Particle morphology, fillers

Several essential properties of cristobalite have influence on its applications. They include lower density than quartz (higher volume at the same mass), purity (low catalytic effect on many polymeric systems, excellent properties in exterior coatings due to low level of iron oxide), very low moisture (no need for drying in moisture sensitive systems), pure white color, less abrasive due to filler particle morphology. 

Particle Morphology, Size, and Distribution. Many fillers have morphological and optical characteristics that allow these materials to be identified microscopically with great accuracy, even in a single particle. Photomicrographs, descriptions, and other aids to particle identification can be found (1). 

In the subsequent hardening phase, precipitation and hydration continue. The set cement consists, essentially, of partly-reacted glass particles embedded in an aluminium phosphate gel. The morphology of the filler particles is one where a glass core is sheathed by silica gel. 

Particle morphology, of fillers, 11 303-304 Particle nucleation, in emulsion polymerization, 14 713-714... 

To be effective, these fillers have to be used at high loadings and it is essential to minimise any associated loss in important properties such as toughness. It is this aspect that largely determines the optimum particle morphology, rather than the flame retardancy. 

An issue that has been receiving increasing attention is the deleterious effect of fillers on the scratch resistance of polymers, as measured by the loss in surface appearance. The understanding of this problem is still at a rudimentary stage, but it appears that the problem can be minimised by control of particle morphology [28] and correct choice of surface treatments [29]. 

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. 

Both of these effects refer to a high surface activity and specific surface of the filler particles [26, 27, 47]. In view of a deeper understanding of such structure-property relationships of filled rubbers it is useful to consider the morphological and energetic surface structure of carbon black particles as well as the primary and secondary aggregate structure in rubber more closely-... 

Polymers, as well as elastomers, are reinforced by the addition of small filler particles. The performance of rubber compounds (e.g. strength, wear resistance, energy loss, and resilience) can be improved by loading the rubber with particulate fillers. Among the important characteristics of the fillers, several aspects can be successfully interrogated by AFM approaches. For instance, the particle and aggregate size, the morphology, and in some cases the surface characteristics of the filler can be assessed. 

Examples, which have in parts already been explicitly mentioned, are defects, such as marks of processing equipment on polymer films, filler particles that were removed from the polymer matrix, irregular ordering and pinholes in latex assemblies, or altered morphologies due to mechanical deformation and concentration of stresses, among others. 

The morphology of filler particles can be compared using the SEM and TEM micrographs included in Chapter 2. Here, only summary is included in the form of table (Table 5.3). 

Figure 20.3. Comparison of the predicted Young s moduli of binary multiphase materials with morphologies best described by the aligned lamellar fiber-reinforced matrix model (Equation 20.1), the blend percolation model (Equation 20.2), and Davies model for materials with fully interpenetrating co-continuous phases (Equation 20.3). The filler Young s modulus in Equation 20.1 was assumed to be 100 times that of the matrix, and calculations were performed at Af=10, At-=100 and Af=l()00 to compare the effects of discrete filler particles with differing levels of anisotropy. It was assumed that E(hard phase)=100, pc=0.156 and (3=1.8 in Equation 20.2. For...

ASTM D 3895 Standard Test Methodfor Oxidative Induction Time of Polyolefins by Differential Scanning Calorimetry Note of the author This procedure cannot be used for filled composite materials regarding Sampling section, particularly for those employing rather large filler particles. Instead of compression-molded test samples into sheet format prior to analysis to yield consistent sample morphology and weight and cut specimen disks (6.4-mm diameter) from the sheet to have a... 

Common fillers exhibit a wide array of particle shapes that are either naturally occurring or specifically synthesized. Particle morphology can be divided into two... 

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