Flame retardants epoxide resins

Early efforts to impart flame retardancy upon epoxide resin formulations involved blending co-reactive halogenated compounds with liquid epoxides. These merely served as diluents and quite often resulted in products with markedly reduced physical properties such as Tg, thermal stability and compressive strengths. In order to avoid these problems, flame retardant epoxide resins have been synthesised containing halogen atoms within their molecular structures and these are now commonly used in epoxide resin based formulations. Their structures... 

Flame-retardant epoxy resins with different silicon contents were prepared using silicon-containing epoxides or silicon-containing prepolymers. The thermal stability and flame-retardant properties of the produced epoxide systems were evaluated and related to the silicon content. The char yields under nitrogen and air atmospheres increased with increase in silicon content. The authors pointed out that the silicon-containing resin has improved flame retardancy over the silicon-free resin as evidenced by the LOI. LOI values increased from 24 for a standard commercial resin to 36 for silicon-containing resins.35... 

The composition of an epoxide moulding material will greatly depend on the specific application, and this has been discussed at length. ". The resin may be of the epoxide novolac type and there will also be present hardeners, fillers (such as silica), a silane coupling agent, pigment, flame retardant and a wax release agent. 

Hou, M., Liu, W., Su, Q., and Liu, Y., Studies on the thermal properties and flame retardancy of epoxy resins modified with polysiloxane containing organophosphorus and epoxide groups, Polym. J. (Japan), 2007, 39, 696-702. 

Flexible PVC (Table 15.6) is made by polymerizing at 40-55°C and then compounding with 20-80 PHR (parts per hundred of resin) of dioctyl phthalate and/or other monomeric liquid plasticizers (e.g., dioctyl adipate for low-temperature flexibility, oligomeric polyesters for permanence, organic phosphates for flame-retardance), plus a synergistic stabilizer system usually composed of barium or calcium soap, zinc soap, epoxidized fatty ester, and organic phosphite. 

A reactive liquid epoxide used as an organic solvent and surfactant intermediate its polymers can be used for polyester, polyurethane, and polyacrylic resins, polyether polyols, flame-retardants, etc. 

Generally these compositions contain an epoxy-novolac, a hardener, a catalyst, silica fillers, and an internal lubricant/mold release compound. Brom-inated epoxies and antimony trioxide are included to provide the required flame retardant characteristics. Other, unspecified additives are used to promote adhesion or to reduce corrosion rates. Because of their superior thermal capabilities and electrical properties, epoxidized novolacs are preferred over epoxy homopolymers. Near stoichiometric amounts of hardeners such as novolacs (Equation 1), anhydrides, and primary amines can be used to cure the resins in the presence of a catalyst. The linkages which are formed include ethers, esters, or secondary amines, respectively. 

In order to take part in the thermosetting reaction, functionalized PPE is used. The curable part is an epoxide resin. Eor PCBs, a flame retardant composition is preferred, such as a bisphenol A diglycidyl ether tetrabro-mobisphenol A-based epoxy resin. " ... 

Cross-linked epoxy resins are combustible and their burning is self-supporting. They require mainly reactive flame-retardants, such as tetrachloro- or tetrabromobisphenol-A and various halogenated epoxides. Even the cross-linking agent may be flame-retardant, as in the case of chlorendic anhydride, tetrabromo- or tetrachloro-phthalic anhydride, or possibly phosphorus compounds. Halogenated agents can be supplemented with antimony trioxide. 

A new type of bismaleimide resin containing a P-heterocyclic unit was prepared by the reaction of a bis(epoxide) and two units of A-(4-carboxylphenyl)maleimide to make available a new flame retardant (Scheme 51). ... 

Although both brominated and chlorinated epoxide resins have been used, the preferred halogen is bromine. This is because less bromine (by weight) is required to impart flame retardancy than with chlorine. Another important reason for the selection of bromine in preference to chlorine is thermal stability. 

Salts such as ammonium polyphosphate have been successfully utilised as flame retardants in filled epoxide resin systems. It is more usual to employ phosphorus/halogen mixtures in epoxide resins. A combination of 1 5-2% phosphorus with 5-6% of chlorine will impart selfextinguishing properties to epoxides. 

Some specific recent applications of the GC-MS technique to various types of polymers include the following PE [49,50], poly(l-octene) [51], poly(l-decene) [51], poly(l-dodecene) [51], 1-octene-l-decene-l-dodecene terpolymer [51], chlorinated polyethylene [52], polyolefins [53, 54], acrylic acid methacrylic acid copolymers [55], polyacrylates [56], styrene-butadiene and other rubbers [57-59], nitrile rubber [60], natural rubbers [61, 62], chlorinated natural rubber [63, 64], polychloroprene [65], PVC [66-68], silicones [69, 70], polycarbonates [71], styrene-isoprene copolymers [72], substituted PS [73], polypropylene carbonate [74], ethylene-vinyl acetate copolymers [75], Nylon [76], polyisopropenyl cyclohexane a-methyl styrene copolymers [77], m-cresol-novolac epoxy resins [78], polymeric flame retardants [79], poly(4-N-alkyl styrenes) [80], polyvinyl pyrrolidone [81], vinyl pyrrolidone-methyl acryloxysilicone copolymers [82], polybutylcyanoacrylate [83], polysulfide copolymers [84], poly(diethyl-2-methacryloxy)ethyl phosphate [85], ethane-carbon monoxide copolymers [86], polyetherimide [87], bisphenol A [88], ethyl styrene [89], styrene-isoprene block copolymer [89], polyvinyl alcohol-co-vinyl acetate [90], epoxide thiol [91], maleic acid-propylene copolymer [92], P-hydroxy butyrate-P-hydroxy valerate copolymer [93], polycaprolactams [39,94], PS [95,96], polypyrrole [95,96], polyhydroxy alkanoates [97], poly(p-chloromethyl) styrene [81], polybenzooxazines and siloxy substituted polyoxadisila-pentanylenes [98,99] poly benzyl methacrylates [100], polyolefin blends after ageing in soil [101] and polystyrene peroxide [43]. 

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