EVA添加POE有哪些優缺點？

What Are the Advantages and Disadvantages of Adding POE to EVA?

PART 1

再加入SEBS改善物性，為何雙螺桿分散才是關鍵？

When SEBS Is Added to Improve Properties, Why Is Twin-Screw Dispersion the Key?

核心觀點｜EVA／POE能快速降低硬度、改善回彈與低溫柔韌，但也可能犧牲結晶支撐、尺寸穩定、黏著與交聯效率。SEBS可補強熔體彈性、韌性與泡孔壁，但前提是形成細小、均勻且具有界面黏著的分散相；若仍以簡單乾混投入，SEBS的高黏度反而容易形成凝膠粒與弱界面。 Core insight | EVA/POE can rapidly reduce hardness and improve resilience and low-temperature flexibility, but it may also sacrifice crystalline support, dimensional stability, adhesion, and crosslinking efficiency. SEBS can reinforce melt elasticity, toughness, and cell walls, provided that it forms a fine, uniform dispersed phase with strong interfacial adhesion. If it is still introduced by simple dry blending, the high viscosity of SEBS instead tends to create gel particles and weak interfaces.

 

一、EVA為什麼常添加POE？先從分子結構理解

I. Why Is POE Commonly Added to EVA? Start with the Molecular Structure

EVA是乙烯—醋酸乙烯酯共聚物。乙烯鏈段提供可結晶區與基本骨架，VA側基會破壞聚乙烯晶格，使材料隨VA含量提高而變得更柔軟、極性與黏著性提高，但熔點、結晶度與耐熱支撐通常下降。POE多為乙烯與α-烯烴的無規共聚物，具有聚烯烴主鏈、低玻璃轉移溫度與柔軟彈性，因此與EVA的乙烯鏈段具有一定相容基礎。

EVA is an ethylene-vinyl acetate copolymer. Its ethylene segments provide crystalline regions and the basic framework, while VA side groups disrupt the polyethylene crystal lattice. As VA content increases, the material becomes softer and gains polarity and adhesion, but its melting point, crystallinity, and heat-resistant support generally decline. POE is typically a random copolymer of ethylene and an alpha-olefin. Its polyolefin backbone, low glass-transition temperature, and soft elasticity provide a degree of compatibility with the ethylene segments of EVA.

EVA加入POE的主要優點

Main Advantages of Adding POE to EVA

1. 降低硬度與彎曲模數：能以聚合物改質取代部分大量充油，降低滲油或表面黏膩風險。

Lower hardness and flexural modulus: Polymer modification can replace part of heavy oil extension, reducing the risk of oil bleed or a tacky surface.

2. 改善低溫柔韌與耐衝擊：POE低Tg可抑制低溫脆化，適合鞋材、護具與緩衝泡棉。

Improve low-temperature flexibility and impact resistance: The low Tg of POE suppresses low-temperature embrittlement, making it suitable for footwear, protective gear, and cushioning foams.

3. 提高回彈潛力：適當POE相可降低能量損失，使壓縮後恢復更快。

Increase resilience potential: A suitable POE phase can reduce energy loss and enable faster recovery after compression.

4. 提高破裂伸長與抗疲勞：細小分散相可鈍化裂紋尖端，延緩裂紋擴展。

Increase elongation at break and fatigue resistance: A finely dispersed phase can blunt crack tips and delay crack propagation.

5. 調整熔體流變：合適牌號可改善發泡過程的泡孔成長與表面手感。

Tune melt rheology: An appropriate grade can improve cell growth during foaming and the surface feel of the product.

但「相容」不代表完全互溶

But "Compatible" Does Not Mean Fully Miscible

EVA與POE通常呈現部分相容或多相結構。VA含量、POE共單體含量、分子量、黏度比與混煉歷史會決定相尺寸。若POE形成過大液滴或局部連續相，物性不再是簡單加成，而會出現撕裂下降、泡孔粗化與收縮放大。

EVA and POE generally form a partially compatible or multiphase structure. VA content, POE comonomer content, molecular weight, viscosity ratio, and compounding history determine domain size. If POE forms oversized droplets or a locally continuous phase, the properties are no longer a simple sum; tear strength may decline, cells may coarsen, and shrinkage may increase.

圖1｜EVA／POE二元共混與加入SEBS後的目標多相形態示意。

Figure 1 | Schematic of an EVA/POE binary blend and the target multiphase morphology after adding SEBS.

