Flame retardance epoxy nanocomposites

Thermosetting nanocomposites exhibit a reduced rate of heat release compared to neat polymer. However, the approach to nanocomposites itself is not sufficient to comply with the actual fire test standards. For this reason, traditional flame retardants are currently used in combination with nanofillers, and researchers are focusing on the individuation of synergistic systems. As an alternative to the most common cationic clays, anionic clays show improved performance in terms of flame retardancy. Epoxy nanocomposites based on anionic clay exhibit unique self-extinguishing behavior in a UL-94 horizontal burning test never observed before in a pure nanocomposite. The formation of a continnous intu-mescent ceramic layer on the surface of a polymer during combustion reduces the heat release rate to a higher extent than do montmorillonite nanocomposites. 

Liao, S.H., Liu, P.L., Hsiao, M.C., Teng, C.C., Wang, C.A., Ger, M.D., Chiang, C.L., 2012. One-step reduction and functionalization of graphene oxide with phosphorus-based compound to produce flame-retardant epoxy nanocomposite. Industrial Engineering... 

G. Das and N. Karak, Vegetable oil ased flame retardant epoxy/clay nanocomposites , Polym Degrad Stab, 2009, 94,1948-54. 

Hsiue, G.H. Liu, Y.L. Liao, H.H. Flame-retardant epoxy resins an approach from organic-inorganic hybrid nanocomposites. 7. Polym. Sci. A Polym. Chem. 2001, 39, 986-996. 

Das, G., Karak, N., 2009b. Vegetable oil-based flame retardant epoxy/clay nanocomposites. Polymer Degradation and Stability 94, 1948—1954. 

Ternary systems are becoming more widely reported with, in addition to epoxy and clay, other materials being present such as rubber, thermoplastic or fibres. Synergies need to be sought. likewise, the addition of additives such as flame retardants, either physically blended, or covalently-incorporated with the epoxy or amine need to be examined in nanocomposites, since this is one of the most important, ongoing requirements of transport industries such as aerospace. 

The addition of unmodified MWCNTs has a negative effect on thermal stability of the epoxy nanocomposites. This is due to the poor affinity between as-received MWCNTs and epoxy resin matrix, which increases vacancies or voids in the nanocomposite. However, the addition of amine-modified MWCNTs enhances the values of the first and second decomposition temperatures, which indicates the thermal stability improvement of the nanocomposite. The reason may be attributed to the fact that amine-modified MWCNTs have a better affinity for the polymer matrix than unmodified MWCNTs. Similar results are reports from Yang and Gu [51] using modified MWCNTs. TGA analysis indicates the thermal stabiUly improvement of the epoxy/MWCNTs nanocomposite. The reason may be due to the fact that triethylenetetramine TETA-grafted MWCNTs possess a good affinity to the epoxy matrix. The incorporation of functionalized CNTs into resin promoted the thermal stability and flame retardancy of the epoxy. 

Fig. 5 Suggested mechanism of flame retardants based in epoxy/CNT nanocomposites. Adapted [81, 95]...

M. Zammarano, M. Franceschi, F. Mantovani, A. Minigher, M. Celotto, and S. Meriani, Flame resistance properties of layered-double-hydroxides/epoxy nanocomposites. In Proceedings of the 9th European Meeting on Fire Retardancy and Protection of Materials, ed. M. Le Bras (Villeneuve D Ascq, France USTL Pub., 2003), pp. 17-19. 

Until 2003, Chen s [28], Qu s [29-31], and Hu s [32] groups independently reported nanocomposites with polymeric matrices for the first time the. In Hsueh and Chen s work, exfoUated polyimide/LDH was prepared by in situ polymerization of a mixture of aminobenzoate-modified Mg-Al LDH and polyamic acid (polyimide precursor) in N,N-dimethylactamide [28]. In other work, Chen and Qu successfully synthesized exfoliated polyethylene-g-maleic anhydride (PE-g-MA)/LDH nanocomposites by refluxing in a nonpolar xylene solution of PE-g-MA [29,30]. Then, Li et al. prepared polyfmethyl methacrylate) (PMMA)/MgAl LDH by exfoliation/adsorption with acetone as cosolvent [32]. Since then, polymer/LDH nanocomposites have attracted extensive interest. The wide variety of polymers used for nanocomposite preparation include polyethylene (PE) [29, 30, 33 9], polystyrene (PS) [48, 50-58], poly(propylene carbonate) [59], poly(3-hydroxybutyrate) [60-62], poly(vinyl chloride) [63], syndiotactic polystyrene [64], polyurethane [65], poly[(3-hydroxybutyrate)-co-(3-hydroxyvalerate)] [66], polypropylene (PP) [48, 67-70], nylon 6 [9,71,72], ethylene vinyl acetate copolymer (EVA) [73-77], poly(L-lactide) [78], poly(ethylene terephthalate) [79, 80], poly(caprolactone) [81], poly(p-dioxanone) [82], poly(vinyl alcohol) [83], PMMA [32,47, 48, 57, 84-93], poly(2-hydroxyethyl methacrylate) [94], poly(styrene-co-methyl methacrylate) [95], polyimide [28], and epoxy [96-98]. These nanocomposites often exhibit enhanced mechanical, thermal, optical, and electrical properties and flame retardancy. Among them, the thermal properties and flame retardancy are the most interesting and will be discussed in the following sections. 

Torre, L. Lelh, G. Kenny, J.M. Cnre kinetics of epoxy/anhydride nanocomposite systems with added reactive flame retardants. J. Appl. Polym. Sci. 2004, 94(4), 1676. 

The total heat evolved from clay nanocomposites reveals little improvement once the reduction in combustible organic material due to the presence of silicate is accounted for. A reduction of about 1 to 3% compared to pure epoxy is observed by cone calorimetry. " This effect is far below that usually resulting from adding traditional flame retardants. For this reason, researchers turned... 

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