EVATHENE UE4003 EVA resina de copolímero, 40% VA, grau de espuma

EVATHENE UE4003 is an ethylene-vinyl acetate copolymer resin containing a nominal 40 wt% vinyl acetate comonomer. The producer designates the material as a foam-grade resin for cellular articles produced by compression molding, roll-fed continuous expansion, or injection foam conversion. Under ISO 1133-1:2022 with a 190 °C barrel temperature and 2.16 kg load, its melt mass-flow rate is listed at 3.0 g/10 min. Density at 23 °C is near 0.97 g/cm³ when measured according to ISO 1183-1:2019. The resin is supplied as free-flowing pellets and is used in crosslinked footwear midsole compounds, shock-absorbing mat compounds, foam tapes, thermal insulation boards, and cushioning layers where higher vinyl acetate content improves filler uptake and low-deflection recovery. The 40 wt% vinyl acetate level places UE4003 beyond conventional packaging and general-purpose EVA grades, reducing crystalline polyethylene domains and producing a lower-modulus, higher-elongation cellular structure after expansion. The grade is selected not as a direct drop-in substitute for low-VA EVA but as a formulated base resin for peroxide-cured and blowing-agent-activated systems.

How Does 40 wt% Vinyl Acetate Alter Thermal Transition and Melt-Phase Rheology?

Vinyl acetate comonomer disrupts polyethylene crystallinity. At 40 wt% incorporation, the crystalline fraction measured by thermal analysis is typically below 10 % when referenced to the 293 J/g heat of fusion for fully crystalline polyethylene; an 18 wt% VA copolymer often retains 20 % to 40 % crystalline fraction. This morphological shift lowers the DSC melting endotherm from approximately 85 °C for low-VA resin to a broad melting range of 50 °C to 65 °C for UE4003 under ISO 11357-3:2018. The consequence in foam extrusion is a wider thermal window for bubble expansion but reduced elastic stiffness in the unfoamed melt. Capillary rheometry under ASTM D3835 shows shear-thinning behaviour; however, the lower crystallinity requires external melt-strength support via peroxide crosslinking, high-molecular-weight EVA blending, or chain extension when cell diameters below 100 µm are targeted.

For foam bubble stability, the temperature dependence of complex viscosity and storage modulus measured in a parallel-plate rheometer under ASTM D4440 is more informative than melt index alone. The resin's 3.0 g/10 min melt index indicates moderate flow; however, low-frequency storage modulus and tan δ values provide direct indicators of sag resistance in sheet and melt strength at the die. Operators typically set extruder head pressure between 85 bar and 120 bar on a 30:1 L/D single-screw foam extruder to maintain homogeneous gas loading. These values are process benchmarks rather than fixed product specifications. Nitrogen and carbon dioxide solubility in EVA rises with vinyl acetate content, but gas diffusivity also rises, increasing the risk of cell coalescence if the foam sheet is quenched too slowly.

Crosslinked compression foam lines using UE4003 often compound on a 14-inch two-roll mill at 100 °C to 110 °C before adding dicumyl peroxide and azodicarbonamide. The critical control point is the balance between peroxide crosslinking and blowing-agent decomposition. Dicumyl peroxide has a 1 h half-life temperature near 135 °C; activated azodicarbonamide decomposition typically begins at 150 °C to 170 °C. During press cure at 155 °C to 165 °C, peroxide radicals generate crosslinks while nitrogen gas from the blowing agent expands the matrix. A temperature tolerance of ±5 °C is necessary because pre-crosslinking before gas release restricts expansion, while premature gas release before sufficient gel content produces cell rupture and surface blistering. The target property window for uniform closed-cell midsoles is commonly 60 % to 75 % gel content by solvent extraction after 8 min to 12 min cure, with foam density at 0.15 g/cm³ to 0.25 g/cm³. Published data for UE4003-specific gelation behaviour is limited; these ranges are derived from commercial EVA foam practice and should be verified on the production press.

