Products · EVA
Ethylene-vinyl acetate (EVA) is one of the most versatile polymers in commercial use. By varying the vinyl acetate (VA) content from 12% to 33%, EVA can be tuned from a low-melting flexible film (low VA) to a high-clarity photovoltaic encapsulation film (high VA) to a soft elastomeric foam (very high VA). Solar-grade EVA with 28-33% VA is the dominant encapsulant for crystalline silicon PV modules, where crosslinkable EVA films are laminated between front glass, cells, and backsheet to provide optical coupling, mechanical cushioning, and electrical insulation. Other major applications include footwear midsoles, hot-melt adhesives, and extrusion coating. Reference grades from Hanwha, ExxonMobil, LyondellBasell, and Sierbang cover the full VA and melt-index range.
Section 1
A reference overview of the molecular architecture and the design variables that govern the performance of this polymer family.
EVA is a random copolymer of ethylene and vinyl acetate (VA), produced by high-pressure free-radial polymerization in autoclave or tubular reactors. The VA comonomer disrupts polyethylene crystallinity: at 12% VA, the polymer is still semi-crystalline and resembles LDPE; at 25% VA, crystallinity is largely suppressed and the material becomes flexible and transparent; at 33% VA, the material is fully amorphous and elastic. Vinyl acetate is the key design variable — not the molecular weight — so EVA grade selection is primarily by VA% and melt index, then by additive package. Solar-grade EVA additionally contains organic peroxide (crosslinker), silane (adhesion promoter), UV absorber, and hindered amine light stabilizer (HALS) for lamination and long-term UV exposure.
Section 2
Typical property ranges across commercial grades. Test methods are listed in the rightmost column for traceability to public manufacturer data sheets.
EVA's property profile changes dramatically with VA content. Low-VA EVA (12-18%) is tough, processable, and resembles LDPE — used for film and extrusion coating. Mid-VA EVA (18-25%) is flexible and transparent — used for hot-melt adhesive and transparent film. High-VA EVA (28-33%) is the workhorse photovoltaic encapsulation grade, where the combination of high clarity, low modulus, and crosslinkability is unique.
| Property · 性能 | Low VA (12-18%) | High VA (28-33%) | Test Method · 测试方法 |
|---|---|---|---|
| Density · 密度 | 0.92 – 0.94 g/cm³ | 0.95 – 0.96 g/cm³ | ASTM D792 |
| Melt Index (190°C/2.16 kg) · 熔指 | 0.3 – 30 g/10 min | 5 – 45 g/10 min (film) | ASTM D1238 |
| VA Content · VA 含量 | 12 – 18 wt % | 28 – 33 wt % | NMR / titration |
| Tensile Strength at Break · 拉伸强度 | 15 – 25 MPa | 8 – 12 MPa | ASTM D638 |
| Elongation at Break · 断裂伸长 | 500 – 800 % | 600 – 900 % | ASTM D638 |
| Vicat Softening · 维卡软化 | 60 – 80 °C | < 40 °C (crosslinked) | ASTM D1525 |
| Crystallinity · 结晶度 | 20 – 35 % | < 5 % (crosslinked) | DSC |
Section 3
The major application areas for this polymer family, each illustrated with a brief description of how the material is specified and used.
Solar-grade EVA with 28-33% VA is the dominant encapsulant for crystalline silicon PV modules. Crosslinkable EVA films are laminated between front glass, solar cells, and backsheet at 140-150 °C under vacuum, where the peroxide crosslinker forms a 3D network. The result is an optical coupling layer with UV resistance, mechanical cushioning for cell breakage prevention, and electrical insulation. Dual-glass bifacial modules use UV-cut grades; single-glass monofacial modules use fast-cure grades.
Mid-VA EVA (18-25%) with added tackifier and wax is the workhorse hot-melt adhesive for bookbinding, packaging, woodworking, and product assembly. Open time, set time, and bond strength are tuned by VA content, MI, and additive package.
High-VA EVA (25-33%) is expanded with chemical blowing agents to produce closed-cell foam sheets for footwear midsoles, yoga mats, and sports padding. The crosslinked foam offers excellent resilience and low density (0.15-0.30 g/cm³).
EVA copolymers with 12-18% VA are used in low-voltage wire insulation and jacketing, where flexibility, low-temperature performance, and filler acceptance are key. Crosslinkable EVA compounds are used in higher-temperature applications.
Low-VA EVA grades (12-15% VA) are used in extrusion coating for paper, board, and aluminum foil where heat sealability, flexibility, and adhesion to polar substrates are needed. Common in food packaging and aseptic carton.
Section 4
Key processing parameters and equipment considerations. Contact our business manager for grade-specific processing recommendations.
| Melt Temperature | 180 – 230 °C for film extrusion; 100 – 120 °C melt for hot-melt adhesive application |
| Lamination | Solar lamination: 140 – 150 °C, 8 – 12 min, vacuum ≥ 0.1 MPa |
High-VA EVA is sensitive to thermal degradation above 230 °C — acetic acid release can corrode equipment and cause odor. Crosslinkable EVA must be kept below 60 °C storage to prevent premature crosslinking. Acetate group absorbs water; drying at 60 °C for 4 hours before film extrusion is recommended.
Section 5
A summary of when this polymer family is the right choice and what to consider as alternatives. For project-specific grade selection, contact our business manager.
EVA is the right choice for solar PV encapsulation (28-33% VA), hot-melt adhesive (18-25% VA), foam and footwear (25-33% VA), or low-voltage wire insulation (12-18% VA). For photovoltaic modules with POE preference (e.g., N-type TOPCon, HJT), POE encapsulant is the modern alternative. For high-temperature resistant adhesive, consider polyurethane hot-melt or reactive acrylic.
Section 6
Reference grades from publicly available manufacturer catalogs. Complete catalog available on request.
| Grade | Manufacturer | Key Properties | Typical Use |
|---|---|---|---|
| Escorene™ Ultra LD 700Internal snapshot · original TDS on request | ExxonMobil | 28% VA · 6 MI · Fast cure | Solar PV encapsulation · Monofacial modules |
| Elvax® 150 | DuPont | 32% VA · 43 MI · Film grade | Solar film · Adhesive base |
| Lupolen® EVA 28400 | LyondellBasell | 28% VA · 400 MI · High flow | Hot melt adhesive · Wax blends |
| Hanwha EVA HP-2835 | Hanwha Solutions | 28% VA · 35 MI · UV-cut | Bifacial solar · Dual-glass modules |
| Sierbang EVA PV-3300 | Sierbang (盛虹斯尔邦) | 33% VA · 30 MI · Solar | Solar film · Domestic supply |
Section 7
Cross-references to industry-specific applications and case studies.