HANWHA EVA 2315

Manufactured by Hanwha TotalEnergies Petrochemical as a random ethylene-vinyl acetate copolymer, HANWHA EVA 2315 is supplied in pellet form for chemically crosslinked foam, injection-molded footwear components, and selected profile extrusion applications. Supplier technical documentation for this designation lists a nominal vinyl acetate content of 23 wt% and a melt index of 1.5 g/10 min when tested to ASTM D1238 at 190 °C under a 2.16 kg load. Density is reported as 0.939 g/cm³ by ASTM D792. Because vinyl acetate units interrupt polyethylene crystallinity, the copolymer exhibits lower melting peak temperatures and lower flexural modulus than high-pressure low-density polyethylene of comparable melt index. The material is not a mechanical polyolefin blend; comonomer incorporation occurs along the ethylene backbone during high-pressure polymerization, affecting residual crystallinity, optical properties, and thermal sealing behaviour.

In compounding operations for crosslinked foam, the resin is typically combined with azodicarbonamide blowing agent, dicumyl peroxide crosslinking agent, and zinc-oxide or zinc-stearate activators in an internal mixer. Published thermal data for azodicarbonamide place the primary decomposition exotherm near 200 °C, while dicumyl peroxide exhibits a half-life of 1 hour at approximately 135 °C. The resulting cure-decomposition balance defines the critical processing window: mix temperatures are normally held below 110 °C to prevent premature peroxide scission, while foaming requires tool or oven temperatures above 160 °C to decompose the blowing agent after a sufficient crosslinked network has formed. On production-scale lines, melt-index drift of ±0.2 g/10 min between lots is commonly offset by adjusting blowing-agent level; failure to do so alters cell diameter and final apparent density. This operational sensitivity is more pronounced than in non-foamed EVA extrusion because gas retention depends on viscosity during bubble nucleation and growth.

When EVA 2315 Replaces Low-Vinyl Acetate Grades in Crosslinked Foam Tooling

Replacement of a lower-vinyl acetate copolymer such as EVA 1315 with EVA 2315 in crosslinked foam tooling modifies the thermal property set before cure. The higher vinyl acetate fraction reduces the crystalline melting point, raises low-temperature flexibility, and lowers compound modulus. In tooling, this shift permits lower preheat oven temperatures and reduces stress-whitening in deep-draw profile sections. However, the same modification increases tack and can reduce green strength in uncured extrudate; contact surfaces in forming dies are therefore specified with a higher release angle and, in some tool configurations, a reduced land length to prevent dragging. The typical processing window for a medium-vinyl acetate EVA is narrower in the pre-cure stage than for low-vinyl acetate grades because the available temperature range between adequate flow and premature blowing-agent decomposition is compressed. Published foam composite literature for EVA systems indicates that a ±5 °C deviation in pre-cure oven setpoint can shift cell elongation from isotropic to oriented, particularly when sheet thickness exceeds 10 mm.

For continuous compounding, EVA 2315 is processed on co-rotating twin-screw extruders with segmented screws, commonly in the L/D 40:1 to L/D 48:1 range, using temperature profiles from 90 °C to 110 °C from feed throat to die. Barrel zones after the mixing elements are often water-cooled to prevent localized temperatures above 120 °C, because the resin's viscosity produces viscous heating in fully filled zones. Foaming operations report that shear heating above 120 °C initiates premature peroxide decomposition, visible as surface pitting and density variability in downstream foam sheet. Screw configuration typically includes low-shear conveying elements before a short kneading block rather than a high-intensity melt seal, because compounded blowing-agent decomposition residue can generate gas pockets in fully filled zones. Die-face pressure is maintained below 12 MPa where possible; higher pressure in a closed zone lowers the activation threshold for blowing-agent nucleation in the melt.

Comparative Property Envelope Against Adjacent Vinyl Acetate Grades

The position of EVA 2315 within the manufacturer's EVA series is defined by intermediate vinyl acetate incorporation. Against a low-vinyl acetate grade designated for extrusion coating, EVA 2315 provides greater low-temperature flexibility and higher elongation at break under ASTM D638, but at the expense of lower tensile strength and higher surface tack. Tensile modulus is reduced, which is advantageous for soft-touch and foam applications but undesirable where dimensional stability under load is required. Against a high-vinyl acetate grade used for high-resilience foam, EVA 2315 exhibits lower elongation, lower permanent set, and a higher crystalline plateau modulus; these properties improve dimensional recovery after compression and reduce swelling in hydrocarbon environments. The trade-off is lower elastomeric recovery at sub-zero temperatures. The balance of 23 wt% vinyl acetate with 1.5 g/10 min melt index places the resin in the viscosity range used for uniform gas dispersion in foamed products while retaining enough melt strength to resist cell coalescence during expansion.

For footwear midsole formulations, EVA 2315 commonly targets closed-cell densities between 0.12 g/cm³ and 0.20 g/cm³. Cell size distributions in uniaxially expanded foam are evaluated by optical microscopy or scanning electron microscopy; comparative production data for medium-vinyl acetate EVA indicate that cell diameter is controlled by blowing-agent decomposition rate and pressure drop at the die lip. Differential scanning calorimetry under ASTM D3418 records a lower melting peak than LDPE, which reduces the energy demand of post-expansion annealing. In extruded tubular insulation, the same vinyl acetate level increases the upper service temperature relative to plasticized PVC but does not provide the high-temperature resistance of crosslinked polyethylene; therefore the material is not specified for continuous operation above 70 °C unless crosslinked.

