Rubber formulation

Tsai et al. have also used RAIR to investigate reactions occurring between rubber compounds and plasma polymerized acetylene primers deposited onto steel substrates [12J. Because of the complexities involved in using actual rubber formulations, RAIR was used to examine primed steel substrates after reaction with a model rubber compound consisting of squalene (100 parts per hundred or phr), zinc oxide (10 phr), carbon black (10 phr), sulfur (5 phr), stearic acid (2 phr). 

Colour. The colour of resins ranges from water-white to dark brown. Colour may be an important factor in resin choice depending on end use. Pale colours are necessary in some types of adhesives, whereas darker colours may be tolerated in rubber formulations, especially where carbon black filler is incorporated. Medium-coloured resins can be used in most adhesive formulations. 

The Goodyear vulcanization process takes hours or even days to be produced. Accelerators can be added to reduce the vulcanization time. Accelerators are derived from aniline and other amines, and the most efficient are the mercaptoben-zothiazoles, guanidines, dithiocarbamates, and thiurams (Fig. 32). Sulphenamides can also be used as accelerators for rubber vulcanization. A major change in the sulphur vulcanization was the substitution of lead oxide by zinc oxide. Zinc oxide is an activator of the accelerator system, and the amount generally added in rubber formulations is 3 to 5 phr. Fatty acids (mainly stearic acid) are also added to avoid low curing rates. Today, the cross-linking of any unsaturated rubber can be accomplished in minutes by heating rubber with sulphur, zinc oxide, a fatty acid and the appropriate accelerator. 

A common loading for antiozonants in rubber formulations is 1.5-3 phr. Combinations of waxes and chemical antiozonants are used when the service conditions involve both long periods of static as well as dynamic stresses. 

Curing systems. Four curing systems can be used for BR and chlorinated butyl rubber formulations. 

Rubber blends with cure rate mismatch is a burning issue for elastomer sandwich products. For example, in a conveyor belt composite structure there is always a combination of two to three special purpose rubbers and, depending on the rubber composition, the curatives are different. Hence, those composite rubber formulations need special processing and formulation to avoid a gross dissimilarity in their cure rate. Recent research in this area indicated that the modification of one or more rubbers with the same cure sites would be a possible solution. Thus, chlorosulfonated polyethylene (CSP) rubber was modified in laboratory scale with 10 wt% of 93% active meta-phenylene bismaleimide (BMI) and 0.5 wt% of dimethyl-di-(/ r/-butyl-peroxy) hexane (catalyst). Mixing was carried out in an oil heated Banbury-type mixer at 150-160°C. The addition of a catalyst was very critical. After 2 min high-shear dispersive melt mix-... 

Isoprene (2-methyl 1,3-butadiene) is the second most important conjugated diolefin after butadiene. Most isoprene production is used for the manufacture of cis-polyisoprene, which has a similar structure to natural rubber. It is also used as a copolymer in butyl rubber formulations. 

For standard or proprietary polymer additive blends there is the need for analytical certification of the components. Blend technology has been developed for two- to six-component polymer additive blend systems, with certified analytical results [81]. Finally, there exist physical collections of reference additive samples, both public [82] and proprietary. The Dutch Food Inspection Service reference collection comprises 100 of the most important additives used in food contact plastics [83-85]. Reference compounds of a broad range of additives used in commercial plastics and rubber formulations are generally also available from the major additive manufacturers. These additive samples can be used as reference or calibration standards for chromatographic or spectroscopic analysis. DSM Plastics Reference Collection of Additives comprises over 1400 samples. 

Applications Identification of polymer additives by TLC-IR is labour intensive and comprises extraction, concentration of extracts, component separation by TLC on silica, drying, removal of spots, preparation of KBr pellets and IR analysis. The method was illustrated with natural rubber formulations, where N-cyclohexyl-2-benzothiazyl sulfenamide, IPPD and 6PPD antioxidants, and a naphthenic plasticiser were readily quantified [765]. An overview of polymer/additive type compounds analysed by transfer TLC-FTIR is given in Table 7.80. 

The materials selected for evaluation included three materials currently being used in these applications Biomer (Thoratec Laboratories Corporation, Emeryville, CA), representative of segmented ether-type polyurethanes Avcothane-51 (Avco Everett Research Laboratory, Inc., Everett, MA), a block copolymer of 10% silicone rubber and 90% polyurethane and Hexsyn (Goodyear Tire and Rubber Company, Akron, OH), a sulfur vulcanized hydrocarbon rubber that is essentially a polyhexene. Also selected, because of their easy availability, were Pellethane (Upjohn Company, North Haven, CT), an ether-type of polyurethane capable of being extruded in sheet form, and a butyl rubber formulation, compounded and molded at the National Bureau of Standards. The material thickness varied, but the sheets were generally about 1 mm thick. 

