Cord-rubber composites

Tyres are very definitely fatigued during use and, as mentioned for fabric/rubber adhesion above, it is very important to carry out dynamic tests to assess bond efficiency. Methods have not apparently been standardised but a variety of procedures have been reported71 79 Some workers have used the same or a similar test piece as in static tests and applied a cyclic tensile stress or strain, whilst others have used some form of fatigue tester operating in compression/shear to repeatedly stress or strain cord/rubber composite, or even to flex samples in the form of a belt. Khromov and Lazareva80 describe a method using test pieces cut from tyres. 

The characteristic features of a cord—rubber composite have produced the netting theory (67—70), the cord—inextensible theory (71—80), the classical lamination theory, and the three-dimensional theory (67,81—83). From structural considerations, the fundamental element of cord—rubber composite is unidirectionally reinforced cord—mbber lamina as shown in Figure 5. From the principles of micromechanics and orthotropic elasticity laws, engineering constants of tire T cord composites in terms of constitutive material properties have been expressed (72—79,84). The most commonly used Halpin-Tsai equations (75,76) for cord—mbber single-ply lamina L are expressed in equation 5 ... 

Requirements for tire cord material will to some extent be driven by new vehicle trends. For example, the dean air emphasis in North America places lightweight vehicles and materials at a premium. For tire cord the fuel economy or rolling resistance provided by the cord—rubber composite may shift the pattern of usage. A common requirement for all types of tire cord surfaces is a high strength-to-weight ratio. 

A tire is essentially a cord-rubber composite. Tires have plies of reinforcing cords extending transversely from bead to bead, on top of which is a belt located below the tread. The belt cords have low extensibility and are made of steel and fabric depending on the tire application. The belt cords are at a relatively low angle, between 12° and 25°, and serve as restrictions to the 90° casing pUes. 

Stress analysis of failures in the form of cracks in cord rubber composites as a result of fatigue has been carried out which is said to be of help in estimating the severity of local failures (35). 

STRESS ANALYSIS OF FAILURES EV CORD-RUBBER COMPOSITES... 

Stress analysis of failures in the form of cracks due to fatigue of cord-rubber composites was carried out using micromechanical 2D and 3D finite element analysis. The von Mises-Tresca stresses were computed from the results of finite element analysis and compared. Results show that crack type, loading and crack size have a strong effect on the values of the von Mises-Tresca stress. Use of the results of the von Mises-Tresca stress should help in estimating the severity of local failures in cord-rubber composites, it is proposed. 12 refs. 

M. Borowc2ak and A. G. Causa, "Eatigue Behaviour of Cord-Reinforced Rubber Composites," Conference Proceedings ACS, RubberDivision, Louisville, Ky., May 1989. 

Materials. Two types of standard tire cord obtained from Gen Corporation were used in this investigation polyester, 1300/3, and nylon 66, 1260/3. The rubber composition to which the adhesively dipped cords were bonded had the following composition in parts by weight styrene-butadiene rubber (SBR) 1502, 100 N330 carbon black, 50 zinc oxide, 5 stearic acid, 0.5 sulfur, 1.7 2-morpholinothio-benzothiazole, 2. Master batches were mixed 7 min in a 350-ml Brabender Plasticorder, and curatives were added on a cool two-roll mill. Cure characteristics at 155 °C were determined with an oscillating disc rheometer (ASTM D 2084). The time to reach 90% of the final cure state was 23 min, and the Shore A hardness of the final vulcanizate was approximately 60. 

The quaternized DHA-4VP copolymers were very useful for promoting adhesion of rubber to polyester cord (Table VIII). The DHA-NVP copolymers were also tested as adhesion promoters for polyester-rubber composites. The... 

A tire is a textile-steel-rubber composite the steel and textile cords reinforce the rubber and are the primary load-carrying structures within the tire. Because of the performance demands of fatigue resistance, tensile strength, durability, and resilience, seven principal materials have been found suitable for tire application cotton, rayon, nylon, polyester, steel, fiberglass, and aramid the latter three materials find primary usage in the tire crown or belt region. 

Processes for production of rubber semifinished products by means of spreading Processes for production of rubber composites and stmctural elements (yams, cord, fibers, threads) and mbber-metal composites. 

