Fillers morphologies

Researchers [37] also compared the storage modulus of a 40 phr carbon black-filled compound and a 10 phr SWNT-NR nanocomposite. The different properties between carbon black- and SWNTs-filled NR nanocomposites can be explained in terms of two different filler morphology, particularly surface area, aspect ratio, and stmcture. It can be observed from Figure 28.22 that... 

It has been well established that wear resistance of filled rubber is essentially determined by filler loading, filler morphology, and polymer-filler interaction. For fillers having similar morphologies, an increase in polymer-filler interaction, either through enhancement of physical adsorption of polymer chains on the filler surface, or via creation of chemical linkages between filler and polymer, is crucial to the enhancement of wear resistance. In addition, filler dispersion is also essential as it is directly related to the contact area of polymer with filler, hence polymer-filler interaction. 

Two points have to be stressed before considering the measurement of morphology. The first point to make in discussing filler morphology is that, except for rare instances such as monomodal glass spheres, the morphology of filler particles is complex and they will have a distribution of shapes and sizes which cannot be expressed as a single parameter. 

Fig. 1 Schematic view of filler morphology in three concentration regimes. For reinforcement is due to hydrodynamic amplification by particles ( < 1) or clusters (cp> +) with eff= or cpeff= / A) respectively. For > reinforcement is due to the deformation of a flexible filler network...

The electrical conduction process depends on several parameters, mainly on filler concentration. But filler morphology such as particle size and structure as well as filler-filler and filler-matrix interactions which determine the state of dispersion and filler orientation are key factors in determining the electrical properties. On the other hand, processing techniques also influence the electrical conductivity of... 

Many of the same arguments apply to interpretation of equilibrium modulus data on filled rubbers. To the extent that relations erf the type of Eq. (1) or (8) are applicable at moderately high strains, the equilibrium stress in a filled rubber will be some multiple of the stress in the unfilled rubber, the constant of proportionality depending on volume loading and filler morphology. The equilibrium stress thus becomes a relative measure of v, provided the vulcanizates contain the same filler at the same loading. For the reasons stated above, estimates of vapp from equilibrium stress data on unswollen filled rubbers are less reliable than those derived from equilibrium swelling. 

Filler morphologies such as particle size, structure, and essentially surface characteristics have a drastic effect on the physical performance of the elastomeric material. The most important of these parameters however, are the surface characteristics and the chemical active sites which determine the interaction between filler and polymer chains. ... 

Fig. 21.4 Filler morphology of Needle-leaf Bleached Kraft Pulp (NBKP), refiner-treated (eight passes) NBKP, and MFC. Reproduced with permission from Iwatake et al. (2008). Copyright 2008, Elsevier Ltd...

Methods currently used to determine this require the filler to be comminuted by means of ultrasound - but this causes severe degradation of the agglomerates in carbon blacks, and also distorts the distribution of silicas. An alternative method has been developed using transmission electronic microscopy, in which the filler morphology retained is similar to that obtained in the incorporation process. 

Vovchenko, L.L., Matzui, L.Y., Oliynyk, V.V., Launetz, Vi., 2011. The effect of filler morphology and distribution on electrical and shielding properties of graphite-epoxy composites. Molecular Crystals and Liquid Crystals 535, 179—188. 

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