Silica with carbon black

Of the various synthetic processes that are available, two are of most relevance in the present context - precipitation from aqueous solution and melt forming. These methods are used where it is not possible to produce adequate products directly from natural sources. This will be because there is no suitable mineral, due to the chemical nature of the product, of particle size and shape requirements, or to purity considerations. The other principal synthetic method in use for filler production is pyrolysis/combustion. This type of process in which the particles are formed in the gas phase is used where very small particles are required, such as with carbon blacks and some silicas. This type of filler is not widely used in thermoplastics and so these processes are not discussed in any detail here, although some information specific to the production of antimony oxide will be found later. 

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. 

For the surface modification of silica and carbon black, a radiofrequency (13.56 MHz) electrode-less tumbler plasma reactor at the University of Cincinnati was used. The schematic reactor design is shown in Fig. 5. It consists of a Pyrex cylinder chamber of 40 cm in length and 20 cm in diameter, with a motor-driven shaft at its center, and two vanes running in opposite directions. The reactor is based on a horizontal mixing principle and is capable of treating 350 g per batch. The powdery materials to be coated are placed at the bottom of the chamber. The plasma... 

White carbon black is the global title for synthetic hydrated silica and silicate, scientifically termed hydrated silicon dioxide (Si02nH20), and is an important additive of rubber etc. [183]. Because of its white color and properties comparable with carbon black, it is termed White Carbon Black , for which the Chinese quality standard is given in Table 13.1. 

H NMR transverse magnetisation relaxation experiments have been used to characterise the interactions between NR, isoprene rubber, BR, EPDM and polyethylacrylate rubbers with hydrophilic silica and silicas modified with coupling agents [124-129]. These studies showed that the physical interactions and the structures of the physical networks in rubbers filled with carbon black and rubbers filled with silicas are very similar. In both cases the principal mechanism behind the formation of the bound rubber is physical adsorption of rubber molecules onto the filler surface. 

The mobility in both tightly and loosely bound BR and isoprene rubbers increases, and the fraction of bound rubber decreases with a decreasing concentration of silanol groups on the silica surface [124], This led to the suggestion that the silanol groups on the silica surface are active sites for the chain adsorption. The grafting of aliphatic chains to the silica surface leads to a decrease in BR-silica interactions [125]. The effect is less pronounced in BR filled with carbon black containing aliphatic chains at the surface. 

Introduction by Michelin et Cie. of the "Green Tyre", with a silica-reinforced tread, rather than with carbon black, and using solution-polymerised rather than emulsion-polymerised SBR, for 30% reduced rolling resistance and corresponding energy saving... 

In conventional composites filled with carbon black or silica, the increase in stiffness is mainly associated with a change in the structure and dynamics of the polymer at the filler surface. On account of the enormous surface-to-volume ratio of the particles, the polymer in the interfacial region represents a significant fraction of the materials and its behavior significantly affects or even governs the properties of the composite. 

Parker [4] end-group functionalized poly(1,3-butadiene) polymers with isopropyl hydroxyl-amines to improve the affinity and interaction with carbon black and silica fillers to extend tire lifetime. 

Halasa [2] reduced hysteresis in tires by anionically copolymerizing functionalized butadiene, (I), and styrene, (II), to enhance elastomer compatibility with carbon black and silica fillers. 

Butadiene has been converted into poly-l,4-(cis-butadiene) in greater than 98.3% by Ziegler-Natta catalysis comprising neodymium versatate, diethyl aluminum chloride, diisobutylaluminum hydride, and triisobutyMuminum. The polymer was then converted into a polybutadiene-polyurethane copolymer by reacting with a diisocyanate and diol. This copolymer exhibited low cold flow and high affinity for silica or carbon black, excellent elasticity, and abrasion resistance. 

Substitution of carbon black filler (or a significant part of it) with white reinforcing fillers (e.g. silica), as carbon black has also been found to act as a nitrosating agent. 

There are also other substances that can be used as fillers that behave like carbon black in terms of the reinforcing action. One example is silica, but it has the drawback of its price, and the properties of the reinforced elastomer are generally inferior to those obtained with carbon black. These... 

Fillers are materials that modify rubber characteristics (e.g., hardness) and improve its physical characteristics (e.g., tensile strength), in addition to reducing costs. Rubber is sometimes compounded without the use of fillers the resultant product is called gum rubber. Typical fillers are calcined and hydrated clays, magnesium silicate (talc), magnesium oxide, and silicas. Carbon black, a common filler used to increase the heat resistance in industrial components such as tires, is not used as a filler in pharmaceutical components but it is used in smaller amounts as a black pigment. Polynuclear aromatic (PNA) hydrocarbons are a concern with carbon blacks but the grades used by manufacturers of pharmaceutical components contain very low concentrations. 

