Resina Copolímero LG EVA 40055 EVA, 40% VA, 55 MI, Adhesivo Termofusible Y Grado De Encapsulación Solar

LG EVA 40055 is an ethylene-vinyl acetate copolymer resin manufactured by LG Chem, characterized by a vinyl acetate content of **40%** by weight and a melt index of **55 g/10 min** determined under a **2.16 kg** load at **190°C** per **ASTM D1238-20**. The grade is specified for two primary downstream conversion routes: hot melt adhesive compounding and photovoltaic encapsulation film extrusion. The **40%** VA monomer fraction disrupts polyethylene crystalline packing to the extent that the resin exhibits a broad melting endotherm between **55°C** and **65°C**, a glass transition temperature near **−32°C**, and a density approximating **0.98 g/cm³** (**ASTM D792-20**). These thermal and physical constants are representative of high-VA EVA copolymer systems reported in open technical literature; lot-specific certificates of analysis from LG Chem should be referenced for the exact melting profile and density of individual production campaigns. The high VA fraction also renders the polymer substantially amorphous, contributing to the optical clarity and initial tack necessary for both encapsulant films and pressure-sensitive adhesive formulations.

Rheological Consequences of a 55 MI Specification

The melt index value of **55 g/10 min** (**ASTM D1238-20**, **190°C/2.16 kg**) positions this grade in the high-flow regime appropriate for slot-die coating, roll-to-roll lamination, and gear-pump-assisted melt delivery. In extrusion terms, a **30:1 L/D** single-screw extruder with a barrier feed section and a low-shear mixing element processes this resin at melt temperatures between **120°C** and **160°C** without generating excessive barrel pressure or requiring a grooved feed throat. Published viscosity data for this specific grade are limited; however, comparable EVA copolymers with **40%** VA and melt index near **55 g/10 min** exhibit apparent viscosities in the range of **1,500–3,000 Pa·s** at **190°C** and shear rates of **0.1–1 s⁻¹**, as measured per **ISO 11443:2021** capillary rheometry. The material displays pronounced pseudoplasticity: at die shear rates of **1,000–10,000 s⁻¹**, apparent viscosity may fall by more than one order of magnitude below the low-shear plateau. This shear-thinning response benefits uniform melt distribution across wide coating dies, yet it simultaneously reduces melt strength, limiting the maximum draw-down ratio in stabilizer-free blown film operations to approximately **3:1** before neck-in and web instability become unacceptable on production lines. In hot melt adhesive compounding, the **40%** VA content provides the polar ester functionality required for adhesion to cellulosic substrates, aluminum foil, polyester film, and primed polyolefin surfaces. Formulations based on this resin are typically processed in mechanically agitated, nitrogen-blanketed melt tanks maintained at **160°C–180°C**, where EVA is compounded with rosin ester or hydrogenated hydrocarbon tackifiers at **40–60 phr**, paraffinic or Fischer-Tropsch waxes at **10–20 phr**, and a hindered phenolic antioxidant at **0.5–1.0 phr**. The high melt index reduces batch cycle time in twin-screw or Banbury-style compounding equipment but correspondingly lowers cohesive strength relative to lower-MI EVA grades. Open time in slot-die-applied adhesive films ranges from **3–8 s** depending on wax loading, line speed, and substrate thermal conductivity; this value is derived from production-scale hot melt coating lines running comparable high-VA EVA systems, and published data for LG EVA 40055 in finished adhesive formulations is limited. As wax content exceeds **15 phr**, the paraffinic phase migrates to the adhesive surface and suppresses tack development on chilled rolls. Peel adhesion on untreated polypropylene is typically below **2 N/25 mm** per **ASTM D903-17**, whereas cohesive failure on aluminum and kraft paper can exceed **35 N/25 mm** under identical test conditions; formulators should verify these values through comparative testing before specifying this grade for demanding bonding applications.

What Limits Processing Temperature in High-VA EVA Systems?

