Elvax 360 EVA resina de copolímero, calçado e adesivos grau

Elvax 360 is a 25 wt% vinyl acetate ethylene-vinyl acetate copolymer with melt index of 2.0 g/10 min measured at 190°C/2.16 kg according to ASTM D1238, density of 0.95 g/cm³ according to ASTM D792, melting point of 77°C by differential scanning calorimetry, and Vicat softening temperature of 54°C according to ASTM D1525. The 25 wt% vinyl acetate comonomer places the resin in the high-VA segment used for flexible foam compounding, hot melt adhesive formulation, and solvent-borne footwear cement. The low degree of crystallinity reduces the melt temperature and broadens compatibility with rosin ester, polyterpene, C9 hydrocarbon tackifier, microcrystalline wax, and selected styrenic block copolymers. The melt index of 2.0 g/10 min provides sufficient cohesive strength in footwear foam compounds while remaining processable in hot melt compounding extruders with L/D ratio of 24:1 or higher. Incoming resin lots are checked for melt index and vinyl acetate content because a shift of ±0.3 g/10 min in melt index changes hot melt viscosity at 180°C by a measurable amount.

What Limits Expansion Ratio When Foaming Gas Evolution Outruns Peroxide Crosslinking?

In compression-moulded EVA midsoles, Elvax 360 is compounded at 100 phr base resin with 2.5–4.0 phr azodicarbonamide, 0.6–1.0 phr dicumyl peroxide on 40% active carrier, 1.0–2.0 phr zinc oxide, 0.5–1.0 phr stearic acid, and 5–15 phr calcium carbonate or talc filler. The compound is fluxed on a two-roll mill at 105–115°C until blowing agent dispersion is uniform. The sheet is pre-shaped and cured in a compression press at 165–175°C under 15–20 MPa platen pressure for 8–12 min. The critical process conflict is the relative rate of peroxide network formation and azodicarbonamide gas liberation. Mould temperatures above 175°C cause gas release before the EVA network develops sufficient melt strength, resulting in blowholes, split sheets, or cell collapse. Mould temperatures below 160°C delay peroxide cure, extend cycle time, and raise compression set because cell walls remain thermoplastic. Moving die rheometer data under ASTM D5289 are used to track t50 and t90 cure times; production troubleshooting on 500-ton compression presses commonly records t90 between 8 min and 12 min at 170°C. Two-roll mill gap is maintained at 0.5–1.0 mm during fluxing; overworking raises compound temperature above 115°C, causing premature peroxide reaction and increased compound viscosity. Apparent density is measured under DIN EN ISO 845 and is controlled between 0.15 g/cm³ and 0.25 g/cm³ for running shoe midsoles. Tensile strength is tested under ISO 1798, compression set under ISO 1856, and Asker C hardness is maintained at 45–60 for thin foam samples. Moisture levels above 0.1 wt% in calcium carbonate and other polar fillers degrade cell structure; a desiccant dryer at 60–70°C for 2–3 h is specified when ambient relative humidity exceeds 60%. Terminal products include expanded midsole sheets, die-cut running shoe midsoles, and compression-moulded sandal soles.

A chemically blown EVA toe puff or heel counter is laminated to non-woven or mesh lining using a hot melt adhesive in which Elvax 360 is blended at 30–40 wt% with rosin ester tackifier and paraffin wax. Application temperature is held at 160–180°C through a gear pump slot die. The resin melting point of 77°C permits lower pot temperature than polyamide or polyester hot melts, reducing heat distortion on heat-sensitive synthetic leather. Viscosity at 180°C is controlled between 1,000 mPa·s and 2,500 mPa·s under ASTM D3236. Viscosity below 1,000 mPa·s causes strike-through into open mesh; viscosity above 2,500 mPa·s reduces wetting on release-coated textile surfaces. T-peel adhesion is tested under ISO 11339 at 23°C and 50% relative humidity; production release specifications commonly require minimum values in the 2.0–3.0 N/mm range. Bonding is poor on untreated polypropylene and high-density polyethylene; corona pre-treatment to surface energy of at least 42 mN/m is required. On six-station rotary presses running indexing times of 8–12 s, the adhesive must develop green strength before ejection; set time is therefore evaluated on a laboratory hot melt tester at the same temperature and substrate combination. Terminal footwear components include fused toe puffs, heel counters, and collar laminates.

