Rubber recipes

Although we made no attempt to elucidate the mechanism of friction decreases in rubbers after surface fluorination, it seems to us that apart from the substitution of H atoms to F in the polymer macromolecule, which forms a fluoropolymer on the surface, there is another phenomenon that makes a significant contribution to the friction decreases, i.e., fluorination of carbon black, which is used in rubber recipes for reinforcement. It appears that when the carbon black in the surface of the rubber is fluorinated it produces a lubricating effect, followed by blooming on the surface of the treated rubber while it is under a friction load. So, in our opinion, two effects contribute to friction decrease of carbon-filled rubbers fluorination of the rubber macromolecules and fluorination of the carbon black rubbers that do not contain carbon black show a much smaller decrease in friction after XeF2 treatment. 

To relate the physical properties of carbon black to rubber properties, we tested these tread blacks in the ASTM natural rubber recipe and in an SBR 1500 test recipe. In both elastomers, we checked standard stress/strain properties of modulus, tensile strength, and hardness. In the natural rubber recipe we also tested Firestone running temperature and rebound, and Goodyear rebound. In the SBR we checked percent swell, extrusion rate, viscosity, and laboratory abrasion. 

ASTM D 3191 -96. Carbon black in SBR (styrene-butadiene rubber) - recipe and evaluation procedure. 

The requirement to use butyl rubber in a factory more used to the processing of natural rubber (NR) and styrene-butadiene rnbber could pose similar problems. These are best avoided by the selection of bromobntyl or chlorobutyl rubber recipes that show tolerance to minor contamination from general-purpose rubber. Acrylate-based rubbers also place limits on contamination and add problems of smell. Use of these polymers may make the manufacturer unpopular with both the work force and the immediate neighbours of the factory. 

Many applications are known for aPP in combination with rubbers. aPP has an excellent compatibility with ethylene/propylene and ethylene/ propylene/diene rubbers (EPM and EPDM, respectively). Incorporation of aPP in EPM- or EPDM-based rubber recipes is accompanied with the following advantages ... 

Compounding. Compared with the large number of ingredients required in a conventional rubber recipe, fluorocarbon elastomer compounding seems simple (Table 4) (see Rubber Compounding). 

The major application of carbon-black-reinforced elastomers is in the manufacture of automotive tires. Table 9.5 illustrates an automotive tire recipe involving synthetic rubber. The synthetic-rubber recipes usually contain two or more elastomers that are blended together with the other ingredients and then covulcanized. 

General classes of elastomers Compounding and the rubber recipe Vulcanization and vulcanizing agents Fillers... 

The two most common activators used with sulfur cure systems are zinc oxide and stearic acid. Virtually all sulfur-cured rubber compounds contain zinc oxide and stearic acid. This means that thousands upon thousands of rubber recipes have these two ingredients. This makes them the most commonly used rubber compounding ingredients, appearing in more different recipes than any other ingredient. 

Zinc oxide is an essential ingredient as an activator in over 90% of all rubber recipes used in commerce. Globally, there was approximately 1 billion pounds of zinc oxide produced in 2010, of which almost one-half was used by the rubber industry. 

Rubber-grade "stearic acid is usually a mixture of stearic acid (a Cl8 saturated fatty acid) and palmitic acid (a Cl6 saturated fatty acid) usually with a very small amount of oleic acid (a Cl8 fatty acid with one unsaturated site per molecule). Just as zinc oxide is ubiquitous in rubber recipes, so is rubber-grade stearic acid. Stearic acid and zinc oxide are almost always used together in rubber compounding. After these two ingredients are mixed in the rubber stock, they react with each other to solubilize the zinc (ion) into the rubber so that it will initiate the vulcanization process. 

Needed for zinc oxide activator used in over 90% of all rubber recipes... 

Rubber Reclaimers Association (RRA) cure test recipe for mixed elastomer and NR reclaim cured 20 min at 141°C. 

Examples of Cure Systems in NR, SBR, and Nitrile Rubber. Table 6 offers examples of recipes for conventional, semi-EV, and EV cure systems ia a simple, carbon black-filled natural mbber compound cured to optimum (t90) cure. The distribution of cross-links obtained is found ia Figure 9 (24). 

The original recipe adopted by the U.S. Government Synthetic Rubber Program was known as the "Mutual Recipe" and is shown iu Table 4. As can be seen, the reaction temperature was set at 50°C, which resulted iu 75% conversion to polymer iu about 12 h. The reaction was then stopped by addition of a "shortstop," such as 0.1 parts hydroquinone, which destroyed any residual catalyst (persulfate), and generated quiuone, which helped inhibit any further polymerisation. 

Table 2. Typical Nitrile Rubber Polymerization Recipes...

An unusual method for the preparation of syndiotactic polybutadiene was reported by The Goodyear Tire Rubber Co. (43) a preformed cobalt-type catalyst prepared under anhydrous conditions was found to polymerize 1,3-butadiene in an emulsion-type recipe to give syndiotactic polybutadienes of various melting points (120—190°C). These polymers were characterized by infrared spectroscopy and nuclear magnetic resonance (44—46). Both the Ube Industries catalyst mentioned previously and the Goodyear catalyst were further modified to control the molecular weight and melting point of syndio-polybutadiene by the addition of various modifiers such as alcohols, nitriles, aldehydes, ketones, ethers, and cyano compounds. 

