Carbon black surface characteristics

Table 1. Carbon black surface characteristics mid adhesion to polymer ...

Fig. 14 Schematic view of the association between morphological arrangements of carbon crystallites and energetic characteristics of carbon black surfaces. Four different types of adsorption sites are distinguished that refer to the de-convolution shown in Fig. 13...

This work investigates the behaviour of elastomeric chains (polybutadienes of identical molecular weight but different microstructures) in the close vicinity of carbon black surfaces in order to attain a better understanding of the structure and properties of interphases. Elastomer-filler interactions are assessed through the study of the thermal properties and NMR relaxation characteristics of the corresponding materials. MAS solid-state NMR provides information on the effect exerted by polymer-filler interactions on the mobility of the various constitutive species of the macromolecular backbone. 

In addition to the fundamental property of particle si2e (and surface area), carbon black possesses a secondary characteristic of stmcture, best described as the tendency of individual particles to agglomerate or associate with one another. These two properties or characteristics of the carbon control the degree and nature of the reinforcing character of the black in mbber. The stmcture of the carbon black is deterrnined by dibutyl phthalate absorption and surface area is estimated by N2 absorption (Table 10). 

The surface of a solid may differ in many ways from its bulk composition. Especially, such solids as commercial carbon black may contain minor amounts of impurities (such as aromatics, phenol, carboxylic acid). This would render surface adsorption characteristics different from that of pure carbon. It is therefore essential that, in industrial production, quality control of the surface from different production batch is maintained. Otherwise, the surface properties will affect the application. Another example arises from the behavior of glass powder and its adsorption character for proteins. It has been found that if glass powder is left exposed to the... 

Carbon black has been reported to possess different kinds of surface chemical groups. These are aromatics, phenol, carboxylic, etc. The different sites can be estimated by comparing the adsorption characteristics of different adsorbents (such as hexane and toluene). 

Composite-based PTC thermistors are potentially more economical. These devices are based on a combination of a conductor in a semicrystalline polymer—for example, carbon black in polyethylene. Other fillers include copper, iron, and silver. Important filler parameters in addition to conductivity include particle size, distribution, morphology, surface energy, oxidation state, and thermal expansion coefficient. Important polymer matrix characteristics in addition to conductivity include the glass transition temperature, Tg, and thermal expansion coefficient. Interfacial effects are extremely important in these materials and can influence the ultimate electrical properties of the composite. 

Abstract Plasma polymerization is a technique for modifying the surface characteristics of fillers and curatives for rubber from essentially polar to nonpolar. Acetylene, thiophene, and pyrrole are employed to modify silica and carbon black reinforcing fillers. Silica is easy to modify because its surface contains siloxane and silanol species. On carbon black, only a limited amount of plasma deposition takes place, due to its nonreactive nature. Oxidized gas blacks, with larger oxygen functionality, and particularly carbon black left over from fullerene production, show substantial plasma deposition. Also, carbon/silica dual-phase fillers react well because the silica content is reactive. Elemental sulfur, the well-known vulcanization agent for rubbers, can also be modified reasonably well. 

The tinting strength of rubber-grade carbon blacks shows a linear relationship with D s shown in Figure 5. Since performance characteristics are known to depend on aggregate volume, surface area, and bulkiness, it appears that the D s values combine the effects of all these factors. As such, it is a valuable addition to carbon black characterization methodology. 

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