Mineral fillers rubber/polymer composites

Fillers are defined as additives in solid form that differ from the polymer/rubber matrix with respect to their composition and structure. A mineral filler is defined as a finely pulverized inert mineral or rock that is included in a manufactured product (e.g. paper, rubber, and plastics) to impart certain useful properties, such as hardness, smoothness, or strength etc (http //www.mindat.org/glossary/ mineral filler). Mineral particulate fillers are used in rubber/polymer composites to reduce the cost of the final product and to add some mineral property with the host (rubber/polymer) matrix, that is, to improve the properties of the matrix [19-22]. Common mineral fillers include asbestos, kaolin, talc, mica, wollastonite, and calcium carbonate etc (http //www.mmdat.org/glossary/mmeral filler) [19]. 

The characteristics which determine the properties filler that will impart to a composite are particle shape, particle size, surface area, and particle-matrix compatibility (Fig. 1). Particle-matrix compatibility relates to the ability of the polymer to coat and adhere to the filler. The shape of most mineral filler particles can be a sphere, cube, block, plate, needle, or fiber whereas some filler also contain a mixture of shapes. Mineral particles resembling plates, needles, and fibers are further characterized by their aspect ratio (http //www.rtvanderbilt.com/ fillersintroweb.pdf). In rubber/polymer composites, applied stress is transferred from the rubber/polymer matrix to the strong and stiff mineral. It seems reasonable that this stress transfer will be better affected if the mineral particles are smaller, because greater surface is thereby exposed for a given mineral concentration. Moreover, if these particles have a high aspect ratio (are needle-like, fibrous or platy in shape), they will better intercept the stress propagation through the matrix (Fig. 2) (http //www.rtvanderbilt.com/fillersintroweb.pdf). 

Whilst many of these areas fall outside the scope of this chapter, particulate polymer composites are becoming increasingly complex and commonly require more than just inclusion of a filler or particle additive in order to achieve optimum properties. For example, rubber modification of mineral-filled thermoplastics to yield a balance of enhanced toughness and stiffness, is an area of commercial importance. In these ternary-phase systems, there is not only a requirement to attain good dispersion of the filler component, but also a need for breakdown of the rubbery inclusion to yield the most effective size and spatial location within the composition. Whilst this may depend to a large extent on characteristics of the material s formulation, it can also be influenced by the material s compounding route. 

Compositional analysis of polymeric rubber products by TGA has been used for many years to determine the quality and content of various rubber products (Kau 1988 Sircar 1997). A polystyrene butadiene rubber composition is illustrated in Fig. 3.20. The protocol for this analysis includes the following heating rate 20°C/min, 30 mg sample mass, and switching the purge gas from nitrogen to air at 500 °C. The results are illuminating for a 30-min determination of composition 8.4 mass% oil, which evaporates prior to the onset of polymer decomposition just below 400°C 50.4 mass% polymer, whose decomposition is complete by 500 °C, at which point the purge gas is switched to air 36.2 mass% carbon black, taken as the mass loss in air and 5.0 mass% residue, either ash or mineral filler plus ash. 

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]. 

Thanks to all these properties, the dolocarbonate seems promising for different applications, first of all for all the applications of traditional low density mineral fillers. This material could for instance be used as a component in thermal insulating materials like panels or foams, as a filler in mortars or plasters or concretes to decrease their thermal conductivity, as a filler in polymer or rubber compositions to improve their fire and/or mechanical properties, as a filler in paints, papers, cosmetic compositions, as a rheology modifier (viscosifying agent) in mineral slurries, glues, bitumen or asphalts, polymer compositions, as an ad- or absorbant in different applications such as water or flue gas treatment or even in the field of catalysis, as e.g. a catalyst support, or as a carrier for perfumes, aromas, active substances, medicines... 

This year s U.S. production of thermoplastics, thermosets, and synthetic rubber is expected to be 29 billion pounds. About 80% of this is based on only a few common monomers. To improve performance, the polymer industry rarely changes to a new, probably more expensive polymer, but instead it shifts from mere homopolymers to copolymers, polyblends, or composites. These three types of multicomponent polymer systems are closely inter-related. They are intended to toughen brittle polymers with elastomers, to reinforce rubbers with active fillers, or to strengthen or stiffen plastics with fibers or minerals. 

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