The last source of NOC that has been a major source for health concern of infants is usage of rubber pacifiers and baby feeding bottles fitted with rubber nipples. NOC present in the rubber formulations can migrate into baby foods and drinks and into meat packed in rubber nettings. 

Like most negative resists, the arylazide rubber formulations function via the photochemical generation of a crosslinked, 3-dimensional network that is insoluble. The photochemical transformations associated with the generation of this network are depicted in Figure 16. The primary photo event is the evolution of nitrogen from the excited state of the arylazide to... 

J. McAndless, Defense Research, Ottawa The C-13 NMR technique seems quite good for identifying the major component in the rubber formulations, namely the rubber itself. Is the technique sufficiently sensitive to pick out the antioxidants and the processing oils without having to go through the normal separation techniques ... 

A typical tire rubber formulation for tire tread will contain various rubbers, mainly styrene-butadiene (50%) and cA-polybutadiene (12%), various processing aids (2%), softeners (3%), vulcanizing agent (mainly sulfur 1%), accelerators, and reinforcing filler (namely carbon black 30%) so that by bulk, carbon black is the second most used material. 

Local exhaust improved-canopy inclosed on 3 sides Rubber formulation change n-nitrosodiphenylamine not used. 

Tristar polybutadienes prepared by the intermediacy of lithium acetal initiators were also converted to three dimensional networks in a liquid rubber formulation using a diisocyanate curing agent. Table IV shows normal stress-strain properties for liquid rubber networks at various star branch Hn s. It can be seen that as the branch Mn increases to 2920, there is a general increase in the quality of the network. Interestingly, the star polymer network with a star branch Mn of 2920 (Mc=5840) exhibits mechanical properties in the range of a conventional sulfur vulcani-zate with a Me of about 6000-8000. 

The substances listed in Table 28 correspond to the basic structure of elastomeric closures. The other components in rubber formulations are curing or vulcanizing agents, accelerators, activators, antidegradants, plasticizers, fillers, and pigments. The most common additives used to compound rubber for the pharmaceutical industry are listed in Table 29. The amount of each component may vary from rubber to rubber, and, depending on the component, the amount can reach more than 50% of the total mass of a formulation. While accelerators are used in amounts of around 1%, fillers may make up more than 50% of the formulation mass. 

Table 30 shows four typical pharmaceutical rubber formulations based on natural, halobutyl, ethylenepropylenediene (EPDM), and silicone elastomers. 

Filler, in general, can be defined as finely divided particles that are often used to enhance the performance and various desirable properties of the host matrix, depending on a typical application. A great deal of research endeavors have been dedicated to the development and the use of different fillers with a dimension at the nanometer level. In rubber technology the term nano is not unfamiliar to a rubber specialist. Since the start of the twentieth century, carbon black and silica have been utilized as effective reinforcing agents in various rubber formulations for a variety of applications. The primary particle sizes of these fillers remain in the nanometer range. However, with these conventional fillers the dispersion toward individual... 

The state of the art in friction and wear of PTFE-filled rubbers include the effects of many important system parameters, such as the composition of the rubber formulation, particle dispersion, bulk mechanical properties, ability of transfer film formation, and the chemistry between PTFE powder and the rubber matrix. Although the present study has explicitly highlighted the potential of PTFE powder in rubber matrixes with significant property improvements in the friction, wear, and physical properties, it has simultaneously opened a new field regarding the use of PTFE powder in rubber compounds, with some challenging tasks for chemists, engineers, and material scientists. 

Ammonium benzoate [1863-63-41], C6HBCOONH4, mp, 198°C. This is a dull white powder which gradually loses ammonia on exposure to air. Its aqueous solution, it is slightly acidic. Ammonium benzoate has been suggested as a component in certain rubber formulations (40) and as a preservative in paints and glues. 

The percentage sulphur (determined in the un-vulcanized reclaim) and the available rubber hydrocarbon are taken into consideration while evolving the compound formulation. It should be noted that reclaimed rubber is not all rubber. In arriving at the total rubber content in the rubber formulation containing reclaim, allowance must be made for its rubber content. For example in the following blend of smoked sheet and whole tyre reclaim, the total rubber content is to be considered as 100 parts instead of 125 parts as below and the proportion of other ingredients should be worked out accordingly on "parts per hundred rubber" (phr) basis. 

EXTENDER. A low-graxily material used in paint, ink. plastic, and rubber formulations chiefly to reduce cost per unit volume by increasing bulk, Extenders include dialomaccou.s earth, wood flock, mineral rubber, liquid asphalt, etc. Microscopic droplets of water fixed permanently in a plastic matrix are an efficient extender tor polyester resins. In the food industry, the term refers to certain extruded proteins, especially those derived from soybeans, which are used in meat products to provide equivalent nutrient values at lower cost. Made from defatted soy flour, they are often called textured proteins. 

Figure 1. 50-Volume loading of nylon fibers in standard natural rubber formulation...

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