Polymer matrix nanocomposites PNCs

A nanocomposite material can be defined as one that consists of two or more different material components, at least one of which has a domension (i.e., length, width, or thickness) below 100 nm. There are many types of nanocomposites presently under research and development including polymer/inor-ganic particle, polymer/polymer, metal/ceramic, and inorganic-based nanocomposites. However, the first named one, commonly called polymer nanocomposite (PNC) and defined as the comhination of a polymer matrix resin (continuous phase) and inclusions having at least one dimension less than 100 nm, is the only type of nanocomposite to date that has seen any significant commercial activity. 

Polymeric nanocomposites (PNCs) are materials composed of a macromolecular matrix and dispersed in it solid particles having at least one dimension within a low-nanometer range (e.g., platelet thickness < 2 nm). Their PVT behavior resembles very closely that of a matrix, and the theoretical models describe the behavior as having precision similar to that of a neat polymer [Utracki, 2007a, 2008a]. The measurements are time consuming since addition of 1 to 5 wt% clay (or 0.4 to 2 vol%) has a small effect on V, and thus high reliability and repeatability of data are critical. 

A polymer composite is a hybrid material that incorporates a non-polymeric component into the bulk polymeric material in order to improve or alter its function. Fiberglass is an example that integrates glass fibers into the interior of a polymeric matrix (polyester) to increase the polymer s strength. A polymer nanocomposite (PNC) is a polymer composite in which the non-polymeric component has at least one dimension in the nanoscale. PNCs can be divided into two major categories those that incorporate the nano-elements as fillers (in the interior of the matrix) and those that incorporate the nano-elements as coatings (on the exterior surface of the matrix) (Fig. 4.2). 

It is no surprise that a combination of different agents that cause polymer instability increases the degradation rate. For example, the presence of heavy metals (left behind catalyst or brought in with, for example, clay nano-particles) enhances photo- or thermo-oxidative degradation. Dynamic flow behavior of the polymeric nanocomposites (PNC) with either PS or PP matrix... 

Since nanoparticles in PNC are orders of magnitude smaller than conventional reinforcements, the models developed for composites are not applicable to nanocomposites. However, development of a universal model for PNC is challenging since the shape, size, and dispersion of the nanoparticles vary widely from one system to another. On the one hand, exfoliated clay provides vast surface areas of solid particles (ca. 800 m /g) with a large aspect ratio that adsorb and solidify a substantial amount of the matrix polymer, but on the other hand, the mesoscale intercalated clay stacks have a much smaller specific surface area and small aspect ratio. However, in both these cases the particle-particle and particle-matrix interactions are much more important than in conventional composites, affecting the rheological and mechanical behavior. Thus, the PNC models must include the thermodynamic interactions, often neglected for standard composites. 

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