The upper processing temperature for LG EVA 40055 is governed by thermal deacetylation of the vinyl acetate comonomer rather than by degradation of the polyethylene backbone. Deacetylation generates acetic acid at measurable rates above **200°C**, following Arrhenius kinetics with activation energies reported between **150 and 200 kJ/mol** for EVA copolymers in published degradation studies. At **220°C**, the emitted acetic acid concentration in the melt can exceed **50 ppm** within **10 minutes** of residence time, which is sufficient to autocatalyze further deacetylation and produce visible discoloration exceeding a yellowness index of **5** per **ASTM E313-20**. The evolved acetic acid also corrodes aluminum heating elements and uncoated steel die surfaces on hot melt application heads, leading to pitting and eventual nozzle blockage. Extrusion barrel temperature profiles for this grade should therefore be capped at **160°C** in the rear zones and **140°C** at the die, with measured melt temperature never exceeding **170°C**. Screw configurations with compression ratios above **3:1** or aggressive kneading blocks generate excessive viscous dissipation that can elevate localized melt temperature beyond this ceiling even when barrel setpoints remain conservative. The lower processing boundary is fixed by minimum flow temperature; below **100°C**, insufficient melt fluidity prevents adequate substrate wet-out during coating or film casting, producing visible striations and thickness non-uniformity in the final article.

Solar Encapsulation Film: Crosslinking Boundary Conditions

For photovoltaic encapsulation, the resin is converted into cast film after compounding with an organic peroxide initiator—tert-butyl peroxy-2-ethylhexyl carbonate (TBEC)—at **0.5–1.5 wt%** and a silane coupling agent (vinyltrimethoxysilane) at **0.3–0.5 wt%**. The **40%** VA content contributes to the optical clarity required for module construction: films extruded from high-VA EVA copolymers exhibit total luminous transmittance above **90%** across the **400–1,100 nm** wavelength band relevant to crystalline silicon photovoltaics, as measured per **IEC 62788-1-4:2020**. The **55 MI** flow characteristic enables the molten filler material to penetrate gaps between ribbon-interconnected cells during vacuum lamination at **145°C–155°C** for **12–20 minutes**, a thermal cycle that simultaneously achieves near-complete peroxide decomposition. Gel content after lamination typically reaches **75–90%** by xylene extraction per **ASTM D2765-16**, providing the creep resistance required to withstand thermal excursions from **−40°C** to **+85°C** over **200 cycles** per **IEC 61215:2021**. The high melt index implies relatively short polymer chains; the uncrosslinked resin alone lacks sufficient melt elasticity for long-term load-bearing service in hot climates. Peroxide crosslinking is therefore mandatory for encapsulant applications, distinguishing this application from hot melt adhesive usage where crosslinking is typically absent. Storage conditions for LG EVA 40055 must account for the hygroscopic character of the vinyl acetate comonomer and the thermo-oxidative susceptibility of the amorphous polymer chains. Bulk pellets should be retained in moisture-resistant packaging at ambient temperatures below **30°C** and relative humidity not exceeding **60%**. Moisture absorption above **500 ppm** promotes hydrolytic degradation during subsequent melt processing, releasing acetic acid and producing surface defects in extruded films. If pellets are exposed to open-hopper conditions at ambient humidity for more than **24 hours**, desiccant-air drying at **60°C–70°C** for **4 hours** is recommended before extrusion; exposure exceeding **72 hours** in humid environments may require **8 hours** of drying. The resin is supplied as pellets, colorless to slightly translucent, and should be shielded from direct sunlight to prevent photo-oxidative yellowing before consumption. Batch-to-batch melt index variance for this grade is typically maintained within **±10%** of the nominal value on LG Chem certificates of analysis; incoming QC inspection per **ASTM D1238-20** is recommended for critical solar encapsulant film lines where lot-to-lot flow stability directly governs thickness uniformity.

When Peroxide Crosslinking Enters the Extrusion Profile

Adding peroxide initiators to LG EVA 40055 for solar encapsulant production introduces a processing conflict that dictates extrusion parameter selection. TBEC peroxide has a 1-hour half-life temperature of approximately **122°C** and a 1-minute half-life near **166°C** according to peroxide manufacturer technical datasheets. Extrusion through a cast film die must therefore proceed at melt temperatures below the 1-minute half-life threshold to prevent premature crosslinking inside the extruder barrel and die land. This requirement conflicts with the grade's high melt index, which would otherwise benefit from elevated temperatures for lower viscosity and improved surface gloss. Production-scale resolution of this conflict involves operating cast film extruders at melt temperatures of **100°C–120°C**, using a **24:1–30:1 L/D** single-screw extruder with a low-shear screw profile and zoned barrel temperature control, while accepting line speeds of **5–15 m/min** depending on film width and thickness. Subsequently, the processed encapsulant film is laminated under vacuum at **145°C–150°C**, achieving nearly complete peroxide decomposition within **15 minutes** and producing gel contents above **75%** per **ASTM D2765-16**. Silane coupling agent hydrolysis and condensation during the same lamination cycle forms covalent siloxane bridges between the EVA matrix and the glass surface, improving wet adhesion from less than **20 N/cm** to above **80 N/cm** in peel testing per **IEC 62788-1-4:2020** after **1,000 hours** of damp-heat aging at **85°C/85% RH**. A practical start-up failure mode observed on production laminating lines involves temperature overshoot exceeding **130°C** in the die land, generating micro-gel particles that appear as surface defects in the cast film and cannot be redissolved by downstream heating; such contaminated film must be scrapped. Comparison with lower-VA and lower-MI EVA grades clarifies the market positioning of LG EVA 40055. The **40%** VA content is substantially higher than the **18–28%** VA found in conventional injection molding and profile extrusion grades; this compositional difference lowers crystalline fraction, raises polarity, reduces tensile modulus, and improves adhesion to glass and metal surfaces. Conversely, the **55 MI** is lower than the **150–400 MI** characteristic of low-viscosity hot melt spray grades; the lower MI provides higher cohesive strength and better creep resistance in the final adhesive bond. The comparative ranges presented below represent general grade families rather than direct lot data for LG EVA 40055.

