Fillers particle geometry

Table 8 Summary of the different models for the gas permeation Model Ref Filler Particle geometry Formula...

The mechanical connectivity between the filler particles is provided by a flexible, nanoscopic bridge of glassy-like polymer, resulting from the immobilization of the rubber chains in the confining geometry close to the gap. 

The developments at Fraunhofer ICT focus on the combination of graphites and carbon black with different particle geometry and size distribution, to obtain as many contacts as possible between the conductive fillers, and thus produce conductive paths. The polymer serves in the material mixture as a binder to achieve a mechanically stable gas-tight system and to make a thermoplastic processing of the material compounds possible (Fig. 10). 

This is the well-known Einstein-Smallwood equation, where c is the volume fraction of the filler and Gn, is the elastic modulus of the rubber matrix. The equation is obtained based on three idealized assumptions, such as (i) freely dispersed particles, i.e. low volume fraction, (ii) a spherical shape (leading to the constant 2.5) and (iii) entirely non-elastic filler particles, i.e. their elastic modulus has to be infinitely large. The reinforcement term contains two factors one is a simple number related only to the geometry of the particles, the other is linear in the volume fraction of the filler particles. 

Kaolin is used only in small quantities in PR The anisotropic particle geometry of wollastonite and mica reinforces the pol)uner. The latter is applied more extensively in USA and Canada due to the closer location of mining facilities. Barite-filled PP has excellent vibration damping properties due to the high density of this filler. Wood flour filled PP is occasionally applied in the automotive industry for the preparation of door panels. Water absorption of this filler creates problems in processing and application. The most important characteristics of mineral fillers are collected in Table 2. 

When compounding there may often be an adhesion problem between a nonpolar polymer matrix and a tiller, so it is essential to obtain perfect wetting of the particles by the matrix. Before it can do anything, a filler has to bond effectively with the polymer matrix. The size and geometry of the filler particles influence... 

Chauhan Deepti, Singhvi Nilima, and Singh Ramvir. Effect of geometry of filler particles on the effective thermal conductivity of two-phase systems. Int. J. Modern Nonlin. Theor. Appl. 1 (2012) 40-46. 

Insulating polymers possessing many desirable mechanical properties may be rendered conductive by mixing them with conductive particles such as carbon bkck, metal powders, flakes or fibers of metal coated particles. The level of electrical conductivity in these heterogeneous materials depends primarily on the concentration and geometries of the conductive filler particles. The observed critical filler content which marks the onset of a sharp increase in conductivity (e.g. the percolation threshold) in the majority of these composites falls between 15-25 % (vol/vol) (4). This percolation threshold has been shown both theoretically and experimentally to be well described by a system of small spheres packed in three dimensions. 

Abstract This chapter deals with the non-linear viscoelastic behaviour of rubber-rubber blend composites and nanocomposites with fillers of different particle size. The dynamic viscoelastic behaviour of the composites has been discussed with reference to the filler geometry, distribution, size and loading. The filler characteristics such as particle size, geometry, specific surface area and the surface structural features are found to be the key parameters influencing the Payne effect. Non-Unear decrease of storage modulus with increasing strain has been observed for the unfilled vulcanizates. The addition of spherical or near-spherical filler particles always increase the level of both the linear and the non-linear viscoelastic properties. However, the addition of high-aspect-ratio, fiber-like fillers increase the elasticity as well as the viscosity. 

The geometry and orientation of filler particles has a significant influence on the thermal conductivity of a composite material. Many of the theoretical treatments are valid for only specific types of filler partkks and composite constructions. The possible scenarios include spherical fiUers, irr ulaily shaped fillers, flakes (3-D random and random in-plat X short fibers (3-D random and random in-plane), long fibers (unidirectional and random in-plane), and continuous fibers (unidirectional and cross-ply laminated). Each of these scenerios needs to be addressed separately, and will be doiK so in the following sections. 

Many filler particles are in the shape of flakes, particles whose basic geometry is that of a disc or plate. These particles have a diaracteristic aspect ratio of some length parameter divided by thickness. Common flake filler particles are mica and talc. Metal flakes have also been inve gated a means of providing electrical ccmductivity to polymers. Hatta and Taya developed a model to describe the ttermal conductivity of a compete filled with flakes [27]. That model uses the same basic equation they devdoped for spherical and irregular filler partides ... 

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