ATEVA 2820AG Copolímero de acetato de vinilo de etileno

ATEVA 2820AG is an ethylene vinyl acetate copolymer supplied in pellet form under the ATEVA trade name. The base resin is specified at 28 wt% vinyl acetate content by ASTM D5594-18a, with a melt mass-flow rate of 20 g/10 min when measured under ASTM D1238-20, condition 190 °C/2.16 kg, or ISO 1133-1:2022, procedure A. Density at 23 °C is reported as 0.950 g/cm³ under ISO 1183-1:2019, method A. Differential scanning calorimetry under ISO 11357-3:2018 at 10 K/min in nitrogen shows a melting peak near 70 °C. The grade is used in hot-melt adhesive compounds, wax-based formulations, polymer modification, masterbatch carriers, and high-flow extrusion coating where a combination of melt fluidity and polar adhesion is required. The 20 g/10 min melt flow rate reduces melt pressure in narrow die slots, while the 28 wt% vinyl acetate content increases compatibility with polar tackifiers, fillers, and high-polarity thermoplastics relative to low-VA EVA or LDPE. Applications should be selected with the low Vicat softening point in mind because the material softens at temperatures that would be acceptable for LDPE but can cause blocking or deformation in thin films if not managed by chilled-roll handling.

Does 28 wt% Vinyl Acetate Move the Bulk Solid Away from Polyolefin-Like Semi-Crystallinity?

At 28 wt% vinyl acetate, the regularity of the ethylene segments is sufficiently interrupted that the bulk solid does not exhibit a sharp LDPE-like crystalline melting plateau. Differential scanning calorimetry under ISO 11357-3:2018 at 10 K/min shows a melting peak near 70 °C and a crystallisation exotherm broader than that of an 18 wt% VA EVA grade. The lower heat of fusion directly reduces Vicat softening and flexural stiffness. Vicat softening temperature under ASTM D1525-17e1, method A50, is reported in the range of 45–47 °C. Shore hardness values obtained under ASTM D2240-15e1 are approximately 80 A and 28 D. Tensile strength at break falls in the range of 11–14 MPa when measured according to ISO 527-2:2012 on 2 mm compression-moulded plaques, with elongation at break in the range of 700–800%. These values distinguish the grade from LDPE, which typically shows a Vicat softening point above 85 °C, Shore D hardness in the 48–55 range, and lower polar wetting. The practical consequence is that ATEVA 2820AG seals at lower temperature, wets polar foils more readily, and retains flexibility at low temperature, but it is not suitable for load-bearing applications above 60 °C unless crosslinked or structurally filled.

Hot-melt compounders typically pre-mix the pellets with rosin ester or hydrocarbon tackifier resins and wax diluents in a sigma-blade mixer at 130–170 °C before discharge to coaters. The 20 g/10 min melt flow rate is high enough to reduce mixing torque in a 50 L kneader by roughly half compared with a 3 g/10 min EVA grade at the same temperature, but the low melt viscosity also narrows the shear-transmitted window for dispersing high-melting tackifiers. If a tackifier with a softening point above 120 °C is used, the mixing temperature may need to exceed 170 °C, which approaches the thermal stability limit of the VA units. Published formulation data for this specific grade in high-speed spiral spray hot-melt systems above 300 m/min is limited; pilot trials should include melt viscosity measurement at 160 °C using a cone-and-plate rheometer and T-peel adhesion testing under ASTM D1876-08(2015) before line commitment.

Processing Boundaries in 40:1 L/D Twin-Screw Compounding and Extrusion Coating

On production-scale twin-screw lines with 40:1 L/D, the feed zone should be maintained below 120 °C to prevent premature pellet softening and bridge formation in the feed throat. Barrel temperatures from 140 °C to 180 °C are typical; melt temperature measured at the die should be kept below 210 °C. Above 230 °C, detectable acetic acid evolution from vinyl acetate side-group elimination can corrode unprotected screw and barrel surfaces and generate pinholes in cast film. Nitrogen-purged venting at atmospheric or vacuum levels of -0.02 MPa to -0.06 MPa removes residual moisture and low-molecular-weight volatiles. Pre-drying is required when pellet surface moisture exceeds 0.05 wt%; a desiccant dryer at 60 °C for 4 h is generally adequate at ambient humidity above 60% relative humidity. In extrusion coating lines with a slot die, the high MFR lowers head pressure; however, at low line speeds below 30 m/min, edge neck-in can be more pronounced than with a lower MFR grade. Differential scanning calorimetry after processing should show no more than a 2 K shift in melting peak if melt temperature controls are adequate.

Thermogravimetric analysis of EVA containing 28 wt% VA typically shows a two-stage mass loss; the first stage near 300–360 °C corresponds to deacetylation of the VA units, while the second stage above 400 °C is polyene backbone degradation. Although extrusion temperatures are much lower, local shear heating in a 40:1 L/D twin-screw extruder running above 400 rpm can create melt-temperature spikes above 230 °C at screw tips. The practical result is an acetic acid odour at the die, reduced pH in quench water, and surface gel specks in cast film. Processors should install melt thermocouples at the die adapter and limit specific mechanical energy input so that melt temperature does not exceed 210 °C; if the melt temperature cannot be maintained, barrel temperatures should be lowered in the metering zones or screw speed reduced. Re-pelletised scrap from edge trim should be limited to 20 wt% in critical film or adhesive applications unless antioxidant topped up, because the oxidative induction time measured by ISO 11357-6:2018 at 200 °C may be shorter than that of LDPE.

For general dry blending, the pellets are mixed by low-intensity tumble blending at room temperature; no specialised surface treatment is required.

Food-contact use under 21 CFR 177.1350 requires end-use extraction testing with the intended additive package; the base resin composition alone does not grant compliance. RoHS evaluations should confirm no intentionally added cadmium, lead, mercury, hexavalent chromium, PBB, or PBDE in the finished compound. The grade is not designed for sustained peroxide-cured crosslinking at elevated temperature; selection of dicumyl peroxide should account for the low softening point and the potential for premature scorch in a 120 °C internal mixer.

When Lower Vinyl Acetate Content or Lower Melt Flow Rate Cannot Meet Process Requirements

Substitution of a lower VA grade such as an 18 wt% EVA typically raises Vicat softening point, increases Shore hardness, and improves tensile strength, but reduces adhesion to polar substrates and raises minimum seal temperature. If a converter requires seal initiation below 80 °C or adhesion to corona-treated aluminium foil, the 28 wt% VA level is the primary enabler. Conversely, when mechanical strength and creep resistance dominate, a lower VA or higher molecular weight EVA should be selected. The 20 g/10 min melt flow rate permits lower processing temperatures in injection moulding and hot-melt coating than a 3 g/10 min grade; however, the high-flow product is not suitable for blown film requiring high melt strength or for thick extruded profiles where sag resistance under gravity is essential.

In coextrusion, ATEVA 2820AG can serve as a seal layer or polar tie layer; the decision to use it instead of a maleic anhydride-grafted adhesive depends on the substrate and barrier layer. On corona-treated aluminium foil, seal strength should be measured under ASTM F88/F88M-21 at a seal pressure of 0.5 N/mm² and 1 s dwell. Published data for this specific product in high-barrier retort structures is limited, so laminators should conduct formal peel testing before specifying it in flexible packaging. Incoming quality control should verify melt mass-flow rate by ISO 1133-1:2022, vinyl acetate content by ASTM D5594-18a, and moisture content by ISO 15512:2019; incoming control data should be trended by statistical process control to detect lot-to-lot shifts before they affect die pressure or adhesion.