Reinforcement carbon black

Carbon black has been used for the reinforcement of polymers, mainly for reinforcing elastomer and for UV protection, electromagnetic interference shielding, and 

Most of the research has been on the mechanical properties of nanocomposites at room temperature, and only a few researchers have studied the cryogenic properties of epoxy and its composite [68-70]. 

A study on the nanocomposite is important since it can affect the structural characteristics of a composite when it is used as a matrix of the laminates or the reinforcement of a foam core. It has been reported that the characteristics of the composite structure can be improved when a nanoclay-reinforced epoxy is used as a matrix of laminates Antonio et al. [71] improved the damping coefficient and the energy dissipation characteristics of a glass-epoxy composite using nanoclay particles. Hosur et al. [72] improved the impact characteristic of a composite sandwich structure using the nanoclay infused foam. 

Kim et al. [73] investigated the fracture toughuess of nanoparticle-reiuforced bisphenol A epoxy composites. In this study, ductile uiaterials such as microsized rubber or polyamide particles were found to increase fracture toughuess but decrease tensile strength. Carbon black also improved fracture toughuess. 

The addition of 2% carbon black bisphenol A epoxy resin increased its fracTure toughness by about 18% from 0.73 to 0.86 MPa. 

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Nitrile Rubber. Vulcanized mbber sheets of NBR and montmorillonite clay intercalated with Hycar ATBN, a butadiene acrylonitrile copolymer have been synthesized (36). These mbber hybrids show enhanced reinforcement (up to four times as large) relative to both carbon black-reinforced and pure NBR. Additionally, these hybrids are more easily processed than carbon black-filled mbbers. 

Processings and Properties. Polybutadiene is compounded similarly to SBR and vulcanised with sulfur. The high cis-1,4 type crystallizes poorly on stretching so it is not suitable as a "gum" stock but requires carbon black reinforcement. It is generally used for automotive tires in mixtures with SBR and natural mbber. Its low T (—OS " C) makes it an excellent choice for low temperature tire traction, and also leads to a high resilience (better than natural mbber) which ia turn results ia a lower heat build-up. Furthermore, the high i j -polybutadiene also has a high abrasion resistance, a plus for better tire tread wear. 

Molecular Structure. The chain stmcture is as shown in Table 1 and molecular weights of 300,000—500,000 are achieved. The Mooney viscosities are in the range of 40—70 leading to a soft elastomer, which requires carbon black reinforcement for higher modulus. 

Polymerization System. This elastomer is prepared by emulsion polymerisation, similar to that used for SBR, but generally carried out to virtually 100% conversion. As for SBR, the chain irregularity leads to a noncrystallising mbber, so that this polymer requires carbon black reinforcement for strength. 

It is an apparent consequence of the second role that SBS polymers with a molecular mass of about 80 000 behave like carbon-black-reinforced elastomers as illustrated in Table 11.16 in respect of tensile strength. 

G.R. Homed and B.H. Park, The mechanism of carbon black reinforcement of SBR and NR vulcanizates. Rubber Chem. TechnoL, 72, 946-959, 1999. 

Previous General Concepts for Carbon Black Reinforcement.519... 

Although many interface models have been given so far, they are too qualitative and we can hardly connect them to the mechanics and mechanism of carbon black reinforcement of rubbers. On the other hand, many kinds of theories have also been proposed to explain the phenomena, but most of them deal only with a part of the phenomena and they could not totally answer the above four questions. The author has proposed a new interface model and theory to understand the mechanics and mechanism of carbon black reinforcement of rubbers based on the finite element method (FEM) stress analysis of the filled system, in journals and a book. In the new model and theory, the importance of carbon gel (bound rubber) in carbon black reinforcement of rubbers is emphasized repeatedly. Actually, it is not too much to say that the existence of bound rubber and its changeable and deformable characters depending on the magnitude of extension are the essence of carbon black reinforcement of rubbers. 