During injection molding of EVA 2315 for footwear shells and midsoles, barrel temperature settings are held between 170 °C and 190 °C, with mold temperatures from 25 °C to 45 °C. The low melt temperature reduces thermal degradation of the vinyl acetate group, which can release acetic acid at sustained temperatures above 220 °C. Clamp force requirements are lower than for semi-crystalline polyolefins of equivalent melt index because the copolymer has lower crystalline solidification shrinkage; however, ejection may require additional draft because the surface is more deformable at demolding temperatures. Dimensional variation is controlled by holding pressure and gate freeze time rather than by melt temperature alone. Mold shrinkage is generally evaluated by ASTM D955; published data for this specific configuration is limited, so shrink must be determined from the actual tool geometry and gate configuration.

In extrusion coating and profile coextrusion, EVA 2315 functions as a heat-seal and adhesion layer where higher vinyl acetate content lowers seal initiation temperature relative to LDPE. The seal initiation reduction depends on layer thickness and comonomer content; laboratory heat-seal curves generated under ASTM F88 may show a seal initiation drop of several degrees Celsius relative to LDPE of comparable melt index, although exact results vary by film thickness and contamination level. Environmental stress crack resistance is evaluated by ASTM D1693; medium-vinyl acetate EVA typically outperforms LDPE in this test. The trade-off in extrusion is a lower maximum draw ratio and a higher surface friction coefficient, which can increase roller wrap and web tracking force. When replacing LDPE in extrusion coating, die temperatures are often reduced by 5–10 °C to prevent edge neck-in from low melt tension.

Where metallocene-catalyzed polyolefin elastomers are evaluated as alternatives, EVA 2315 offers a broader molecular weight distribution and more developed shear thinning. This favours high expansion ratios in chemically foamed sheet but demands tighter barrel-temperature control because the peroxide and blowing-agent response windows are narrower. In comparison with LDPE foam resin, the vinyl acetate content of EVA 2315 reduces the energy barrier for cell nucleation at a given pressure drop; however, the same property lowers melt strength and increases the risk of bubble coalescence when die temperature exceeds the recommended upper limit. No direct substitution for LDPE foam tooling should be made without adjusting screw speed and melt pressure setpoints, because published data for this specific configuration is limited.

What Limits Peroxide Uptake in High-Shear Comminution?

Peroxide uptake in EVA 2315 is constrained by shear heating generated during granulation, melt mixing, and die extrusion. Dicumyl peroxide has a half-life of approximately 1 hour at 135 °C; the practical upper limit for compounding is therefore set at 110 °C to keep decomposition below observable levels during mixing. In high-shear comminution, the resin's shear-thinning behaviour initially reduces viscous dissipation, but the low thermal conductivity of the ethylene-vinyl acetate matrix permits local hot spots near rotor tips. If these hot spots exceed the peroxide decomposition onset, premature crosslinking produces gel particles and causes torque fluctuation in downstream extrusion. The maximum peroxide loading is also limited by the residual acidity of certain blowing-agent activators; zinc stearate and zinc oxide alter the decomposition pathway of azodicarbonamide and shift the gas evolution temperature. Formulation cannot be adjusted by increasing peroxide alone without rebalancing activator content and mixer speed. Production-scale mixing records for vinyl acetate copolymers show that a 10 °C increase in discharge temperature can halve the safe residence time at a given peroxide loading.

Lot-to-lot control for EVA 2315 in production is managed through melt-index and density checks before compounding. Incoming inspection laboratories measure melt index by ASTM D1238 and density by ASTM D792; records from converting operations indicate that variation in these two values within the supplier specification is sufficient to require adjustment of blowing-agent loading and extruder speed. The resin is not standardized by a single compounding recipe; therefore each downstream conversion line maintains a narrow acceptance band for melt index and vinyl acetate content, typically within ±0.15 g/10 min and ±0.5 wt%, to preserve foam apparent density and cell uniformity.

Under normal warehouse conditions, storage of EVA 2315 requires protection from prolonged ultraviolet exposure and contact with copper-containing materials, which can accelerate thermo-oxidative degradation. Pre-drying is not mandatory at relative humidity below 60%, but pellets exposed to humid air should be dried at 60–70 °C for 2–4 hours using a desiccant dryer when surface moisture is detected; the copolymer is not highly hygroscopic, but surface water can hydrolyze retained peroxide or generate steam defects in foam. The material should not be blended with amine-based additives where peroxides are used, because amine-induced peroxide degradation lowers the crosslink density achievable at a fixed peroxide level. If reprocessed foam scrap is added, the proportion is typically limited to 10–20 wt% to control gel content and viscosity drift; higher levels reduce cell wall strength and increase apparent density variance in foam sheet.

For regulatory compliance, EVA 2315 must be confirmed against the current supplier certificate of analysis and the specific food-contact or electrical application. The olefin copolymer may fall under FDA 21 CFR 177.1520 when used in food-contact articles, subject to end-use restrictions and migration testing. Electrical and electronic applications are assessed for compliance with Directive 2011/65/EU (RoHS) and EC 1907/2006 (REACH). The product does not contain an intentionally added plasticizer; however, slip agents and antioxidants are lot-dependent and must be disclosed by the supplier.