Why Does Softer POE Make EVA Foam Products More Prone to Shrinkage?

Sep 07,2026 | Published in：Advanced Foaming Solutions for OEM Manufacturing

為什麼 POE 越軟，EVA 發泡成品反而越容易收縮？

Why Does Softer POE Make EVA Foam Products More Prone to Shrinkage?

PART 2

六、IUS-4065 不是直接替換：DCP 配方必須重新校正

VI. IUS-4065 Is Not a Direct Replacement: The DCP Formulation Must Be Recalibrated

將現有 POE 等重量換成 IUS-4065，而 DCP、發泡劑與模壓條件完全不變，未必能得到最佳結果。不同聚合物結構對過氧化物自由基的反應效率、熔體黏度與結晶速度不同，可能改變交聯—產氣平衡。

Replacing the existing POE with an equal weight of IUS-4065 while keeping DCP, the blowing agent, and molding conditions completely unchanged may not produce the best results. Different polymer structures have different reaction efficiencies toward peroxide radicals, melt viscosities, and crystallization rates, which may alter the crosslinking–gas-generation balance.

需要重校正的項目

Items Requiring Recalibration

可能影響

Potential Impact

建議方法

Recommended Method

DCP 有效添加量

Effective DCP Addition Level

交聯不足會收縮；過高則倍率與延伸受限

Insufficient crosslinking causes shrinkage; excessive crosslinking limits expansion ratio and elongation.

以 3 階用量搭配流變／硫化曲線篩選

Screen using three dosage levels together with rheological/vulcanization curves.

發泡劑與活化系統

Blowing Agent and Activator System

產氣時序與新材料成網速度不匹配

The gas-generation timing may not match the network-formation rate of the new material.

固定密度目標，觀察泡孔及開模膨脹

Fix the density target and observe cell structure and expansion after demolding.

混煉料溫

Compounding Temperature

低熔融材料易提前軟化，分散及焦燒風險改變

Low-melting materials soften earlier, changing dispersion and scorch risks.

記錄實際料溫，而不只記錄設備設定

Record the actual material temperature, not only the equipment setting.

模壓與開模時間

Molding and Demolding Time

決定交聯完成度、倍率及殘留應力

Determines the degree of crosslink completion, expansion ratio, and residual stress.

以中心溫度及尺寸穩定建立窗口

Establish the process window based on core temperature and dimensional stability.

冷卻與停放

Cooling and Conditioning

影響結晶定型與後收縮

Affects crystallization setting and post-shrinkage.

統一冷卻、堆疊及 24／72 小時量測條件

Standardize cooling, stacking, and the 24/72-hour measurement conditions.

七、建議的驗證設計：不要只測剛開模的硬度

VII. Recommended Validation Design: Do Not Measure Only Hardness Immediately After Demolding

要證明 IUS-4065 的價值，試驗必須模擬客戶真正的二次加工與使用條件。建議至少設置原配方對照、等比例替換及目標硬度最佳化三組，並控制成品密度。

To demonstrate the value of IUS-4065, testing must simulate the customer's actual secondary-processing and use conditions. It is recommended to include at least three groups: the original formulation as a control, an equal-ratio replacement, and a target-hardness optimization group, while controlling finished-product density.

