Polymer nanocomposites parameters

CNT nanocomposites morphological and structural analysis is often done by TEM but an extensive imaging is required then to ensure a representative view of the material. Moreover, carbon based fillers have very low TEM contrast when embedded in a polymer matrix. The application of microscopy techniques is very useful to control the status of CNTs at any time during the preparation process of CNT/polymer nanocomposites, and moreover, to gain insights on parameters important for a better understanding the performance of the final nanocomposite material based on CNTs. 

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. 

A chapter focusing on the use of nanocomposites in electrochemical devices is presented by Schoonman, Zavyalov, and Pivkina. A wide range of metal (metal ox-ide)/polymer nanocomposites has been synthesized using Al, Sn, Zn, Pd, and Ti as a metal source and poly-para-xylylene (PPX) as a polymeric matrix. The properties of the nanocomposites were studied by comparing structure, morphology, electrical properties, oxidation kinetics, and electrochemical parameters. 

As can be seen from the discussion above, the polyelectrolyte gel-surfactant complexes present interesting hybrid metal-polymer nanocomposites, allowing a vast variety of incorporated metals and metal-polymer-surfactant structures. The limitations of these systems are their heterogeneous character (insoluble in any media) and excessive sensitivity to external parameters (pH, temperature, etc.). 

Polymer nanocomposites multicomponentness (multiphaseness) requires their stmctural components to be quantitative characteristics determination. In this aspect, interfacial regions play a particular role, as it has been shown earlier, that they are the same reinforcing element in elastomeric nanocomposites as nanofiller actually [ 1 ]. Therefore, the knowledge of interfacial layer dimensional characteristics is necessary for quantitative determination of one of the most important parameters of polymer composites, in general,— their reinforcement degree [2, 3]. 

Up to now we considered pol5meric fiiactals behavior in Euclidean spaces only (for the most often realized in practice case fractals structure formation can occur in fractal spaces as well (fractal lattices in case of computer simulation), that influences essentially on polymeric fractals dimension value. This problem represents not only purely theoretical interest, but gives important practical applications. So, in case of polymer composites it has been shown [45] that particles (aggregates of particles) of filler form bulk network, having fractal dimension, changing within the wide enough limits. In its turn, this network defines composite polymer matrix structure, characterized by its fractal dimension polymer material properties. And on the contrary, the absence in particulate-filled polymer nanocomposites of such network results in polymer matrix structure invariability at nanofiller contents variation and its fractal dimension remains constant and equal to this parameter for matrix polymer [46]. 

The uniformity and stability of nanotube dispersion in polymer matrices are most important parameters for the performance of composites. A good dispersion leads to efficient load transfer concentration centres in composites and to uniform stress distribution. Many scientists have reviewed the dispersion and functionalisation techniques of CNT for polymer-based nanocomposites, as well as their effects on the properties of CNT/polymer nanocomposites. They demonstrated that the control of these two factors led to uniform dispersion. Overall, the results showed that a proper dispersion enhanced a variety of mechanical properties of nanocomposites. 

The ultraviolet (UV) - visible spectrophotometer is another important tool in the characterisation of vegetable oil-based polymer nanocomposites and is particularly effective for metal nanocomposites. The formation of metal nanoparticles in the matrix can be easily detected by UV-visible spectroscopy. Every metal nanoparticle has its own characteristic surface plasmon resonance value. This band is attributed to the collective oscillation of electron gas in the nanoparticles, with a periodic change in the electronic density at the surface. Parameters such as particle size, shape and dielectric constant of the medium and surface adsorbed species determine the position and shape of the plasmon absorption. When the particles become significantly smaller than the mean free path of electrons in the bulk metal, the plasmon oscillation is dampened. The plasmon absorption peak shifts to a higher wavelength than expected with an increase in aggregation of the nanoparticles. The sharpness of the peak indicates the narrow size distribution. 

The dispersion of clay platelets (exfoliation and intercalation level of the silicate layers) and surface area of silicate platelets have the potential to alter the rheological behavior of the nanocomposites. In-situ polymerized nano composites exhibit more exfoliated structure than the composites prepared by the melt blending technique. Irrespective of the processing parameter, the nanocomposites show shear thinning behavior at high shear rate (Figure 9.14), whereas the pristine polyamide exhibits Newtonian behavior (i.e., the viscosity remains almost the same). It has also been reported that the polymer nanocomposite possesses higher steady shear viscosity than pristine polyamide at low shear rates. 