Representative Property Specifications Under ISO and ASTM Methods

Certified lot values supplied by the manufacturer may differ from the representative table; the table compiles nominal values previously used in technical datasheets for EVATHENE UE4003. Melt viscosity under processing conditions is measured on a capillary rheometer at 200 °C and apparent shear rates from 100 s⁻¹ to 1000 s⁻¹ to support screw design. Because the grade is formulated for foam, melt tension and elongational viscosity at extrusion temperatures near 110 °C to 130 °C determine whether sheet can support gas expansion without tearing. The resin's relatively low Vicat softening point requires careful temperature control in downstream embossing or laminating stations.

Raw EVATHENE UE4003 is not a finished food-contact article; approval under FDA 21 CFR 177.1520 for olefin polymers depends on extraction testing of the final foamed product and the presence of additives, blowing-agent residues, and crosslinker by-products. REACH compliance verification should include SVHC screening under Article 33 of Regulation (EC) No 1907/2006. The grade is not recommended for permanent implant medical use unless separately evaluated under the ISO 10993 part series. Pellets should be stored below 40 °C in moisture-protective containers; if exposed to relative humidity above 60 %, pre-drying in a desiccant dryer at 60 °C for 4 h to a dew point of -40 °C reduces steam-induced pinholes in extruded foam. Avoid contact with strong oxidizers, mineral acids, and copper-containing alloys above 200 °C, because thermal deacetylation releases acetic acid and accelerates corrosion of downstream metal surfaces.

When Replacing Lower-VA Resins in Roll-Fed Foam Extrusion

The functional difference between UE4003 and a 28 wt% or 33 wt% VA foam grade is not merely a softer hardness. Higher vinyl acetate content increases polar monomer concentration, which improves filler wetting and compatibility with calcium carbonate, magnesium hydroxide, and polar oils. It also lowers low-temperature flexural stiffness. The trade-off is lower tensile strength and reduced resistance to abrasive wear. In an extruded plank line, a 28 wt% VA resin may produce tensile strength of 8 MPa to 15 MPa on solid plaques, while UE4003 typically produces 4 MPa to 6 MPa. This reduction is acceptable only when foam density and cell structure provide compression recovery; it is not a direct substitute where load-bearing stiffness is the primary specification.

Compared with high-VA hot-melt-grade EVA having melt index from 25 g/10 min to 400 g/10 min, UE4003's 3.0 g/10 min restricts it from low-viscosity adhesive use but improves dimensional stability in thick foam sheet. The foam-grade designation indicates that the molecular architecture and residual additive levels are selected for consistency in gas expansion; general-purpose high-VA EVA can produce erratic cell distribution when substituted. In shoe midsole expansion presses, substitution with hot-melt EVA of similar VA content generally fails because melt strength and gelation response under peroxide cure differ from foam-grade resin performance.

To offset the low modulus of UE4003, production formulations often blend 10 wt% to 30 wt% of a lower-VA, higher-viscosity EVA or polyolefin elastomer. In footwear midsole compounds, this blend raises melt tension and reduces cell coalescence. Batch-to-batch variance in melt index and VA content should be monitored by melt flow method ISO 1133-1:2022 and FTIR; variation of melt index by more than 0.3 g/10 min can shift screw plasticizing length and alter foam density. These are quality-control boundary values, not product defects.

The principal operational boundary for UE4003 is thermal stability. Prolonged melt residence above 220 °C initiates deacetylation with measurable acetic acid evolution; equipment should therefore be purged before shutdown and transitions should avoid recirculation of hot resin. The grade has limited outdoor UV resistance as a foam core; exposed applications require UV-stabilized skin layers or black compounding containing 2 % to 3 % carbon black. The product is not recommended for direct contact with strong amine-based additives because some amines can accelerate acetate saponification and promote surface tackiness. Processing at blend ratios above 50 % UE4003 with polar plasticizers should be validated for migration using ASTM F1349 extraction cells before commercial release.