Tread composition

Experiments were performed using a tire-tread composition as shown in Table 29.1, representing a common silica recipe corresponding to the fuel-saving green-tire technology [2,24]. 

The approach that has been used in our laboratories for synthetic rubber research for improved tire tread composition is shown in Figure 1. 

This tread has iaflueaced the supply and availability of cerium, particularly ia comparison to the availability of lanthanum-rich cerium-poor materials. The iacrease ia La demand for ECC catalysts up to the mid-1980s, together with the need to separate out cerium ia order to make the La-rich Ce-poor compositions increasingly preferred, led to a glut of Ce-based raw materials at that time. Ia 1991, the La-rich Ce-poor portioa of the raw material was ia excess supply over demand. 

There is one obvious drawback of high-hysteresis rubber. In normal rolling operation, considerable elastic deformations still take place in the tyre wall, and high-loss tyres will consume fuel and generate considerable heat. The way out is to use a low-loss tyre covered with a high-loss tread - another example of design using composite materials (Fig. 26.9). 

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. 

An NR-rich undertread layer can enhance the adhesion between belt or cap-ply and tread whilst a thicker subtread compound may be included to offer some additional benefits of low hysteresis for car tires and low heat generation for truck tires within the bulk of a thick section. The cure system needs better flexibility and low heat generation. Typically the cure system will be based on CV/SEV. Tread base is generally having a composition as depicted in Table 14.40. 

Standardisation of EPDM characterisation tests (molecular composition, stabiliser and oil content) for QC and specification purposes was reported [64,65]. Infrared spectroscopy (rather than HPLC or photometry) is recommended for the determination of the stabiliser content (hindered phenol type) of EP(D)M [65]. Determination of the oil content of oil-extended EPDM is best carried out by Soxhlet extraction using MEK as a solvent [66], A round robin test was reported that evaluated the various techniques currently used in the investigation of unknown rubber compounds (passenger tyre tread stock formulations) [67]. 

Tire shredding, mechanical, 21 470-472 nylon, 19 765-766 reclaimed rubber in, 21 784-785 Tire-to-energy facilities, 21 466 Tire tread compounds, composition of, 21 806t... 

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. 

Butadiene can form three repeat units as described in structure 5.47 1,2 cw-1,4 and trans-, A. Commercial polybutadiene is mainly composed of, A-cis isomer and known as butadiene rubber (BR). In general, butadiene is polymerized using stereoregulating catalysts. The composition of the resulting polybutadiene is quite dependent on the nature of the catalyst such that almost total trans-, A, cis-, A, or 1,2 units can be formed as well as almost any combination of these units. The most important single application of polybutadiene polymers is its use in automotive tires where over 10 t are used yearly in the U.S. manufacture of automobile tires. BR is usually blended with NR or SBR to improve tire tread performance, particularly wear resistance. 

There are two main situations concerning deflection of boards that may not pass the building code requirements deck boards at a certain span (distance between neighboring joists) and stair tread at a certain span. Let us consider these situations using the same examples Trex composite deck boards and GeoDeck composite deck boards. These examples would illustrate general shortcomings of plastic-based composite deck boards in terms of their flexibility and deflection. 

This is a rather high figure for flexural modulus for composite deck boards (see the next section). Hence, for many composite deck boards stair tread, in order to satisfy AC 174, support span for stair tread should be a step down from 16 in., that is, 12 in. 

That is why Trex recommends its composite boards only for a 12-in. span, and only for thick 2X6- and 2 X 8-in. boards, when used as a stair tread. For a standard 5/4 X 6-in. board, Trex recommends only a maximum center-to-center spacing of... 

Calculations show that for a stair tread with a 24-in. span (allowed deflection 0.133"), a composite board should have aEX I value of 548,016 lb X in.. This would be applicable to a hollow GeoDeck Heavy Duty composite deck board (8.1" X 1.55,1 = 1.858 in., E = 374,000 psi, and EX I = 694,892 lb X in. ). For a solid board of a standard dimension (5.5" X 1.25", I = 0.895 in. ), flexural modulus should be at least 776,416 psi, and composite deck boards of such stiffness are not available as yet on the current market (see Table 7.34), except those made of wood. For thin solid board, such as 5.5" X 15/16" (/ = 0.378 in. ), flexural modulus applicable for stair tread with 24" span should be at least 2,054,000 psi, which is much higher than that for typical wood (Table 7.34). 

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