 

二、EVA添加POE的缺點：問題多半來自結晶、界面與反應稀釋

II. Disadvantages of Adding POE to EVA: Most Problems Arise from Crystallinity, Interfaces, and Reaction Dilution

潛在缺點 Potential Disadvantage	高分子機理 Polymer Mechanism	發泡成品可能表現 Possible Effect in the Foamed Product
耐熱與尺寸穩定下降 Reduced Heat Resistance and Dimensional Stability	POE通常降低整體結晶度；低熔點晶區在貼合溫度下失去支撐 POE generally lowers overall crystallinity; low-melting crystalline regions lose support at lamination temperatures.	二次收縮、翹曲、邊緣捲曲 Secondary shrinkage, warpage, and curled edges
撕裂未必同步提升 Tear Strength May Not Improve in Parallel	相尺寸過大或界面黏著不足，裂紋沿相界面傳播 Oversized domains or insufficient interfacial adhesion allow cracks to propagate along phase boundaries.	柔軟但不耐撕，動態疲勞提早破壞 Soft but prone to tearing, with premature dynamic-fatigue failure
交聯效率改變 Changed Crosslinking Efficiency	POE稀釋EVA，且不同鏈結構對DCP自由基反應效率不同 POE dilutes EVA, and different chain structures react with DCP-derived radicals at different efficiencies.	凝膠率不足或需重調DCP Insufficient gel content or a need to recalibrate DCP
發泡倍率與泡孔漂移 Drift in Expansion Ratio and Cell Structure	黏度、熔體強度及產氣—成網時序被改變 Viscosity, melt strength, and gas-generation/network-formation timing are altered.	密度不穩、粗孔、併孔或回縮 Unstable density, coarse cells, cell coalescence, or shrink-back
黏著與印刷性下降 Reduced Adhesion and Printability	低極性的POE增加後，表面能與極性降低 As the amount of low-polarity POE increases, surface energy and polarity decrease.	布貼合、膠黏、塗裝或印刷難度提高 More difficult fabric lamination, adhesive bonding, coating, or printing
永久變形可能惡化 Compression Set May Worsen	過軟且網路不足時，鏈段滑移增加 When the material is too soft and the network is inadequate, chain-segment slippage increases.	壓縮永久變形與長期支撐下降 Higher compression set and reduced long-term support
重要提醒｜不能在不同密度下直接比較硬度或回彈。POE配方若發泡倍率較高，自然會更軟；研發評估必須先固定成品密度，才能判斷真正的材料效應。 Important reminder | Hardness or resilience cannot be compared directly at different densities. A POE formulation with a higher expansion ratio will naturally be softer; R&D evaluations must first hold finished-product density constant to identify the true material effect.

相態的關鍵參數：黏度比與界面張力

Key Parameters of Phase Morphology: Viscosity Ratio and Interfacial Tension

在共混剪切場中，分散相尺寸受界面張力、剪切應力與黏度比控制。可用毛細數 Ca = ηm·γ̇·R/σ 理解液滴變形：基體黏度ηm、剪切速率γ̇或液滴半徑R增加，分散相更容易被拉伸；界面張力σ越高則越抗拒破碎。但若分散相黏度過高、停留時間不足或破碎後快速聚併，仍會留下粗大顆粒。

In a shear field during blending, dispersed-phase size is governed by interfacial tension, shear stress, and viscosity ratio. Droplet deformation can be understood through the capillary number, Ca = ηm·γ̇·R/σ: increases in matrix viscosity ηm, shear rate γ̇, or droplet radius R make the dispersed phase easier to stretch, whereas higher interfacial tension σ resists breakup. Even so, coarse particles remain if the dispersed phase is too viscous, residence time is insufficient, or droplets rapidly coalesce after breakup.

 

三、為什麼再加入SEBS？它補的是POE不擅長的部分

III. Why Add SEBS as Well? It Compensates for What POE Does Not Do Well

SEBS是苯乙烯—乙烯／丁烯—苯乙烯嵌段共聚物。常溫下，聚苯乙烯端段形成硬質微區，像可逆物理交聯點；中間的乙烯／丁烯軟段與POE及EVA的乙烯鏈段具有相互作用基礎。因此，SEBS能在不完全依賴結晶的情況下，提供熔體彈性、韌性與阻尼。

SEBS is a styrene-ethylene/butylene-styrene block copolymer. At room temperature, the polystyrene end blocks form hard microdomains that act like reversible physical crosslinks, while the ethylene/butylene midblock can interact with POE and the ethylene segments of EVA. SEBS can therefore provide melt elasticity, toughness, and damping without relying entirely on crystallinity.