The variety of substances used as additives in polymers is considerable. For example, the fillers may include china clay, various forms of calcium carbonate, talc, silicas (diatomaceous silica), silicates, carbon black, etc. The impact modifiers typically include other polymers. Plasticizers include certain polymers with low (oligomers), dialkyl phthalates, dialkyl sebacates, chlorinated paraffin waxes, liquid paraffinic fractions, oil extracts, etc. Heat stabilizers include heavy metals salts such as basic lead carbonate, basic lead sulfate, dibasic lead phosphite (also acting as a light stabilizer), dibasic lead phthalate, stearates, ricinoleates, palmitates and octanoates of cadmium and barium, epoxide resins and oils, amines, diphenylurea, 2-phenylindole, aminocrotonates. The antioxidants include tris-nonyl phenyl phosphite, 2,6-di-ferf-butyl-p-cresol (BHT), octadecyl-3,5-di-terf-butyl-4-hydroxyhydrocinnamate, etc. The UV stabilizers include modified benzophenones and benzotriazoles. Processing lubricants include calcium stearate, stearic acid, lead stearate, various wax derivatives, glyceryl esters and long-chain acids. Fire retardants include antimony oxide, some pyrophosphates, etc. 

Fig. 3.65 Left TM-AFM images left height, right phase) showing the filler microdispersion in the unvulcanized compounds, (a) unvulcanized EPDM filled with modified silica (Compound 1) (z-scale height, 310 nm, phase, 30°) (b) unvulcanized EPDM filled with carbon black (Compound 2) (z-scale height, 365 nm, phase, 35°). Right (c), (d) filler distributions as determined from the analysis of the phase images (a) and (b) Reproduced with permission from reference [141]. Copyright 1999. American Chemical Society...

SBR filled with intercalated montmorillonite had substantially lower toluene uptake compared with the same rubber filled with carbon black (see Figure 15.42). Figure 5.28 shows that the diffusion coefficient of kerosene, which defines penetration rate, decreases when the concentration of carbon black in SBR vulcanizates is increased. Figure 15.33 compares the uptake rate of benzene by unfilled rubber and by silica and carbon black filled rubber. Both fillers reduce the solvent uptake but carbon black is more effective. 

Solvents produce different effects than do corrosive chemicals. Both silica and carbon black filled natural rubbers were more resistant to solvents than unfilled rubber. Also, the cure time was important, indicating that the bound rubber plays a role in the reduction of a solvent sorption. The diffusion coefficient of solvents into rubbers decreases with longer cure times and higher fillers loadings. Polychloroprene rubber swollen with solvent has a lower compression set when it is filled with carbon black. 

Figure 7.35. taiiS of natural rubber filled with carbon black and silica vs. interaggregate distance, 833. [Adapted, by permission, from Wang M-J, Wolff S, Tan E-H, Rubb. Chem. Technol., 66, No.2, 1993, 178-95.]... 

Diamine salts of fatty acids are used as multifunctional additives in natural rubber compounds filled with carbon black.They affect the elastomer-carbon black interface. With an increased concentration of multifunctional additive, the concentration of bound rubber decreases but dispersion of carbon black is improved. In silica filled rubber, multifunctional additive also improves the dispersion of silica, but in addition, it decreases the negative influence of silica filler on vulcanization rate. 

Testing procedure In general, standard methods were used, with some improvements to obtain better resolution. A photoacoustic detector was used to obtain spectra of fumed silica. A carbon black background was used. In studies of adhesion of coatings on metal substrates, a gold coated background was used as the reference. 4 Diffuse respectra, and kaolin. 2 A... 

Silica fillers play a prominent role in the paste rheology of polyurethane and rubber coating mixtures. Silica fillers are also used for surface matting. In polyurethanes, the layer thickness is even thinner than is used with PVC. Dispersion is enhanced by dispersion aids. Fillers are used at relatively low concentrations in PU formulation. But in rubber coatings, large quantities of calcium carbonate are used to decrease cost. Rheology and reinforcement are adjusted with carbon black. 

In 50% sulfuric acid at 90 °C butyl rubber shows the best resistance with carbon black loading particularly with channel and lamp blocks. Silica filled compounds lose up to one-third of the strength of the rubber with considerable swelling at 70% concentration of sulfuric acid. 

Silicone polymers, crosslinked by radiation in the absence of fillers, form rubbers with poor tensile and tear strength. Much better properties can, however, be obtained for small doses by the inclusion of a filler such as silica or carbon black [425]. 

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