Key Benefits of E-TPU in Footwear
- High rebound and resilience
- Excellent mechanical properties
- Long-term durability
- Wide temperature range (down to -20°C)
- Low density (140–240 g/L)
Performance Polymers
Infinergy® Revolution (E-TPU)
Is Infinergy® E-TPU easily to be processed?
Infinergy® Revolution (E-TPU) provides access to a variety of molding processes while keeping the Infinergy® identity of making shoes very comfortable to wear and delivering excellent running properties. Due to new processing methods the expanded thermoplastic polyurethane (E-TPU) material can be fused into soles in a much more energy-efficient and material-friendly manner. With endless design possibilities many surface textures are available. Its durability and recyclability allow Infinergy® Revolution (E-TPU) to strive for a more sustainable future of the footwear industry.
Heat press process – applicable for existing machinery
Cooling and water content influences the surface appearance and effective part density.
Cooling rate
- Cooling time: ~ 3 min
- Demolding temperature: ~ 25-70°C
- Dimensional stability, warpage control
Mold preparation
- Mold design: modified or engraved surface to change part surface
- Preheating
- Release agent if necessary
- Surface quality, reproducibility
Heat press curing
- Tool temperature: ~ 130-145°C
- Curing time: ~ 5 min
- Inter-bead bonding, surface appearance
Filling & compaction
- Homogenous filling
- ~ 50% compression
- Uniform distribution of density and mechanical performance
Material conditioning
- Dry condition for transport and storage <0.8% water content
- Moisture control, up to 2% for process support
- Affects bonding, shrinkage and surface integrity
Pressure loading to reduce part density
Simple process
- Just air pressure is needed
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Applying pressure around 3 bar for 5 hours
- Material is stable in this condition for about 30 minutes and ready for processing
Did you know?
Known from EPP production process, a pressure loading of Infinergy® beads is likewise possible to reduce the final part density significantly.
Pressure loading enables post expansion of Infinergy®
Effect of using pressurized beads
Part density vs. Mechanical properties
Physical effect
Compressed air diffuses into Infinergy® bead. After releasing the system pressure at theend of the process, the pressure remains inside the beads for some time leading to twoeffects:
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The bulk density can slightly reduce
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The internal pressure stabilizes the bead for the welding process in the heat press.
This internal stabilization enables an effective reduction of the component density.
Infinergy® Revolution (E-TPU) midsole examples
Casual
Sport
Trends in footwear manufacturing
- Lightweight and comfort
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Automation: reduced manpower, „one shot“ production of bottom unit or full shoe
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Customization: iconic look, brand DNA integrated in design
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Sustainability: PCF reduction, recyclability, waste reduction
Outstanding performance of Infinergy® Revolution (E-TPU)
From process innovation to production scale-up
Infinergy® Revolution (E-TPU) energy-efficient processing in action
Jens Dierrsen and Anna Cristadoro - Infinergy® Revolution (E-TPU) from concept to creation
Consult with an expert
Self-service solutions:
FAQ
Q: What is the Heat Press Process for Infinergy® Revolution (E-TPU) and what is it used for?
The Heat Press Process is the core manufacturing method for Infinergy® Revolution (E-TPU) components, especially shoe soles. In this process, expanded TPU beads are fused together under heat and pressure to produce lightweight, elastic, and performance components with high energy return.
Q: How does the Heat Press Process work for Infinergy® Revolution (E-TPU)?
The Heat Press Process for Infinergy® Revolution (E-TPU) consists of five steps: material conditioning, mold preparation, filling and compression, heating to approximately 130–145 °C, and cooling and demolding. Uniform heat transfer is critical to ensure that the particles fuse completely and stably.
Q: Why is the Heat Press Process important for the performance of shoe soles?
The Heat Press Process determines the mechanical properties of Infinergy® components. Optimized processing ensures high cushioning, strong energy return, and long-lasting performance. These are key factors for applications such as midsoles in performance footwear.
Q: What factors influence quality in the Heat Press Process?
The main influencing factors are temperature (approx. 130–145 °C), pressure distribution, process time, and cooling conditions. These parameters define density, surface quality, and the mechanical stability of the component.
Q: What is Pressure Loading in Infinergy® Revolution (E-TPU) and what advantages does it offer?
Pressure Loading is an advanced processing method for Infinergy® Revolution (E-TPU) in which the material is deliberately compressed under pressure to create controlled expansion after pressure release. This results in lighter components with lower density while maintaining high performance.
Q: How does Pressure Loading work in E‑TPU?
During Pressure Loading, the cell structures of the Infinergy® Revolution (E-TPU) beads are first compressed. After the pressure is released, the cells expand again, increasing the component’s volume and reducing its density.
Q: Why is Pressure Loading crucial for lightweight shoe soles?
Pressure Loading enables a significant reduction in the weight of shoe soles without compromising mechanical stability or energy return. This leads to improved comfort and better running performance.
Q: How does Pressure Loading affect material properties?
Pressure Loading improves the weight efficiency of Infinergy® Revolution (E-TPU), enhances cushioning properties, and maintains structural stability. This results in an optimal balance of weight, comfort, and performance.
Q: What is the difference between Infinergy® Revolution (E-TPU) with and without Pressure Loading?
Without Pressure Loading, the material has a higher density and a more compact structure. With Pressure Loading, a more expanded cell structure is created with lower density, resulting in lighter yet performance components.