Layered Silicate Compound

Graphene-polymer nanocomposites share with other nanocomposites the characteristic of remarkable improvements in properties and percolation thresholds at very low filler contents. Although the majority of research has focused on polymer nanocomposites based on layered materials of natural origin, such as an MMT type of layered silicate compounds or synthetic clay (layered double hydroxide), the electrical and thermal conductivity of clay minerals are quite poor [177]. To overcome these shortcomings, carbon-based nanofillers, such as CB, carbon nanotubes, carbon nanofibers, and graphite have been introduced to the preparation of polymer nanocomposites. Among these, carbon nanotubes have proven to be very effective as conductive fillers. An important drawback of them as nanofillers is their high production costs, which... 

Fig. 5.13 TFA results of NR/layered silicate compounds and an NR/silica vulcanizate [llRei].

Keywords layered silicate compound, copper oxides, glass-ceramics, transparency... 

Pol Tner Nanocomposites are novel plastic compounds with a filler having dimensions between 1 and 100 nm. They have attracted much attention in the past because nanocomposites exhibit markedly improved properties like stiffness, thermal flammability, improved barrier properties and others compared to the unfilled matrices [3], Among all potential fillers, those based on easily available clay and layered silicates have been more widely investigated for some time now. 

We have presented several examples of the successful preparation of rubber nanocomposites with layered silicate as the inorganic phase. This review explores the idea that the designing and compounding are key factors in obtaining the... 

Clay size layer silicates also have the ability to catalyze the polycondensation of phenolic compounds and amino acids. Wang et al. (1985) examined the catalytic effect of Ca-illite on the formation of N-containing humic polymers in systems containing various phenolic compounds and amino acids. The yields and N contents... 

Layered Silicates Associated with Flame-Retardant Compounds.303... 

Layered Silicates Associates with Brominated Compounds.315... 

In numerous works dealing with the combination of nanoparticles and FR compounds, surface modifications of nanoparticles were only aimed to promote good dispersion of the nanoparticles into the polymer matrix (with intercalated or exfoliated morphologies for layered silicates as nanoparticles), even in the presence of the usual FRs, for example ammonium polyphosphate (APP) or magnesium hydroxide (MH). The initial aim was to combine the individual effects of each component to achieve strong synergistic effects. 

Moreover, the development of new strategies for surface modifications of nanoparticles with compounds having FR activity could provide a new field of research on FR systems. The use of novel phosphorus-, nitrogen-, or halogen-containing modifiers, instead of alkylammonium ions, for layered silicates seems promising. FR action conferred by the surface modifier can be combined with action due to composite morphology, particularly when the host polymer is a polymer blend instead of a pure polymer. 

This chapter develops at first the more frequent combinations of nanoparticles that concern layered silicates associated with phosphorus compounds, as well as metallic hydroxides and halogen compounds. The association of natural layered silicates with intumescent FR (IFR) systems represents one of the main contributions of the combined use of nanoparticles and FRs. Moreover, combinations of layered silicates with other phosphorus compounds have been studied and have led to significant improvements for fire retardancy. 

LAYERED SILICATES ASSOCIATED WITH FLAME-RETARDANT COMPOUNDS... 

Layered Silicates Associated with Other Phosphorus and Nitrogen Compounds... 

Phosphorus FR compounds cover a wide range of chemical structures not only as additives incorporated in the molten state in thermoplastics but also as reactive components introduced as monomers in thermoset polymers phosphates, phosphonates, phosphinates, phosphine oxides, phosphites, red phosphorus, etc. They can be also used as layered silicate modifiers. Organic phosphates and red phosphorus are among the most frequent additive FRs used in various non-polyolefinic polymers. 

Among the conventional FR, which can be potentially associated with organomodified layered silicates, nitrogen compounds play a specific role in improving the flame retardancy of some polymers, particularly polyamides. Melamine and its salts are widely used, due to its ability to release... 

Besides the use of additive FR containing phosphorus into the host polymer nanocomposite, the modification of the layered silicates with P-based compounds seems promising. However, even taking into account the high specific surface area available, the quantity of phosphorus incorporated into the polymer is significantly lower than that obtained by the additive route. 

To take advantage of both modified layered silicate and the substantial presence of phosphorus, the combined use of phosphorus-modified silicates and phosphorus compounds may represent an innovative solution to achieve high levels of flame retardancy. Phosphonium-modified layered silicates in epoxy resins were associated with organo-phosphorus FRs by Schartel et al.59 Ion exchange of Na-montmorillonite was carried out using tetraphenyl phosphonium bromide. Triphenyl phosphate and a reactive phosphorus compound were used as FR incorporated in the epoxy resin. 

---