Fillers, reinforcement elastomers rubbers

For the preparation of filler reinforced elastomer composites, most frequently commercial rubber grades with variable microstructure and broad molar mass distribution are applied. The typical rubber grades, considered in the present review, are as follows ... 

Rei Reincke, K., Grellmann, W., Heinrich, G. Fracture mechanical investigations of filler-reinforced elastomers. In Boukamel, A., Laiarinandrasana, L., Meo, S., Verron, E. (eds.) Constitutive models for rubber V, Taylor Francis Group London, (2008) 221-227. 

Kluppel M, Schramm M (2000) A generalized tube model of rubber elasticity and stress softening of filler reinforced elastomer systems. Macromol Theory Simul 9 742-54... 

We restrict, in this paper, the discussions related to the reinforcement of elastomers to the investigation of a single filler, carbon black. We, moreover, mostly focus on the part played by surface chemical interactions in the properties of filler reinforced rubbers. 

The reinforcement of rubber by the presence of active fillers is a complex phenomenon that depends on the characteristics of the elastomer network and the properties of the fillers. The influential properties are the particle size, the morphology of particle aggregates, and the surface properties. The role of the geometrical characteristics of the tiller is well understood, whereas the significance of the surface properties is more difficult to analyze. This situation stems essentially from the lack of adequate methods to analyze the surface of such small particles and from the fact that fillers differ from each other and need to be considered individually. 

Hubersil . [J.M. Huber] Hydrated silica reinforcing filler, carrier for rubber parts incl. hose, belting, molded and extruded parts, tires, footwear, wire and cable, thermqilastic elastomers, caulks and sealants. 

Addition of fillers can dramatically change mechanical properties of elastomer materials. For example, a pure gum vulcanizate of general purpose styrene-butadiene rubber (SBR) has a tensile strength of no more then 2.2 MPa but, by mixing in 50 parts per hundred weight parts of rubber (p.p.h.r) of a active CB, this value rises more than 10 times to 25 MPa. How CB, being fine powder of practically no mechanical strength, can make reinforcement in rubbers, similar to... 

The presence of reinforcing fiUers also increases the non-Newtonian behavior of elastomers. This effect is mainly due to the fact that the incorporation of fillers in elastomers decreases the volume of the deformable phase. As discussed in the following text, this decrease is not limited to the actual volume of the filler, but must also include the existence of occluded rubber. So, when filled mixes are submitted to shear forces, because of the lower deformable volume, the actual deformation and speed of deformation are much higher than in unfilled mixes [1,134]. This phenomenon is usually called strain amplification effect, obviously strain amplification is not specific to reinforced systems but to any filled polymer. 

TPO materials are defined as compounds (mixtures) of various polyolefin polymers, semicrystalline thermoplastics, and amorphous elastomers. Most TPOs are composed of polypropylene and a copolymer of ethylene and propylene called ethylene—propylene rubber (EPR) [2]. A common rubber of this type is called ethylene propylene diene monomer rubber (EPDM), which has a small amount of a third monomer, a diene (two carbon-carbon double bonds in it). The diene monomer leaves a small amount of unsaturation in the polymer chain that can be used for sulfur cross-linking. Like most TPEs, TPO products are composed of hard and soft segments. TPO compounds include fillers, reinforcements, lubricants, heat stabilizers, antioxidants, UV stabilizers, colorants, and processing aids. They are characterized by high impact strength, low density, and good chemical resistance they are used when durability and reliability are primary concerns. 

Automotive tires constitute the classic example of carbon-black reinforced elastomers. The elastomer can be either natural rubber—as typically is the case of truck and aircraft tires, or else a synthetic mbber—as is typical for automobile tires. However, reinforcing fillers constitute only one of many additives. There are also antioxidants, light stabilizers,... 

Finite elements analysis has shown that filler properties such as surface area, shape and structure have strong infiuence on the filler reinforcement and filler rubber properties. Another approach to understand the filler network and the filler-rubber interactions more closely is to study the electrical and mechanical behaviour of the filled elastomer under strain for various different conditions. Jha et have investigated the effect of surface area and structure of filler... 

The reinforcement of rubber composites by CB and/or silica is greatly affected by the rubber filler interactions, the agglomeration of the filler particles within the rubber matrices, and the occlusion of the rubber into the internal voids of the dispersed aggregates. Furthermore, filler-elastomer interactions play a major role in the filler dispersion achievable during mixing process. 

Fillers. Fillers for elastomers are not generally used just to fill space and cheapen the compositions. They are very important to modify the properties of rubber compositions in very positive ways. This is especially true for the so-called reinforcing fillers. Their presence in the compound can improve the strength- and durabihty-related properties of vulcanizates and can strongly enhance processing characteristics. The choice and amount of filler can have a profound effect on vulcanizate properties. These effects depend on several factors level of use (concentration), primary particle size, surface area (inverse function of primary particle size), and structure (shape factor, e.g., spherical, chain or rod-like, plate-like, and so forth). 

An extremely important example of the beneficial effects of fillers is the reinforcement of elastomers. The properties of elastomers can be enhanced by the addition of certain fillers to the rubber compound before vulcanization or cross-linking. Fillers for rubber can be divided into two classes inert fillers, such as clay, whiting, and barites, which may make the rubber mixture easier to handle before vulcanization but have little effect on its physical properties and reinforcing fillers, which do improve the physical properties. 

---