化學發泡 vs. 超臨界發泡 

Chemical Foaming vs. Supercritical Foaming 

PART 2

不只是泡孔大小：從原理、設備、成本到材料回收性的完整選擇指南

Not Just Cell Size: A Complete Selection Guide from Principles, Equipment, and Cost to Material Recyclability

適用於 EVA、POE、TPU、TPE、PP、PE 與工程發泡材料開發

Applicable to the Development of EVA, POE, TPU, TPE, PP, PE, and Engineering Foams

七、環保與可回收性：不要只看「是否使用 CO₂」

VII. Environmental Performance and Recyclability: Do Not Look Only at Whether CO₂ Is Used

超臨界 CO₂ 或 N₂ 不會像化學發泡劑一樣留下固體分解殘留，因此在低氣味、配方潔淨度及某些回收情境具有優勢。但「使用 CO₂」本身不能直接證明成品碳足跡較低。高壓壓縮、加熱、冷卻、良率、設備稼動率與材料減量，都必須納入生命週期評估。

Supercritical CO₂ or N₂ does not leave solid decomposition residues like chemical blowing agents, giving it advantages in low odor, formulation cleanliness, and certain recycling scenarios. However, the “use of CO₂” alone cannot directly prove that the finished product has a lower carbon footprint. High-pressure compression, heating, cooling, yield, equipment utilization, and material reduction must all be included in a life-cycle assessment.

同樣地，化學發泡並不必然不可回收。如果基材仍是熱塑性材料、交聯程度低且污染可控，仍可能進行機械回收；反之，若採 DCP 高度交聯，即使使用物理發泡氣體，也可能因形成三維網絡而降低熔融再加工能力。真正影響回收性的關鍵，經常是樹脂結構與交聯狀態，而不只是發泡氣體。

Likewise, chemical foaming is not necessarily unrecyclable. If the substrate remains thermoplastic, the degree of crosslinking is low, and contamination is controllable, mechanical recycling may still be possible. Conversely, if highly crosslinked with DCP, even when physical foaming gas is used, the formation of a three-dimensional network may reduce melt reprocessability. The factors that truly affect recyclability are often resin structure and crosslinking state, rather than the foaming gas alone.

八、不同材料的適用性

VIII. Applicability to Different Materials

材料 Material	化學發泡重點 Chemical Foaming Focus	超臨界發泡重點 Supercritical Foaming Focus
EVA／POE EVA/POE	成熟配方；需平衡 DCP 交聯與產氣 Mature formulations; balance DCP crosslinking and gas generation	柔軟材料易收縮，需控制交聯／結晶與冷卻定型 Soft materials tend to shrink; crosslinking/crystallization and cooling/setting must be controlled
TPU TPU	控制熱歷史、水分與氣體副產物 Control thermal history, moisture, and gaseous by-products	CO₂ 溶解度較佳，但需處理收縮、表皮及尺寸穩定 CO₂ solubility is favorable, but shrinkage, skin, and dimensional stability must be addressed
PP／PE PP/PE	需足夠熔體強度，常用支化、交聯或共混改善 Sufficient melt strength is required; branching, crosslinking, or blending is often used to improve it	長鏈支化、高熔體強度及結晶窗口是關鍵 Long-chain branching, high melt strength, and the crystallization window are key
PLA PLA	熱降解與結晶速度影響泡孔固定 Thermal degradation and crystallization rate affect cell fixation	scCO₂ 研究成熟，但乾燥、結晶與可加工窗口仍敏感 scCO₂ research is mature, but drying, crystallization, and the processing window remain sensitive
TPE／TPV TPE/TPV	相結構會影響泡孔均勻性 Phase structure affects cell uniformity	氣體在不同相中的溶解與擴散差異需驗證 Differences in gas solubility and diffusion among phases need to be validated

九、哪一種更適合量產？

IX. Which One Is More Suitable for Mass Production?

圖 3｜技術選擇矩陣：分數表示一般傾向，不代表特定設備或材料的絕對結果

Figure 3 | Technology selection matrix: Scores indicate general tendencies and do not represent absolute results for specific equipment or materials

優先選擇化學發泡的情況

Situations Favoring Chemical Foaming

· 已有成熟密煉、模壓、押出或射出設備，希望以較低投資切入。

· Mature internal-mixing, molding, extrusion, or injection equipment is already available, and entry with lower investment is desired.

· 產品尺寸厚、形狀複雜，且現有配方已可穩定控制泡孔。

· Products are thick or geometrically complex, and the existing formulation can already control cell structure stably.

· 訂單量或產品生命週期不足以支撐高壓設備投資。

· Order volume or product life cycle is insufficient to support investment in high-pressure equipment.

· 允許使用符合要求的化學發泡劑，氣味與殘留可透過配方及後處理控制。

· Use of compliant chemical blowing agents is acceptable, and odor and residues can be controlled through formulation and post-treatment.

優先評估超臨界發泡的情況

Situations Favoring Evaluation of Supercritical Foaming

· 產品對低氣味、潔淨配方、材料減重或高細胞密度有明確價值。

· The product has clear value in low odor, clean formulations, material weight reduction, or high cell density.

