In high-volume liquid logistics, especially over long distances, Flex Cracks are a critical but often underestimated failure point. These micro-fractures in barrier layers result from mechanical stress, film fatigue, and environmental variation. Though invisible to the eye, they can compromise the oxygen barrier, accelerate product degradation, and lead to batch loss, contamination, or regulatory non-compliance.

While barrier performance is often viewed as a single-layer property, in reality, different materials respond differently to mechanical stress, making film structure a system-level consideration.

The Science Behind Flex Cracks

Flex Cracks typically develop in multilayer coextruded films, where thin high-barrier layers (such as EVOH or metallized films) are subjected to cyclic mechanical stress, including:

• Vibration during transport (especially in intermodal shipping)
• Friction and abrasion within outer packaging
• Stress concentrations from filling, emptying, or stacking
• Temperature fluctuations causing expansion and contraction of incompatible layers

Once a barrier layer is compromised, even partially, oxygen ingress and microbial contamination can occur, especially in aseptic and extended shelf-life applications.

Barrier Sensitivity: Metallized Films vs. EVOH

Metallized films offer strong OTR performance but are brittle and highly sensitive to mechanical fatigue, making them more prone to Flex Cracks under vibration or bending. A single microcrack can lead to full barrier failure.

EVOH (Ethylene Vinyl Alcohol), while still sensitive to humidity, offers greater elasticity and flexural fatigue resistance. It can absorb and disperse mechanical energy more effectively, reducing the likelihood of crack formation under dynamic conditions.

Aran often combines multiple barrier layers to create redundancy, ensuring that even if one layer is compromised, the package retains its protective function.

Flexibility by Design: Material Engineering for Movement

In addition to barrier selection, film structure and processing are critical to Flex Crack prevention. Aran applies proprietary techniques during coextrusion to enhance the film’s flexibility and resistance to fatigue.

These refinements result in films with improved elastic response and structural stability under dynamic conditions like vibration, compression, and repetitive movement. The film structure adapts more effectively to stress, lowering the risk of microcrack formation throughout transport and storage.

Aran’s Technical Response: Premium Flex 2.0

To address Flex Cracks at their source, Aran developed Premium Flex 2.0, a high-performance aseptic bag designed for mechanical durability and consistent oxygen barrier protection.

Key design elements include:

• Barrier Optimization
  EVOH layer <5% to maintain recyclability and high barrier performance. EVOH is coextruded between flexible tie layers to prevent strain-induced delamination.
• Mechanical Reinforcement
  Tailored PE layers with controlled molecular weight distribution ensure tensile strength, puncture resistance, and flexural fatigue resistance, minimizing risk of cracking during long-haul transport.
• Stress Dispersion Architecture
  Layer thicknesses are engineered to distribute mechanical load. The inner film’s elasticity reduces stress transfer to the barrier layer, while the outer layer provides abrasion resistance.
• Flex-Crack Resistance Testing
  All Premium Flex 2.0 structures undergo ASTM F392 flex-durability testing and shipping simulation trials. Results show a >90% reduction in microcrack formation compared to conventional structures.

Built to Withstand the Journey

Flex Cracks are not a surface defect, they’re a system-level challenge that threatens product integrity. At Aran, we treat them as a design parameter from the start. Premium Flex 2.0 represents a multi-variable engineering solution that balances barrier performance, mechanical durability, and environmental compliance.