階段 Stage	測試項目 Test Items	判定重點 Key Evaluation Points Key Evaluation Points
原料	Shore A、DSC 熔融峰／焓、MFR、密度	確認軟度、熔融區間與流動差異 Confirm differences in softness, melting range, and flow behavior. Confirm differences in softness, melting range, and flow behavior.
發泡後 24 h	密度、硬度、尺寸、泡孔、回彈	先排除倍率差造成的假性優勢 First eliminate apparent advantages caused by differences in expansion ratio. First eliminate apparent advantages caused by differences in expansion ratio.
後熟化 72 h	長寬厚尺寸與硬度漂移	觀察自然收縮與結晶重整 Observe natural shrinkage and crystal reorganization. Observe natural shrinkage and crystal reorganization.
模擬貼合	50、60、70°C × 不同時間	建立溫度—時間—收縮率曲線 Establish a temperature–time–shrinkage-rate curve. Establish a temperature–time–shrinkage-rate curve.
力學性能	拉伸、延伸、撕裂、壓縮永久變形	確認降硬沒有犧牲耐久性 Confirm that hardness reduction does not sacrifice durability. Confirm that hardness reduction does not sacrifice durability.
量產驗證	模穴位置、批次、良率、返工率	把材料差異轉換成製造效益 Translate material differences into manufacturing benefits. Translate material differences into manufacturing benefits.
建議核心指標｜尺寸收縮率 (%) =（加熱前尺寸 − 加熱後尺寸）÷ 加熱前尺寸 × 100%。長、寬、厚度應分別量測，並明確規定樣品停放時間與量測溫度。 Recommended core metric \| Dimensional shrinkage (%) = (Dimension before heating − Dimension after heating) ÷ Dimension before heating × 100%. Length, width, and thickness should be measured separately, with the sample conditioning time and measurement temperature clearly specified. Recommended core metric \| Dimensional shrinkage (%) = (Dimension before heating − Dimension after heating) ÷ Dimension before heating × 100%. Length, width, and thickness should be measured separately, with the sample conditioning time and measurement temperature clearly specified. Recommended core metric \| Dimensional shrinkage (%) = (Dimension before heating − Dimension after heating) ÷ Dimension before heating × 100%. Length, width, and thickness should be measured separately, with the sample conditioning time and measurement temperature clearly specified.

八、適合優先導入的產品

VIII. Products Suitable for Priority Adoption

· 需要低硬度與高回彈的 EVA／POE 發泡鞋墊與中底。

· EVA/POE foamed insoles and midsoles requiring low hardness and high resilience.

· 後續需布貼合、熱壓或烘箱處理的發泡片材。

· Foamed sheets requiring subsequent fabric lamination, hot pressing, or oven treatment.

· 對尺寸公差、外觀平整度與翹曲敏感的成型部件。

· Molded components sensitive to dimensional tolerances, surface flatness, and warpage.

· 運動護具、緩衝墊及需要柔軟貼合感的產品。

· Sports protective gear, cushioning pads, and products requiring a soft conforming feel.

· 現行 DF 640、ENGAGE 8842 或其他低熔點軟質 POE 配方，已有二次收縮問題的產品。

· Products currently using DF 640, ENGAGE 8842, or other low-melting-point soft POE formulations that already experience secondary shrinkage.

結論：真正有價值的超軟材料，是軟化產品而不是軟化製程穩定性

Conclusion: The Truly Valuable Ultra-Soft Material Softens the Product, Not the Stability of the Process

EVA 添加 POE 的傳統邏輯，是利用軟質彈性體降低硬度並提高回彈；但當 POE 的熔融區間太低，泡棉在貼合或二次加熱時可能失去晶區支撐，使殘留應力、泡孔收縮與尺寸變形被放大。這也是許多配方「剛開模很好，後加工卻不穩」的根本原因之一。

The traditional logic of adding POE to EVA is to use a soft elastomer to reduce hardness and increase resilience. However, when the POE melting range is too low, the foam may lose crystalline-region support during lamination or secondary heating, amplifying residual stress, cell shrinkage, and dimensional deformation. This is one of the fundamental reasons why many formulations are “excellent immediately after demolding but unstable during post-processing.”

IUS-4065 的技術定位，是以約 Shore A 40 的超軟硬度搭配約 64°C 的較高熔點，嘗試把柔軟度、回彈與尺寸穩定性放在同一個材料平台上。對研發端而言，它最值得驗證的不是單一硬度數據，而是能否在相同密度與性能要求下，降低二次收縮、擴大加工窗口並提高量產良率。

The technical positioning of IUS-4065 is to combine an ultra-soft hardness of approximately Shore A 40 with a relatively high melting point of approximately 64°C, attempting to bring softness, resilience, and dimensional stability onto the same material platform. For R&D, what is most worth validating is not a single hardness value, but whether, under the same density and performance requirements, it can reduce secondary shrinkage, expand the processing window, and improve mass-production yield.

研發決策原則｜不要只問「哪一支 POE 最軟」，而要問：「在客戶的貼合溫度與使用條件下，哪一支材料仍能維持泡孔與尺寸？」

R&D decision principle | Do not ask only, “Which POE is the softest?” Instead ask: “Under the customer's lamination temperature and use conditions, which material can still maintain the cells and dimensions?”

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