Rubber well dispersed state

Properties such as viscosity and die swell, which are related to the effective volume fraction of rubber in the mix, approach a steady-state value at the end of the dispersion stage. A well dispersed mixture always has a lower viscosity and a higher die swell than a comparable less homogeneous mixture. 

Unlike other well-defined areas of NMR, LR-NMR applications cover all states of matter (solid state, solution, etc.), and all possible areas of chemistry in industry and research. Probe head size assures representative sampling for measuring inhomogeneous materials. The technique requires calibration only once, albeit with separate calibrations for different problems e.g. for powder and granulate of the same material). The unique discrimination power of the technique is based on the discrimination in mobility between various components of a sample e.g. oil in rubber, solubles, rubber content, dispersion of fillers) or between different physical structures of a molecule e.g. crystallinity, density, tacticity, copolymer content, melt properties, tensile strength, etc.). Phase analysis by nuclear spin relaxation time measurements rests upon the assumption that each phase present will give a unique relaxation time which can be found by a multiexponential fit of a relaxation... 

Polymer composites have attracted a great deal of interest in recent years. In most cases, fillers are used as additives for improAdng the mechanical behavior of the host polymeric matrix. The reinforcement of elastomers by mineral fillers is essential to the rubber industry, because it yields an improvement in the service life of rubber compounds. The state of filler dispersion and orientation in the matrix, the size and aspect ratio of the particles as well as the interfacial interactions between the organic and inorganic phases haw been shown to be crucial parameters in the extent of property improvement [1,2]. 

The simplest method of polyblending involves equipment such as rolls or extruders, which can effect the mechanical blending of the two polymeric components in the molten state (Matsuo, 1968). High-impact polystyrene (HiPS) is an important example of a polyblend made by this technique. Such materials commonly contain 5-20 % of rubber, usually polybutadiene, dispersed in a polystyrene matrix. As shown in Figure 3.1, electron microscopy studies on specimens stained with osmium tetroxide reveal well-defined, irregular rubber particles (1-10 fim in diameter) dispersed in the polystyrene matrix. The elastomer domains appear dark because the osmium tetroxide stains the elastomer preferentially (see Section 2.4). 

In the case of rubber blend clay composites good state of exfoliation of the clay, sufficiendy strong filler-rubber interactions as well as the compatibility between different rubber phases are playing major role. The presence of intercalated organoclays restricts the mobility of the rubber chains due to their confinement between the layers. As the concentration of nano filler increases the loss modulus increased. This can be explained in terms of the friction between the filler particles and the rubber matrix when the filler particles are uniformly dispersed in the mbber matrix. The damping values are found to decrease with the amount of filler due to the restricted mobility of the polymer chains owing to the intercalation of polymer chains into the layers of silicates. 

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