How to maximize the service life of rubber components?

In many industries, rubber components play a vital safety role in everyday activities. For this, rubber components need to be durable. Although in many cases, rubber components have many ways to fail during use, mechanical fatigue is probably the most common failure mechanism, affecting almost all rubber-related components. In the future, we will also explore solutions for other failure mechanisms, such as wear and chips, chemical erosion, expansion and inelastic failures.

When it comes to mechanical fatigue, we are concerned with the long-term performance and service life of rubber components subjected to repeated mechanical loading and unloading cycles. Conveyors, synchronous conveyor belts, different tire components, AV bases require repeated mechanical cycles when working.

Rubber mechanical fatigue begins with homogeneous fracture (precursor to fracture) in rubber composites. Then, the cracks in the rubber body continue to increase, leading to catastrophic failures as the loading cycle progresses. Based on this failure mechanism, we need to consider two aspects, one is fracture nucleation (i.e. the uniformity of the composite) and the inherent fatigue crack propagation resistance.

Rubber selection
The selection of suitable rubber is the most important for mechanical fatigue performance. Natural rubber is an excellent choice for crack and tear resistant composites. Its crystallization ability under strain leads to automatic strengthening of the crack tip. This mechanism prevents and passivates cracks during cyclic relaxation and non relaxation deformation. Of course, natural rubber is not suitable for all applications. Specific synthetic rubber is required for high-temperature operations or harsh chemical conditions. Compared to natural rubber, the strain crystallization performance of most synthetic rubbers is not outstanding. On the contrary, synthetic rubber relies entirely on particle strengthening operations to achieve the required crack propagation and tear resistance.
 

Selection of reinforcing agents
Reinforcing agents such as carbon black play a crucial role in determining the crack propagation and tear resistance of rubber components. The key lies in selecting the correct load level, surface area and structural layer of carbon black. The selected carbon black needs to exhibit good dispersibility and minimal physical impurities during the composite mixing process, in order to achieve further improvement. The same factors need to be considered when selecting other granular formulations. Filler aggregates and impurities in raw materials can lead to an increase in the size and quantity of crack precursors in the composite, both of which can have adverse effects on fatigue life.

The characteristics of mechanical fatigue
In fact, the failure of rubber components is rarely consistent with fast, inexpensive, and widespread rubber experimental testing, which is a common phenomenon in our industry. Relatively simple tests, such as tensile failure or tear testing, cannot fully understand and design the fatigue performance of rubber composites. Fortunately, at Bora Carbon Black, we have advanced equipment that can study and explain mechanical fatigue mechanisms, and link them with actual rubber synthesis. This type of equipment includes high-throughput fatigue crack propagation equipment or crack nucleation testing related to fracture mechanics, as well as world-class miniaturization equipment.
Carbon black in natural rubber can reduce the displacement level required for strain crystallization by increasing the local strain in the rubber matrix. This essentially enhances the self strengthening ability of natural rubber. Carbon black integrates excess energy consumption mechanisms into rubber composites, which is also one of the main reasons for the increase in tear strength and crack resistance of rubber with added carbon black compared to rubber without added carbon black. To cause the filling rubber to fracture, more external force needs to be applied to compensate for the energy consumed by carbon black in the viscoelastic processing area before reaching the crack tip. This is particularly important for amorphous rubber.