Elvax 150W EVA resina de copolímero, adesiva e revestimento grau

Elvax 150W EVA Copolymer Resin, Adhesive & Coating Grade is supplied in pellet form and is specified for hot-melt adhesive, solvent-based coating, and wax-blend modification. The grade carries a nominal vinyl acetate comonomer content of 32 wt%, a melt index of 43 g/10 min measured under ASTM D1238 at 190°C with 2.16 kg load, and a solid density of 0.95 g/cm³ determined by ASTM D1505 or ISO 1183-1:2019. These three parameters define the specification envelope: comonomer fraction controls polarity, melt index controls flow, and density reflects reduced crystalline packing. The random incorporation of 32 wt% vinyl acetate along the polyethylene backbone shortens crystallizable ethylene sequences, lowers the melting range, and increases solubility in aromatic, ketone, and ester solvents relative to lower-VA ethylene-vinyl acetate grades. The resin is therefore positioned between low-VA extrusion/lamination resins and high-VA coating resins in the supplier’s adhesive and coating product portfolio.

For adhesive and coating grades, tensile and peel data on the neat resin are less decisive than melt index and vinyl acetate content. Compounded formulations are tested under ASTM D903, ASTM D1002, or ASTM D1876 according to end-use substrate. Published data for the unbonded ultimate tensile strength of Elvax 150W is limited because the grade is supplied for formulated systems rather than as a stand-alone structural polymer.

How Does a 32 Weight Percent Vinyl Acetate Fraction Alter Adhesive Cohesion and Tack?

At 32 wt% vinyl acetate, the copolymer has a lower crystalline fraction than low-VA grades in the 18–20 wt% range, which reduces elastic modulus and shifts failure from brittle to ductile in thin adhesive layers. The glass transition remains below −20°C, so low-temperature flexibility is retained in packaging and bookbinding applications. The polar acetate carbonyl groups increase interactions with aluminum, corona-treated polyester, and paper fiber; however, adhesion to untreated polyolefins remains diffusion-limited. In hot-melt adhesives, Elvax 150W functions as the base polymer rather than the tack source. Cohesive strength in the final formulation is dominated by tackifier softening temperature and wax crystal network. Standard ASTM D903 T-peel testing on stainless steel is used to balance interface adhesion and cohesive failure; a shift from peel failure to cohesive stringing often occurs when rosin ester tackifier loading exceeds 40 wt% of the total adhesive. Published data for this exact threshold in every formulation is limited because substrate preparation and coating weight alter the transition.

Hot-melt adhesive compounding with Elvax 150W places the resin at 20–35 wt% of the total formulation. Twin-screw extrusion with L/D 48:1, modular kneading blocks, and vacuum devolatilization is used on production lines because the low melt viscosity can cause insufficient shear in single-screw equipment. Barrel set points of 120–160°C and screw speed of 250–400 rpm are typical starting conditions; the melt temperature should not exceed 180°C to limit vinyl acetate ester degradation. Slot-die coating lines operating at 150–200 m/min use gear-pump pressure control to compensate for ±5% batch-to-batch melt index variation. The lower molecular weight of Elvax 150W reduces melt strength; formulators seeking higher heat resistance in low-pressure bonding often blend the grade with a low-MI EVA at 10–15 wt% addition while retaining the melt-flow contribution of Elvax 150W. In high-speed carton and case-sealing lines, the resin permits clean nozzle cut-off because its low melt strength reduces stringing at application temperatures between 150°C and 170°C; however, pot stability above 180°C becomes the limiting parameter rather than application viscosity.

When Elvax 150W Is Dissolved in Solvent-Based Coating Formulations

Solvent-based coating lines employ Elvax 150W because the high vinyl acetate fraction permits dissolution in toluene, xylene, methyl ethyl ketone, and ethyl acetate at 40–60°C under high-shear mixing. Lower-VA EVA grades of equivalent melt index require higher temperatures or chlorinated co-solvent additions. At 20 wt% resin solids in toluene, the solution is pseudoplastic; Brookfield viscosity is measured with an RV spindle series at 25°C after 24 h equilibration because chain disentanglement time influences apparent viscosity. Reverse-roll and comma coating equipment benefit from low die swell and reduced ribbing defects. Drying of films above 25 μm dry film thickness requires staged ovens at 60°C, 90°C, and 120°C to reduce residual solvent below 1 wt%; forced-air velocity above 5 m/s at the wet layer is typical but is not a product constant. The low molecular weight of Elvax 150W also lowers solution elasticity, which can reduce edge bead rupture during coating start-up; this advantage is offset by lower extensional viscosity during fiber coating, where high-molecular-weight EVA may be preferred.