Whilst the ASA materials are of European origin, the AES polymers have been developed in Japan and the US. The rubber used is an ethylene-propylene terpolymer rubber of the EPDM type (see Chapter 11) which has a small amount of a diene monomer in the polymerisation recipe. The residual double bonds that exist in the polymer are important in enabling grafting with styrene and acrylonitrile. The blends are claimed to exhibit very good weathering resistance but to be otherwise similar to ABS. 

Vulcanisation can be effected by diamines, polyamines and lead compounds such as lead oxides and basic lead phosphite. The homopolymer vulcanisate is similar to butyl rubber in such characteristics as low air permeability, low resilience, excellent ozone resistance, good heat resistance and good weathering resistance. In addition the polyepichlorohydrins have good flame resistance. The copolymers have more resilience and lower brittle points but air impermeability and oil resistance are not so good. The inclusion of allyl glycidyl ether in the polymerisation recipe produces a sulphur-curable elastomer primarily of interest because of its better resistance to sour gas than conventional epichlorhydrin rubbers. 

Solutions of the two recipes were blended in varying proportions to provide tie coats of continuously varying composition. The patent shows an example of eight plies or layers of graded composition between the rubber and the metal substrate. Because of the high fraction of reactive filler, the material closest to the metal substrate would be the most rigid and polar. The stiffness and polarity... 

Since 1960, the inner core has been made from c/5-poly-butadiene by the compression moulding technique. This replaced the earlier material made from a suspension of barytes or bentonite clay in water and glycerine or the winding of rubber threads made from t /5-polyisoprene, either from latex or a dry rubber compound. A typical thread recipe is given Table 4. 

The most common adhesive system used for bonding continuous fibers and fabrics to rubber is resorcinol-formaldehyde latex (RFL) system. In general, RFL system is a water-based material. Different lattices including nitrile and SBR are used as the latex for the adhesive system. 2-Vinylpyridine-butadiene-styrene is the common latex used in the adhesive recipe. RFL system is widely being used in tires, diaphragms, power transmission belts, hoses, and conveyor belts because of its dynamic properties, adhesion, heat resistance, and the capacity to bond a wide range of fabrics and mbbers. 

Rubber compounds were made using A1 and A2 shown in Table 17.2 and using a model tire recipe shown in Table 17.4. The ingredients listed in Table 17.4 are in grams per 100 g of rubber (PHR). The mixing procedure used for the samples presented in Table 17.5. Both cured and un-cured compounds were tested and the mechanical testing results are shown in Table 17.6. 

Compound Recipe of Natural Rubber (NR) Vulcanizate without Filler... 

Ic. Cross-Linking of Polymer Chains.—Formation of chemical bonds between linear polymer molecules, commonly referred to as cross-linking, also may lead to the formation of infinite networks. Vulcanization of rubber is the most prominent example of a process of this sort. Through the action of sulfur, accelerators, and other ingredients present in the vulcanization recipe, sulfide cross-linkages are created by a mechanism not fully understood (see Chap. XI). Vulcanized rubbers, being typical network structures, are insoluble in all solvents which do not disrupt the chemical structure, and they do not undergo appreciable plastic, or viscous, flow. 

In an acetone extract from a neoprene/SBR hose compound, Lattimer et al. [92] distinguished dioctylph-thalate (m/z 390), di(r-octyl)diphenylamine (m/z 393), 1,3,5-tris(3,5-di-f-butyl-4-hydroxybenzyl)-isocyanurate m/z 783), hydrocarbon oil and a paraffin wax (numerous molecular ions in the m/z range of 200-500) by means of FD-MS. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out (Chapter 2). The method of Dinsmore and Smith [257], or a modification thereof, is normally used. Mass spectrometry (and other analytical techniques) is then used to characterise the various rubber fractions. The mass-spectral identification of numerous antioxidants (hindered phenols and aromatic amines, e.g. phenyl-/ -naphthyl-amine, 6-dodecyl-2,2,4-trimethyl-l,2-dihydroquinoline, butylated bisphenol-A, HPPD, poly-TMDQ, di-(t-octyl)diphenylamine) in rubber extracts by means of direct probe EI-MS with programmed heating, has been reported [252]. The main problem reported consisted of the numerous ions arising from hydrocarbon oil in the recipe. In older work, mass spectrometry has been used to qualitatively identify volatile AOs in sheet samples of SBR and rubber-type vulcanisates after extraction of the polymer with acetone [51,246]. 

Figure 15. Behavior under strain of an unvulcanized tire ply (conventional recipe) based on NR (natural rubber 100%), 1R (synthetic cis-7,4-polyisoprene 100%), BP/1R (a 50/50 blend of IR and txans-butadiene-piperylene copolymer).

The earliest courses which considered polymeric materials dealt with them on an empirical basis, with recipes directing additions of specified amounts or treatments of materials being typical rather than the exception. These early courses concentrated on adhesives, oils and coatings, resins, textiles, paper and pulp and natural rubber. Specific examples are given in the following sections. 

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