Hot Melt Viscosity Curves for Carton Sealing Lines Running Above 200 m/min

For high-speed case and carton sealing, Elvax 360 is combined with a C5/C9 aliphatic-aromatic hydrocarbon tackifier and microcrystalline wax at a typical ratio of 35:35:30 by weight, with 0.5–1.0 phr hindered phenolic antioxidant. The adhesive is compounded on a twin-screw extruder with L/D ratio of 30:1 and barrel zones set from 120°C to 180°C; the EVA is dry-blended with tackifier flake and wax prill before entering the feed throat. Viscosity at 180°C is held between 500 mPa·s and 1,200 mPa·s under ASTM D3236 because carton lines running above 200 m/min require open time below 8 s and rapid set to achieve fibre-tear failure on corrugated board. Application is performed with a heated slot nozzle or wheel applicator at 165–180°C. Pot temperature stability is critical because EVA oxidation increases viscosity and char formation in the melt tank. Thermal stability is evaluated by measuring viscosity under ASTM D3236 before and after circulating air oven exposure at 177°C for 72 h; viscosity increase above 20% indicates thermal degradation. Heat-fail temperature is measured under ASTM D4498 with a 500 g shear load. Adhesion to corrugated board is measured by T-peel under ASTM D1876, and fibre tear percentage is recorded at 4°C and 23°C after conditioning for 24 h. For food-grade carton closing, the formulated adhesive is checked against FDA 21 CFR 175.105 and relevant migration limits under Regulation EC 1935/2004 when contact with dry or fatty food is intended. Low-temperature flexibility in unheated warehouses is evaluated at -20°C using T-peel specimens conditioned for 24 h; formulations containing 40 wt% Elvax 360 and a lower-melting microcrystalline wax typically retain fibre tear at this temperature. Terminal products include sealed corrugated cases, tray-formed boxes, and food-contact secondary packaging.

Edge banding and profile wrapping adhesives represent a higher-viscosity melt system than carton sealing. The compound is filled with 20–30 wt% calcium carbonate or barium sulfate, and the Elvax 360 content is increased to 40–50 wt% to provide hot tack on PVC, ABS, melamine edging, and wood veneer. Application temperature is 180–200°C, and viscosity at 200°C is controlled between 8,000 mPa·s and 25,000 mPa·s under ASTM D3236. The adhesive is applied by roller coater to the edge banding and pressed to MDF or particleboard at line speeds of 15–40 m/min. Open time is below 5 s and set time below 2 s; delayed set results in spring-back of PVC edge banding and poor edge adhesion. The finished furniture panel is tested under DIN EN 204 for water resistance and heat resistance, with D3 or D4 classification depending on the end-use environment. Moisture content in filler above 0.2 wt% causes steam release, nozzle spitting, and inconsistent adhesive film weight; filled compounds are therefore dried before extrusion when ambient relative humidity exceeds 60%. A positive-displacement gear pump is preferred over screw pumping because of the high melt viscosity and need for constant coating weight on profiled edges. Terminal products include edge-banded furniture panels, kitchen cabinet doors, and profile-wrapped window frame sections.

