Carbon black incorporation time

Figure 18.16 shows that carbon black incorporation time, BIT, is affected by the addition of ZnO and by the properties of carbon black. If no ZnO is added, the incorporation time decreases as the carbon black structure increases. The opposite is true when ZnO is present during carbon black dispersion. The overall quality of the dispersion improves when ZnO is present and when mixing is carried out at elevated temperature Dispersion quality was assessed by optical measurements. 

Figure 18.16. Carbon black incorporation time vs. DBPA adsorption. [Adapted, by permission, from Urabe N, Takatsugi H, Ito M, Toko II. Fukui M, Int. Polym. Sci. Technol., 22, No.5, 1995, T/68-72.]...

The rotor speed also influences carbon black incorporation time (Figure 18.18). The characteristics of both relationships are similar but longer times are required to disperse rubber with no ZnO added. 5... 

Using the mixing method described in the previous paper in this series, which produces reproducible data, the authors investigated each factor that affects the black incorporation time. Various carbon blacks, oil-extended rubber and oil were used as the materials in the tests. The mixing conditions used were the rotational speed, rotational ratio of the rotor, fill factor and ram pressure. The authors studied the effect of these factors on the black incorporation time by the new theory based on static electricity phenomena and rabber viscoelasticity. 7 refs. Articles from this journal can be requested for translation by subscribers to the Rapra produced International Polymer Science and Technology. 

Studies on the kinetics of carbon black dispersion in various rubbers have been reported using a Brabender mixer fitted with cam-type rotors [110]. Dispersion rating, determined by visual inspection of photomicrographs, was found to depend strongly on mixing time. For an SBR emulsion, it was observed that there was an initial delay period where the carbon black agglomerates were thought to be fractured and incorporated into the rubber. Subsequently, the process of dispersion continued for a considerable time thereafter. 

In the literature, there are several reports that examine the role of conventional fillers like carbon black on the autohesive tack (uncured adhesion between a similar pair of elastomers) [225]. It has been shown that the incorporation of carbon black at very high concentration (>30 phr) can increase the autohesive tack of natural and butyl rubber [225]. Very recently, for the first time, Kumar et al. [164] reported the effect of NA nanoclay (at relatively very low concentration) on the autohesive tack of BIMS rubber by a 180° peel test. XRD and AFM show intercalated morphology of nanoclay in the BIMS rubber matrix. However, the autohesive tack strength dramatically increases with nanoclay concentration up to 8 phr, beyond which it apparently reaches a plateau at 16 phr of nanoclay concentration (see Fig. 36). For example, the tack strength of 16 phr of nanoclay-loaded sample is nearly 158% higher than the tack strength of neat BIMS rubber. The force versus, distance curves from the peel tests for selected samples are shown in Fig. 37. 

From time to time attempts have been made to make plastics conductive enough to be plated directly, by immersion in the solutions in the same way as with metals. The method usually was to incorporate a conductive material, such as carbon black. 

In the one-stage vulcanization process, NR and EPDM are first masticated separately and then mixed with each other. Additives such as ZnO, stearic acid, carbon black (or silica), and process oil are added. The mix thus obtained is allowed to cool to room temperature. Finally, coupling agent known as DIPDIS and sulfur are added to the mix on the cooled mill. The stocks are finally cured under pressure at 160°C (32-33). In the two-stage process, NR and EPDM are first masticated separately. Then, additives such as ZnO, stearic acid, DIPDIS, and sulfur are incorporated in the EPDM. The compounded EPDM mix is then heated at 160°C in the hydraulic press for the predetermined time to yield the grossly undercured mix. The undercured mix is then blended with NR to the required blend ratio. The blend compound is finally vulcanized to the optimum cure time values (32-33). 

Although electrically conductive plastics are not of very great economic significance at the present time, there are many specialised technical applications that would be unthinkable without these materials. Today they are mostly produced by incorporating conductive carbon-black in a variety of polymers, above all thermoplastic polymers. Other conductive additives (carbon fibres, steel fibres, aluminium flakes, metal coated carbon... 

A reduction of the required energy could be reached by the incorporation of conductive fillers such as heat conductive ceramics, carbon black and carbon nanotubes [103-105] as these materials allowed a better heat distribution between the heat source and the shape-memory devices. At the same time the incorporation of particles influenced the mechanical properties increased stiffness and recoverable strain levels could be reached by the incorporation of microscale particles [106, 107], while the usage of nanoscale particles enhanced stiffness and recoverable strain levels even more [108, 109]. When nanoscale particles are used to improve the photothermal effect and to enhance the mechanical properties, the molecular structure of the particles has to be considered. An inconsistent behavior in mechanical properties was observed by the reinforcement of polyesterurethanes with carbon nanotubes or carbon black or silicon carbide of similar size [3, 110]. While carbon black reinforced materials showed limited Ri around 25-30%, in carbon-nanotube reinforced polymers shape-recovery stresses increased and R s of almost 100% could be determined [110]. A synergism between the anisotropic carbon nanotubes and the crystallizing polyurethane switching segments was proposed as a possible... 

---