Polymer clay nanoparticles

Concerns regarding the toxicity and environmental effects of polymer-based nanocomposites, such as those derived from clay nanoparticles or carbon nanotubes, throughout their life cycle, from formulation, polymerisation, compounding, fabrication, use, disposal and degradation, are described. The potential of nanoparticles to enter the body by skin contact or inhalation is discussed. Accession no.927669... 

Insulating interlayers separates the inclusions from each other and from the matrix polymer in such system degradation catalyzed by nanoparticles starts within the interlayer. This layer should provide less combustible degradation products. A new method for the formation of PEP resin has been proposed recently [21]. A detailed analysis of PEP revealed the combined (gas and solid phase) mechanism of FR action in this material [41], This polymer was selected for forming an interlayer around clay nanoparticles. The monomer components were introduced during the compounding process and the interlayer was formed by in situ curing. 

Examples of the use of nanostructured materials for packaging applications have been given in Chaudhry et al. (2008) and references therein. One of the first market entries into the food packaging arena was polymer composites containing clay nanoparticles (montmorillonite). The natural nanolayer structure of the clay particles impart improved barrier properties to the clay-polymer composite material. Some of the polymers which have been used in these composites for production of packaging bottles and films include polyamides, polyethylene vinyl acetate, epoxy resins, nylons, and polyethylene terephthalate. 

The rheological behavior of these materials is still far from being fully understood but relationships between their rheology and the degree of exfoliation of the nanoparticles have been reported [73]. An increase in the steady shear flow viscosity with the clay content has been reported for most systems [62, 74], while in some cases, viscosity decreases with low clay loading [46, 75]. Another important characteristic of exfoliated nanocomposites is the loss of the complex viscosity Newtonian plateau in oscillatory shear flow [76-80]. Transient experiments have also been used to study the rheological response of polymer nanocomposites. The degree of exfoliation is associated with the amplitude of stress overshoots in start-up experiment [81]. Two main modes of relaxation have been observed in the stress relaxation (step shear) test, namely, a fast mode associated with the polymer matrix and a slow mode associated with the polymer-clay network [60]. The presence of a clay-polymer network has also been evidenced by Cole-Cole plots [82]. 

Immiscible polymer blends normally have a sea-island stmcture, where one polymer is dispersed as (normally spherical) particles in the other polymer, which forms the matrix, or a co-continuous structure, where both polymers are equally distributed in the blend without one polymer forming a continuous phase. For the blends to have good mechanical properties, it is also important that there is good interaction between the different components in the blend. To ensure this, researchers have tried a variety of methods to compatibilize the polymers in blends. The most used method is to add a third polymer, which interacts well with the other two polymers, into the blend. Reactive blending is another well-used method, and recently, a lot of investigation went into the use of (especially clay) nanoparticles to improve the interaction between the polymer components by locating themselves on the interfaces between the polymers. 

I. Labaume, J. Huitric, P. Mederic, T. Aubry, Stiuctural and rheological propaties of different polyamide/polyethylene blends filled with clay nanoparticles a comparative study. Polymer 54, 3671-3679 (2013)... 

Layered nanoparticles, like the aggregates of silicates talc and mica, form close proximity sheets of polymer—clay hybrids due to the immiscibility of clay in polymer. The degree of dispersion in these composites is normally referred to as the following ... 

Besides clay-based nanocomposites, there has been huge discussion on the metallic and semiconductor-based hybrid materials. The ability of polymer materials to assemble into nanostructures describes the use of polymers providing exquisite order to nanoparticles. Finally, a discussion on potential applications of polymer—nanoparticle composites with a special focus on the use of dendrite polymers and nanoparticles for catalysis should follow (Polymer-Nanoparticle Composites Part 1 (Nanotechnology), 2010) (Figure 1.15). 

Organoclays have also similar effects on polymers thermal stability and in this case the achieved clay dispersion (intercalated-exfoliated) as well as the used modifier can also alter thermal decomposition of polymers. Cationic compounds used for organomodification of MMT have a negative effect in thermal degradation while the exfoliated stmcture due to the finer dispersion of the clay nanoparticles can lead to thermal stabilization than intercalated structure. 

The addition of nanoparticles to synthetic rubber resulting in enhancement in thermal, stiffness and resistance to fracture is one of the most important phenomena in material science technology. The commonly used white filler in mbber industry are clay and silica. The polymer/clay nanocomposites offer enhanced thermo mechanical properties. Bourbigot et al. observed that the thermal stability of polystyrene (PS) is significandy increased in presence of nanoclay [75]. Thermal and mechanical properties of clays multiwalled carbon nanotubes reinforced ethylene vinyl acetate (EVA) prepared through melt blending showed synergistic effect in properties [76]. 

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