Flex Resistance in Synthetic Leather: What Buyers Need to Know About Repeated Bending and Cracking

Synthetic leather used in wallets, bags, footwear, automotive interiors and upholstery may be bent, folded or flexed thousands of times during processing and daily use.

A material can feel soft and flexible when it is new but still develop surface cracks, coating damage or other visible changes after repeated bending.

This is why flex resistance should be treated as a separate performance property rather than judged only by hand feel, thickness or material type.

For buyers, the most important principle is:

A material that feels flexible when new is not necessarily resistant to repeated flexing over time.

What Is Flex Resistance?

Flex resistance describes the ability of a material to withstand repeated bending or flexing without unacceptable damage.

For many coated synthetic leather constructions, repeated flexing can place stress on the surface coating, intermediate layers, bond between layers and textile backing.

ISO 7854:1995 specifies several methods for assessing the resistance of rubber- or plastics-coated fabrics to damage caused by repeated flexing, including the De Mattia, Schildknecht and crumple/flex methods. The standard was reviewed and confirmed again in 2025. ISO

ISO 32100:2018 provides another method for determining flex resistance of coated fabrics in the folded condition. The specimen is repeatedly flexed while folded, and its appearance after a specified number of cycles is used to assess flex resistance. ISO

This means that “flex resistance” is not simply a description of how easily a material bends by hand.

It is a performance property that should be evaluated under defined test conditions.

Why Does Repeated Bending Matter?

Different products place different types of bending stress on synthetic leather.

A wallet may be repeatedly folded in the same area.

A shoe upper may flex continuously while walking.

A handbag may bend around edges, handles and opening areas.

Automotive and furniture upholstery can also experience repeated deformation around seams, cushions and curved structures.

Damage may gradually appear in high-flex areas even when the rest of the material still looks normal.

For this reason, buyers should identify where and how the material will flex in the final product before deciding what level of flex resistance is required.

Flex Resistance Is Not the Same as Abrasion Resistance

These two properties are often confused.

Abrasion resistance evaluates damage caused mainly by rubbing or friction.

Flex resistance evaluates damage caused by repeated bending or deformation.

A material may perform very well in an abrasion test but still develop cracking after repeated flexing.

Likewise, a material with good flex resistance may not necessarily have exceptional resistance to surface rubbing.

The tests measure different failure mechanisms and should not be used as substitutes for each other.

This distinction is especially important for products such as wallets, shoes and bags, where both rubbing and repeated folding can occur.

What Can Cause Cracking During Repeated Flexing?

Visible cracking after repeated flexing can be influenced by more than one factor.

The complete synthetic leather construction matters, including the surface coating, polymer formulation, layer structure, backing, thickness and bonding between layers.

Temperature and environmental aging can also affect how a material behaves during bending.

This is why a crack seen in a finished product should not automatically be diagnosed as a “flex resistance problem” without considering other possible degradation mechanisms.

For example, hydrolytic degradation, poor coating adhesion or environmental aging may weaken a material and make cracking more likely during later flexing.

In other words:

Cracking is a visible symptom; repeated flexing is only one possible contributor.

How Does the Surface Coating Affect Flex Resistance?

The surface coating must tolerate repeated deformation without becoming excessively brittle or losing integrity.

Different PU, PVC and other polymer systems can have different flexibility and aging behavior depending on their formulation.

However, material name alone is not enough to predict flex performance.

It would be too simplistic to say:

PU always flexes better than PVC.

or:

Microfiber always has the best flex resistance.

Actual performance depends on the specific resin system, coating structure, backing and processing conditions.

For demanding applications, the correct approach is to test the finished material specification rather than rely on the material category.

How Does Backing Affect Flexing?

The backing helps support the coated surface during deformation.

Woven, knitted and nonwoven substrates can behave differently when bent or stretched because their fiber or yarn structures distribute deformation differently.

A more extensible backing may help a material conform to curved structures, while a more dimensionally stable backing may limit deformation.

Neither characteristic is automatically better.

The correct backing depends on how the final product is expected to bend, stretch and recover.

This is another reason why two synthetic leathers with the same thickness and similar surface grain can still behave differently during repeated flexing.

Does Thicker Synthetic Leather Have Better Flex Resistance?

Not necessarily.

Total thickness can affect bending stiffness and the way stress is distributed through the material, but thicker does not automatically mean more flex-resistant.

A thicker construction may contain:

• a heavier backing
• a thicker coating
• an expanded layer
• additional intermediate layers

Each of these can change bending behavior differently.

A thinner material with a well-designed flexible coating and backing can perform better in repeated flexing than a thicker material with a less suitable construction.

