Elastomer reinforcement

Important are behaviors associated and interrelated with plastic materials (thermoplastics, thermosets, elastomers, reinforced plastics, etc.) and fabricating processes (extrusion, injection molding, blow molding, forming, foaming, reaction injection molding, etc.). They are presented so that the technical or non-technical reader can readily understand the interrelationships. 

Donnet, J.B. and Voet, A., Carbon Black Physics, Chemistry and Elastomer Reinforcement, Marcel Dekker, New York, 1976. 

The elastomer reinforcement industry is poised for technological growth in the following areas ... 

Some elucidation of the mechanism of elastomer reinforcement is being obtained by precipitating chemically-generated fillers into network structures rather than blending badly agglomerated filler particles into elastomers prior to their cross-linking. This has been done for a variety of fillers, for example, silica by hydrolysis of organosilicates, titania from titanates, alumina from aluminates, etc. [85-87], A typical, and important, reaction is the acid- or base-catalyzed hydrolysis of tetraethylorthosilicate ... 

It would be presumptious to deal with such a tremendous field as elastomer reinforcement within the scope of a single review. Therefore, this discussion will be restricted to the investigation of a single filler, carbon black, and will mostly focus on the part played by surface chemical interactions in the properties of filler reinforced rubbers. 

Fu FS, Mark JE (1988) Elastomer reinforcement from a glassy polymer polymerized in-situ. J Poly Sci Part B Poly Phys 26(ll) 2229-2235... 

The materials being reviewed in this book, as in the industry, are identified by different terms such as polymer, plastic, resin, elastomer, reinforced plastic (RP), and composite unreinforced or reinforced plastic. They are somewhat synonymous. Polymers, the basic ingredients in plastics, can be defined as high molecular weight organic chemical compounds, synthetic or natural substances consisting of molecules. Practically all of these polymers are compounded with other products (additives, fillers, reinforcements, etc.) to provide many different properties and/or processing capabilities. Thus plastics is the correct technical term to use except in very few applications where only the polymer is used to fabricate products. 

Carbon black is produced industrially in the form of different products (e.g., furnace black, thermal black, channel black, lampblack, acetylene black) with specific properties. In addition to the relevance of carbon black for basic research on adsorption, or as a reference sohd, appUcations of this material in fields such as elastomer reinforcement, as modifier of certain properties of plastics (UV protection, electrical conductance, color), or as xerographic toners make its surface and interfacial properties extremely important. Soot is a randomly formed particulate material similar in nature to carbon black. The main (pragmatic, rather than conceptual) difference between these two carbon forms is that soot is generally formed as an unwanted by-product of incomplete combustion of pyrolysis, whereas carbon black is produced under strictly controlled conditions. Bansal and Donnet [78] have reviewed various possible mechanisms for the formation of soot and carbon black. Soot can retain a number of tars and resins on its surface. There is therefore some interest in studying the adsorption of polyaromatic hydrocarbons in soots, especially those of environmental significance such as diesel soot. 

See e.g. Donnet J.-B. and Voet A. "Carbon Black. Physics, Chemistry and Elastomer Reinforcement", p. 276, Marcel Dekker Inc., New York and Basel, 1976. 

Donnet, J. B., Voet, A. Carbon black - physics, chemistry and elastomer reinforcement. New York Dekker 1976... 

The development of highly reinforcing furnace blacks paralleled the creation of the synthetic-rubber industry. Improved cold butadiene-styrene elastomers reinforced with these new blacks give vulcanizates that are superior to natural rubb m tire treads. 

Polymers II a-f were found by X-ray diffraction to be noncrystalline amorphous materials. Similar structured polymers were prepared for free radical vulcanization by the introduction of vinyl crosslinking sites. The polymers were formulated Into high consistency elastomers reinforced with silica and were free radical vulcanized. The properties for only lib and Ild are shown In Table I with a commercial elastomer prepared from polymethyl (3,3,3-tr1flu-oropropyl)s11oxane (LS) shown for comparison. Also included Is an elastomer prepared from the following copolymer (III),... 

The situation is very different for elastomers the use of reinforcing fillers induces a simultaneous increase modulus and deformation at break. Curiously, the replacement of a part of the deformable matrix by solid objects doesn t reduce its deformability. The increase of these two antagonistic properties characterizes elastomer reinforcement. This fascinating paradox, despite not being fully understood, explains the ability of reinforced elastomers to provide... 

Compared to morphology, filler chemistry has been only slightly studied, partly because of the difficulty of such characterizations and more probably because since the 1970s reinforcement is broadly considered as a physical interaction between elastomer and filler. So carbon black chemical characterizations mainly date from the 1960s, and few new technical methods have been applied to carbon black surface characterization since then. The situation is somewhat different for silicas, because silica reinforcement is the consequence of a chemical reaction of silane with silica surface. Few studies have been published in the elastomer reinforcement area, probably because silica surface was already well characterized for other applications. 

Elastomer reinforcement by carbon black is generally considered as the consequence of the adsorption of polymeric chains onto carbon black surface. Therefore carbon black surface energy knowledge is of primary importance in carbon black characterization. However, very few carbon black surface energy measurements have been published this can be easily understood considering the difficulty of such measurements on a highly heterogeneous and tortuous surface. 

Structure (Sone, 1999). This very interesting result underlines the decisive influence of interaggregate distances in elastomer reinforcement. 

In contrast to carbon black, it is necessary to use a coupling agent to achieve silica elastomers reinforcement. TESPT, triethoxysilylpropyltetrasulfide, is the most widely used coupling agent. 

In the simplest approach to obtaining elastomer reinforcement, some of the organometallic material is absorbed into the cross-linked network, and the swolloi sarrqrle placed into water containing the catalyst (typically a volatile Ime such as ammonia or ethylamine). Hydrolysis to form the desired silica-like particles proceeds rapidly at room temperature to yield the order of 50 wt % filler in less than an hour. - - The polymer most studied in this regard is hydroxyl-terminated poly(dimethylsiloxane) (PDMS), of repeat unit [-Si(CH3)20-]. 

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