Natural rubber tire components

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. 

Generally speaking, commercial rubber products are manufactured as a composite from a rubber and a nano-filler, which is in a group of fillers of nanometer size (mainly, carbon black and particulate silica). For an example, a pneumatic tire for heavy-duty usages such as aircrafts and heavyweight tracks is made from natural rubber (NR) and carbon black and/or silica. Their reinforcing ability onto rubbers makes them an indispensable component in the rubber products [1,2]. 

Isoprene may be the naturally occurring alkene with the greatest economic impact. This compound, a major component of the sap of the rubber tree, is used to make the long-chain molecules of natural rubber (polyisoprene). As we describe in Chapter 13. the synthetic rubbers that make up most of today s tires are made from other alkenes. 

Insoluble Sulfur. In natural rubber compounds, insoluble sulfur is used for adhesion to brass-coated wire, a necessary component in steel-belted radial tires. The adhesion of rubber to the brass-plated steel cord during vulcanization improves with high sulfur levels ( 3.5%). Ordinary rhombic sulfur blooms at this dose level. Crystals of sulfur on the surface to be bonded destroy building tack and lead to premature failure of the tire. Rubber mixtures containing insoluble sulfur must be kept cool (<100°C) or the amorphous polymeric form converts to rhombic crystals. 

A catalyst combination consisting of the barium salt of tri(ethyleneglycol)ethyl ether, Ba(0CH2CH20CH2CH20CH2CH3)2, with tri-n-octyl aluminum and n-butyl lithium has been used to prepare random poly(styrene-co-butadiene) containing a high butadiene transcontent. These polymers were designed to be co-cured with natural rubber and used as components in automotive tires. 

Blends of elastomers are routinely used to improve processability of unvulcanized rubbers and mechanical properties of vulcanizates like automobile tires. Thus, cis-1,4-polybutdiene improves the wear resistance of natural rubber or SBR tire treads. Such blends consist of micron-sized domains. Blending is facilitated if the elastomers have similar solubility parameters and viscosities. If the vulcanizing formulation cures all components at about the same rate the cross-linked networks will be interpenetrated. Many phenolic-based adhesives are blends with other polymers. The phenolic resins grow in molecular weight and cross-link, and may react with the other polymers if these have the appropriate functionalities. As a result, the cured adhesive is likely to contain interpenetrating networks. 

A considerable number of reports regarding the formation of compounds that may represent a health hazard are related to the formation of polycyclic aromatic hydrocarbons (PAHs) during industrial pyrolysis processes (recycling of waste, incineration, etc.). This interest is particularly geared toward the study of polyolefins pyrolysis and synthetic and natural rubber pyrolysis. The formation of PAHs during polyethylene pyrolysis has been reported frequently in literature [6, 12] and is further discussed in Section 6.1. The formation of PAHs during tire pyrolysis is also of considerable concern. The concentrations of some components in the oils generated from the pyrolysis of used tires as a function of temperature are indicated in Table 5.3 1 [13]. 

Polyblends with Soft Matrix and Soft or Rigid Dispersed Phase. Polyblends in which both components are soft are mixtures of various elastomers. For example, treads of automobile tires are made of a polyblend of SBR with either natural rubber or cis-polybutadiene. 

Aromatic Natural rubber SBR Polybutadiene Tires Automotive components... 

Tread The wear resistance component of the tire in contact with the road. It must also provide traction, wet skid, and good cornering characteristics with minimum noise generation and low heat buildup. Tread components can consist of blends of natural rubber, polybutadiene (BR), and styrene-butadiene rubber (SBR), compounded with carbon black, silica, oils, and vulcanizing chemicals. 

Namral rubber composition is polymerized c -l,4-poly-isoprene. However, synthetic attempts of duplicating natural rubber have been largely unsuccessful. Namral rubber is the largest polymer component of a tire. The preparation of natural rubber nanocomposites will add value to a very large segment of the rubber industry. Because natural rubber can be obtained as an aqueous dispersion from the rubber tree and as a dried solid phase, one can disperse an aqueous dispersion of nanoparticles into the latex before drying or compound the organic modified nanoparticles into the solid phase to obtain the rubber nanocomposite. 

Malaysian and Indonesian natural rubber growers have established a system based on technical characteristics. A summary of the standard technical specification scheme shown in Table 4 for natural rubber can be foimd in ISO 2000 (14,15). In addition to the solid form of natural rubber, it is available as a suspension in water and is known as latex. Synthetic rubbers are also available in latex form. Latex has become an important commodity used in the manufacture of dipped goods for pharmaceutical applications. The principal uses of natural rubber are as follows tires and tire retreading, 70% latex (eg, gloves), 12% mechanical goods, 9% load-bearing components, 4% and other, 5%. 

Zhou et al. [12] fabricated an extremely durable superhydrophobic tridecafluorooctyl triethoxysilane modified poly(dimethylsiloxane) (PDMS)/silica nanoparticle composite coating for use on different fabrics (Figure 10.5). Inspiration for the robust composite coating was obtained from a tire, a classic and highly durable nanocomposite material, where the main components are natural rubber and carbon black. 

PEG is suitable as a mold release agent and lubricant for natural rubber and all kinds of synthetic rubber, whether for soft or hard rubber articles. In the tire sector, PEG is often combined with other components to produce special mold release agents. Higher concentrations are used for foam rubber molds, for example, aqueous solution of PEG 4000. 

The development of compormds and blends of polymers dates back almost two centmies to the early rubber and plastics industry, when rubber was mixed with substances ranging from pitch [3] to gutta percha [4]. As each new plastic has been developed, its blends with previously existing materials have been explored. Thus, synthetic rubbers, in the early period of the plastics industry, were mixed into natural rubber and formd to produce superior performance in tire components. Polystyrene (PS) was blended with natiual and synthetic rubbers after its commercialization, and this led to high impact polystyrenes (HIPS), which now hold a... 

PB is the polymer of 1,3-butadiene and is a synthetic rubber. Natural rubber is plant-derived and is a polymer of isoprene. Isoprene is also a 1,3-diene but has an additional methyl group. The main uses of PB are in the manufacture of tires in the transport industry and also as one of the components of materials based on a polyst Tene or styrene-acrylonitrile copolymer. 

The main chemical characteristic of tire chips and tire shreds is their nonreactivity under normal environmental conditions. The principal chemical component of tires is a blend of natural and synthetic rubber, but additional components include carbon black, sulfur, polymers, oil, paraffins, pigments, fabrics, and bead or belt materials. 

---