Both of these curatives are added in the lower temperature, final mixing stage. HMTA must be isolated from the other rubber curatives during storage and batch preparation since its basicity can cause premature decomposition of the rubber cure accelerators and can accelerate the conversion of insoluble sulfur into the soluble form. The structure of HMTA and the reaction with resorcinol are illustrated in Scheme 4.1. Classical chemical studies indicate that as much as 75% of nitrogen remains chemically bonded to the rubber though some ammonia is released during the cure of the resin and the rubber, which can have detrimental effects on rubber composites reinforced with brass coated steel cords. 

Modeling is the method of choice for analyzing passenger car cord-reinforced rubber composite behavior. Large scale three-dimensional finite element analysis (FEIA) improves imderstanding of tire performance, including tire and tread behavior when the rubber meets the road. ... 

Nakano, H. Rubber compositions with water-resistant adhesion to Zn-plated steel cords. Jpn. Kokai Tokkyo Koho JP 2006176580, 2006 Chem. Abstr. 2006,145,125802. 

As with most rubber composites the adhesion system used in power transmission belts is based on an resorcinol/formaldehyde/latex (RFL) type system. General overviews of RFL adhesion systems from a tyre cord perspective have been previously published by Takeyama and Matsui [31], and more recently by Solomon [32]. Bonding with RFL systems is achieved through applying an RFL coating to the fibre structure prior to the... 

The pneumatic tire has the geometry of a thin-wallcd toroidal shell. It consists of as many as fifty different materials, including natural rubber and a variety ot synthetic elastomers, plus carbon black of various types, tire cord, bead wire, and many chemical compounding ingredients, such as sulfur and zinc oxide. These constituent materials are combined in different proportions to form the key components of the composite tire structure. The compliant tread of a passenger car tire, for example, provides road grip the sidewall protects the internal cords from curb abrasion in turn, the cords, prestressed by inflation pressure, reinforce the rubber matrix and carry the majority of applied loads finally, the two circumferential bundles of bead wire anchor the pressnrized torus securely to the rim of the wheel. 

There has been an increasing global trend in the wire and cable industry to restrict and remove the presence of lead in materials used for insulation and jacketing applications. The various standards that apply to lead in electrical applications are discussed. One of the issues is how to define the low levels of lead. Many minerals contain trace levels of lead as a chemical impurity. These minerals are used in rubber and plastics and thus the final composition is likely to contain trace amounts of lead. With modem analytical techniques, lead can be found at levels lower than five parts per million. Therefore, to satisfy increasing demands on wire and cable materials, a new series of thermoplastic vulcanisates (TPV) has been introduced that contains no added lead chemicals. These TPV materials have recently been granted a UL listing for flexible cord applications. The properties of these materials are presented and highlighted. 6 refs. 

Pentaerythritol tetranitrate (PETN) is a colorless crystalline solid that is very sensitive to initiation by a primary explosive. It is a powerful secondary explosive that has a great shattering effect. It is used in commercial blasting caps, detonation cords, and boosters. PETN is not used in its pure form because it is too sensitive to friction and impact. It is usually mixed with plasticized nitrocellulose or with synthetic rubbers to form PBXs. The most common form of explosive composition containing PETN is Pentolite, a mixture of 20 to 50% PETN and TNT. PETN can be incorporated into gelatinous industrial explosives. The military has in most cases replaced PETN with RDX because RDX is more thermally stable and has a longer shelf life. PETN is insoluble in water, sparingly soluble in alcohol, ether, and benzene, and soluble in acetone and methyl acetate. 

The rubber stock, once compounded and mixed, must be molded or transformed into the form of one of the final parts of the tire. This consists of several parallel processes by which the sheeted rubber and other raw materials, such as cord and fabric, are made into the following basic tire components tire beads, tire treads, tire cords, and the tire belts (fabric). Tire beads are coated wires inserted in the pneumatic tire at the point where the tire meets the wheel rim (on which it is mounted) they ensure a seal between the rim and the tire. The tire treads are the part of the tire that meets the road surface their design and composition depend on the use of the tire. Tire cords are woven synthetic fabrics (rayon, nylon, polyester) impregnated with rubber they are the body of the tire and supply it with most of its strength. Tire belts stabilize the tires and prevent the lateral scrubbing or wiping action that causes tread wear. 

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