Activated filler

Of some interest is also co-crosslinking of various synthetic polymers, their blends with natural ones as well as compositions with inert or active fillers numerous patents are devoted to these materials (for example, Refs. [87, 88]). Low doses of crosslinking allow to introduce various physiologically active additives into SAH without any danger of radiation damage. This possibility is particularly attractive for the technology of SAH. 

With increasing MM the swelling increases faster in systems with a more active filler and is also somewhat greater by an absolute value than in systems with an inactive filler [183]. 

The same situation, as stated in papers of G. V. Vinogradov s school in the 1950s, takes place during creep of plastic dispersion systems, i.e. low-molecular-weight liquids with netforming (active) fillers. 

It seems that results rather close in their meaning should be obtained, provided that monodisperse polymers are taken as dispersion media. Investigations into dynamic (viscoelastic) properties of such liquids with highly active filler have shown that [6],... 

Fig. 12. Flow curves of poly(isobutylene), containing different concentrations of active filler (acetylene carbon black). Concentration (in volume percent) is indicated near the curves. A is the region of flow for stresses exceeding the yield stress B is the region directly adjacent to the yield stress...

This formula may be useful as a rheological method for determining the thickness of adsorption layer, which is formed as a result of interaction between a dispersion medium and filler, by the results of measuring the t] versus q> dependence. Especially curious phenomena, connected with surface effects, arise when a mixture of fillers of different nature is used according to concentration of an active filler the introduction of the second (inert) filler can either increase or decrease the viscosity of a multicomponent system [35],... 

One of the most important phenomena in material science is the reinforcement of mbber by rigid entities, such as carbon black, clays, silicates, calcium carbonate, zinc oxide, MH, and metal oxide [45 7]. Thus, these fillers or reinforcement aids are added to mbber formulations to optimize properties that meet a given service application or sets of performance parameters [48-53]. Although the original purpose is to lower the cost of the molding compounds, prime importance is now attached to the selective active fillers and their quantity that produce specific improvements in mbber physical properties. 

The developed micromechanical model of reinforcement by active fillers allows for a better control of material properties and a more fundamental engineering praxis in mbber industry. In particular. 

Silicates are semi-active fillers which, even at high loading, give soft and elastic vulcanisates. 

Fillers are solid materials that are dispersed in plastics and elastomers. One distinguishes between inactive fillers that are used in the first place to make the plastics less expensive and active fillers (reinforcing fillers) that improve specific mechanical properties and thus effect a reinforcement . With the aid of these fillers, the elastic modulus, hardness, and thermostability are enhanced predominantly, whereas the impact strength of thermoplastic niaterials is re-... 

Zinc oxide (ZnO) is widely used as an active filler in rubber and as a weatherability improver in polyolefins and polyesters. Titanium dioxide (TiOj) is widely used as a white pigment and as a weatherability improver in many polymers. Ground barites (BaS04) yield x-ray-opaque plastics with controlled densities. The addition of finely divided calcined alumina or silicon carbide produces abrasive composites. Zirconia, zirconium silicate, and iron oxide, which have specific gravities greater than 4.5, are used to produce plastics with controlled high densities. 

Discussion - The morphological properties of active fillers are important aspects of rubber reinforcement. The structure of the reinforcing filler is characterized by aggregates of primary particles, which form cavities for attachment and penetration of polymer molecules. The SEM pictures show that the three-dimensional morphology is basically maintained. 

While carbon black was exclusively used as a pigment until the beginning of this century, its use as an active filler in rubber was the starting point for a new rapidly expanding application. In the production of automobile tires, it was found that... 

Graftcopolymerization onto silicone rubber is rather difficult to achieve and is often accompanied by unwanted changes in physico-mechanical properties of the polymer caused by initiating agents. To overcome the problem, silica was introduced into the rubber matrix as an active filler capable of binding cationic compounds such a cationic compound being y-aminopropyltriethoxysilane. Schematically the pathway for heparinization of the latter may be presented as follows ... 

From a fit of Equation (10) to spatially resolved relaxation curves, images of the parameters A, B, T2, q M2 have been obtained [3- - 32]. Here A/(A + B) can be interpreted as the concentration of cross-links and B/(A + B) as the concentration of dangling chains. In addition to A/(A + B) also q M2 is related to the cross-link density in this model. In practice also T2 has been found to depend on cross-link density and subsequently strain, an effect which has been exploited in calibration of the image in Figure 7.6. Interestingly, carbon-black as an active filler has little effect on the relaxation times, but silicate filler has. Consequently the chemical cross-link density of carbon-black filled elastomers can be determined by NMR. The apparent insensitivity of NMR to the interaction of the network chains with carbon black filler particles is explained with paramagnetic impurities of carbon black, which lead to rapid relaxation of the NMR signal in the vicinity of the filler particles. 

Junctions that are formed due to chain adsorption at the surface of active fillers,... 

Methylphenyldimethoxysilane is used as a stabiliser (antistructuring additive) in the production of rubber compounds based on silicone elastomers and highly active fillers. Introducing up to 10% (weight) of methylphenyldimethoxysilane into a rubber mixture improves the physicochemical properties of vulcanised rubbers and helps to preserve the technological characteristics of the compounds in storage. 

Silicone elastomer-based rubber compounds are prepared in conventional apparatuses (closed agitators, roll mills, etc.) and consist of the following ingredients elastomer, active fillers, vulcanising agent, stabiliser, pigment additives. 

The high mechanical strength of natural and organic rubbers as used in tires is due to the incorporation of pyrogenic carbon blacks as active fillers. Elastomers of a more polar polymer backbone, such as polyacrylates, polyurethanes or polysulphides, require fillers of higher polarity. In particular the performance of polydimethylsiloxane elastomers (silicone rubber) is basically related to the addition of fumed silica. 

The presence of active fillers causes significant changes in the elastomer matrix adjacent to the filler surface due to ... 

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