Application: Vertical Form Fill Seal (VFFS) Packaging Machine
Component Type: Custom Silicone-Coated Rubber Timing Belt
The Core Issue: Coating delaminated from the base belt after 6 months due to interfacial shear fatigue over small pulley diameters.
1. The Customer’s Challenge & Background
Our client operates high-speed Vertical Form Fill Seal (VFFS) packaging lines. Originally, they utilized standard timing belts with rough rubber backings to pull the packaging film. However, the rubber lacked sufficient wear resistance, wearing out completely in less than 2 months, causing film slippage and unstable bag lengths.
To upgrade their system, we previously supplied them with a 60 Shore A silicone-coated timing belt. The silicone coating offered exceptional grip and excellent abrasive wear resistance, significantly improving initial performance. However, at the 6-month mark, a new problem emerged: the client reported that the silicone coating had begun delaminating and peeling away from the rubber base belt along the flex zones, although the silicone surface itself showed no abrasive wear.
The customer loved the high friction of silicone but urgently asked: “Can TRANDVOX eliminate this delamination issue? We still want to use silicone.”
2. Engineering Failure Analysis: Shear Stress & Interfacial Delamination
TRANDVOX’s technical team immediately analyzed the returned failed samples. We discovered that the separation occurred precisely at the bonding interface between the silicone coating and the rubber base belt.
In compact VFFS machines, the belt must travel around very small diameter idler pulleys, forcing the belt into sharp counter-flexing. According to polymer mechanics and ASTM D2240 standards, a 60 Shore A silicone compound possesses a high Elastic Modulus (flexural rigidity).
When a rigid coating bends sharply around a tight radius, a strong stiffness differential exists between the silicone layer and the rubber timing belt. This dynamic bending generates excessive interfacial shear stress along the bonding line. Over 6 months of continuous, high-frequency operation, this alternating shear stress broke down the interfacial bond, resulting in Flex Fatigue Delamination.
Engineer’s Insight: In industrial belt design, coating hardness directly dictates interfacial shear. While 60 Shore A provides great abrasive resistance, its higher rigidity creates extreme shear forces at the bonding boundary over tight radii, leading to delamination. To prevent bond failure, the flexibility of the compound must match the system’s minimum pulley limits.
3. The Optimized Solution: Engineering a 40 Shore A Compound
To eliminate the delamination without sacrificing the necessary friction, TRANDVOX engineers formulated a specialized 40 Shore A soft silicone coating. This targeted adjustment achieved three critical goals:
Drastic Shear Stress Reduction: Lowering the durometer from 60 to 40 Shore A significantly reduced the flexural stiffness of the coating. This cut the interfacial shear stress during bending by nearly 40%, preserving the bond between the silicone layer and the rubber base belt.
Enhanced Interfacial Resilience: The 40 Shore A compound boosted Elongation at Break to over 450%, allowing the soft silicone to dynamically deform alongside the base belt without straining the adhesive boundary.
Improved Grip: Naturally, a softer silicone compound conforms better to the film surface, providing a higher coefficient of friction, which enhanced the film-pulling accuracy even further.
4. The Result & Proven Long-Term Reliability
We delivered the newly engineered 40 Shore A VFFS belts for on-site testing. The results were flawless. The belts have now been running for over 14 months without a single sign of delamination, micro-peeling, or bond degradation. The film feeding remains perfectly smooth, and unscheduled production downtime has dropped to zero.
The client has officially standardized this TRANDVOX 40 Shore A silicone formulation across their entire packaging machinery fleet.
Technical Call-to-Action (CTA):
“Facing timing belt delamination or peeling issues on your packaging machinery? Fill in your minimum pulley diameter and belt speed, and TRANDVOX’s engineering team will provide a free material optimization review within 24 hours.”
