Rubber grades

Table 7. Typical Properties Rubber-Grade Carbon Blacks ...

The dry adhesive films on the two substrates to be joined must be placed in contact to develop adequate autoadhesion, i.e. diffusion of polymer rubber chains must be achieved across the interface between the two films to produce intimate adhesion at molecular level. The application of pressure and/or temperature for a given time allows the desired level of intimate contact (coalescence) between the two adhesive film surfaces. Obviously, the rheological and mechanical properties of the rubber adhesives will determine the degree of intimacy at the interface. These properties can be optimized by selecting the adequate rubber grade, the nature and amount of tackifier and the amount of filler, among other factors. 

Rubber-grade resins are mostly in the softening point range 70-100°C R B. A deviation of 5-10°C in softening point may cause problems. The softening point of a resin affects the properties of adhesives. Hence, for pressure-sensitive rubber adhesives the decrease in the softening point of the resin produces a more tacky adhesive with less cohesive strength. 

The simultaneous polymerization and sol-gel reaction often brings complexity to the overall reaction. Moreover, it is difficult to control the molecular weight of the sample. Recently, Patel et al. [51] have synthesized the rubber grade acrylic copolymers and terpolymers-/n situ silica hybrid nanocomposites using this technique. 

TMDES) in conjunction with TEOS to resist brittleness in Nafion-silica hybrids. Contrastingly, rubber grade organic-inorganic hybrids can comfortably take fairly high TEOS loading without any coprecursor, possibly due to the inherent flexibility of the rubbers. 

Better cross-linking with the latter also improves post Tg viscoelastic responses of the rubber vulcanizates. Similar effect has also been observed with polychloroprene as investigated by Sahoo and Bhowmick [41]. Figure 4.8 represents the comparative tensile stress-strain behavior of polychloroprene rubber (CR) vulcanizates, highlighting superiority of the nanosized ZnO over conventional rubber grade ZnO [41]. 

The effects of carbon black morphology on dispersibility described above have been borne out by practical experience. Higher surface area and lower-structure blacks are known to be more difficult to disperse. Traditionally, carbon blacks with surface areas higher than 160 m /g and CDBP lower than 60 mL/100 g cannot be sufficiently well dispersed using normal dry-mixing equipment, so they are not considered rubber grades. Figure 33.4 shows the ASTM carbon black spectrum used in the mbber industry, expressed by compressed DBPA versus surface area. 

FIGURE 33.4 Surface area versus structure for rubber grades of carbon black with some nonrubber grades. 

The remaining latex is processed into dry rubber as sheets, crepes and bales. There is an International Standard for the Quality and Packing for Natural Rubber grades, the so-called Green Book , published by the Rubber Manufacturers Association. The following grades of NR listed in the Green Book are sold to visual inspection standards only ... 

Rubber-grade carbon blacks, 4 775 classification, 4 777 composition, 4 765t properties of, 4 778t spectrum of available products, 4 779 uses of, 4 793-796, 794t Rubber industry... 

Both types of surface oxides are found on technical products. Rubber grade carbon blacks are produced in different processes. Channel blacks are made by cooling a flame on iron plates, the so-called channels. The resulting carbon blacks are acidic in character because an excess of air is present (25). In the production of furnace blacks, the fuel, mostly oil or natural gas, is burned with a limited supply of air. Thermal blacks are obtained by thermal cracking of the gas, which sometimes is diluted with hydrogen. In consequence, both types show weakly basic reaction in aqueous suspension. 

The Green Book," International Standards of Quality and Packingfor Natural Rubber Grades, Rubber Manufacturers Association, Inc., Washington, D.C., 1975. 

The tinting strength of rubber-grade carbon blacks shows a linear relationship with D s shown in Figure 5. Since performance characteristics are known to depend on aggregate volume, surface area, and bulkiness, it appears that the D s values combine the effects of all these factors. As such, it is a valuable addition to carbon black characterization methodology. 

Fig. 11. Electron micrographs of rubber-grade carbon blacks where (a) is N110, (b) is N220, (c) is N550, and (d) is N762.

Another standard industry method for surface area is based on the adsorption of cetyhrimethylammonium bromide (CTAB) from aqueous solution. This is ASTM method D3765-85 (2). This method measures the specific surface area of carbon black exclusive of the internal area contained in micropores that are too small to admit the large CTAB molecules. For rubber-grade nonporous blacks the CTAB method gives excellent agreement with nitrogen... 

The increasing demand led to new production processes. The most important process today is the furnace black process. It was developed in the United States in the 1930s and substantially improved after World War II. It is a continuous process, which allows the production of a variety of carbon black types under carefully controlled conditions. Nearly all rubber grades and a significant part of pigment-grade carbon blacks are now manufactured by the furnace black process. Nevertheless, other production processes, such as gas black, lamp black, thermal black, and acetylene black processes, are still used for the production of specialties. 

In the past decades the rapidly expanding automobile industry required increasing numbers of tires with various characteristics. This led not only to the development of new rubber grades, but also to the development of new carbon blacks required by the increasingly refined application processes and to the development of a new and better manufacturing process, the furnace black process. Unlike the old channel black process, this process allows the production of nearly all types of carbon black required by the rubber industry. It also meets the high economic and ecological requirements of our times. 

Rubber grades with high molar mass to which oil is added during the finishing stage of the raw rubber production cycle. By the incorporation of oil the viscosity of the raw rubber is reduced and rubber processing is facilitated. 

The monomers used were (1) styrene, rubber grade, Dow Chemical Co., 99.2% of pure styrene with 12 p.p.m. of p-ferl-butylcatechol inhibitor (2) 2-ethylhexyl acrylate (Celanese Corp.) 99.0% purity by weight with 50 p.p.m. of monomethyl ether of hydroquinone (3) glycidyl acrylate (Dow Chemical Co.) 90% purity with 0.1% monomethyl ether of hydro-... 

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 ... 

In addition to the commercial rubber grades, model polymers with variable molar mass and narrow molecular weight distribution are often used for studying reinforcement mechanisms. (In Sect. 4.3 we consider a special S-SBR type with 29 vol.% vinyl and 25 vol.% styrene units Mw/Mn=l.l). 

W. M, Hess V. E, Chirico "Classification of Rubber Grade Carbon Blacks from Different Suppliers," Paper Presented at Akron Rubber Group Symposium, Ohio, Jan. 22, 1971. 

Stearic Acid RG (rubber grade) Akrochem Corporation... 

Snofil, Snofil Plus, Hi White - clays for paper industry of different particles sizes Snobrite, Snobrite Special, Snobrite PG, Apex, Kaolloid, Hi White R - adhesive, caulk, paint, roofing, rubber grades... 

CTAB). The method is used to characterize rubber grades of carbon black. A sample of carbon black, previously dried at 125°C is treated with a standard solution of hexadecyltrimethylammonium bromide and mixed to aid its adsorption. The excess of hexadecyltrimethylammonium bromide is determined by titration of the filtrate. 

Characteristic Limits for rubber grades Test method... 

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