At present, the most commonly plastic materials used for air cushions are polyurethane (PU), polyvinyl chloride (PVC), and thermoplastic polyurethane (TPU). The following mainly introduces the thermoplastic polyurethane stretch tube air cushion and the thermoplastic polyurethane oil-gas cushion.

Thermoplastic polyurethane is a polymer material that has both rubber elastic properties and plastic plasticity. It features with excellent physical properties and mechanical properties, such as high tensile strength and high elongation. Otherwise TPU is also with good resilience and excellent abrasion resistance and puncture resistance, great longitudinal bending strength And high impact strength in low-temperature,  good oil resistance and weather resistance. So, TPU is widely used in shoes parts, such as cushion which abrasion resistance and Good resilience is necessary.

Thermoplastic polyurethane stretch tube air cushion mainly used on the heel part, which relies on high resilience performance, excellent puncture resistance, crack growth resistance, and high impact resistance of thermoplastic polyurethane to get a remarkable shock absorption function. Plus, the colorful TPU air cushion let sports shoes get great visual effect.

So called "liquid cushion" actually is thermoplastic polyurethane oil-filled air cushion. Mainly function of TPU oil-filled air cushion is absorb shock. It is often used in the heel and waist area to absorb shock and stabilize the turnover of the foot.

Classified by structural

◆ Full palm TPU shoes air cushion: The contour is the same as that of the outsole. The thickness of the air chamber at the edge of the outsole is about 10-20mm, and the wall thickness is 1-1.4mm. It is soft and with high resilience; The air chamber is as a support for the beam; The solid part is as a connection. The entire air cushion is a wedge-shaped structure from the heel to the forefoot.

◆Half Palm TPU shoes Air Cushion: From the metatarsophalangeal joint to the heel area, the thickness of the air chamber at the waist is the thickest part of the entire air cushion. It has the same design function of the full palm air cushion such as shock absorption and support to stability. The thickness of the air chamber at the waist is 20-25mm, and the heel part is generally 18-20mm.

TPU half palm air cushion and TPU full palm air cushion have different requirements for the viscosity of TPU materials. TPU has low viscosity and fluidity is too fast. The production of TPU full palm air cushion with low viscosity will lead the TPU melt sag too fast to fill the full palm. It will resulting in dissatisfaction products and air leakage of the TPU full palm air cushion. Compared with TPU full palm air cushion, the fluidity has less impact on TPU half palm air cushion.

Thermoplastic polyurethane is recyclable. Adding a small amount of recycled TPU to the new TPU granule will not have any impact on the quality of the product. However, please noted that the viscosity of the recycled TPU is relatively low and it reduced every time the TPU is recycled. If the TPU is recycled too too many times, the viscosity of recycle TPU and new TPU granule will be too much difference which is easy to cause pinholes and pimples defects in TPU air cushion.