SEBS可帶來的改善

Improvements That SEBS Can Provide

1. 提高熔體彈性與泡孔壁強度：有利於抑制併孔、破孔及開模回縮。

Increase melt elasticity and cell-wall strength: Helps suppress cell coalescence, cell rupture, and shrink-back after demolding.

2. 改善撕裂與裂紋鈍化：細小SEBS相可吸收裂紋能量，尤其適合反覆彎折與動態使用。

Improve tear resistance and crack blunting: Fine SEBS domains can absorb crack energy, which is especially useful under repeated flexing and dynamic service.

3. 調整回彈—阻尼平衡：POE偏向彈性回復，SEBS可依牌號、苯乙烯含量及充油量提高阻尼與柔韌。

Tune the resilience-damping balance: POE favors elastic recovery, while SEBS can increase damping and flexibility depending on grade, styrene content, and oil loading.

4. 降低單純依賴低熔點POE降硬的比例：有機會保留更多EVA結晶支撐與尺寸穩定。

Reduce reliance on low-melting POE alone to lower hardness: This may retain more of EVA's crystalline support and dimensional stability.

5. 改善低溫韌性及觸感：EB軟段維持低溫柔軟，PS微區提供常溫形狀保持。

Improve low-temperature toughness and feel: The soft EB segments remain flexible at low temperature, while PS microdomains preserve shape at room temperature.

SEBS也不是沒有代價

SEBS Also Has Tradeoffs

風險 Risk	原因 Cause	控制方向 Control Strategy
分散困難 Difficult Dispersion	高分子量SEBS熔體黏度高、顆粒溶脹慢 High-molecular-weight SEBS has high melt viscosity, and its pellets swell slowly.	預乾燥／預混、提高停留與分散混煉 Pre-dry/preblend and increase residence time and dispersive mixing.
硬點或凝膠粒 Hard Specks or Gel Particles	SEBS未塑化或局部濃度過高 SEBS is not fully plasticized or is locally overconcentrated.	雙螺桿預造粒、篩壓與顯微切片 Twin-screw pre-pelletization, screen-pressure monitoring, and microscopic cross-sectioning
表面粗糙 Rough Surface	相尺寸大、黏度不匹配或揮發物 Large domains, viscosity mismatch, or volatiles	調螺桿組合、溫度、真空排氣 Adjust the screw configuration, temperature, and vacuum venting.
DCP反應被重新分配 DCP Reactions Are Redistributed	SEBS、EVA、POE的自由基反應與降解傾向不同 SEBS, EVA, and POE differ in radical reactivity and degradation tendency.	聚合物預混後，另階段加入DCP並重建硫化曲線 Preblend the polymers, add DCP in a separate stage, and re-establish the cure curve.
成本與回收複雜度提高 Higher Cost and More Complex Recycling	三元配方、母粒與兩段加工增加成本 A ternary formulation, masterbatch, and two-stage processing increase cost.	以良率、撕裂與壽命的總效益評估 Evaluate total benefit in terms of yield, tear strength, and service life.

四、SEBS為何更需要雙螺桿？關鍵是「分散」與「分布」不同

IV. Why Does SEBS Need a Twin-Screw Extruder Even More? Dispersion and Distribution Are Different

分布混合（distributive mixing）是把材料搬運到整個體積；分散混合（dispersive mixing）則是用足夠應力打碎團聚體與大相域。SEBS顆粒即使肉眼看似混均，內部仍可能存在未塑化核心。密煉機或單螺桿可以完成部分配方，但若要穩定建立細小相尺寸、連續量產與批次一致性，共旋雙螺桿預混煉通常是更可靠的工業路徑。

Distributive mixing moves materials throughout the entire volume, whereas dispersive mixing applies enough stress to break up agglomerates and large domains. Even when SEBS pellets appear evenly mixed to the naked eye, they may still contain unplasticized cores. An internal mixer or single-screw extruder can process some formulations, but co-rotating twin-screw pre-compounding is generally the more reliable industrial route for consistently creating fine domains, supporting continuous production, and maintaining batch-to-batch consistency.