Rubber Deterioration Over Time And What Causes It?

Rubber is a common material that is malleable and can be very useful. Yet, like most materials, rubber degradation occurs over time affecting the functionality of essential rubber parts components such as seals and O-rings used in hydraulic and pneumatic systems. This is due to common environmental factors such as heat, light and ozone. Learn about common causes of rubber deterioration and practical ways to prevent it.

What is Rubber Deterioration?

Rubber is a polymer-type material, known for its elastic properties. Rubber deterioration is the process of rubber (elastomer) properties declining over time. The deterioration of rubber may be chemical, caused by oxidation or hydrolysis. Or it may be physical, or biological. For example, the strength and flexibility of the rubber may decline. The most common causes of rubber deterioration are exposure to light, oxygen (ozone) and heat. The changes due to these exposures can impact the performance of rubber components such as O rings and other seals.

Additionally, rubber deterioration can cause a visual change. The surface of the rubber can become cracked due to shrinkage. But, this is only a significant issue if there are many cracks on the surface. Small individual cracks are insignificant in respect of rubber performance.

Colour changes may also occur, caused by reactions that change the molecules of the polymers. Additionally, changes in dyes or pigments that accompany general deterioration can also result in colour changes.

How Does Rubber Deteriorate?

There are two main forms of rubber deterioration, hardening (also known as embrittlement) and softening. The chemical structure of the rubber will determine what mechanism will act during the rubber’s life.

As mentioned above heat, light, chemical exposure, and oxygen exposure can all cause the rubber to deteriorate. When exposed to any of these causes, the chain of molecules begins to break down.

Heat shortens the molecular chains, which causes the material to stretch once cooled down. UV degradation, which is exposure to light, can cause the rubber to become hard, crack, and even fade. When exposed to oxygen, it attacks the double bonds in rubber chains, also leading to deterioration.

For example, free radicals produced by heat, oxygen and light combine with the rubber molecules to form new crosslinks. The combination of these molecules reduces the rubber’s flexibility and leads to hardening.

Rubbers created by polymerisation (where monomer molecules are joined together to create polymer chains) undergo softening. This is a result of chain scission, and the main polymer chain degrading.

How To Stop Rubber Deterioration

Before a rubber component is manufactured, finite element analysis (FEA) modelling is completed. The modelling predicts the rubber material’s response to its conditions that cause stress or strain. Computer-based modelling helps determine if the type of rubber and the proposed design will meet the requirements and perform its function. Such methods provide cost benefits by maximising the rubber for its conditions.

After the design stage, the number one method of preventing rubber deterioration is maximising storage conditions. They need to be stored in a cool, dry, dark and oxygen-free space – the most optimal conditions.

For rubber that shows signs of deterioration in storage, there are ways to reinstate them to full functionality. Restoration techniques can uplift rubber seals to a state where they can be used again. Below are the steps to can achieve that:

Step 1: Clean and Prepare – Clean around the rubber seal and remove dirt, water, or any other debris – including the removal of excess grime or hardened debris.