Montmorillonite flame retardant mechanisms

Montmorillonite is an effective complex with the initiator in the polymerization of methyl methacrylate." It not only accelerates the polymerization but also improves such mechanical properties as hardness and compression strength. Pentabromobenzyl acrylate was mechano-polymerized in the presence of Mg(0H)2. The polymerization occurred at a reduced temperature and a flame retarded product was produced. 

Koo and co-workers [78] attempted to develop polyamides 11 and 12 with enhanced flame retardancy and thermal and mechanical properties by the incorporation of montmorillonite clays, silica and carbon fibre-polymer nanocomposites. Flammability properties of the nanocomposites were compared with those of the virgin polyamides, using cone calorimetry with an external heat flux of 50 kW/m. Cone calorimetry was also used in an evaluation of polyamide 6 - anion modified Mg/Al interlayer formulation [79]. The data from the cone calorimeter shows that the heat production rate (HPR) and mass loss weight of the sample with 5 wt% MgAl(H-DS) decrease considerably to 664 kW/mVs and 0.161 g/mVs from 1064 kW/mVs and 0.252 g/mVs... 

Depending on the distribution of micro/nanofiller in the polymer matrix, the composites may be classified as microcomposites or nanocomposites. These two types of composites differ significantly with respect to their properties. The nanocomposites show improved properties compared to pure polymer or that of microcomposites. It started only back in 1990, when Toyota research group showed that the use of montmorillonite can improve the mechanical, thermal, and flame retardant properties of polymeric materials without hampering the optical translucency behaviour of the matrix. Since then, the majority of research has been focused in improving the physicochemical properties, e.g. mechanical, thermal, electrical, barrier etc. properties of polymer nanocomposites using cost effective and environmental friendly nanofillers with the aim of extending the applications of these materials in automotive, aerospace, construction, electronic, etc. as well as their day to day life use. The improvements in the majority of their properties have invariably been attributed... 

Wang, B.B., Song, L., Hong, N.N., Tai, Q.L., Lu, H.D., Hu, Y. Effect of election beam irradiation on the mechanical and thermal properties of intumiscent flame retarded ethylene-vinyl acetate copolymer/orcanically modified montmorillonite compositions. Radiat. Phys. Chem. 80, 1275-1281 (2011)... 

L. Yang, Y. Hu, H. D. Lu, and L. Song, Morphology, thermal, and mechanical properties of flame-retardant silicone rubber/montmorillonite nanocomposites. Journal of Applied Polymer Science, 99 (2006), 3275-80. 

Ristolainen et al." used modified montmorillonite as a partial substitute for ATH in PP-ATH composites and observed enhanced flame retardancy with composites containing both fillers. Wilkie and Zhang" studied the fire behavior of PE combined with ATH and a modified montmorillonite. The combination of PE with 2.5% modified montmorillonite and 20% ATH gave a 73% reduction in the peak heat release rate, which was the same as that obtained when 40% ATH alone was used. A further increase in the montmorillonite loading did not improve the fire properties. Mechanical properties such as elongation at break could be improved in comparing compounds with or without montmorillonite at the same reduction in peak heat release rate. 

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