Adhesion to low-density polyethylene and untreated polypropylene remains limited without surface oxidation. Corona discharge treatment to a wetting tension of 38–42 mN/m is usually specified; flame treatment is an alternative for irregular profiles. On aluminum foil, the vinyl acetate carbonyl groups interact with surface hydroxyls but do not form covalent bonds; primers such as epoxy silane are required for retort or hot-water immersion performance. On paper and cellulosic substrates, the grade can penetrate fiber voids at coating temperatures of 150–170°C, increasing mechanical interlocking but also increasing strike-through if viscosity falls below 1000 mPa·s.

Wax Blend Modification and Viscosity Depression Limits

In wax-based coatings, investment casting patterns, and paper saturants, Elvax 150W is added at 2–10 wt% to paraffin or microcrystalline wax to reduce brittleness and improve low-temperature flex resistance. The resin does not fully co-crystallize with long-chain n-paraffin; differential scanning calorimetry under ASTM D3418 shows a broad melting endotherm and a lowering of the sharp paraffin solid-solid transition. The congealing point of the blend, tested under ASTM D938, increases as the resin content approaches 10 wt%; beyond 15 wt% addition, phase inversion may occur, producing a tacky surface that complicates release from slush-molding tooling. In cone-and-plate viscometry at 100°C, the molten wax-EVA blend shifts from Newtonian to shear-thinning as the EVA forms a dispersed elastomer-rich phase. This behavior is used to control sag resistance in dip-coating operations but reduces effectiveness of filtration through 100 μm mesh filters when the EVA phase remains undispersed. Published data for the exact phase-inversion point in complex commercial wax blends is limited; the 15 wt% boundary should be validated on the specific paraffin grade and cool-down profile used in production.

Evaluating the Difference from Low-Melt-Index Extrusion and High-VA Coating Grades

Elvax 150W occupies a narrow formulation window between low-VA structural grades and high-VA coating resins. The comparison below is based on nominal property ranges for typical adhesive and coating EVA types; lot-specific certificates should be used for specification limits.

The difference between Elvax 150W and lower-VA grades is not solely polarity. Melt index also controls wetting speed and penetration into porous substrates. A lower-MI EVA with similar VA content forms higher molecular weight networks, giving higher cohesive strength but requiring higher processing temperature and shear. A higher-MI high-VA grade may offer better solubility and adhesion to polar substrates, but its lower molecular weight reduces heat resistance and can cause tackifier bleed in aged bonded assemblies. Elvax 150W is therefore selected when the formulator requires a balance of low melt viscosity, moderate polarity, and solubility in standard solvent systems without the high-temperature processing burden of low-MI ethylene-vinyl acetate copolymers.

Regulatory Conformance and Substrate Compatibility Boundaries

Formulations based on Elvax 150W may be assessed under FDA 21 CFR 175.105 for food-contact adhesives and 21 CFR 177.1350 for ethylene-vinyl acetate copolymer food-contact articles, provided the migration and end-test criteria of the referenced sections are satisfied. European food-contact assessment uses EU 10/2011 for overall migration and specific migration of vinyl acetate monomer; REACH registration status should be confirmed on the supplier’s safety data sheet, and RoHS directive 2011/65/EU restricts cadmium, lead, mercury, and hexavalent chromium in electrical and electronic applications. The main incompatibility is with strong oxidizing agents and amine-based additives at processing temperatures above 180°C; basic amine species can accelerate ester hydrolysis and release acetic acid, increasing corrosion risk in downstream die and roll equipment. This boundary is especially relevant in high-speed adhesive coating where recycled process trim may carry residual amine-functional inks or coatings into the melt loop.

Pre-drying at 60°C for 2–4 h is recommended when pellets have been exposed to relative humidity above 60%. Storage in sealed containers below 40°C and inert-gas blanketing of bulk conveying lines reduce moisture pickup and oxidative yellowing. In hot-melt tanks, prolonged residence time above 180°C can produce detectable acetic acid within 4–8 h; thermal stabilizers extend the hold time but may reduce peel adhesion when added above 0.5 wt%. Equipment cleanout after processing Elvax 150W should be performed with a low-MI polyethylene purge rather than high-acid purges to avoid cross-contamination of subsequent low-VA extrusion runs.