Elvax 40W EVA Copolímero Resina,40% VA,Alta Grau de Elastómero

Elvax 40W is an ethylene-vinyl acetate copolymer resin containing a nominal vinyl acetate comonomer content of 40 wt% and is classified as a high-elastomer EVA grade. The polymer is supplied as pellets for hot-melt adhesive compounding, sealant formulation, wax modification, and polymer blending. Published typical values from the manufacturer’s technical data include a melt flow rate of 52 g/10 min at 190°C under a 2.16 kg load measured according to ISO 1133-1:2022 /ASTM D1238-20, a density of 0.965 g/cm³ under ISO 1183-1:2019 /ASTM D792-20, tensile strength at break in the range of 5–6 MPa and elongation at break of 1000% under ISO 527-2:2012 /ASTM D638-14, Shore A hardness of 40 under ISO 48-4:2018 /ASTM D2240-15(2021), and ring-and-ball softening point of approximately 104°C under ASTM E28-18. These values are typical lot data, not release specifications; the certificate of analysis for the supplied batch controls conformance.

The elevated vinyl acetate content alters the crystalline–amorphous balance of the ethylene backbone. Differential scanning calorimetry shows a broad melting endotherm rather than the sharp crystalline melt associated with low-vinyl-acetate ethylene copolymers. The reduction in polyethylene-type crystallinity produces the Shore A hardness of 40, the high elongation at break, and pronounced low-temperature flexibility observed on production-scale adhesive lines. The polar acetate groups also increase interaction with polar substrates such as corona-treated polyester, anodized aluminium, and glass. The same polarity broadens solubility in ketones, esters, aromatic hydrocarbons, and selected alicyclic solvents, which is exploited in solvent-borne adhesives and gravure coating binders.

What Distinguishes a 40 Wt% Vinyl Acetate Copolymer from Lower VA Grades?

The principal difference between Elvax 40W and lower-vinyl-acetate EVA grades is the suppression of crystallinity and the corresponding shift toward elastomeric behaviour. A grade at 25 wt% vinyl acetate retains greater room-temperature stiffness and higher tensile strength, while a grade at 18 wt% vinyl acetate is harder and more resistant to creep at elevated service temperature. Elvax 40W, by contrast, delivers greater surface tack, better wetting of polar films, and a softer failure mode. The melt flow rate of 52 g/10 min also differentiates it from lower-flow grades used in blown film or extrusion lamination; the higher flow reduces melt pressure in narrow slot die coating and permits lower processing temperatures in hot-melt mixing.

When compared with a 28 wt% vinyl acetate grade of lower melt flow rate, Elvax 40W shows lower elastic recovery and lower cohesive strength after hot-melt setting. This makes it suitable as a high-tack component in formulations where rapid polar-substrate wetting is more important than high shear resistance. In contrast, a lower-VA grade is preferred when a bond must retain holding power under constant load in a warm warehouse. These differences are evaluated on production lines through peel adhesion tests on aluminium foil or treated PET film using 90° or 180° geometries adapted from ASTM D6862-11 and ASTM D903-98(2022). The measured values are formulation-dependent because tackifier and wax ratios modulate the final adhesive hardness, set speed, and thermal resistance.

The high vinyl acetate level also alters melt rheology. At a given temperature, Elvax 40W exhibits a lower zero-shear viscosity than a low-MI EVA with the same comonomer content, but its polar interactions can produce more pronounced shear thinning when compounded with rosin ester tackifiers. Rotational rheometry using parallel-plate geometry at 160°C and 1 rad/s is used on some compounding lines to monitor the influence of tackifier acidity on the EVA phase. Batch-to-batch variation in tackifier acid number, typically 5–15 mg KOH/g for rosin esters, can shift the apparent cross-link density or cause catalytic ester exchange during extended heating; this is a practical reason to control incoming tackifier quality rather than to rely solely on resin specification.

When a Hot-Melt Adhesive Holding Tank Reaches the 180°C Upper Processing Boundary

Hot-melt processing of Elvax 40W is commonly performed in jacketed vertical or sigma-blade mixers at 150–180°C. The upper temperature limit is governed by the onset of acetic acid elimination from the vinyl acetate comonomer. In production trials on a 500 L nitrogen-blanketed holding tank, melt held at temperatures exceeding 180°C for more than 4 h has shown measurable viscosity drift and the development of an acrid odour. The degradation route is deacetylation followed by chain scission and colour formation; it accelerates as liberated acetic acid lowers the local pH in the melt. A nitrogen cover and a short first-in, first-out melt schedule are common controls on continuous coating lines.

Stabilization is usually achieved with a hindered phenolic primary antioxidant and a phosphite secondary antioxidant at combined loadings of 0.1–0.3 wt%. The exact package must be validated in the full adhesive formulation because acidic tackifiers and fillers can deactivate certain phosphites. Quality-control laboratories track viscosity stability on a cone-and-plate rheometer at 160°C and monitor the carbonyl index after accelerated ageing at 150°C in forced-air ovens. A rise in carbonyl absorbance above a formulation-specific threshold indicates deacetylation and oxidative degradation; this is a more reliable control than visual colour alone because some tackifiers darken without creating acidic decomposition products.

