thermoset resin in acetone. To the resulting solution, additives may be added, for example, pigments, flame retardants, lubricants or cure accelerators, e.g., hexamethylenetetramine. 

Historically, PEB has been used as an additive flame retardant for thermoset polyester and thermoplastic resins during the 1970s and 1980s. In 1977, the production of PEB was 45-450 metric tons [60]. The production of PEB declined to 5-225 metric tons in 1986, and in 1988, there was no ongoing or intended production or processing of this substance [60]. Information on the current manufacturers or processors of PEB is not publicly available in addition, information on the amount of PEB currently produced (if any) is confidential. However, PEB is listed as a low-production-volume chemical manufactured by Albemarle in France according to the European... 

Several commercial products have resulted from our phosphorus oligomer research. Fyrol 99, a 2-chloroethyl ethylene phosphate oligomer, has been successfully used as a flame retardant additive in rebonded urethane foam, in thermoset resins, in intumes-cent coatings, adhesives, paper air filters (13), and related uses. This product is less volatile and has a higher flame retardant efficacy than the parent compound tris(2-chloroethyl) phosphate. A related product was developed especially for use in flexible polyurethane foams. A vinylphosphonate/methylphospho-... 

The thermal- and flame-retardant properties of the copolymers obtained could be varied by changing the ratio of both monomers. Furthermore, in a related work, unsaturated polyesters containing pendant hydroxyl groups were prepared via ADMET and subsequently acrylated [130]. Further radical cross-linking afforded flame-retardant thermosets. 

There are several classes of amine phosphates commercially available to flame retard a wide variety of polymeric substrates, both natural and synthetic.24 A classic example is the three variations of melamine phosphate melamine orthophosphate, dimelamine orthophosphate, and melamine pyrophosphate. Of these, the pyrophosphate is the least soluble and the most thermally stable. Melamine orthophosphate is converted to the pyrophosphate upon heating, with the loss of water. All the aforementioned variations are available as finally divided solids, are used commercially in coatings, and have utility in a wide variety of thermoplastics and thermosets (mostly presented in the patent literature). 

Cyclic oligomeric phosphonates with the varying degrees of structural complexity (Structure 5.4) are also available in the market.25 They are widely used as flame-retardant finishes for polyester fabrics. After the phosphonate is applied from an aqueous solution, the fabric is heated to swell and soften the fibers, thus allowing the phosphonate to be absorbed and strongly held. It is also a useful retardant in polyester resins, polyurethanes, polycarbonates, polyamide-6, and in textile back coatings. A bicyclic pentaerythritol phosphate has been more recently introduced into the market for use in thermosets as well as for polyolefins (preferably, in combination with melamine or ammonium polyphosphate)... 

In thermosetting systems, the reactive flame retardant can be incorporated either in one or more of the principal chain-forming components, or in the cross-linking agent. Both strategies have been employed with P-containing flame retardants in a variety of thermosets. 

The predominant mode of action of phosphorus-containing flame retardants (both additives and reactives), when present in thermoplastics or thermosets, is considered to be in the condensed phase. Generally, as with cellulose, flammable gas generation is reduced and char formation is promoted. In some cases, the char cohesiveness is also enhanced. The retention of phosphorus in the chars in... 

Joseph, P. and Ebdon, J. R., Recent developments in flame-retarding thermoplastics and thermosets, in Fire Retardant Materials, Horrocks, A. R. and Price, D. (Eds.), 2000, Woodhead Publishing Limited, Cambridge, U.K., pp. 220-263. 

Wood Composites—these are resin-bonded composite boards where the particles are wood shavings, flakes, chips, or fibers bonded with thermosetting adhesives that can be urea formaldehyde, melamine formaldehyde, phenol formaldehyde, or diisocyanate. In recent years, the markets for OSB and MDF board have been rapidly increasing. Most particle board production uses urea-formaldehyde as a binder that is acid setting. Hence, sodium borates (alkaline) can interfere with the setting. As a result, boric acid has been the major boron compound used as the flame retardant in particle board.28 29 Typically, a loading of 12%-15% of boric acid in MDF is required to meet the ASTM E-84 Class A rating. If sodium borate is used as a flame retardant, phenol-formaldehyde binder, that is compatible with alkaline chemicals, is commonly used. 

Incorporation of modified clays into thermosetting resins, and particularly in epoxy35 or unsaturated polyester resins, in order to improve thermal stability or flame retardancy, has been reported.36 A thermogravimetric study of polyester-clay nanocomposites has shown that addition of nanoclays lowers the decomposition temperature and thermal stability of a standard resin up to 600°C. But, above this temperature, the trend is reversed in a region where a charring residue is formed. Char formation seems not as important as compared with other polymer-clay nanocomposite structures. Nazare et al.37 have studied the combination of APP and ammonium-modified MMT (Cloisite 10A, 15A, 25A, and 30B). The diluent used for polyester resin was methyl methacrylate (MMA). The... 

Zammarano, M. 2007. Thermoset fire retardant nanocomposites. In Flame Retardant Polymer Nanocomposites, Eds. A. Morgan and C. Wilkie, New York John Wiley Sons. 

Sumner, M. J., Sankarapandian, M., McGrath, J. E., Riffle, J. S., and Sorathia, U. Flame retardant novolac-bisphthalonitrile structural thermosets, Polymer 2002, 43, 5069. 

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