The purpose of this report is to bring the author s model and theory for carbon black reinforcement of rubbers to a conclusion, with additional experiments and discussion. This research consists of three papers (Part 1, Part 2, and Part 3), where the reinforcement of elastomers is generalized with the universal and common concept. Now, preceding the detailed discussion, we would like to discuss the previous concept generally accepted for carbon black reinforcement of rubbers and the author s new model and theory. 

Author s New Interface Model and Concept for Carbon Black Reinforcement of Rubbers... 

The new interface model and the concept for the carbon black reinforcement proposed by the author fundamentally combine the structure of the carbon gel (bound mbber) with the mechanical behavior of the filled system, based on the stress analysis (FEM). As shown in Figure 18.6, the new model has a double-layer stmcture of bound rubber, consisting of the inner polymer layer of the glassy state (glassy hard or GH layer) and the outer polymer layer (sticky hard or SH layer). Molecular motion is strictly constrained in the GH layer and considerably constrained in the SH layer compared with unfilled rubber vulcanizate. Figure 18.7 is the more detailed representation to show molecular packing in both layers according to their molecular mobility estimated from the pulsed-NMR measurement. 

As shown in Figure 18.1, in the stress-strain curve of the real unfilled SBR vulcanizate, the stress upturn does not appear and as a result, tensile strength and strain at break are only about 2 MPa and 400%-500%, respectively. Nevertheless, the stress-strain curve of the SBR vulcanizate filled with carbon black shows the clear stress upturn and its tensile stress becomes 30 MPa. This discrepancy between both vulcanizates is actually the essential point to understand the mechanism and mechanics of the carbon black reinforcement of mbber. 

It is not too much to say that the existence of bound rubber (SH layer) and its changeable and deformable characters depending on the magnitude of extension are the essence of carbon black reinforcement of rubbers. 

Chapter 18 Mechanism of the Carbon Black Reinforcement of Rubbers.517... 

Obviously, there are many subtle differences in the structure, morphology, or network topology between radiation cured and sulfur cured elastomers, but their physical properties may be nearly equal, provided that precautions are taken to avoid the occurrence of chain scissions. A comparison of radiation cross-linked and sulfur cured natural rubber (gum and carbon-black-reinforced compounds) is in Table 5.4. ... 

Extender oils were foxmd to cause a considerable increase in the dose required to attain the optimum cure. This can be explained by reaction of transienf infermediafes formed on the irradiated polymer chain with the oil and with the energy transfer, which is particularly effective when the oil contains aromatic groups. Thus, the ranking of oils as to their cure inhibition is aromatic > naphtenic > aliphatic. This aspect is very important because many carbon-black-reinforced EPDM compounds contain frequently 100 phr or more oil. 

Irradiation of carbon-black-reinforced polychloroprene compounds produced a maximum tensile strength of 20 MPa (2,900 psi) at a dose of 20 Mrad (200 kGy), which is a value obtained typically from chemically cured compounds. The addition of 20 phr of N,N -hexamethylene-bis methacrylamide as a prorad in the above compound produced a tensile strength of 18 MPa (2,610 psi) at a dose of 7 Mrad (70 kGy). Further addition of 6 phr of hexachlo-roethane caused the deterioration of the tensile strength by 50% at the 7 Mrad (70 kGy) dose. ... 

Abstract Plasma polymerization is a technique for modifying the surface characteristics of fillers and curatives for rubber from essentially polar to nonpolar. Acetylene, thiophene, and pyrrole are employed to modify silica and carbon black reinforcing fillers. Silica is easy to modify because its surface contains siloxane and silanol species. On carbon black, only a limited amount of plasma deposition takes place, due to its nonreactive nature. Oxidized gas blacks, with larger oxygen functionality, and particularly carbon black left over from fullerene production, show substantial plasma deposition. Also, carbon/silica dual-phase fillers react well because the silica content is reactive. Elemental sulfur, the well-known vulcanization agent for rubbers, can also be modified reasonably well. 

Fig. 32 Stress-strain properties of carbon-black-reinforced SBR containing different polyacetylene-coated sulfur samples...

Fig. 2. Evolution with strain of different parameters playing a role in the modulus of carbon black reinforced elastomer (from Ref.10>)...

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