Clay-nanoparticle polymer composites

In nanoparticle-polymer composites, thermal stability is one of the most important property enhancements. Recently, some theoretical efforts have been made to predict the thermal stability of such composites. For example, FEM and the theory of Chow have been used to predict the thermal expansion of clay-polymer nanocomposites. The results indicate that it is possible to considerably reduce and eventually match the thermal expansion of metal and polymer parts by dispersing a small amount of exfoliated muscovite mica platelets into a polymer matrix. Moreover, reduction is controlled by the product of aspect ratio and volume fraction of the platelets. 

T. D. Fornes and D. R. Paul. Modeling properties of nylon 6/clay nanoparticles using composite theories. Polymer, 44 (2003), 4993 5013. 

Currently, the study on ternary polymer composites containing both clay and CNTs is still at its primary stage, but it is promising and exciting to assemble two types of nanoparticles to break the limitation of single nanofiller in composites. Furthermore, we would like to propose some issues that should be addressed in future work in this field ... 

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. 

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 ... 

Almost all types of vegetable oil-based polymer nanocomposites, that is clay/polymer nanocomposites, carbon nanotubes/polymer nanocomposites, metal nanoparticles/polymer nanocomposites (metals such as Ag, Cu, Fe and their oxides) are found in the literature. These have several advantages over their respective pure polymers, or conventional polymer composite systems, and thus have the potential to meet the current demand for advanced polymeric materials. 

Recently, a big window of opportunities has opened for polymer nanocomposites just to overcome the limitations of traditional microcomposites. Although, the chemistry of clay minerals and composites based on some nanoscale particles is known for several decades, the research and development of nanoscale-filled polymers has been skyrocketed in recent years, for numerous reasons. First, unprecedented combinations of properties have been observed in some polymer nanocomposites. For example, incorporation of isodimensional nanoparticles into thermoplastics increases the modulus, the yield stress, and the ultimate tensile strength (Sumita et al. 1983). 

Nowadays, ordered inorganic/organic PNs with a finely tuned structure have displaced a lot of traditional composite materials in a variety of applications because the intimate interactions between components can provide enhancement of the bulk polymer properties (i.e., mechanical and barrier properties, thermal stabihty, flame retardancy, and abrasion resistance). The reinforcing nanoparticle/ polymer adhesion is of primarily importance, as it tunes the final properties of the nanocomposite. Polymer/clay nanocomposites (PCNs) meet this demand due to the platelet-type dispersion of the clay filler in the organic matrix [1]. 

The extent of clay dispersion and clay-polymer interaction is crucial in determining the formation of natural rubber based nanocomposites. Due to the low polarity and high viscosity of natural rubber, direct blending of clay nanoparticles into natural rubber will only yield micro-scale composites. Thus, it is more effective to blend clay nanoparticles into another polymer component before blending with natural rubber. 

Polymer nanocomposites consist of a polymer matrix with embedded filler particles with at least one dimension at the nanometre level, (i.e. 1-100 nm), much smaller than for the conventional polymer composites described above. The inclusion of nanoparticles can effect significant improvements in mechanical properties such as modulus, yield stress and fracture toughness for filler levels as low as a few per cent by weight. This is much lower than in conventional polymer composites, as illustrated in Figure 9.7, where the effect of talc reinforcement and clay nanoparticle reinforcement in a polypropylene matrix are compared. Talc filler is regarded as a conventional reinforcement, with particle diameters in the range 1-10 qm and thickness around 20 times less, whereas the clay particles are of length around 100 nm and thickness as low as 1 nm. Clay occurs in the form of platelets and has been... 

Natural polymer research has included use of these alternative materials with nanoparticles [487] because of three significant properties multifunctionality, biodegradabihty, and bio-compatibihty. Breakthroughs in cost of production and property profiles for biomaterials will be needed before they become reasonable to market. Research has been conducted on melt formation of a starch-clay nanocomposite for bioplastic applications [487] however, an issue is the high water uptake and thus loss in mechanical properties requiring modification of the clay and the composite process. As with other nanocomposites, microstructural characterization is typically by TEM and AFM. 

---