中底踩两次就塌，回弹没了，跑着跑着脚先累。鞋中底的回弹档没选对，缓震就是摆设。
中底踩两次就塌，回弹去哪了
鞋中底是“管缓震回弹的件”：回弹、缓震、轻量。材料要回弹好、缓震好、轻量——结论先给：鞋中底用 PEBA 是高端主流；常规中底，TPU 发泡或 EVA 复合更划算。
鞋中底最大的坑：软硬差一档，用途两回事。硬度差一档，回弹缓震完全两回事——按用途选，别按名字选。
鞋中底是功能件：回弹差、变硬都是问题。材料选对，跑鞋才稳——功能件，别省料钱。
PEBA 凭什么又弹又轻
鞋中底用 PEBA 的理由：回弹好、轻量、耐疲劳、缓震好——四条合起来，适合高端中底。
回弹是核心：跑步回弹。回弹率测试写进验收——回弹差，就是问题。
轻量不能省：中底轻一克，脚感好一分。密度数据写进验收——轻量，是中底的加分项。
跑步缓震疲劳，三道关
跑步工况：反复压缩。回弹数据要验——回弹差，就是问题。
缓震工况：落地冲击。缓震数据要验——震脚，就是问题。
疲劳工况：长期使用。疲劳数据要验——变硬，就是问题。
PEBA 还是 TPU？一张表看清
| 维度 | PEBA | TPU |
|---|
| 回弹 | 极好 | 好 |
| 轻量 | 轻 | 中 |
| 缓震 | 好 | 好 |
| 成本 | 高 | 中高 |
| 耐疲劳 | 好 | 好 |
| 用途 | 高端 | 常规 |
表格读法：PEBA 回弹轻量极好但贵；TPU 性价比高——高端鞋 PEBA，常规鞋 TPU。
按定位选：高端 PEBA，常规 TPU。
中底验收：回弹轻量这两笔账
| 项目 | 方法 | 标准 |
|---|
| 回弹率 | 回弹测试 | 按标准 |
| 密度 | 密度杯 | 按目标 |
| 缓震 | 冲击测试 | 按能量 |
| 疲劳 | 循环压缩 | 按次数 |
表格读法：回弹率、缓震、密度四项验收下来，这双中底是跑鞋还是健走鞋就清楚。
用途，才是中底的裁判。
按名字选料，三个坑埋一堆
坑一：按名字选。PEBA 和 TPU 都叫中底料，软硬差一档用途全变——按用途选。
坑二：回弹虚标。报告写回弹，实际偏硬——回弹按实测验收。
坑三：密度漏测。中底重——密度数据，必验。
下单前先把这三个数问死
三问：回弹率多少、密度多少、按什么定位。一验：实际跑步实测——三问一验，供应商底细清楚。
用途验证要先行：先定要回弹还是要缓震，再谈价格——用途，才是中底的裁判。
留样要成习惯：每批留样，回弹密度按批次复测。批次换料先对比再放量——批次稳，客诉少。
中底回弹是核心——PEBA 发泡回弹率高，TPU 发泡耐磨好。超临界发泡对熔体强度和发泡窗口要求高，批次稳定性要验。
中底选型，回弹和发泡工艺一起算。
中底跑几百公里回弹衰减——疲劳数据没测，回弹衰减率不透明。衰减低的中底才配长跑，衰减高的穿几个月就塌。
回弹衰减率，是中底的寿命证据。
夏天回弹变冬天变硬不是料差——温度环境影响材料表现，按实际温度做测试。温度适应性窗口要覆盖全年。硬软变化，先查温度适应性。
PEBA 贵在原料，TPU 贵在工艺——成本结构不同，按结构比价才公平。PEBA 回弹高，TPU 耐磨好，按用途选。同是中底料，硬度档错一档，鞋就跑错了场。
超临界发泡数据要拿出来——熔体强度、发泡窗口、批次稳定性三样验。厚度设计按目标缓震和稳定推配方。发泡数据齐了，中底才做得稳。
鞋中底常见问题与对策表
| 现象 | 原因 | 对策 |
|---|
| 回弹差 | 档位选错 | 按用途选 |
| 震脚 | 缓震不足 | 升缓震档 |
| 变硬 | 老化 | 换耐疲劳料 |
| 尺寸波动 | 收缩率漂 | 小批试产 |
| 超重 | 密度高 | 换轻量料 |
PEBA 发泡中底密度 0.10-0.15 g/cm³，回弹率 60% 以上。 EVA 发泡回弹 30-40%，PEBA 回弹高一倍但贵三倍——竞速鞋用 PEBA，训练鞋用 EVA。
中底压缩永久变形按 50% 形变 70℃×6h 测，超 30% 三个月就塌。 PEBA 压变 <15%，EVA 压变 25-35%——压变数据决定中底寿命，别只看新鞋回弹。
中底材料成本按每克单价乘以密度算，PEBA 比 EVA 贵三倍但回弹高一倍。 竞速鞋为回弹买单，训练鞋为预算买单——按鞋定位算材料账，别一刀切上 PEBA。
科隆客户案例：收缩率不稳尺寸波动，小批试产续三单
中山一家鞋材厂，鞋中底收缩率不稳，尺寸波动大。科隆配合小批试产验证后再放量，尺寸稳定，客户连续三个批次续单。小批试产，把尺寸锁死在放量前——收缩率问题，试产阶段就该暴露。
小结
鞋中底的选型，用途先定，回弹再测，软硬差一档用途两回事，别按名字选。
十几年，只做一件事：把尼龙改成能用的样子。
PA6、PA66 是基本盘，PA46、PA6T、PA9T 是耐高温的门槛，PA11、PA12 管水路和油路，尼龙合金补单一树脂给不了的平衡。改性热塑性弹性体、改性尼龙、改性 PPO、PPS 并行，还有各大化工巨头的尼龙树脂、副牌料、大包料现货。
同一块料，用错地方就是事故。所以先问件，再问料。
The midsole collapses after stepping twice, and the rebound is gone. My feet get tired while running. The rebound setting of the shoe's midsole wasn't chosen correctly, so the cushioning is just for show.
The midsole collapses after just two steps, where did the rebound go?
The shoe midsole is the 'component for guided cushioning and rebound': rebound, cushioning, lightness. The material should have good rebound, good cushioning, and be lightweight — conclusion first: using PEBA for the shoe midsole is the high-end mainstream; for regular midsoles, foamed TPU or EVA composites are more cost-effective.