Formulating Solvent-Based Cements for EVA Midsole Bonding

At 10–15 wt% solids, Elvax 360 is dissolved in a blend of toluene, methyl ethyl ketone, and cyclohexane for use as a primer or base cement in bonding EVA foam midsoles to rubber outsoles, leather, or synthetic textile uppers. The solution is prepared in a jacketed high-torque mix tank at 40–50°C with slow agitation to avoid shear-induced stringing; complete dissolution requires 4–6 h. Finished cement viscosity at 25°C is maintained between 1,500 mPa·s and 4,000 mPa·s on a Brookfield viscometer. The cement is applied by roll coater or brush to both substrates and dried in a forced-air tunnel at 55–65°C for 2–3 min before heat reactivation at 70–80°C and pressing. Peel adhesion is tested under ISO 11339 or ASTM D903; acceptable failure mode is cohesive within the foam or substrate, not adhesive at the interface. Solvent retention above 0.5 wt% causes bubble formation during heat reactivation and is measured by gas chromatography on conditioned specimens. Compliance requirements include the Industrial Emissions Directive 2010/75/EU Chapter V for volatile organic compound discharge, REACH Annex XVII restrictions on toluene supply to the general public, and national occupational exposure limits for methyl ethyl ketone. Chlorinated solvents are technically feasible but avoided in export footwear because of REACH Annex XVII restrictions on dichloromethane. The terminal process is a reactivated primer layer that supports the chloroprene or polyurethane adhesive system used in final footwear assembly.

Softcover spine gluing at 8,000–12,000 cycles/h requires an adhesive with wetting time long enough to penetrate folded signatures but short enough to avoid blocking. Elvax 360-based bookbinding hot melts are formulated at 30–35 wt% resin, 40–45 wt% hydrogenated hydrocarbon tackifier, and 20–25 wt% paraffin/microcrystalline wax blend. Application temperature is 150–170°C, and viscosity at 170°C is maintained between 400 mPa·s and 800 mPa·s under ASTM D3236. The adhesive is applied by roller wheel to the spine and side joints; open time is 10–20 s and set time is 5–10 s. Page pull strength is measured with a universal tensile tester at 23°C; production control limits are set at a minimum of 6 N/cm for coated paper spine stock, but published data for this specific configuration are limited. The main failure mode at high cycle speeds is cold adhesive starved penetration on high-clay coated papers, corrected by raising application temperature within the 150–170°C window or increasing nip pressure. Antioxidant loading is 0.5–1.0 wt% hindered phenolic plus secondary phosphite to limit viscosity drift during continuous running in the glue pot. Terminal products include softcover books, catalogues, and magazine blocks.

The following table consolidates three hot melt converting segments in which Elvax 360 serves as base polymer or modifier; values are representative manufacturing window ranges, not intrinsic resin specifications.

When Elvax 360 Replaces Low-VA Grades in Pressure-Sensitive Tape Formulations

In pressure-sensitive tape formulations, Elvax 360 is not a primary base polymer but is used at 5–15 wt% as a modifier in styrene-isoprene-styrene and styrene-butadiene-styrene hot melt pressure-sensitive adhesives. The 25 wt% vinyl acetate content increases the polar contribution to the solubility parameter and improves wetting on polyester film and PVC masking tape substrates compared with 12–18 wt% VA copolymers. The formulation is compounded at 160–180°C with a hydrogenated rosin ester or liquid C5 tackifier and mineral oil. After cooling, the adhesive is coated at 20–30 g/m² onto release paper and transferred to the film substrate. Peel adhesion at 180° is measured under ISO 29862 or PSTC-101; loop tack under PSTC-16; and shear resistance under PSTC-107. Addition above 15 wt% Elvax 360 raises room-temperature storage modulus too far and lowers loop tack below 5 N/25 mm, limiting use to non-critical masking and surface protection applications. The melt index of 2.0 g/10 min is less suitable for low-viscosity sprayable pressure-sensitive adhesive systems; slot die coating is preferred. Oxidative stability is checked by aging at 70°C for 7 days and measuring 180° peel retention; antioxidant loading is set at 0.5–1.0 wt% hindered phenolic plus secondary phosphite. Terminal products include surface protection films and low-adhesion masking tapes where clean removal and moderate peel are the primary specification.