Surface area of fillers

An extensity factor—the total amount of surface area of filler per unit volume in contact with the elastomer. 

Table 4. Effect of specific surface area of filler and its concentration on concentration shift factors aci and ac for composites copolymer + ash (the reference concentration 10%)...

The specific surface area of fillers is closely related to their particle size distribution however, it also has a direct impact on composite properties. Adsorption of both small molecular weight additives, and also that of the polymer is proportional to the size of the matrix/filler interface [14]. Adsorption of additives may change stability, while matrix/filler interaction significantly influences mechanical properties, first of all yield stress, tensile strength and impact resistance [5,6]. 

Applications. Determination of specific surface area of filler which is used as a factor relative to particle size, porosity, and surface activity of filler. 

Figure 18.9 shows the effect of filler particle size on extruder throughput for PP filled with talc. Several reasons account for reduction in throughput as the particle size decreases. Increasing the surface area of filler makes mixing more difficult because of agglomerate formation. Smaller particle sized talc has lower bulk density which decreases the conveying efficiency of screw. The relatively large amount of air supplied with the particles decreases the conveying efficiency and increases the time required to extract air. The amount of talc added affects the ratio of throughput, Q, to the screw speed. Ns (Figure 18.10). As the concentration...

Filler types and levels also have a significant effect on size requirement. Some typical surface areas of fillers are ... 

Particle size diameter can be done only by TEM characterization and is difficult and costly, so surface area of fillers usually is obtained by different adsorption methods. (From Janzen and Kraus (1971) and Janzen (1982).)... 

The significant increase in specific surface area of filler particles contributes to the enhanced physical property of the polymer matrix. Nanosized fillers increase barrier properties by creating a maze or tortuous path that slows the progress of gas molecules through the polymer matrix, thereby substantially improving the gas/air permeability of the polymer. Nanosized fillers in a polymer matrix substantially improve surface properties like gloss, surface finish, grip (friction), etc. 

The properties of the composite samples produced by each method are shown in Table 5.3. The particle size distribution and surface area of filler have been determined by the methods described earlier in Sect. 5.2.2.1. 

One of the filler samples can be selected as a reference column and the probe Tj values in the sample column can plotted as a function of respective Tj values in the reference column. The surface area of filler in each column must be identical. If the surface chemistry of the samples is exactly equivalent a linear plot will result. The direction and magnitude of deviation from linearity provides a measure of the relative strength of interaction. The multiple probe temperature programmed approach to IGC certainly shows potential for rapid screening of fillers and yields data that can be treated using chemometric classification tools such as principle component analysis. 

Fig. 2 Effect of size, shape and surface area of filler particles on stress transfer (http //www. rtvanderbilt.com/fillersintroweb.pdf)...

Dissanayake et aL observed an increase in conductivity for PEO9 LiCF3S03 with the addition of AI2O3. The enhancement increases with increasing specific surface area of filler (Fig. 4.3). This evolution is consistent with the interpretation that Lewis acid-base type surface interactions are largely responsible for the observed increase in conductivity. 

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