Morphology characterization, filler dispersibility

Simple morphological characterization by TEM gives only qualitative information on the filler micro-dispersion and it becomes more dilficult on increasing the amount of the filler, as shown in Figure 23.4. 

As will be demonstrated later, morphology and physicochemical properties of reinforcing fillers are of crucial importance because they directly define their reinforcement ability. Their characterization formerly was based essentially on morphological properties (surface area and structure), but because of the use of silicas as reinforcing filler, there is now a strong need for dispersibility and surface chemistry characterization. 

From a practical point of view, an accurate morphological characterization of the filler dispersion allows us to ascertain the homogeneity of the filler network, responsible for the material s performance, as well as to detect structural differences in the filler aggregates and to relate them to the final properties of the composite material. 

The morphology characterization of hybrid membranes is very important to identify the possible interfacial morphology and particle dispersion in the final membrane matrix. Electron microscopy is typically used to investigate the filler dispersion and the hybrid membrane morphology. Scanning electron microscopy is the most frequently used technique, and it allows the characterization of the sample surface. The sample s cross-sections can be examined to analyze the inner morphology. Transmission electron microscopy is also a very useful technique because it allows a direct evaluation of the inner morphology of the sample. 

It is well known that experimental techniques are fundamental for proper characterization of the morphology of polymer/inorganic hybrids. In this scenario, microscopy techniques, such as SEM, TEM, and SPM, play a fundamental role in the characterization of the microstructure of particles, giving deep insight into the dispersion of inorganic fillers into the polymer matrices and helping to establish a more precise relationship between polymerization conditions and morphological characteristics of the particles. 

The exfoliated system is almost always quoted as the most desirable, since nanometric dispersion of day platelets maximizes the interfacial region between the filler and the polymer matrix, thus allowing to exploit the excellent mechanical properties of the individual day layers. Moreover, when exfoliation is attained, the number of reinfordng components is dramatically increased, since each day particle contains a very large number of day sheets. To further complicate matters, often a mixed dispersion is observed for day with different populations of tactoids or with partial exfoUation of single layers. Transmission electron microscopy (TEM) and WAXD are by far the most employed characterization techniques that assess the morphology of PLSN. 

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