Parameter	LG EVA 40055	Low-VA EVA (18–28%)	High-MI EVA (≥150)
VA content (wt%)	**40%**	**18–28%**	**28–40%**
Melt index (**ASTM D1238-20**, 190°C/2.16 kg)	**55 g/10 min**	**2–25 g/10 min**	**150–400 g/10 min**
Melting point range	**55–65°C**	**80–105°C**	**55–70°C**
Density (**ASTM D792-20**)	**0.98 g/cm³**	**0.92–0.95 g/cm³**	**0.95–0.98 g/cm³**
Tensile modulus range	≤**50 MPa**	**70–200 MPa**	<**30 MPa**
Typical processing window	**100–160°C**	**160–220°C**	**100–150°C**
Primary suitability	HMA, solar encapsulation	Injection molding, profile extrusion	Spray-grade HMA, wax blending

Compliance Derives from Regional Mandates and Test Method Designations

The regulatory position of LG EVA 40055 is established through the manufacturer's published compliance statements and the general framework governing EVA copolymers in global markets. Verification against current certificates of analysis and safety data sheets is required before specifying the grade for medical, food contact, or photovoltaic applications subject to mandatory third-party certification.

Regulation /Standard	Scope	Designation
REACH	Registration, Evaluation, Authorisation and Restriction of Chemicals	**EC No. 1907/2006**
RoHS	Restriction of Hazardous Substances in electrical and electronic equipment	**2011/65/EU**, **2015/863/EU**
Food contact (US FDA)	Ethylene-vinyl acetate copolymers intended for repeated food contact	**21 CFR 177.1350**
Melt flow rate	Determination of melt mass-flow rate and melt volume-flow rate	**ASTM D1238-20**, **ISO 1133-1:2022**
Density	Solid polymer density by displacement method	**ASTM D792-20**
Yellowness index	Optical assessment of polymeric films after thermal aging	**ASTM E313-20**
PV encapsulant testing	Measurement procedures for EVA-based encapsulants in photovoltaic modules	**IEC 62788-1-4:2020**
Module qualification	Thermal cycling, damp-heat durability, and mechanical load testing	**IEC 61215:2021**, **IEC 61730-1:2023**
Gel content	Determination of gel fraction in crosslinked ethylene plastics	**ASTM D2765-16**
Peel adhesion	Peel or stripping strength of adhesive bonds	**ASTM D903-17**

The operational boundaries of LG EVA 40055 extend to chemical compatibility constraints that must be observed in melt processing and finished article service. Contact with chlorinated compounds, strong mineral acids, or concentrated alkalis at processing temperatures accelerates deacetylation and produces corrosive by-products that attack tool steel surfaces and reduce equipment service life. The resin should not be co-processed with PVC or chlorinated polyethylene in shared extruders without aggressive purging, since residual hydrogen chloride catalyzes degradation of the VA comonomer and causes gel deposition on die lips. Amine-containing additives are similarly problematic: primary and secondary amines react with acetic acid released during processing to form amide salts that deposit on die lips and degrade film clarity. For solar encapsulant film production, the presence of transition metal ions (iron, copper, manganese) above **50 ppm** catalyzes premature peroxide decomposition during extrusion, generating micro-gels in the melt; corrosion-resistant screw and barrel metallurgy with hardened chrome plating or bimetallic liners is therefore recommended for continuous encapsulant film lines. The resin is not suitable for prolonged outdoor exposure in its unmodified form; UV stabilization and peroxide crosslinking are mandatory for photovoltaic or exterior glazing applications where service life must exceed **5 years** per **IEC 61215:2021** accelerated aging criteria.