Elvax 470 EVA resina de copolímero, adesivos e selantes grau

Elvax 470 EVA Copolymer Resin, Adhesives & Sealants Grade, is an ethylene-vinyl acetate copolymer supplied as solid pellets. The resin has a nominal vinyl acetate content of 18 wt% and a melt mass-flow rate of 0.7 g/10 min measured at 190 °C with a 2.16 kg load according to ASTM D1238 and ISO 1133-1:2022. Density is 0.940 g/cm³ by ASTM D1505. The product sits at the high-molecular-weight end of the 18 wt% vinyl acetate series and is selected where a high-viscosity, low-flow adhesive or sealant base is required. In compounded hot-melt adhesives, the low melt index produces higher cohesive strength and lower substrate penetration than lower-molecular-weight grades; the unmodified resin is not intended for unsupported film extrusion without plasticizer or tackifier modification.

How Does the 0.7 g/10 min Melt Index Alter Hot-Melt Rheology?

At a fixed addition level, Elvax 470 raises Brookfield viscosity at 180 °C more than Elvax 450 or Elvax 460 because of its higher weight-average molecular weight. The melt mass-flow rate of 0.7 g/10 min is 11.4 times lower than the 8 g/10 min nominal value for Elvax 450 and 3.6 times lower than the 2.5 g/10 min nominal value for Elvax 460. This difference appears most directly in hot-melt pump pressure and bead profile. Formulations using Elvax 470 at 20–25 wt% in a wax-tackifier carrier generally require application temperatures of 170–190 °C to maintain nozzle flow; viscosity is generated and recorded by ASTM D3236 with a Thermosel. The high molecular weight increases melt tension and reduces squeeze-out; however, tackifier compatibility decreases and phase separation should be checked by hot-stage microscopy or by a controlled cooling viscosity sweep from 180 °C to 120 °C. Published data for this specific grade in all tackifier combinations is limited.

Compounding of Elvax 470 in a jacketed twin-screw extruder with L/D 40:1 is carried out with barrel setpoints of 150 °C, 160 °C, 170 °C, and 175 °C across zones 1–8 and a die temperature of 180 °C. Because the resin has a melt mass-flow rate of 0.7 g/10 min, viscous dissipation can increase melt temperature by 8–15 °C above the barrel setpoint at screw speeds above 200 rpm; barrel vents are maintained open to remove acetic acid from any thermal deacetylation. Continuous processing above 220 °C accelerates deacetylation and can cause corrosion of non-stainless steel surfaces. In open sigma-blade mixers, nitrogen blanketing is recommended when residence time exceeds 30 minutes at 180 °C. Pellet moisture is low; however, condensation from storage in unheated warehouses at relative humidity above 60% may require drying at 55–60 °C for 3–4 hours to prevent steam bubbles in extruded bead.

Solvent-Based Adhesive and Sealant Formulation Boundary

In solvent-borne systems, Elvax 470 dissolves in toluene, xylene, methyl ethyl ketone, and mixtures thereof; dissolution requires high-shear mixing and heating to 60–80 °C because of the high molecular weight. Typical solids contents in production batches are 25–35 wt%; final solution viscosity is measured by ASTM D2196 and adjusted with solvent composition. High-molecular-weight EVA grades require longer wet-out time on porous substrates and produce films with higher tensile modulus after solvent evaporation, but the resin is not a standalone structural adhesive and must be compounded with tackifiers, fillers, and antioxidants. For sealants, the resin contributes slump resistance and flexibility; slump is checked by ASTM D2202 or ASTM D3730.

In hot-melt packaging adhesives, Elvax 470 is typically added at 15–25 wt% to a carrier containing 20–35 wt% paraffin wax and 45–60 wt% tackifying resin. Application temperature is set at 170–190 °C for wheel, slot, and jet applicators. The high melt viscosity reduces penetration into corrugated board and improves bead definition. Heat-fail temperature is measured by ASTM D4498; formulations with Elvax 470 generally show higher heat-fail values than Elvax 450 because the higher molecular weight resists creep. Low-temperature adhesion is assessed by ASTM D1876 T-peel on conditioned substrates at -18 °C. Published data for this specific configuration is limited.

In wax-blend modifiers, Elvax 470 increases melt viscosity, flexibility, and block resistance. Addition of 5–15 wt% to paraffin wax raises the softening point and reduces brittleness; the viscosity shift is measured by ASTM D3236 at 120 °C. The high molecular weight produces a more continuous polymer network in the wax matrix than Elvax 450, which improves scuff resistance and low-temperature flex cracks. However, addition above 15 wt% can raise melt viscosity beyond the operating range of standard wax coaters; this is a transition zone where phase inversion may occur, visible as a change in optical clarity and a sharp viscosity increase. Published data for this specific concentration range is limited.

The 18 wt% Vinyl Acetate Series Spans a Wide Processing Window

The same 18 wt% vinyl acetate content is available across a range of melt indices from 0.7 g/10 min to 500 g/10 min. Selection is governed by application method, required cohesive strength, and substrate penetration.

Elvax 470, with 18 wt% vinyl acetate, is less polar than 28 wt% vinyl acetate grades and therefore exhibits greater compatibility with paraffin wax and lower moisture vapor transmission, but less specific adhesion to polar substrates such as untreated aluminum and glass. When bonding to polyethylene terephthalate or aluminum, adhesion is improved by using rosin esters or hydrocarbon tackifiers rather than by increasing vinyl acetate content. The 18 wt% vinyl acetate level also provides a wider processing window in wax blends because lower polarity reduces phase separation on cooling. The resin is not a direct replacement for 28 wt% vinyl acetate grades in applications requiring maximum adhesion to polar surfaces.

When Thermal Degradation Limits Continuous Run Time

Thermal deacetylation of the vinyl acetate component is the principal process conflict. At melt temperatures above 220 °C, acetic acid evolution becomes measurable, and above 250 °C the reaction rate accelerates autocatalytically. The acetic acid attacks mild steel and can cause pinholing in thin-wall extrusion dies; stainless steel 316L wetted parts and chromed dies are used when production runs exceed 8 hours. Ventilated extraction is required at the die face, with acetic acid exposure maintained below applicable occupational exposure limits. The resin should not be processed with zinc oxide or alkali-metal compounds at high temperature because these catalyze deacetylation. Re-grind should be limited to 20 wt% in single-screw extrusion to avoid viscosity drift.

Operational limitations include continuous melt temperature below 220 °C, avoidance of prolonged storage above 40 °C in unvented bulk bags, and exclusion of strong oxidizing agents. Elvax 470 is not designed for solvent-free structural bonding or for continuous load-bearing service above 80 °C without crosslinking; creep is a limitation under sustained stress. For applications requiring low viscosity at 150 °C, Elvax 450 or Elvax 460 may be selected instead to reduce pump pressure and nozzle stringing.

Regulatory status is application-specific and must be confirmed with current manufacturer certifications. The following matrix lists test methods and typical controls.