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Comparison of Supercritical Foaming in EVA and ETPU Materials

Views: 19     Author: Site Editor     Publish Time: 2024-10-25      Origin: Site

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Comparison of Supercritical Foaming in EVA and ETPU Materials

Keywords:EVA、 ETPU、shoe soles

Both EVA (Ethylene-Vinyl Acetate) and ETPU (Expanded Thermoplastic Polyurethane) are commonly used foamed materials in the footwear and sports goods industry. However, they differ significantly in terms of physical properties, production processes, and application fields. Supercritical foaming technology can significantly enhance the performance of these two materials. Below is an analysis of the differences between EVA and ETPU as base materials under supercritical foaming technology:

(Ethylene-Vinyl Acetate Copolymer)

1. Material Characteristics


• EVA (Ethylene-Vinyl Acetate Copolymer):

• Lightweight: EVA has a relatively low density, making it ideal for products that require weight reduction, such as shoe soles and sports goods.

• Flexibility: EVA is soft with good elasticity and impact resistance, but its durability is relatively weaker, and it tends to deform and wear out over time.

• Chemical Resistance: EVA offers good resistance to acids and bases, making it suitable for various environmental conditions, though it has poor oil resistance.

• Insulation: EVA has excellent thermal insulation properties, making it ideal for applications requiring heat insulation.

• ETPU (Expanded Thermoplastic Polyurethane):

• High Resilience: ETPU, also known as the “popcorn” material, boasts excellent elasticity and resilience, particularly after supercritical foaming, offering significantly better rebound properties than EVA, ideal for high-performance shoe soles.

• Durability: ETPU is more wear-resistant and better at resisting compression deformation than EVA, offering longer service life. It also has strong weather and UV resistance, suitable for outdoor products.

• Chemical Resistance: ETPU shows better resistance to oils, acids, and bases, making it suitable for products requiring higher chemical resistance.

(Application scenarios of supercritical foam materials)

2. Impact of Supercritical Foaming Technology on Material Performance


• Supercritical Foamed EVA:

• Weight Reduction: Supercritical foaming creates a uniform cellular structure within the EVA material, further reducing product weight, making it suitable for lightweight applications like running shoes and beach shoes.

• Improved Cushioning: Supercritical foaming enhances EVA’s cushioning performance, making it better suited for applications like sports shoes and mats, though its rebound performance is still slightly weaker than ETPU.

• Environmental Benefits: Using supercritical CO₂ foaming can reduce the use of chemical foaming agents in the process, minimizing environmental impact and aligning with green trends.

• Supercritical Foamed ETPU:

• Enhanced Rebound: Supercritical foaming significantly improves ETPU’s elasticity, with rebound performance far superior to conventionally foamed materials, making it ideal for high-energy return applications like running shoes.

• Increased Durability: The uniform cellular structure enhances ETPU’s wear resistance and impact resistance, making it suitable for long-lasting outdoor use in footwear and sports goods.

• Environmental Advantage: Supercritical foaming eliminates the need for chemical blowing agents, reducing harmful emissions and improving environmental friendliness, aligning with sustainable manufacturing practices.


(lightweight shoe soles)

3. Application Scenarios


• EVA: Primarily used in products that emphasize lightweight and comfort, such as lightweight shoe soles, flip-flops, yoga mats, children’s shoes, and cushioning mats. EVA is also more cost-effective and easy to process, suitable for mass production.

• ETPU: More suitable for high-end markets, especially in applications requiring high energy return, such as running shoe soles, professional sports shoes, and shock-absorbing mats. ETPU’s superior elasticity and durability make it the preferred material for high-performance products.

(High rebound comfort sole)

4. Cost and Processing Complexity


• EVA: The production cost of EVA is relatively low, with mature manufacturing processes and minimal equipment investment, making it ideal for mass production. The use of supercritical foaming can further reduce material costs by lowering material density, but EVA remains a budget-friendly option.

• ETPU: ETPU’s material cost and processing difficulty are higher than EVA, especially with the increased complexity of the supercritical foaming process, leading to higher product prices. However, for high-end footwear markets that prioritize high rebound, durability, and comfort, ETPU offers higher added value.


Conclusion

(A widely used shoe midsole)

EVA is ideal for lightweight, cost-effective, and comfort-oriented products where durability is less critical, while ETPU, with its excellent rebound, durability, and environmental benefits, is the ideal material for high-performance, high-quality products. The use of supercritical foaming enhances the lightweight and environmental performance of both materials, but ETPU stands out even more with superior rebound and durability after supercritical foaming, making it suitable for premium and high-performance applications.


This translation maintains the technical detail and comparison between the two materials, as well as the benefits and challenges of supercritical foaming technology.


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