Two-dimensional fillers

Recently, studies have shown that the grafting of hydroxyl groups present on layer surfaces of pristine montmorillon-ite (MMT) and organo-modified MMT could fadhtate the entry of more polymer chains in between the interlameller space of MMT [80]. 

Layered double hydroxides (LDH) are another emerging class of layered crystals due to their wide range of applications in catalysis, sorbent, ion exchangers, stablizer and fire retardance [81, 82]. The LDHs have a brucite-like structure, where divalent octahedrally coordinated M(II) ions are partially substituted by trivalent M(III) ions. As a result, the positively charged metal oxide/hydroxide layers are neutralized by other charge-balancing anions. The general chemical formula of LDHs is [M , M (0H)J i+(A ) -nH,0 where, M = Li+, Mg, Co, Zn, Ni, etc. M + = Al +, Cr , Fe, etc., and A = Cl, NOj, COj, , etc. [83]. The 

---

Lipatov (22) investigated the effects of interphase thickness on the calorimetric response of particulate-filled polymer composites. Based on experimental evidence, his analysis led to the conclusion that the interphase region surrounding filler particles had sufficient thickness to give rise to measurable calorimetric response. The proposed existence of a thick interphase region correlates with limitations of molecular mobihty for supermolecular structures extending beyond the two-dimensional filler boundary surface. 

Nonlinear Viscoelasticity of Two Dimensional Filler Reinforced Rubber Nanocomposites... 

Keywords Clay Composites Graphene Nanocomposites Rubbers Two-dimensional fillers... 

Graphitic fillers and layered silicates are the main two dimensional fillers used to reinforce elastomer matrices. Here the significance of the most important nanoplatelets—nanoclay and graphene—on the nonlinear viscoelasticity of rubbers is discussed. Figure 1 gives the structural representation of these nanoparticles. 

TEM is still the most powerful technique to elucidate the dispersion of nano-filler in rubbery matrix. However, the conventional TEM projects three-dimensional (3D) body onto two-dimensional (2D) (x, y) plane, hence the structural information on the thickness direction (z-axis) is only obtained as an accumulated one. This lack of z-axis structure poses tricky problems in estimating 3D structure in the sample to result in more or less misleading interpretations of the structure. How to elucidate the dispersion of nano-fillers in 3D space from 2D images has not been solved until the advent of 3D-TEM technique, which combines TEM and computerized tomography technique to afford 3D structural images, incidentally called electrontomography . 

In this section, we show the morphological changes of stretched NR without filler by AFM. Two-dimensional mappings of topography and elasticity for elongated NR will be given to confirm the breakdown of the long-beheved assumption of affine deformation. 

The blend morphology containing conductive filler (e.g., carbon black) was simulated by the model based on Cahn s approach. Figure 16.10 shows the two-dimensional cut explaining the localization of carbon black between two incompatible phases, and Figure 16.11 shows the effect of carbon black concentration on the prediction of conductivity. This simple model of interfacial film partitioning... 

Recently, Vaia et al. [8] reported a new process for direct polymer intercalation based on a predominantly enthalpic mechanism. By maximization of the number of polymer host interactions, the unfavorable loss of conformational entropy associated with intercalation of the polymer can be overcome leading to new intercalated nanostructures. They also reported that this type of intercalated polymer chain adopted a collapsed, two-dimensional conformation and did not reveal the characteristic bulk glass transition. This behavior was qualitatively different from that exhibited by the bulk polymer and was attributed to the confinement of the polymer chains between the host s layers. These types of materials have important implications not only in the synthesis and property areas, where ultrathin polymer films confined between adsorbed surfaces are involved. These include polymer filler interactions in polymer composites, polymer adhesives, lubricants, and interfacial agents between immiscible phases. 

Increasing the concentration of metal particles in an insulating adhesive matrix changes the electrical properties of the composite in a discontinuous way. Assuming a random dispersion of the metal filler, as the concentration increases no significant change occurs until a critical concentration, pc, is reached. This point, where the electrical resistivity decreases dramatically, called the percolation threshold, has been attributed to the formation of a network of chains of conductive particles than span the composite. A two-dimensional cartoon of a conductive adhesive below p and just above pc is shown in Fig. 3. A typical plot showing the relationship between particle concentration and electrical resistivity is shown in Fig. 4. 

D NMR was used to characterize native and acid hydrolyzed ethylcellulose (EC), a Hercules product widely used as a film-former in ink and coatings applications and as a binder and filler in pharmaceutical applications. An important parameter in controlling the properties of ethylcellulose is the degree of substitution (DS) of ethyl functionalities on the cellulose backbone. NMR is one technique that was used to determine both the total and positional DS (ethylation at the 2,3 and 6 positions of the anhydroglucose unit (AGU)). This analysis requires complete hydrolysis of the sample, and an improved acid hydrolysis technique was developed for this application. Two-dimensional (2-D) NMR techniques were used to confirm peak assignments related to positional DS determinations that were previously made by comparison with standards. In addition, 2-D NMR methods were used to evaluate positional DS of native ethylcellulose prior to acid hydrolysis. A comparison of the analytical results for the acid hydrolysate and native polymer will be discussed. 

Some attempts have been made to use TEM measurements to determine structure of fillers. But in spite of the well-constructed studies [42,43], the qualification of TEM images that are two-dimensional do not lead to a three-dimensional image. 

Since a conventional TEM produces a projected three-dimensional (3D) image on a two-dimensional (2D) plane, quantitative information on the filler dispersion can be attained by using AIA techniques. 97,99,102,115,125,127,134 this way, it is possible to recognize, select, measure and compare size and shape of the complex structures dispersed in the matrix through the use of descriptors based on geometrical parameters, such as area, perimeter, diameter and morphometric parameters, such as shape ratio and roundness (Figure 23.3). However, TEM image analysis of filler microdispersions is more difficult to... 

Auger electron spectroscopy (AES) activates the sample through electrons producing ionization of atoms on the outer silane layer. During refilling of this hole by an outer electron, the energy released can be transferred to a third electron that leaves the solid and can be detected. By this method, two-dimensional silane-coated surfaces can be analyzed [27]. Although it may be assumed that comparable processes wiU take place on the surfaces of mineral fillers, AES cannot be used for analysis since mineral fillers are three-dimensional. 

---