Currently, supercritical foaming technology – as the mainstream physical foaming route – has achieved mature commercialisation and large‑scale production in China. However, in actual mass production, the technology is still in a critical phase of “cost reduction, efficiency improvement, and yield ramp‑up”. With production capacity expanding rapidly in regions such as Vietnam, the embryos expand to large embryos foaming process is expected to accelerate its iteration and gradually reach full maturity.
1、Materials
At present, high‑end product lines commonly use pure PEBA as the base material. Its excellent resilience and lightweight properties are highly favoured by brands, but the high raw material cost raises the price threshold, limiting such products to the premium market segment.
To address the mass‑market consumer segment, the industry’s mainstream approach is to blend TPUwith EVA. However, these blended materials suffer from resilience loss, making it difficult to achieve both low cost and high rebound performance. To solve issues such as cell collapse and rough morphology during the foaming process, the industry is also actively modifying the materials.
In early June this year, Professor Zhang Zhenxiu’s team at Qingdao University of Science and Technology independently developed an autoclave‑based supercritical green foaming platform technology that integrates “process‑equipment‑materials” in a trinity approach. The technology was evaluated by a panel of experts from the China Chemical Society and was deemed to have reached an internationally leading level.
Professor Zhang’s team started from the molecular structure level and innovatively constructed a multi‑level network structure control method. They first built flexible “small bridges” and extensible networks between rubber molecular chains, and then reinforced the woven structure. This allows the material to be effectively stretched during foaming expansion without breaking or collapsing, significantly broadening the foaming temperature window and successfully overcoming the technical bottleneck of ultra‑low‑density foaming for specialty rubbers.
2、Process control
The supercritical foaming process imposes stringent requirements on the precision of process parameters such as temperature and pressure. The processing window is narrow, leaving limited room for error. Even slight fluctuations in parameters can compromise product consistency, leading to poor batch‑to‑batch stability. Moreover, current production still relies heavily on manual experience for adjustment and intervention – from process tuning to finished product removal – making it difficult to achieve fully automated closed‑loop control across the entire workflow.
The uniformity of the cell structure determines the resilience and support of the foamed products. If the cell density distribution is uneven, rebound performance drops significantly, failing to meet the demands of footwear materials for dynamic foot feel and energy return. Unqualified foamed products must be scrapped, resulting in additional material loss. According to current industry feedback, the yield rate for embryos expand to large embryos foaming generally hovers around 80%, making the cost per qualified unit relatively high.
To meet the demand for more precise control of process parameters, major domestic manufacturers of supercritical foaming equipment—such as Tai’an Shili Machinery, Kaiyuan Chemical, Xinyuan Chemical, Yitong Machinery, and Jingang Machinery—have all launched customizable high‑precision equipment to support downstream processors in achieving greater R&D flexibility and improved production efficiency.
Therefore, there is still much to explore in the field of cost reduction and efficiency improvement for embryos expand to large embryos supercritical foaming.
Source from :Aibang Shoes Forum(TPE) （Please contact us if there is any infringement.）