Therefore, thickness should be considered together with the complete material structure.

Does Softer Synthetic Leather Always Have Better Flex Resistance?

No.

Initial softness and long-term flex resistance are not the same property.

A soft material may bend easily during handling, but repeated bending can still cause damage if the coating, backing or layer adhesion cannot tolerate long-term cyclic deformation.

Likewise, a slightly firmer material may still achieve good flex resistance if its construction is designed for repeated movement.

Hand feel is useful for evaluating comfort and processing, but it cannot replace a flex test.

Which Applications Need More Attention?

Flex resistance is particularly important when the final product contains areas that are repeatedly bent or folded.

Examples include:

• wallet folds and card-pocket edges
• handbag openings, straps and folded seams
• footwear uppers
• automotive upholstery around curved or repeatedly compressed areas
• furniture seams and high-deformation zones

The important point is not simply the product category.

A rigid decorative panel may require much less repeated flexing than a wallet hinge or shoe upper, even if both use synthetic leather.

The material specification should therefore reflect the actual deformation experienced in service.

How Is Flex Resistance Tested?

There is no single universal flex test for every synthetic leather product.

ISO 7854:1995 describes several repeated-flexing methods for coated fabrics, while ISO 32100:2018 evaluates flex resistance using a flexometer in the folded condition. ISO

For low-temperature applications, temperature becomes another important variable.

ISO 4675:2017 specifically evaluates the resistance of coated fabrics to bending at specified low temperatures. The standard also warns that no general relationship between this test and real service performance can automatically be assumed. ISO

This is an important lesson for buyers:

A test result is meaningful only when the test method and conditions are known.

Why Cycle Count Alone Is Not Enough

A supplier may say:

“This material passes 100,000 flex cycles.”

That sounds impressive, but the number alone is incomplete.

To compare flex results properly, buyers should know:

Test Method → Flexing Mode → Temperature → Number of Cycles → Evaluation Method → Acceptance Criteria

Two materials tested for the same number of cycles may not have experienced equivalent conditions.

One test may use a different folding geometry.

Another may be conducted at a different temperature.

The endpoint may also differ.

One laboratory may stop when the first visible crack appears, while another customer specification may allow minor surface changes but reject coating separation.

Therefore:

Do not compare flex cycle numbers before confirming how the test was performed.

Why Low Temperature Can Matter

Synthetic leather that performs well at room temperature may behave differently when cold.

Polymeric materials can become less flexible at lower temperatures, which is why low-temperature bending is treated as a separate test condition.

ISO 4675:2017 evaluates coated fabrics after exposure to specified low temperatures and subsequent bending. ISO

For products intended for cold climates, outdoor use or temperature-sensitive applications, buyers should confirm whether low-temperature flex performance is relevant to the project.

Room-temperature flex results alone may not answer that question.

Flexing and Rubbing Can Also Occur Together

Real products do not always experience only one type of stress.

A surface may bend while also rubbing against another surface.

ISO 5981:2007 specifically addresses the combined effect of shear flexing and rubbing in coated fabrics, illustrating that combined mechanical stresses can require a different evaluation from simple flexing alone. ISO

This is particularly relevant when a product contains moving folds, tight seams or surfaces that contact each other during use.

What Should Buyers Confirm Before Ordering?

Instead of simply asking:

“How many flex cycles can this material pass?”

a more useful purchasing sequence is:

Application → Flexing Area → Thickness → Backing → Material Construction → Test Method → Temperature → Required Cycles → Acceptance Criteria

The buyer should first explain where the material will be used and how it will deform.

If a specific test standard or customer requirement already exists, it should be provided before material selection.

Depending on the application, flex resistance may also need to be considered together with abrasion resistance, coating adhesion, tear strength, hydrolysis resistance, heat aging, cold resistance and other properties.

Testing every property is not always necessary.

The goal is to identify the performance requirements that actually match the final product.

Conclusion

Flex resistance is an important property for synthetic leather used in products that experience repeated bending, folding or deformation.

However, flex performance cannot be reliably predicted from thickness, softness or material name alone.

The complete construction matters:

Surface Coating → Polymer System → Backing → Thickness → Bonding → Test Conditions → Application

A soft material is not automatically flex-resistant.

A thicker material is not automatically more durable.

And a high cycle count is not meaningful unless the test method and acceptance criteria are known.

For buyers, the most reliable approach is to define the actual application and flexing conditions first, then select and test a material construction that meets those requirements.

CIGNO Leather supplies PU, PVC, microfiber and other synthetic leather materials for bags, furniture, automotive interiors, footwear and other applications. Material specifications can be developed according to application, thickness, backing, hand feel and required performance.