Elastomer Properties – 5 Performance Tests
Rubber is renowned for its resilience. This hard-wearing material is used throughout numerous industries (e.g. Mining, Pulp and Paper) especially those subjected to high levels of impact and abrasion. Yet, over time these conditions take their toll.
Whether it be conveyor belts, protective linings or expansion joints, all experience deterioration, eventually leading to necessary maintenance. Instead of replacement or using traditional rubber repair methods, such as vulcanisation, Belzona offers a range of polymeric repair and protection solutions.
In this post, we examine five application and performance benefits of these materials and put them to the test!
How fast can Belzona elastomers return to service?
In today’s world, time is of the essence. Maintenance needs to be quick and simple, something difficult to achieve with traditional rubber repair methods, such as vulcanisation.
As an alternative to this specialist hot work method, Belzona elastomers are hand applied and cold curing, allowing repairs to be carried out in situ with speed and ease.
Eliminating the need for specialist tools makes Belzona elastomer applications simple. Plus, the fast-curing nature of the materials allows repairs to be reinstated quickly.
For example, conveyor belts like this can be repaired using Belzona 2311 (SR Elastomer), an emergency repair system that, at 25°C (77°F), achieves full mechanical cure in 50 minutes. A fast return to service minimises downtime, optimising efficiency.
How well do Belzona elastomers adhere?
Among important elastomer properties are their abilities to maintain good adhesion. Especially when subjected to stress. This method is used to assess the adhesion of flexible materials under peel conditions when applied to rigid substrates.
Test samples are prepared by first applying the appropriate conditioner to a suitably prepared substrate. Usually 2.0mm (0.08in)-thick grit blasted mild steel of 200 x 25.4mm (7.9 x 1 in) dimensions.
Once the conditioner has cured, a layer of elastomer is applied and a strip of Belzona 9341 Reinforcement Tape is embedded into the wet material, with some length extending beyond the end of the substrate. This process is repeated until there are three strips of reinforcement tape encapsulated in the elastomer system.
Once cured, samples are clamped into the grips of a 25 kN tensometer, such that any applied force will exert peel forces at 90° to the elastomer-metal bond. The tensometer then applies force at a constant rate of 50mm/minute to promote adhesive failure and progress bond separation.
The peel force across the full length of the bond is then monitored, allowing an average failure force to be calculated.
How flexible are Belzona elastomers?
Without good flexibility, any rubber maintenance material will quickly fail. Once in service, the material can experience extensive tensile and tearing forces – stresses that Belzona’s series of elastomers are specially designed to cope with. Within the video, two separate tests were highlighted:
An extensometer is used to measure the degree of extension of a specimen when subjected to a tensile load. For this test, dumbbell-shaped samples are used, typically with a 4mm linear width.
The extensometer grips are clamped within the narrow section of a test sample with a set gauge length of 25mm (1in).
As the sample is stretched, the change in length as a function of the applied load is monitored, until failure is achieved. The value of interest is the elongation at break, expressed as a percentage elongation. For example, Belzona 2211 (MP Hi-Build Elastomer) possesses outstanding elongation, registering up to 700%.
Building joint sealants can be prone to failure when active i.e. expansion and contraction of the joint under natural movement. Failure can be cohesive (within the sealant) or adhesive (between the sealant and the substrate).
In order to assess the material’s suitability as a joint sealant, its performance must be evaluated when subjected to cyclical movement of the substrate. Based on this test, the movement accommodation factor of a sealant can be determined.
Belzona elastomer properties are most commonly tested within a + or -25% compression and extension threshold. These are cast and bonded to two substrate blocks, typically concrete or steel.
These then enter a cyclical testing phase, within which they ensure cycles of compression and extension at 20°C at a rate of 3mm per hour. During this phase, the samples are also exposed to high temperatures and immersion, as it is repeated for several cycles.
How do Belzona elastomers perform under abrasive conditions?
Just as significant among elastomer properties is abrasion and impact resistance. Dependent on the industrial environment, Belzona offers a versatile range of systems, capable of withstanding specific abrasive conditions. These are rigorously tested to deliver durable repair and long-term protection.
This in-house test method is used to measure the impingement abrasion resistance of highly abrasion resistant materials.
The sample is held at the appropriate angle, typically at 90° or 30° to the nozzle, and a standard weight, usually 2kg (4.4lb), of abrasive material is fired at the product using an air-powered blast pistol at 5.5 bar (80 psi).
The abrasive media used will depend on the properties of the material under test and the envisaged end use applications. In this instance, the abrasive media used was chilled iron grit.
How can Belzona elastomers be applied?
The cold-curing nature of these materials makes them extremely versatile.
The whole range can be adapted depending on the application scenario. Whether hand-applied or poured, Belzona’s series of elastomers are easy to use and apply. They can even be cast to specific dimensions – moulding entire components with the benefits built in.