Carbon black moisture removal

The tolerance allowed on mass of ingredients is fairly tight at 1% generally but down to 0.02g for sulphur and accelerators. For miniature internal mixers this reduces even further to 0.002g. There are limits on the difference between the sum of the masses of the ingredients and the final mass of the mixed batch of between + 0.5% and - 1.5%. Carbon black is required to be conditioned before use to remove moisture but it seems curious that this is not required for other fillers. 

A large amount of water is usually contained in the dictyo-structure of the hydrated silica precipitated, including both free and combined moisture. The precipitate is separated out by filtering and washed to remove impurities, mainly Na and acid radical ions. The cake is made into slurry again by stirring and the latter is then spray-dried to yield the powdery product of white carbon black. 

Heating loss is used to determine moisture content in carbon black. The drying is performed at 125°C for 30 min. Under these conditions moisture is removed but some other volatile materials may also be lost. The automatic equipment such as drying balances is also used (note that carbon black does not absorb infrared rapidly therefore, other sources of heat are normally used). This method gives precise readings because it avoids errors due to reabsorption of moisture. 

Antistatic agents such as carbon black, metal powders, surfactants or other hydrophilic substances can be blended with polymer matrices to dissipate electronic charge. However, carbon black makes materials black, so if a light colour is required, carbon black cannot be used. If some low-MW antistatic agents like surfactant are used, their antistatic effect is brought about by the equilibrimn moisture adsorbed on the surfactant, so sufficient antistatic effect is not achieved under low humidity. Furthermore, the surfactant is removed by rubbing or washing back and forth, and the antistatic effect disappears easily [54]. 

The stone fruits usually dried are plums/prunes, apricots and peaches. Plums are first dipped for 5-15 s into a hot, diluted solution of sodium hydroxide, or into 0.7% aqueous K-carbonate and then rinsed and dried at 70-75 C or dried in the sun. Plum peels are often fissured to facilitate drying. In order to clean and to provide a black, glossy surface, dried plums are steamed additionally at 80-85 °C for a short time. The plum yield is 25-30% at a moisture content of not more than 19%. Apricots and peaches are treated alternately with cold and hot water, then are halved, the stone seed is removed and the fruit is dried in the sun or in drying installations at 65-70 °C. The yield, depending on fruit size, is 10-15%. SO2 (sulfurous acid) treatment is common for apricots and peaches. Cherries play a less important role as dried fruit. To avoid substantial aroma losses, cherries are dried slowly and with a number of precautions. 

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