What Are The Factors That Affect The Elasticity Of Rubber Seals?

Fillers and additives for rubber seals

The type and content of filler

Different fillers are often added to rubber seal materials to improve their mechanical properties, wear resistance, heat resistance, etc., but these fillers can also affect elasticity.

Carbon black: Carbon black is one of the most commonly used fillers, which can enhance the strength and wear resistance of rubber seals, but excessive carbon black will cause the elasticity of the rubber to decrease. The particle size and dispersibility of carbon black are also key factors affecting the elasticity of rubber. The fine and evenly dispersed carbon black particles can better enhance the mechanical properties of rubber, but too much will limit the free extension of the molecular chains, which in turn will affect the elasticity.

Silicone: As an alternative filler to carbon black, silica typically provides a lower coefficient of friction and improved abrasion resistance of rubber with less impact on elasticity.

Oils and softeners

Oils and softeners are commonly used additives to improve the processability and reduce the hardness of rubber seals. They can reduce the coefficient of friction of rubber and increase its fluidity during processing, but they can also affect elasticity to a certain extent.

Softeners: The right amount of softener can make rubber softer, but too much softener can cause the elasticity of the material to decrease, especially at low temperatures, and the migration of softeners may lead to embrittlement of rubber.

Enhancers

Certain reinforcing agents (e.g., polymer reinforcers, glass fibers, etc.) can enhance the strength and abrasion resistance of rubber seals, but they can also cause a decrease in elasticity. This is because the addition of a reinforcing agent alters the molecular structure inside the rubber and may limit the free movement of the polymer chains.

Vulcanization process of rubber

The vulcanization process has a decisive influence on the elasticity of rubber. In the vulcanization process, the molecular chains of the rubber are cross-linked through the action of vulcanizing agents, which improves the mechanical properties of the material.

Vulcanization temperature and time

Vulcanization temperature and time are key factors that affect the degree of curing (crosslinking) of rubber and the final elasticity. Too high a vulcanization temperature or too long a vulcanization time can cause the rubber to be over-crosslinked, which reduces elasticity and the material can become hard and brittle.

Low vulcanization: Rubber with incomplete vulcanization has good elasticity, but poor mechanical properties.

High vulcanization: Excessive vulcanization will result in stiffer rubber and poor elasticity, but heat resistance and durability will increase.

Selection of vulcanizing agent

The type and amount of vulcanizing agent have a direct impact on the elasticity of rubber. Common vulcanizing agents are peroxides and sulfur. Sulfur vulcanization generally provides better elasticity, while peroxide vulcanization can result in higher hardness and high-temperature resistance.

Environmental factors

Temperature

The elasticity of rubber is closely related to temperature changes. Temperatures that are too high or too low can affect the elasticity of rubber.

High temperatures: High temperatures can intensify the movement of rubber molecular chains, which may lead to a decrease in the elasticity of the material, and even softening and rheology.

Low temperatures: Low temperatures can make rubber more fragile and reduce the degree of freedom of the molecular chains, resulting in a decrease in elasticity.

Humidity and oxygen

Moisture and oxygen can also affect the elasticity of rubber. Some rubbers (e.g., EPDM, NBR, etc.) undergo moisture absorption in high humidity or humid environments, resulting in changes in their physical properties. The long-term effects of oxygen also accelerate the aging process of rubber and reduce its elasticity.

Ultraviolet rays and ozone

Ultraviolet light and ozone have a particularly significant effect on rubber. Prolonged exposure of rubber to ultraviolet light and ozone can cause molecular chains to break, which can reduce elasticity and even lead to embrittlement of rubber.

Stress and fatigue

Rubber seals are subjected to multiple stretches and compressions over long periods of use. These stresses and fatigues can cause the rubber to gradually lose its elasticity or even to deform permanently. Therefore, rubber seals must be designed with fatigue life and recovery capability in mind over long periods of use.

To sum up, the factors affecting the elasticity of rubber seals involve the composition of rubber itself, fillers, vulcanization processes, environmental factors, and other aspects. The elasticity of rubber is the embodiment of its comprehensive properties, and it is the key to whether it can show excellent performance in different applications. To optimize the elasticity of rubber seals, it is necessary to comprehensively consider various factors, from the selection of raw materials to the control of processing technology to the adaptation of the use environment.