The biggest trap of midsoles in shoes: a slight difference in hardness and softness can mean two completely different uses. Even a small difference in hardness can make rebound and cushioning entirely different—choose according to purpose, not the name.
The midsole of a shoe is a functional component: poor rebound or hardening are both problems. Choosing the right material makes running shoes stable—functional components, don't skimp on materials.
Why is PEBA both elastic and lightweight?
Reasons for using PEBA in shoe midsoles: good rebound, lightweight, fatigue resistance, and good shock absorption—combined, these four qualities make it suitable for high-end midsoles.
Rebound is key: running rebound. Incorporate rebound rate testing into the acceptance—if the rebound is poor, it's a problem.
Lightweight should not be compromised: for every gram the midsole is lighter, the foot feel improves by a fraction. Record the density data in the acceptance check — lightweight is a bonus for the midsole.
Running cushioning fatigue, three barriers
Running condition: repeated compression. Rebound data needs to be checked — if the rebound is off, that's the problem.
Cushioning condition: landing impact. Cushioning data needs to be checked—vibration in the feet is the problem.
Fatigue condition: long-term use. Fatigue data need to be verified—if it hardens, it's a problem.
PEBA or TPU? See clearly in one table
| Dimension | PEBA | TPU |
|---|
| rebound | Excellent | Good |
| Lightweight | Light | middle |
| Cushioning | Good | Good |
| Cost | Tall | Medium-high |
| Fatigue-resistant | Good | Good |
| Purpose | High-end | Regular |
Table reading: PEBA has excellent rebound and is very lightweight but expensive; TPU has high cost performance — high-end shoes use PEBA, regular shoes use TPU.
Choose by positioning: high-end PEBA, regular TPU.
Midsole inspection: accounting for resilience and lightweight
| Project | Method | standard |
|---|
| Resilience | Rebound Test | According to the standard |
| Density | Density cup | By target |
| Cushioning | Impact test | By energy |
| Fatigue | Cyclic compression | By frequency |
How to read the table: After checking the four items of rebound rate, cushioning, and density, it will be clear whether this midsole is for running shoes or walking shoes.
Purpose is the real judge of the midsole.
Choosing materials by name, three holes bury a heap
Pitfall 1: Choosing by name. Both PEBA and TPU are called midsole materials, but a difference in softness can completely change their use—choose based on purpose.
