Morphology of Polymer Nanocomposites

In addition to monosized nanopartide, the morphology of binary nanopartides filled in microphase separating AB diblock copolymers has also been studied. For chemically identical spherical partides, large particles are concentrated in the preferred, compatible phase and small partides spread out in the interfacial regions and in the incompatible phase of the diblock copolymer [17]. Theoretical efforts have also been made toward the morphology of copolymer filled with anisotropic particles (e.g., rod-like partides, plate-like partides, or the mixtures of particles of different shapes). It is found that the distribution of partides within the copolymers depends not only on the relative interaction energies between nanopartides and different blocks but also on the aspect ratio of the rod-like nanopartides. 

Mechanical properties of polymer nanocomposites can be predicted by using analytical models and numerical simulations at a wide range of time- and length scales, for example, from molecular scale (e.g., MD) to microscale (e.g., Halpin-Tsai), to macroscale (e.g., FEM), and their combinations. MD simulations can study the local load transfers, interface properties, or failure modes at the nanoscale. Micromechanical models and continuum models may provide a simple and rapid way to predict the global mechanical properties of nanocomposites and correlate them with the key factors (e.g., particle volume fraction, particle geometry and orientation, and property ratio between particle and matrix). Recently, some of these models have been applied to polymer nanocomposites to predict their thermal-mechanical properties. Young s modulus, and reinforcement efficiency and to examine the effects of the nature of individual nanopartides (e.g., aspect ratio, shape, orientation, clustering, and the modulus ratio of nanopartide to polymer matrix). 

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TEM. However, this observation is in all cases qualitative and highly localised. A general idea of the morphology of polymer nanocomposites can also be obtained by SEM. The dispersion pattern of the nanomaterial in the polymer matrix may be visualised from SEM micrographs. In addition to topographical information, this also provides the chemical composition near the surface of the nanocomposites or nanomaterials (energy dispersive X-ray spectroscopy, EDX system). 

Liu, J. et al. (2006) A review on morphology of polymer nanocomposites reinforced by inorganic layer structures. Mater. Manuf. Process, 21, 143-151. 

FIGURE 2.14 Tapping mode phase morphology of the nanocomposites (a) poly[styrene-(ethylene-co-butylene)-styrene] (SFBS)-Cloisite 20A and (b) its 3D image. (From Ganguly, A., Sarkar, M.D., and Bhowmick, A.K., J. Polym. ScL, Part B Polym. Phys., 45, 52, 2006. Courtesy of Wiley InterScience.)... 

Solvent-polymer and solvent-clay interactions are very important in determining the morphology of polymer/clay nanocomposites. There are many reports describing the preparation of PNCs by solution mixing [65, 231-235]. Ho and Glinka [38]... 

Provided in this chapter is an overview on the fundamentals of polymer nanocomposites, including structure, properties, and surface treatment of the nanoadditives, design of the modifiers, modification of the nanoadditives and structure of modified nanoadditives, synthesis and struc-ture/morphology of the polymer nanocomposites, and the effect of nanoadditives on thermal and fire performance of the matrix polymers and mechanism. Trends for the study of polymer nanocomposites are also provided. This covers all kinds of inorganic nanoadditives, but the primary focus is on clays (particularly on the silicate clays and the layered double hydroxides) and carbon nanotubes. The reader who needs to have more detailed information and/or a better picture about nanoadditives and their influence on the matrix polymers, particularly on the thermal and fire performance, may peruse some key reviews, books, and papers in this area, which are listed at the end of the chapter. 

Most of the previous studies on flame retardation of polymer nanocomposites are focused on the relationship between macroscopic morphologies of chars and the flammability properties. Fang et al. studied the relationship between evolution of the microstructure, viscoelasticity and graphitization degree of chars and the flammability of polymers during combustion (68). The flame retar-dancy of ABS/clay /MWNTs nanocomposites was strongly affected by the formation of a network structure. Flammability properties... 

This chapter reports the results of the literature that concerns the photooxidation of polymer nanocomposites. The published studies concern various polymers (PP, epoxy, ethylene-propylene-diene monomer (EPDM), PS, and so on) and different nanofillers such as organomontmorillonite or layered double hydroxides (LDH) were investigated. It is worthy to note that a specific attention was given to the interactions with various kinds of stabilizers and their efficiency to protect the polymer. One of the main objectives was to understand the influence of the nanofiller on the oxidation mechanism of the polymer and on the ageing of the nanocomposite material. Depending on the types of nanocomposite that were studied, the influence of several parameters such as morphology, processing conditions, and nature of the nanofiller was examined. 

Studies indicate the formation of an intercalated morphology in the nanocomposites due to favorable interactions between the polymer matrix and the clay. The morphology of the nanocomposite is intricately linked to the amount of silicate in the system. With clay content >15 wt%, mechanical properties are further improved but the formation of an apparent superlattice structure correlates with a loss in the electrical properties of the nanocomposite [25]. 

Hyde, J. Licence, P. Carter, D. Poliakoff, M. (2001) Continuous Catalytic Reactions in Supercritical Fluids. Appl. Catal., A. Vol.222, No.1-2, pp.119-131 Jin, S. Kang, C Yoon, K Bang, D. Park, Y. (2009) Elect of compatibilizer on morphology, thermal, and rheological properties of polypropylene/functionalized multi-walled carbon nanotubes composite. /. Ayyl. Polym. Set. Vol.lll, No.2, pp.1028-1033 Joen, H Jung, H Lee, S. Hudson, S. (1998) Morphology of polymer/Silicate Nanocomposites Hieh Density Polyethylene and a Nitrile Copolymer. Polym. Bull. Vol.41, No.l, pp.107-111... 

On a thermodynamic ground, nanoscale mixing of layered silicates with polymers is only possible if the chemical structure of both components is such to grant favorable energetic interactions [4-8]. However, the morphology of experimental nanocomposites will be dependent on kinetics as well, and, consequently, on the pathway of their preparation. 

The mechanical performances of polymer nanocomposites are influenced not only by several factors such as properties and amounts of the constituent phases (matrix and nanofiller), nanoparticle dispersion, morphology, and orientation, the matrix-filler interactions but also by the degree of crystallinity and crystalline phases of the polymer, as described... 

The art of filler dispersion in polymer matrix is easily determined by X-ray analysis especially WAXS analysis. The intensity and position of X-ray diffraction peaks reveals the exact idea regarding the morphological structure of polymer nanocomposites. Figure 22.11 compares reduced graphite oxide dispersions in NR matrix by different processes such as milling and solution casting methods. 

P. Hajji, L. David, J.E. Gerard, J.P. Pascault, G.J. Vigier, Journal of Polymer Science Part B Synthesis, structure, and morphology of polymer—silica hybrid nanocomposites based on hydroxyethyl methacrylate. Polymer Physics 37 (1999) 3172. 

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