· 訂單量大且規格長期穩定，可攤提高壓設備與開發成本。

· Order volume is high and specifications are stable long-term, allowing high-pressure equipment and development costs to be amortized.

· 材料具備合適的氣體溶解度、熔體強度及尺寸定型能力。

· The material has suitable gas solubility, melt strength, and dimensional-setting capability.

· 團隊能控制壓力、氣體濃度、溫度、壓降速率與模具熱管理。

· The team can control pressure, gas concentration, temperature, pressure-reduction rate, and mold thermal management.

十、導入超臨界發泡前的六個驗證問題

X. Six Validation Questions Before Introducing Supercritical Foaming

1  材料能否吸收足夠氣體？｜先取得 CO₂／N₂ 溶解度與擴散行為，不要只憑材料名稱判斷。

2  熔體強度是否足以固定泡孔？｜觀察合泡、破泡、後收縮及泡孔壁穩定性。

3  產品表面是否允許微孔痕跡？｜射出表面可能受到氣體逸出、模溫與流動前緣影響。

4  減重能否轉化為商業價值？｜把原料節省、週期、良率與設備折舊放入同一成本模型。

5  規格是否具足夠量產週期？｜高壓設備較適合長週期、穩定且可複製的產品平台。

6  是否真的改善環境績效？｜以能耗、材料減量、報廢率與回收路徑做完整評估。

結論：不是新技術取代舊技術，而是產品價值決定製程

Conclusion: It Is Not About New Technology Replacing Old Technology; Product Value Determines the Process

化學發泡的優勢是成熟、彈性高、設備投資相對低，適合多品種與既有量產平台；超臨界發泡則在細胞密度、減少發泡劑殘留及材料輕量化方面具備發展潛力，但必須付出更高的設備、控制與材料工程成本。

The advantages of chemical foaming are maturity, high flexibility, and relatively low equipment investment, making it suitable for multiple product types and existing mass-production platforms. Supercritical foaming has development potential in cell density, reduction of blowing-agent residues, and material lightweighting, but it requires higher equipment, control, and materials-engineering costs.

如果產品只要求降低密度，成熟的化學發泡往往已具備良好成本效益；如果產品同時要求低氣味、精細泡孔、材料減量、高性能與可建立長期量產平台，超臨界發泡才可能創造足以支撐投資的差異化。最佳方案甚至可能不是二選一，而是依材料與產品採用物理發泡、化學發泡、交聯或成核技術的組合。

If the product only requires reduced density, mature chemical foaming often already offers good cost-effectiveness. If the product simultaneously requires low odor, fine cells, material reduction, high performance, and a long-term mass-production platform, supercritical foaming may create sufficient differentiation to justify the investment. The best solution may not even be an either-or choice, but a combination of physical foaming, chemical foaming, crosslinking, or nucleation technologies depending on the material and product.

研發決策原則｜先定義成品要解決的問題，再決定泡孔、材料與製程；不要先購買一種發泡技術，再要求所有產品配合它。 R&D decision principle | First define the problem the finished product needs to solve, then decide on the cell structure, material, and process; do not purchase a foaming technology first and then require all products to conform to it.

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主標題 Main Title	化學發泡 vs. 超臨界發泡：不只是泡孔大小，成本、性能與回收性的完整比較 Chemical Foaming vs. Supercritical Foaming: A Complete Comparison of Cost, Performance, and Recyclability—not Just Cell Size
Meta Description Meta Description	專業解析化學發泡與超臨界 CO₂／N₂ 發泡的原理、設備、泡孔、性能、成本、環保性與材料適用性，協助 EVA、POE、TPU、TPE 與鞋材產品選擇正確製程。 A professional analysis of the principles, equipment, cells, performance, cost, environmental considerations, and material applicability of chemical foaming and supercritical CO₂/N₂ foaming, helping EVA, POE, TPU, TPE, and footwear products select the right process.
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參考資料

References

· Tsivintzelis, I. et al. “Foaming of polymers with supercritical CO₂.” Polymer, 2007.

· Tsivintzelis, I. et al. “Foaming of polymers with supercritical CO₂.” Polymer, 2007.

· Tomasko, D. L. et al. “A review of CO₂ applications in the processing of polymers.” Industrial & Engineering Chemistry Research, 2003；以及後續 polymer foam applications 回顧。

· Tomasko, D. L. et al. “A review of CO₂ applications in the processing of polymers.” Industrial & Engineering Chemistry Research, 2003; and subsequent reviews of polymer foam applications.

· Jin, F.-L. et al. “Recent Trends of Foaming in Polymer Processing: A Review.” Polymers, 2019.

· Jin, F.-L. et al. “Recent Trends of Foaming in Polymer Processing: A Review.” Polymers, 2019.

· Zhou, Y. et al. “Applications and Challenges of Supercritical Foaming Technology.” Polymers, 2023.

· Zhou, Y. et al. “Applications and Challenges of Supercritical Foaming Technology.” Polymers, 2023.

· Kmetty, Á. et al. “Characterization of Different Chemical Blowing Agents and Their Applicability to Produce Poly(Lactic Acid) Foams.” Applied Sciences, 2018.

· Kmetty, Á. et al. “Characterization of Different Chemical Blowing Agents and Their Applicability to Produce Poly(Lactic Acid) Foams.” Applied Sciences, 2018.