Pitfall 2: Rebound overstatement. The report states rebound, but it is actually on the harder side — the rebound is accepted based on actual measurement.
Pitfall 3: Density omission. Midsole weight — density data must be checked.
Before placing the order, make sure to ask about these three numbers thoroughly
Three questions: What is the rebound rate, what is the density, and what is the positioning based on? One test: Actual running measurement — three questions and one test make the supplier’s details clear.
Purpose verification comes first: first decide whether you want rebound or cushioning, then discuss the price — purpose is the judge of the midsole.
Making sample retention a habit: retain samples from each batch and re-test the rebound density by batch. When changing materials between batches, compare first before scaling up—the batch is stable, and customer complaints are few.
Midsole rebound is key — PEBA foam has a high rebound rate, and TPU foam is wear-resistant. Supercritical foaming requires high melt strength and a precise foaming window, and batch stability needs to be tested.
The midsole selection considers both rebound and foaming process together.
Midsole rebound decay after running several hundred kilometers—fatigue data was not measured, and the rebound decay rate is not transparent. Only midsoles with low decay are suitable for long-distance running, while those with high decay will collapse after wearing for a few months.
Rebound attenuation rate is evidence of the midsole's lifespan.
The material becoming soft in summer and hard in winter is not due to poor quality—the temperature environment affects material performance, so testing should be done at actual temperatures. The temperature adaptability window should cover the entire year. For changes in hardness, first check temperature adaptability.
PEBA is valued for its raw materials, while TPU is valued for its process—since their cost structures are different, comparing prices by structure is fair. PEBA has high rebound, TPU has good wear resistance, so choose according to the use. Even for the same midsole material, if the hardness grade is off by one level, the shoe will perform in the wrong field.
Supercritical foaming data needs to be pulled out—check three things: melt strength, foaming window, and batch stability. Thickness design should follow the target cushioning and stability to adjust the formula. Only when the foaming data is complete can the midsole be made stable.
Table of Common Problems and Countermeasures of Shoe Midsoles
| Phenomenon | Reason | Countermeasure |
|---|
| Poor rebound | Wrong gear selected | Select by use |
| Stomp your foot | Insufficient cushioning | Increase cushioning mode |
| harden | Aging | Replace with fatigue-resistant material |
| Size fluctuation | Shrinkage rate drifting | Small batch trial production |
| Overweight | High density | Switch to lightweight material |
PEBA foam midsole density is 0.10-0.15 g/cm³, with a rebound rate over 60%. EVA foam rebound is 30-40%, PEBA rebound is twice as high but three times as expensive—PEBA is used for racing shoes, EVA for training shoes.
Midsole compression permanent deformation is measured at 50% deformation, 70°C × 6h; if it exceeds 30%, it will collapse in three months. PEBA compression deformation is <15%, EVA compression deformation is 25-35% — compression deformation data determines midsole lifespan, don’t just look at the rebound of new shoes.
The cost of midsole materials is calculated by multiplying the unit price per gram by the density. PEBA is three times more expensive than EVA but has twice the rebound. Racing shoes pay for rebound, while training shoes pay according to the budget — calculate the material cost based on the shoe's positioning, and don't just apply PEBA across the board.
Cologne Customer Case: Unstable Shrinkage Rate and Size Fluctuations, Small Batch Trial Production Continues with Three Orders
A shoe material factory in Zhongshan has unstable shrinkage rates in the midsoles, with large size fluctuations. Cologne coordinated small batch trial productions for verification before scaling up, and the sizes became stable, with the customer placing consecutive orders for three batches. Small batch trial production locks the sizes before mass production—the shrinkage problem should be exposed during the trial production stage.
Summary
When selecting the midsole for a shoe, first determine its purpose, then measure its rebound. A difference in softness or hardness by one level corresponds to different uses; don’t choose based on the name.
For more than ten years, I’ve only done one thing: turning nylon into a usable form.
PA6 and PA66 are the basics. PA46, PA6T, and PA9T are the entry points for high-temperature resistance. PA11 and PA12 handle water and oil channels. Nylon alloys compensate for what single resins cannot balance. Modified thermoplastic elastomers, modified nylon, modified PPO, and PPS run in parallel, along with major chemical manufacturers’ nylon resins, secondary brands, and bulk material in stock.
Using the same material in the wrong place leads to accidents. So always ask about the part first, then the material.
