Which Elastomer Offers The Best Flex Resistance?

When a product or component is required to operate under dynamic bending stress, there is a need to select a base elastomer which is able to withstand such forces without experiencing cracking or other damage.

As with all of the different properties of various base materials, some elastomers perform better than others in terms of flex resistance and, whilst the inherent characteristics of a polymer can be improved through the inclusion of additives, it is important to develop an understanding as to which base elastomers offer the most suitable properties.

The term flex resistance does not mean resistance to flexing or bending, rather, the ability to withstand numerous flexing cycles without damage or deterioration. Flex-crack resistance is the ability to withstand a number of flexing cycles without experiencing the occurrence of surface cracks as a result of stress. Most commonly, rubber products and components are damaged by repeated flexing cycles in the form of surface cracks.

In selecting a rubber which can withstand flex resistance for use in any particular application, it is necessary to understand the different base elastomers available and, as such, which can be used as a base for developing a unique blend to meet the requirements of a specific product or component.

Primarily utilising 12 different elastomers for the manufacture of rubber sheeting, reinforced rubber sheeting and rubber coated textiles, our technicians are on hand to help inform decisions and to help make the research stage that little bit more straightforward.

Below you’ll find a comparison of our 12 most commonly utilised elastomers based upon their flex resistance properties rated ‘poor’ to ‘excellent’:

Please note: Whilst most main rubbers are outlined below, our capabilities and experience allow us to manufacture a much wider range of blends and formulations. The inherent characteristics of a polymer can be improved through the inclusion of additives, including the flex resistance properties.

Elastomer	Flex Resistance
Natural Rubber	Excellent
Polyurethane	Excellent
Thermoplastic Elastomer	Good / Excellent
Butyl	Good
Hypalon	Good
Neoprene	Good
SBR	Good
Vamac	Good / Fair
EPDM	Fair
Nitrile	Fair
Silicone	Poor / Fair
Viton	Poor / Fair

Whilst faced with a number of options surrounding the most suitable base elastomer judging by it’s flex resistance, we can clearly see that the main considerations should be either natural rubber or polyurethane.

Natural Rubber
Whilst not suitable for use in instances where the product or component will be exposed to ozone, oils or solvents, natural rubber offers excellent flex resistance alongside superior resistance to tear and abrasion, good tensile strength, high tear strength and good flexibility at low operating temperatures.

Polyurethane
Most formulations of polyurethane offer extremely high flex resistance and can be expected to outlast other base elastomers where this is an important requirement of a particular product or component. It is possible to enhance this base material through the inclusion of additives to further improve the flex resistance as well as to enhance other such characteristics as necessary, depending upon the operating environment.

When analysing the requirements of any given product or component, the selection of the correct base material is often required to be a compromise between a number of different factors including individual usage specifications and the economics of any particular blend.

Here at White Cross Rubber Products, our expertise and capabilities allow us to manufacture a wide range of blends and formulations dependent upon a number of characteristics including the operating environment and economic factors. Should you be looking for in-depth, backed up information and data surrounding the flex resistance of any number of our main elastomers, or wish to discuss your specific needs and requirements, we welcome you to give our technicians a call on 01524 585200.