Elastomers are important materials that fulfil critical roles and are typically overlooked. Whether it be a car tyre, a timing belt or rubber tubing used in a medical procedure, elastomers often play a part in our everyday life. In a single substance you can find a wide range of properties. These include:
- Abrasion resistance
- Tear resistance
- Tensile strength
- Tensile modulus
- Compression set
Different properties will be more, or less, important in each application. For example, seals for use in the automotive or offshore sectors may have to withstand constant exposure to high temperatures and aggressive chemicals, while a rubber compound formulated for use in bicycle tyres will be designed to withstand extended wear while minimising damage from road surface debris.
Improving elastomer tear strength
The tear strength of an elastomer is generally defined as the force needed to create a tear in a sample of material and then to cause the tear to continue to develop until the sample separates. Force is applied in a direction that is perpendicular to the direction of stress. Tear strength is normally calculated using a measure of the applied force and the thickness of the material.
Although different compounds will exhibit varying degrees of tear strength, it is often possible to improve the ability of an elastomer to withstand tear forces. In some formulations, the addition of carbon black can act both as a filler, to reduce cost, and a reinforcement, while combining rubber with a textile reinforcement layer can offer a considerable improvement in tear resistance. The addition of graphene can make significant improvements in the level of tear resistance by strengthening the crosslink bonding within the rubber matrix. These improvements can be up to 50%, often by adding just 1% by volume of graphene to the masterbatch.
Research carried out at the University of Manchester showed that the best results are achieved by manufacturing the elastomer/graphene compound using a solution mixing method, rather than melt mixing. The former tends to exfoliate or intercalate the graphene platelets, while the latter shortens and distorts the length and shape of the platelets, creating larger voids between the constituent components within the elastomer matrix.
To learn more about the use of graphene in elastomers, follow these links: