Aslan Kauçuk Compound

Natural rubber combines high tensile and tear resistance with excellent fatigue resistance.

Its excellent green strength and adhesion - the ability to adhere to itself and other materials - makes natural rubber products easier to manufacture.

It exhibits excellent dynamic properties with low hysteresis, leading to low heat generation.

Natural rubber has been successfully used as an engineering material for many years. The range of properties listed below demonstrates how versatile natural rubber is for engineers:

• Can be adjusted to a hardness from very soft to very hard (ebonite)
• Appearance and color vary from transparent (soft) to black (hard)
• Can be compounded to meet virtually any mechanical requirement
• Can provide electrical insulation or full conductivity
• Offers sealing and insulation properties
• Capable of absorbing vibration and reducing noise
• Available in almost every surface texture and shape option

The hardness of natural rubber products is determined by the amount and type of filler, degree of dispersion, and crosslink density. In engineering applications, the most common rubber filler is carbon black. To achieve maximum tensile properties, approximately 25% by volume of carbon black is required.

To achieve low creep properties, the level of carbon black used should be kept to the minimum acceptable level. If the application requires high abrasion resistance, a carbon black with a small particle size should be used. The overall hardness of a natural rubber product is a result of the modulus of the rubber, the shape and dimensions of the product, and the form of deformation.

The modulus of a rubber compound is also determined by the amount of filler used. To achieve a low-modulus product, typically low-reinforcing blacks or non-reinforcing white fillers are used. Modulus can also be affected by rubber quality, viscosity, and the vulcanization system used.

Low modulus properties can be obtained using an efficient vulcanization (EV) system, which relies on soluble accelerators, activators, and low levels of sulfur.

In natural rubber compounds, elasticity decreases as the filler level increases. To achieve high elasticity, the filler level must be kept at an acceptable level to maintain physical properties.

For natural rubber products used in outdoor applications, low compression set can be achieved using vulcanization with organic peroxides. However, since peroxide-vulcanized products have poor tear resistance and are incompatible with anti-ozonants, the common practice is to use conventional vulcanization (CV) or semi-efficient vulcanization (SEV) systems.

To achieve good creep/relaxation resistance, the filler content should be kept to a minimum, and blacks with medium particle size should be used. For low creep/relaxation, a soluble EV system is also recommended.

In natural rubber compounds, the degree of crosslinking affects various properties. For maximum tear resistance, crosslink density should be slightly lower than that required for maximum tensile strength and abrasion resistance. Compression set, elasticity, creep, and relaxation resistance are best achieved at higher levels of crosslinking.