For slot-die adhesive coating, the melt temperature at the die is normally maintained between 150°C and 180°C to achieve uniform coat weight without exceeding the degradation threshold. The melt flow rate of 52 g/10 min permits low melt pressure in die internal cavities, but it also reduces the film strength of the applied molten layer before setting. Coaters handling low-VA grades at higher temperatures may need to lower the die temperature by 10–20°C when switching to Elvax 40W. The same principle applies to extrusion of tapes and profiles: barrel settings should not copy higher-melting polyolefin profiles, and the feed zone should remain below 40°C to prevent pellet bridging.

Moisture management is another boundary condition. Although EVA is not as hygroscopic as polyamide or TPU, the high vinyl acetate content increases moisture uptake relative to nonpolar polyethylene. Pellets stored in humid warehouses can adsorb surface moisture, which may hydrolyse ester groups during extended hot-melt hold times and create surface defects in extruded profiles. A desiccant dryer operating at 55–65°C for 4 h is a standard precaution when ambient relative humidity exceeds 60% or when the finished surface must meet strict visual criteria. The use of a nitrogen blanket on the melt also reduces hydrolytic degradation by displacing humid air at the melt surface.

Compounding and Dispersion Boundaries in Polymer Modification

Elvax 40W is used as a flexibilising modifier in compounds based on PVC, polyolefin recyclates, bitumen, and selected engineering thermoplastics. Dispersion is best achieved in a co-rotating twin-screw extruder with an L/D ratio of 44:1 and a screw profile that includes kneading blocks in at least two zones. The polar vinyl acetate groups promote compatibility with chlorinated polymers and with polyolefin matrices that contain oxidized or maleated fractions. In PVC sheet modification, the resin is typically added at 10–30 phr to improve low-temperature impact; the exact loading depends on the plasticizer system and the desired hardness. Mechanical property validation is performed under ISO 527-2:2012 for tensile behaviour and ISO 6721-10:2015 for dynamic mechanical analysis.

The high melt flow of Elvax 40W does not guarantee simple feeding. Pellet surface softening at feed-zone temperatures above 40°C has caused bridging and flow interruptions in dilute-phase conveying systems on production lines handling this grade. A cooled feed throat and a grooved barrel section are standard. In addition, the resin should not be preblended with calcium carbonate or other acid-sensitive fillers in a high-shear mixer for long periods because local heating can generate traces of acetic acid that attack filler surfaces and increase die lip build-up. If calcium carbonate is required, it is usually introduced downstream in the twin-screw process, after the EVA has fully melted and been dispersed into the matrix.

In bitumen modification, Elvax 40W is dispersed into hot bitumen at 160–180°C in a rotor-stator mixer or a high-torque paddle mixer. The high VA content improves low-temperature elastic recovery of the modified binder, but it also increases storage viscosity more than an equivalent loading of a lower-VA EVA. Addition levels are usually kept below 5 wt% of the binder to avoid phase separation or excessive viscosity build. Storage stability is tested by a tube test at 180°C for 72 h, with the difference in softening point between top and bottom sections used as a control metric. Published data for this specific configuration are limited because local bitumen composition and asphaltene content strongly influence the result; pilot testing is therefore required before production implementation.

Polymer modification also benefits from the elastomeric character of the 40 wt% vinyl acetate comonomer. In polyolefin recyclate streams, addition of Elvax 40W at 5–15 wt% can reduce brittle failure and improve weld-line strength in injection-moulded parts. The process is performed on injection moulding machines with clamp force settings between 800 kN and 1200 kN for medium-sized parts, with melt temperature typically between 130°C and 160°C. Higher melt temperatures are avoided to limit deacetylation. The resulting compound is evaluated by notched Izod impact testing under ISO 180:2019 /ASTM D256-10 and by melt flow rate measurement under ISO 1133-1:2022. These data allow the compounder to adjust let-down ratios without pushing the blend into an overly soft, creep-sensitive region.

For solvent-borne adhesive applications, Elvax 40W is commonly dissolved in toluene or methyl ethyl ketone at 20–30 wt% solids using a high-torque anchor stirrer operating at 60–80 rpm. The high acetate content reduces the energy input required to reach a clear solution compared with lower-VA EVA grades, but the resulting solution remains sensitive to moisture condensation during storage because both the polar solvent and the polar comonomer attract atmospheric water. In gravure printing inks and overprint varnishes, the resin is used as a binder component where low-temperature flexibility and pigment wetting are required. The finished ink should be filtered through a 10 μm absolute filter after letdown to remove microgel particles that may form if the solution is overheated above 60°C during dilution. Food-contact status must be evaluated on the finished article because migration limits are governed by the complete adhesive or ink system under FDA 21 CFR 175.105, FDA 21 CFR 177.1350, or EU Regulation 10/2011 as applicable.

The resin should not be combined with amine-based additives without preliminary oven ageing. Although amine stabilizers are effective in some polyolefin systems, they can contribute to colour instability in high-VA EVA melts because the amine functionality interacts with acidic decomposition products. Accelerated ageing at 150°C in a forced-air oven for 7 days is a practical screening test for additive packages intended for long-term hot-melt stability. If a formulation requires a nitrogen-containing rheology modifier or adhesion promoter, the supplier’s technical recommendation should be confirmed by measuring colour change, acidity, and melt viscosity retention in the full compound rather than in the neat resin.