Milky, white latex, containing rubber globules, is obtained by making an incision into the bark of rubber trees, the cultivation of which requires specific climatic conditions and rainfall.
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Rubber tree plantations are mainly located in Southeast Asia (including Thailand, the world’s largest producer and Indonesia), Latin America and Africa.
In compound formulations, natural rubber reduces internal heat generation in tires, whilst offering high mechanical resistance. It is used in many parts of the tire, mainly used for truck and earthmover tire tread
60% of rubber used in the tire industry is synthetic rubber, produced from petroleum-derived hydrocarbons, although natural rubber is still necessary for the remaining 40%.
Synthetic elastomers deform under stress and return to their original shape when the stress is removed (hysteresis).This property is extremely valuable for the manufacture of high-grip tires.
Synthetic rubber also provides other specific properties, most notably in the areas of longevity and rolling resistance. It’s mainly used for passenger car and motorcycle tire as it gives them good grip performances.
Discovered in , carbon black added to the rubber compound produces a tenfold increase in wear resistance of the tires. It represents 25 to 30% of the rubber composition and gives tires their distinctive color.
Indeed, this color is very effective in acting against ultraviolet rays to prevent the rubber from fissuring and cracking
Silica, obtained from sand, has properties that have long been recognized, including the improved resistance of rubber compounds to tearing.
In , Michelin took a major step forward by combining an original silica and a specific elastomer with a special bonding agent using a special “mixing” process.
The compounds obtained make tires with a low rolling resistance, good grip on a cold surface and exceptional longevity. This innovation is at the origin of the green tires with low rolling resistance.
Pioneers in drawing fine wire from hard steel, Michelin introduced steel into its tire reinforcements in . This major technical advance, combined with the development of a coating providing a strong physical-chemical bond between the rubber and steel, was industrialized production in in the Michelin Metalic truck tire.
Since then, steel has been adopted in the reinforcement of belts for radial tires. Metal reinforcements give the tire resistance and rigidity.
Textile has always been used to strengthen tires. In , thanks among other things to an innovation in this field, Michelin tires enabled Concorde to take to the air once again.
Fabric reinforcement currently plays an important role in high-performance, high-speed tires. Polyester, nylon, rayon and aramid are all used to manufacture the reinforcements, which provide added resistance, endurance and comfort.
Polyester tire cord fabric is characterized by its heat resistance, good thermal stability, low elongation, and high wet strength. However, compared to nylon tire cord fabric, it has lower fatigue resistance and strength, poorer aging resistance, and higher costs. Hence, its application in the rubber industry is not as extensive as nylon tire cord fabric. It is mainly used in passenger tire carcasses and can also be employed in aircraft tires.
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In the production of dipped polyester tire cord fabric, conventional Resorcinol Formaldehyde Latex (RFL) dipping alone may not achieve ideal adhesion with rubber. Instead, the following dipping systems are used:
Closed isocyanate and epoxy resin dipping system: Suitable for the double-bath method, where these tyre cord fabrics undergo the first bath with a solution composed of epoxy resin, closed isocyanate, etc., followed by heat treatment. It then undergoes the second bath with RFL dipping solution.
Vulcabond E dipping system: Involves chlorophenol compound water-based dipping solution, which can be mixed directly into the RFL dipping solution for single-bath dipping.
Surface activation treatment of fibers: Involves applying compounds like closed isocyanate, epoxy resin, oleic esters, and glycerol triacetate to untreated single filaments during spinning, stretching, or twisting processes.
Potential Issues:
Polyester tire cord fabric undergoes chemical degradation under the influence of amine substances, with degradation occurring more rapidly in the early stages of aging. This degradation primarily occurs in the amorphous regions within the polyester fibers, with the crystalline regions showing slower degradation, resulting in minimal loss of strength.
Different rubber accelerators have varying effects on the degradation of polyester tire cord fabric. Factors such as the thermal stability of the accelerators, the activity of the amine groups formed during decomposition, and the thermal stability of the complexes formed with other additives in the rubber compound all influence the degradation process.
Sulfur accelerators, such as thiazole accelerators, have the most significant effect on amine degradation of polyester tire cord fabric, followed by dithiocarbamate accelerators, while the impact of sulfenamide accelerators is minimal.
Impurities in natural rubber, such as fatty acids and esters, can also cause degradation of polyester tire cord fabric.
The higher the carboxyl group content in polyester fibers, the more susceptible they are to chemical degradation, resulting in greater loss of strength.
Mitigation Measures:
To prevent amine degradation, it is advisable to minimize or avoid the use of amine-containing substances in the polyester tire cord fabric coating formula.
Heat treatment of polyester tire cord fabric after dipping not only enhances its adhesion to rubber but also improves its resistance to degradation.
The addition of anti-amine degradation agents can inhibit the amine degradation effect of accelerator decomposition products on polyester tire cord fabric, effectively enhancing its resistance to amine degradation under heat, thereby significantly improving its strength retention.
In conclusion, understanding the properties and considerations of dipped polyester tire cord fabric is crucial for ensuring its effective application in tire manufacturing processes, enhancing tire performance, and extending tire lifespan.
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