Polymer nanocomposites metal hydroxide

Marosi, G., Keszei, S., Matko, S., and Bertalan, G. 2006. Effect of interfaces in metal hydroxide-type and intumescent flame retarded nanocomposites. In Fire and Polymers TV Materials and Concepts for Hazard Prevention, Vol. 922, eds. Wilkie, C. and Nelson, G. Washington, DC ACS, pp. 117-30. 

The heat release rate curves shown in Fig. 4A are consistent with the characteristic burning patterns of intermediate thick, non-charring samples (II). The PHRR values for PE-ZCHS-5 and PE-ZCHS-10 nanocomposites are reduced by 27 and 25% relative to the pure PE respectively. For smectite clay/polymer nanocomposites, reduction in PHRR has been shown to be correlated with nanodispersion of the additive in the polymer matrix (72). With HDS and related layered metal hydroxide additives, we have also only found PHRR reduction in the case of PVE with CHDS, a system with some... 

The pol5mier nanocomposite field has been studied heavily in the past decade. However, polymier nanocomposite technology has been around for quite some time in the form of latex paints, carbon-black filled tires, and other pol5mier systems filled with nanoscale particles. However, the nanoscale interface nature of these materials was not truly understood and elucidated until recently [2 7]. Today, there are excellent works that cover the entire field of polymer nanocomposite research, including applications, with a wide range of nanofillers such as layered silicates (clays), carbon nanotubes/nanofibers, colloidal oxides, double-layered hydroxides, quantum dots, nanocrystalline metals, and so on. The majority of the research conducted to date has been with organically treated, layered silicates or organoclays. 

Three different types of nanomaterials, based on their dimensional characteristics, are generally used to prepare polymer nanocomposites. These include nanomaterials with only one dimension in the nanometre range (e.g. nano-clay), those with two dimensions in the nanometre scale (e.g. carbon nanotubes) and those that have all three dimensions in the nanometre scale (e.g. spherical silver nanoparticles), as stated earlier. Thus nanosize thin layered aluminosilicates or nanoclays, layer double hydroxide (LDH), a large number of nanoparticles of metals and their oxides, carbon nanotubes and cellulose nanofibres are used as nanomaterials in the preparation of vegetable oil-based polymer nanocomposites. 

Nanofillers may be nanoclays, carbon nanotubes (single or multiwall) (CNTs), silica, layered double hydroxides (LDHs), metal oxides, etc., offering the promise of a variety of new composites, adhesives, coatings, and sealant materials with specific properties [32-37]. Among the fillers mentioned, nanoclays have attracted most of the academia and industry interest, due to their abrmdance as raw materials and to the fact that their dispersion in polymer matrices has been studied for decades [38]. In fact, there are three major polymer nanocomposites categories in terms of nanofiller type that are expected to compile the global nanocomposites market in 2011 nanoclay-reinforced (24%), metal oxide-reinforced (19%), and CNTs-reinforced (15%) ones [39-41]. 

J. Zhang and C. A. Wilkie, Fire retardancy of polypropylene-metal hydroxide nanocomposite. In Fire and Polymers, A.C.S. Symposium Series 922, ed. C. Wilkie and G. Nelson (Washington, DC American Chemical Society, 2006), pp. 61-74. 

Layered double hydroxides (LDHs) are a different kind of layered crystalline filler for nanocomposite formation. Because they combine the flame retardant features of conventional metal hydroxide fillers (magnesium hydroxide and aluminum hydroxide) with those of layered silicate nanofillers (montmorillonite), LDHs are considered to be a new emerging class of nanofillers favorable for the preparation of flame retardant nanocomposites. In the present chapter, recent progress in the study of polymer/LDH flame retardant nanocomposites is reviewed. 

Nanodispersed metal hydroxides have been proved as efficient flame retardants for polymeric materials. It has been shown [107] that the LOI obtained from EVA containing 50 wt% Mg(OH)2 increases from 24% to 38.3% when micrometric Mg(OH)2 (2-5 irm) is replaced with nanometric Mg(OH)2. The enhancement of EVA flame retardancy by nanosized Mg(OH)2 was attributed to the good dispersion of the nanoparticles, which leads to the formation of more compact and cohesive charred layers during the combustion test. Therefore, the nanodispersed LDH layers may also contribute to the flame retardancy of polymer/LDH nanocomposites. 

C. Manzi-Nshuti, P. Songtipya, E. Manias, M. M. Jimenez-Gasco, J. M. Hossenlopp, and C. A. Wilkie, Polymer nanocomposites using zinc aluminum and magnesium aluminum oleate layered double hydroxides Effects of LDH divalent metals on dispersion, thermal, mechanical and fire performance in various polymers. Polymer, 50 (2009), 3564-74. 

In Chapter 7 the combination of nanocomposites with metal hydroxide flame retardants has generally been discussed. Since the use of metal hydroxide usually requires very high concentrations within the polymer matrix (often higher than 50% w/w), to achieve desired levels of flame retardancy as noted above regarding the work of Beyer, - the influence on rheology and hence processability can be significant. Hornsby and Roflion have discussed this issue and they report that compounded polymer melt viscosities and shear sensitivities, for example. 

The LDH materials can be very interesting to industry as they combine the features of conventional metal hydroxide-type fillers, like magnesium hydroxide (MH), with the layered silicate type of nanofillers, Hke montmorillonite. The major area of interest in this regard is the role of LDH materials as potential non-halogenated, non-toxic flame retardant for polymer matrices. For years, scientists have been using the concept of nanotechnology to improve the flame retardancy of polymer nanocomposites. This approach involves the dispersion of inorganic filler, in nanoscale, as flame retardants into a polymer matrix. Usually, for this purpose, layered silicates and various other nanoparticles (MgO, MH, etc.) are used after suitable pretreatment. Several research reports have already shown that such an approach indeed improves the flame retardancy of the composites [22,23]. 

In this chapter, we have dealt with LDHs used as a new kind of inorganic filler and the related polymer-LDH nanocomposites. As nanofillers, the LDH materials combine the features of the conventional metal hydroxide type of... 

Inorganic layered materials with positive charges, such as layered double hydroxides, LDH, can be used in nanocomposite polymer electrolytes. Experiments were performed on LDHs composed of positive charged layers M ,M i. ,(OH)2 and interlayer exchangeable anions (A "T/m nH20), where A was the anion, and M and M were divalent and trivalent metal... 

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