Copolímero de acetato de vinilo de etileno ELVAX CE9619-1

ELVAX CE9619-1 Ethylene Vinyl Acetate Copolymer is a pelletized ethylene-vinyl acetate copolymer supplied under the DuPont ELVAX trademark. Supplier technical literature identifies the grade as having a nominal vinyl acetate comonomer content of 28 wt% by ISO 8985, a nominal melt mass-flow rate of 6 g/10 min at 190°C under 2.16 kg load by ISO 1133-1:2022, and a nominal density of 0.950 g/cm³ by ISO 1183-1. The resin is stabilized against oxidative degradation during compounding and storage, but the exact additive package and lot-specific values must be confirmed against the certificate of analysis. Its comonomer content places it in the polar, flexible segment of ethylene copolymers; the material is therefore specified for hot-melt adhesive compounding, wax-based coating modification, polymer modification, and extrusion laminating where adhesion to polar substrates and low-temperature flexibility are process requirements.

Molecular Architecture and Comonomer Distribution Consequences

The 28 wt% vinyl acetate content disrupts polyethylene crystallinity by shortening methylene sequences and introducing acetate side groups. Differential scanning calorimetry under ISO 11357-3 typically shows a broad crystalline melting peak in the 65–75°C range for this comonomer level, compared with a melting peak above 90°C for a 12 wt% VA grade. The reduced crystallinity lowers the Vicat softening point to approximately 60°C or below and reduces tensile modulus; under ISO 527-2, a 28 wt% VA ethylene copolymer typically exhibits a secant modulus below 50 MPa, whereas a 12 wt% VA grade may exceed 80 MPa. The acetate group also increases polarity, improving compatibility with rosin ester tackifiers, pentaerythritol tetraesters, and partially hydrogenated wood rosins. The same polarity increases equilibrium moisture sorption relative to low-VA EVA; pellets stored at relative humidity above 60% can pick up sufficient surface moisture to require pre-drying before extrusion. These molecular differences are the basis for product substitution decisions: CE9619-1 is selected over low-VA grades where adhesion to aluminium, polyester, or paper fibres is more important than stiffness, heat resistance, or moisture-barrier performance.

In hot-melt adhesive production, the resin is compounded in heavy-duty sigma-blade mixers or planetary mixers at jacket temperatures of 150–180°C. In a 40:1 L/D co-rotating twin-screw extruder, a typical barrel profile runs from 140°C in the feed zone to 190°C at the die, with melt temperature held below 230°C. The thermal stability limit is not an arbitrary value; vinyl acetate sequences begin acetic acid elimination at elevated temperature, and production lines that exceed 230°C for more than 10 min often observe viscosity drift, gas generation, and corrosion pitting on unplated screw and barrel surfaces. For formulation monitoring, melt viscosity is checked by a Brookfield viscometer at 180°C; a typical carton-sealing hot melt based on 30–35 wt% CE9619-1, a compatible tackifier, and 20–30 wt% paraffin or microcrystalline wax falls in the 0.5–2.0 Pa·s range at application temperature. Open time is application-dependent, but formulations applied at 150–170°C through slot nozzles generally produce open times of 5–20 s and fibre-tearing bonds on recycled corrugated stock at surface temperatures above 5°C. Below that surface temperature, substrate heat loss quenches the melt before fibre penetration, producing adhesive failure at the starch-coated surface layer.

When CE9619-1 Replaces a 12 wt% VA Grade in Wax-Based Coating Formulations

When the resin is evaluated as a replacement for a 12 wt% VA grade in paraffin or microcrystalline wax coating compounds, the crystallisation behaviour and failure mode change. A 28 wt% VA grade forms smaller, less ordered crystallites, which lowers the onset of the crystalline freezing transition and extends the tack-free time. In a model coating containing 60 wt% fully refined paraffin wax, 30 wt% CE9619-1, and 10 wt% rosin ester, a 50 µm coating on kraft stock may require 10–30 s longer to reach non-blocking under 23°C forced air than the equivalent low-VA formulation. The benefit is an improvement in flex crack resistance at freezer temperatures and higher adhesion to paper fibres; the penalty is an increase in water vapour transmission rate. Under 38°C and 90% RH with ASTM E96/E96M or DIN 53122-1, EVA-containing wax coatings with 28 wt% VA are reported to transmit water vapour at rates 2–5× those of 12 wt% VA formulations of equal thickness. If the coating is intended for frozen-food barrier packaging, the higher WVTR must be offset with a thicker coating or an additional barrier layer. On a production wax coater running at 300 m/min, the replacement usually requires a 5–10°C reduction in application temperature because the lower crystallinity of CE9619-1 reduces hot-melt viscosity at the same temperature.

What Pellet Handling and Extrusion Precautions Apply to CE9619-1?

