LG EVA 28005 resina de copolímero EVA,28% VA,5 MI,Grau geral do filme

LG EVA 28005 is an ethylene-vinyl acetate copolymer resin supplied as a general film grade with a nominal vinyl acetate content of 28% by mass and a melt index of 5 g/10 min when determined at 190 °C under a 2.16 kg load in accordance with ISO 1133-1 or ASTM D1238. The grade is positioned for blown-film and cast-film processes in which the converter requires lower crystalline melting, increased low-temperature flexibility, improved heat-seal initiation, and higher optical clarity than a conventional low-vinyl-acetate EVA. The 28% comonomer content is high enough to suppress polyethylene crystallinity, while the 5 g/10 min melt index is low enough to retain bubble stability in high-blow-up-ratio film lines.

Published class data for ethylene-vinyl acetate copolymers with approximately 28% vinyl acetate indicate a density of 0.945–0.955 g/cm³ by ASTM D1505 or ISO 1183-1, a differential scanning calorimetry melting peak commonly in the 70–78 °C range at 10 K/min, and a Vicat softening temperature in the 55–65 °C range under ASTM D1525. These are polymer-class reference values, not guaranteed lot specifications. The resin reduces polyethylene crystallinity sufficiently to produce a broad melting endotherm and low-temperature flexibility suitable for freezer film structures, but exact tensile strength, elongation, dart impact, and haze must be obtained from a supplier certificate of analysis and measured on finished film.

What Distinguishes a 28% VA EVA Film Resin from Lower-VA and Higher-VA Grades?

Compared with an 18% vinyl acetate EVA of equivalent melt index, the 28% vinyl acetate fraction introduces a larger amorphous phase and reduces flexural modulus. The polar acetate side groups increase the resin’s surface energy and alter adhesion to inks, coatings, and polar substrates. Film formed from the 28% VA grade generally exhibits lower seal initiation temperature and better retention of flexibility at freezer temperatures. Heat-seal initiation is commonly 10–15 °C lower than an 18% VA grade of similar melt index. The trade-off is lower modulus, greater blocking tendency, and reduced stiffness, which can limit machinability in high-speed form-fill-seal lines unless antiblock and slip additives are incorporated.

Against a high-melt-index EVA with the same 28% vinyl acetate content, the 5 g/10 min melt index provides higher melt tension and lower neck-in. This benefits blown-film bubble stability and wide-web cast-film edge control. A 25 g/10 min grade may be preferred for injection molding or thin-wall compounding because it fills complex flow paths at lower pressure, but it does not provide the same gauge uniformity in thick blown film.

Blown-Film Extrusion Parameters and Melt Rheology

Rheologically, a melt index of 5 g/10 min is a single low-shear point. Two EVA grades with identical melt index can differ in molecular weight distribution, long-chain branching, shear thinning, and extensional viscosity. A capillary rheometry sweep from 100 s⁻¹ to 1000 s⁻¹ at 190 °C is a more reliable comparison than melt index alone. In general, the 5 g/10 min grade exhibits higher zero-shear viscosity and higher melt tension than a 25 g/10 min grade of the same vinyl acetate content, but the difference narrows at high shear.

On production-scale blown-film lines equipped with a 25:1 L/D barrier screw and a 0.8–1.5 mm die gap, the resin is commonly started at barrel temperatures from 160 °C to 190 °C and die temperatures from 180 °C to 210 °C. A blow-up ratio of 2.0:1 to 3.0:1 and a frost-line height of 3 to 5 die diameters are typical initial settings. Increasing the blow-up ratio improves transverse-direction tear strength but reduces machine-direction tensile strength.

On cast-film lines, a melt temperature of 210–230 °C, a die gap of 0.5–1.0 mm, a chill-roll temperature of 15–25 °C, and an air gap of 10–20 mm are common starting conditions. Higher melt temperatures reduce haze but accelerate gel formation; line speed and chill-roll surface finish determine film surface roughness and release behavior.

Base LG EVA 28005 is supplied without a tailored additive package. Antiblock, slip, UV-stabilizer, and processing-aid masterbatches are selected by the converter and control blocking, haze, coefficient of friction, and weatherability. The resin should be evaluated before combining with amine-containing colorants or stabilizers, because acetic acid by-products at high temperature can react with basic moieties and cause color shifts.

When the Melt Temperature Is Held Above 230°C in High-VA EVA Processing

Thermal exposure above 230 °C accelerates acetic acid elimination and oxidative chain scission in EVA copolymers with vinyl acetate content above 25%. The released acetic acid creates a corrosive vapor that attacks unplated carbon steel die lips, air rings, and downstream handling equipment. Continuous film lines processing LG EVA 28005 therefore use chromium-plated or stainless steel die surfaces and maintain nitrogen or low-humidity cooling air to reduce oxidative yellowing. If screen-pack pressure rises above 25–30 MPa, the screen is changed; a pressure increase at constant screw speed indicates gel accumulation.

Batch-to-batch variance observed on production lines commonly appears as surging, die-lip buildup, and variable film haze. These defects are minimized by controlling melt temperature below 220 °C, maintaining a stable hopper feed, and using a melt pump to isolate die pressure from extruder screw output. During shutdown, the barrel is purged with low-density polyethylene before cooling to displace residual EVA and reduce black speck formation on restart. Published grade-specific degradation kinetic data for LG EVA 28005 are limited, but the behavior described is representative of EVA copolymers in this vinyl acetate range.

Commercial film structures using LG EVA 28005 include greenhouse film, extrusion lamination, surface-protection film, and high-clarity packaging. Extrusion lamination may use melt temperatures of 220–240 °C and a chill-roll temperature of 15–25 °C; adhesion to aluminum foil and polyester is typically higher than with an 18% VA EVA, but bond values must be verified by peel testing such as ASTM F904.

Regulatory Status and Compliance Documentation

Food-contact status for film made from LG EVA 28005 is formulation-dependent and must be confirmed on the finished article. The resin’s 28% vinyl acetate content may place it outside the comonomer scope of certain general clearances, and converters should not rely solely on the resin grade designation.

Continuous service above 70 °C can produce creep and loss of seal strength; the resin is therefore not recommended for retort, autoclave, or high-temperature sterilization applications. Solvent resistance is lower than polyethylene in contact with polar solvents because the 28% vinyl acetate content increases swelling; finished-film testing is required.

Storage in dry conditions at or below 45 °C is recommended. EVA is not highly hygroscopic, but surface condensation on pellets can produce bubbles and film defects. When exposure to relative humidity above 60% is suspected, pre-drying at 55 °C for 2 to 4 hours is used before extrusion.

Differences from other products are most visible in heat-seal and low-temperature performance. A lower-VA EVA of the same melt index gives higher stiffness and lower blocking but seals at a higher temperature; a higher-VA EVA gives lower melting and higher softness but reduces melt strength. The 5 g/10 min melt index differentiates this grade from injection-molding and compounding resins and keeps its film extrusion window suitable for both blown and cast equipment.