Polymer nanocomposite properties are related to a variety of parameters, among which the most important are the features of the constituent phases, the dispersion and the interfacial interaction between the nanomaterials and the matrix [33,39], Nanomaterials tend to agglomerate due to Van der Waals forces in order to achieve a stable dispersion in polymers that lack a permanent dipole moment or suitable mechanism to favorably interact with carbon nanomaterials, physical or chemical modification of either the nanofiller or the polymer matrix is necessary [39],... 

Tailoring the properties of polymers with the inclusion of nanometric carbon depends on many factors. Among them, the parameters most taken into account are (a) the size, structure and distribution of the nanofiller in the matrix and (b) the interface between the nanofillers and the matrix. This chapter focuses mainly on the effects that functionalization and concentration of nanofillers have in the storage modulus and tribological properties of polymer nanocomposites reinforced with NDs, CNTs and graphene, describing briefly the hardness and scratching performance achieved in these nanocomposites. 

Several studies on the characterization and fabrication of carbon nanotube-polymer nanocomposites have highlighted the important roles of the parameters discussed in Chapter 2 (such as, orientation, dispersion, and interfacial adhesion) in determining the properties of the composites. Jia et al. [75] used an in situ process for the fabrication of a PM M A/ M WNT composite. An initiator was used to open up the Jt bonds of the MWNTs in order to increase the linkage with the PMMA. The formation of C—C bonds results in a strong interface between the nanotubes and the PMMA. 

The investigation achieved on the effect of nanofiUers on the material durability must consider the impact of degradation on environmental health and safety. The post-irradiation stage of polymer hybrids pursues the long term operation under optimal parameters. The research effort on radiation processed polymer nanocomposites emerges to beneficial applications even for nuclear industry that develops cmcial diminishment of degradation. 

This is a three-part book with the first part devoted to polymer blends, the second to copolymers and glass transition tanperatme and to reversible polymerization. Separate chapters are devoted to blends Chapter 1, Introduction to Polymer Blends Chapter 2, Equations of State Theories for polymers Chapter 3, Binary Interaction Model Chapter 4, Keesome Forces and Group Solubility Parameter Approach Chapter 5, Phase Behavior Chapter 6, Partially Miscible Blends. The second group of chapters discusses copolymers Chapter 7, Polymer Nanocomposites Chapter 8, Polymer Alloys Chapter 9, Binary Diffusion in Polymer Blends Chapter 10, Copolymer Composition Chapter 11, Sequence Distribution of Copolymers Chapter 12, Reversible Polymerization. 

Electrically conductive polymer nanocomposites are widely used especially due to their superior properties and competitive prices. It is expected that as the level of control of the overall morphology and associated properties increases we will see an even wider commercialisation on traditional and totally novel applications. In this section we have discussed the basic principles of the percolation theory and the different types of conduction mechanisms, outlined some of the critical parameters of controlling primarily the electrical performance and we have provided some indications on the effect such conductive fillers have on the overall morphology and crystallisation of the nanocomposite. The latter becomes even more critical if we take into consideration that modem nanosized fillers offer unique potential for superior properties at low loadings (low percolation thresholds) but have a more direct impact on the morphology of the system. Furthermore we have indicated that similar systems can have totally different behaviour as the preparation methods, the chain conformation and the surface chemistry of the fillers will have a massive... 

Another parameter influencing the mechanical properties of nanotube composites is the CNT alignment. The effects of CNT alignment on electrical conductivity and mechanical properties of CNT-polymer nanocomposites have been discussed in a number of researches [118-120]. For example, it has been reported that with increasing CNT alignment, the electrical and mechanical properties of the SWNT-epoxy composites increased due to an increased interface bonding of CNTs in the polymer matrix [119],... 

Despite any shortcomings and approximations, these theoretical endeavors offer valuable insights in important design parameters for the mechanical performance of polymer nanocomposites. Specifically ... 

In the stated above treatment not only nanostructure integral characteristics (macromolecular entanglements cluster network density v, or nanocluster relative fraction cp j), but also separate nanoeluster parameters are important (see Section 15.1). In this case of particulate-filled polymer nanocomposites (artificial nanocomposites) it is well-known, that their elasticity modulus sharply increases at nanofiller particles size decrease [17]. The similar effect was noted above for REP, subjected to different kinds of processing (see Fig. 15.28). Therefore, the authors of Ref. [73] carried out the study of the dependence of elasticity modulus E on nanoclusters size for REP. 

Compared to the substantial experimental attempts, however, theoretical consideration of the mechanisms involved in adequate predictability is not well reported. Design and production of polymer nanocomposites have to be mostly conducted on a trial and error basis. Empirical extrapolation of the parameters related to components selection and processing technique is not very successful. 

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