Moisture control is the first process boundary. Although EVA is not hydrolytically sensitive in the same manner as PET or polyamide, surface moisture on pellets entering a melt stream above 180°C can produce splay, bubbles, and local viscosity reduction. Pre-drying is recommended at 60–70°C for 4 h in a desiccant-bed dryer with a dew point of at least -20°C whenever pellet moisture exceeds 0.1 wt%. The resin should be processed at melt temperatures no higher than 230°C; for thin-gauge cast film or extrusion coating, a vented barrel and a corrosion-resistant screw/barrel combination are recommended. At shutdown, the machine should be purged with a low-MFI LDPE at 200°C until the melt appears clear; EVA residue left in a hot barrel degrades to acetic acid and can cause pitting on nitrided surfaces. On a production-scale 30:1 L/D single-screw cast-film line, a typical temperature profile is 120–180°C from feed to die, with die temperature at 180°C and chill roll at 15–25°C. Because the melt strength of CE9619-1 is lower than that of a 12 wt% VA grade, draw resonance and edge neck-in appear at lower draw ratios; an air knife positioned close to the die and a short air gap reduce these defects.

Compounding CE9619-1 into polypropylene or polyethylene is performed on a co-rotating twin-screw extruder; the EVA pellets should be side-fed into the melt or introduced through a cooled feed throat because hopper temperatures above 35°C can soften the pellet surface and cause bridging. In polypropylene impact modification at 10–15 wt%, dispersing the EVA domains requires a viscosity ratio near 1.0. If the ratio deviates by more than one decade, the phase morphology becomes coarse and the notched Izod impact energy under ISO 180 does not improve proportionally. At 6 g/10 min, CE9619-1 is in a moderate melt-flow range; it disperses more easily than an EVA grade below 2 g/10 min but provides less cohesive strength in a compound than a grade below 1 g/10 min. In olefin-based antifog or cling masterbatches, addition levels above 20 wt% reduce flexural modulus by roughly 30–50 MPa per 10 wt% when measured by ISO 178. The exact offset depends on host crystallinity and whether the EVA is grafted or crosslinked in a subsequent peroxide step.

Tensile and dynamic mechanical behaviour follow the same comonomer trade-off. Under ISO 527-2, a 28 wt% VA EVA of this melt-flow class typically exhibits elongation at break above 700%, Shore A hardness near 80 by ISO 868, and tensile strength below 25 MPa. The storage modulus at 23°C is lower than that of a 12 wt% VA EVA by approximately 40–60%, while the loss tangent peak shifts to a lower temperature. This shift matters in injection-molded footwear components or extruded gaskets: CE9619-1 provides softer feel and greater energy dissipation at ambient temperature but reduces creep resistance under load above 45°C. In dynamic mechanical analysis at 1 Hz, the plateau modulus begins to fall between -20°C and 0°C; above 70°C, viscous flow becomes pronounced, limiting continuous service in load-bearing applications. These properties distinguish the grade from high-VA EVA materials: a 40 wt% VA grade is softer and has lower heat resistance, while a 12 wt% VA grade is stiffer and more creep-resistant but less adhesive to polar substrates.

Food-Contact Migration Limits Are Not Identical to PVC Requirements

For food-contact evaluation, the grade may be assessed under 21 CFR 177.1350 for ethylene-vinyl acetate copolymers, provided the finished article meets the extractives limitations and use restrictions in that section. In the European Union, the finished article is evaluated under Regulation (EU) No 10/2011; overall migration must not exceed 10 mg/dm² of food-contact surface area unless the specific food type and worst-case time/temperature support a different limit. Paper and board coatings containing CE9619-1 and paraffin wax are commonly tested with food simulant D1 for aqueous foods and simulant D2 for fatty foods under 40°C for 10 days or 70°C for 2 h depending on the intended use. REACH Regulation 1907/2006 and RoHS Directive 2011/65/EU documentation are normally supplied through the raw material compliance statement. Because ethylene-vinyl acetate copolymer is not a PVC compound, the restrictions on cadmium-based stabilisers and certain phthalate plasticisers that apply to flexible PVC are not the same; however, this does not imply automatic food-contact approval for every formulation. Published migration data for CE9619-1 in direct retort contact are limited, and end-users must conduct specific migration testing before commercial approval.

Compared with ethylene acrylic acid copolymers and ionomers, CE9619-1 has lower oil and grease resistance because the acetate ester group is more hydrolytically labile and lacks ionic crosslinks. Under ASTM D543, a 7-day exposure to IRM 903 oil at 23°C commonly produces 10–20% mass uptake in a 28 wt% VA EVA, while a partially neutralised ionomer may show <5% uptake under the same conditions. EVA is therefore not recommended for under-hood seals or oil-contact parts with sustained service above 80°C. Conversely, CE9619-1 processes at lower temperatures than ionomers and has broader compatibility with rosin ester and hydrocarbon tackifiers, which is the reason for its use in hot-melt adhesive systems. In a 50/50 melt blend with rosin ester, the cloud point is typically 15–25°C lower than a comparable low-VA EVA blend because polar-polar interactions suppress phase separation.