Rubber Friction mechanism

In the design and development of rubber product such as tire , rubber seal , rubber automotive part , it is important to evaluate the contact load dependency of the friction coefficient. Mechanism of friction in rubber generates three different forms of friction: adhesion, deformation, and wear, which  adhesion force is the most influential component in rubber friction in dry conditions and low speed so that  adhesion friction is dominant for smooth contact at low speeds and dry conditions. Therefore increasing friction adhesion is possible by increasing the contact area of the product. Product samples that influence of the adhesion force is the industrial tire used in the warehouse where the floor is smooth and dry.

The hysteresis component of friction is caused by the bulk deformation of rubber material as it comes into contact with pavement asperities. Such deformation causes energy losses as rubber slides over the pavement surface. These energy losses are caused by the hysteretic.  In the case of contact between a rubber specimen and a rough hard surface , such as contact between tire and asphalt, the hysteresis component becomes dominate. 

The third major component of friction (cohesion losses) is caused by the wearing of rubber as it slides over the pavement surface. Pavement texture has an important role in the friction components—a recent study showed that higher pavement microtexture and macrotexture result in higher frictional properties. 

Rubber in Automotive

Approximately 500 - 600 application in the automobile involve the use of elastomer. These uses vary from model to model and from year to year. Automotive people are continully faced with material, design, process and cost decision in choosing elastomers to established performance goal. These goals can include durability, economy and meeting government regulation depending on the application.

Automotive standard for elastomer.
A complete rubber component standard is necessary for the following reasons

1. To ensure selection of material that meet requirement.
2. To prevent change in production material without the users's knowledge.
3. To correlate design requirement  with material properties.
4. To make certain that the material are commercially available.
5. To maintain uniform quality in production shipments.

The requirements of a rubber component specification are as follow:

1. Material requirement such as color , type of materials finished part quality.
2. Performance requirement such as density, tensile , elongation and tear.
3. Description of test methods including SAE, ASTM, and other laboratory procedure.
4. Construction requirement for composite materialsuch as hoses head gaskets .
5. Dimensional requirement , any information on tolerance or thickness of material referred to in the standard is required.
6. Sampling instruction , including sample size and number of sample to be submited.
7. Packaging instruction, to ensure clean, distortion-free part after shipment and storage.