Elastomers such as rubber are known for their ability to repeatedly return to their original shape and dimensions after being stretched or distorted. These properties are generally referred to as elasticity, resilience or rebound.
In many industrial applications, however, it is the ability of an elastomer to provide abrasion resistance that is often most important to manufacturers and OEM’s.
Abrasion testing of rubber
The term abrasion resistance simply describes the ability of an elastomer to withstand repeated abrasion by a rubbing, scratching or scraping motion.
Abrasion testing of rubber to determine its operating life is normally carried out using a sample of material held against a rotary abrasive drum for a predetermined period of time, with the results being expressed as volume loss in mm³. Other test methods include Taber abrasion, using rotary wheels, or NBS abrasion using a downward force.
Changing the mechanical properties of elastomers
The properties of an elastomer such as natural rubber are traditionally modified using a process of vulcanisation, where the material is heated and mixed with a vulcanising agent such as sulphur, together with other additives or compounds to create the required characteristics to improve subsequent processing and use.
At a molecular level, the vulcanisation reaction, in conjunction with the various additives, improves the cross linking between the naturally occurring isoprene compounds, while fillers such as carbon black, clay or silica provide varying degrees of reinforcement.
Although there is an extensive range of compounds that can be added to elastomers, perhaps the most exciting addition in recent years has been the availability of graphene.
Graphene is a 2D allotrope of carbon, formed from a single or small number of layers of atoms arranged in an sp² network; the latter occurs as a hexagonal array of carbon atoms that can be stacked to form a lattice structure. This unique construction provides exceptionally high levels of mechanical strength, electrical mobility, thermal conductivity and gas impermeability.
When graphene is blended and dispersed evenly through a rubber masterbatch it has the potential to significantly impact the wear properties of the material.
For example, recent work to manufacture industrial wear linings, carried out by First Graphene in partnership with newGen Group, used standard graphene powder mixed into a polyurethane elastomer in conventional industrial mixing equipment. This was achieved without the need for pre-treatment of the graphene additive or changes to the original formulation of the polyurethane. <1% PureGRAPH® was added to the formulation.
Graphene in wear liners for mining and quarrying
Liners cast from these graphene-enhanced polyurethane resins showed an improvement in tensile strength of 37%, greater tear strength, enhanced elongation and an increase in abrasion resistance of between 100% and 500% (as determined by Taber testing).
newGen Group has now launched a range of graphene-enhanced wear-protection liners for applications in the mining and quarrying sectors, including reclaimer buckets, pipe spooling, dryer chutes and conveyor applications. These linings last far longer than traditional parts, reducing their need to be replaced and thereby lowering costs associated with production stoppages. They are already in use as part of a wear lining system for heavy-duty iron ore mining equipment.
Want to learn more about graphene in elastomers? Here are some other blogs that might be of interest: