HANWHA EVA 1319

Marketed as a pelletized ethylene-vinyl acetate copolymer for melt-compounded foam and adhesive applications, HANWHA EVA 1319 occupies the 1.9 g/10 min nominal melt-flow index position in the producer’s 18 wt% vinyl acetate series. Representative supplier data list a resin density of 0.940 g/cm³ under ASTM D1505-20, a melt flow index of 1.9 g/10 min under ASTM D1238-20 at 190 °C with 2.16 kg, and a vinyl acetate content of 18.0 wt% by ASTM D5594-18a. The grade is supplied as free-flowing pellets, and the producer specifies pre-drying at 70–80 °C for 2–4 h when ambient relative humidity exceeds 60%. A second-heat differential scanning calorimetry scan at 10 °C/min under ASTM D3418-21 typically places the melting peak near 84 °C, which is consistent with an 18 wt% vinyl acetate random copolymer and supports its use in low-temperature flexible foam systems.

Documented melt-compounding applications include chemically crosslinked closed-cell footwear midsoles, injection-molded sport-shoe soles, and high-viscosity hot-melt adhesive base resins. Selection of EVA 1319 within this product family is driven by the balance between melt extensibility and shear viscosity; a higher melt-flow index than lower-flow grades reduces screw pumping energy but also reduces bubble stability in direct-gas foaming. Consequently, processing conditions are set from capillary rheometry or torque-rheometer data rather than from melt-flow index alone, and cell stabilizers such as zinc stearate are added at 0.5–1.5 phr to widen the foam density tolerance.

What Limits the Peroxide Crosslinking Window in Standard EVA 1319 Foamed Formulations?

Peroxide-crosslinked EVA foam production with this grade is a heat-history-sensitive process because the decomposition of dicumyl peroxide and the gas yield from azodicarbonamide must be synchronized inside a closed mold. Dicumyl peroxide exhibits a half-life of approximately 1 min at 171 °C, 1 h at 135 °C, and 10 h at 117 °C. Azodicarbonamide, by contrast, undergoes rapid gas release between 200 °C and 210 °C under atmospheric heating, but its effective decomposition temperature can be lowered to the 165–175 °C molding range by the presence of zinc oxide or urea-based activators. The processing window is therefore bounded on one side by the scorch time required for compound flow and mold filling and on the other by the pressure needed to retain the blowing gas before the ethylene-vinyl acetate network has developed sufficient gel strength.

In a production Banbury internal mixer with 75 L working capacity and 0.75 fill factor, EVA 1319 is fluxed at a rotor speed of 35 rpm and dropped at 105–115 °C. The drop temperature must remain below the decomposition onset of the peroxide. The discharged batch is then homogenized on a two-roll mill with a 0.5 mm nip and roll surface temperature of 85 °C before being cut into preforms. Compression molding is performed at 165 °C under 15 MPa for approximately 8 min, using a 300 mm × 300 mm × 10 mm plaque tool. Cavity pressure transducers record the decomposition pressure plateau; a drop of more than 0.2 MPa before the cure plateau indicates gas leaking through an insufficiently crosslinked cell wall, which generates collapsed foam at the plaque center.

Gel content on a cured unfilled compound is checked by xylene extraction in accordance with ASTM D2765-16; values below 2% are interpreted as insufficient crosslinking, while values above 60% may indicate over-cure and embrittlement. Moving-die rheometer cure curves under ASTM D5289-12 are used to monitor batch-to-batch variance in scorch time and torque rise. A variance in minimum torque of more than 0.5 dN·m has been observed on production lines when dicumyl peroxide dispersion is inadequate, and this condition is corrected by extending the masterbatch mixing interval by 30–60 s rather than by raising the drop temperature. Amine-based antioxidants and amine-functional release agents are excluded from formulations because they accelerate peroxide decomposition and can shift the foaming onset before the melt reaches adequate homogeneity.

Injection molding of EVA 1319 compounds for sport-shoe soles is conducted on a reciprocating-screw machine with a short shut-off nozzle and a barrel temperature profile of 80–110 °C in the feed zone rising to 160–180 °C at the nozzle. Clamp force is specified at 2–3 kN per cm² of projected part area, while mold temperature is held between 40 °C and 55 °C to stabilize expansion at the flow front. Screw back-pressure is maintained at 0.5–1.0 MPa to prevent premature gas nucleation in the melt. Residence time at 180 °C is limited to 20 min; prolonged heating promotes thermal deacetylation, releasing acetic acid that corrodes tool surfaces and reduces elongation at break. When surface appearance defects increase, the first corrective action is to reduce the feed-zone temperature by 5 °C rather than to increase back-pressure, because the latter can heat the melt by viscous dissipation and aggravate gas nucleation.

Continuous foam-sheet extrusion uses a single-screw extruder with an L/D ratio of 24:1 to 32:1 and a screw compression ratio of 2.5:1 to 3.5:1. The barrel profile is set from 90 °C to 160 °C, with the adapter and die held at 150–165 °C. A gear pump is placed between the screw and the sheet die to reduce pressure pulsation. Cell-size distribution is measured on microtomed sections under ASTM D3576-20; a mean cell diameter above 300 μm is corrected by raising the die pressure through a lower die gap rather than by increasing screw speed alone.

Rheological, Mechanical, and Thermal Specification Context

The nominal property set below is reproduced from the producer’s technical documentation and applies to natural, unfilled EVA 1319 pellets after conditioning at 23 °C and 50% relative humidity for 40 h. The values are not end-use design limits; they vary with pigment, blowing-agent, filler, and crosslinker loading.

Within the same vinyl acetate series, adjacent melt-flow grades differ mainly in their rheological response under industrial shear rates. The following comparison uses the producer’s nominal melt-flow index for each grade; direct substitution should be verified by capillary rheometry because the melt-flow index is a low-shear single-point measurement.

Dynamic oscillatory shear measurements on unfilled EVA 1319 at 190 °C typically show a terminal storage modulus slope of 2 and loss modulus slope of 1 on a logarithmic frequency sweep at strain below 5%. The crossover where storage modulus equals loss modulus is observed near 0.5–1.5 rad/s, depending on lot and additive package. This crossover frequency is used on production lines as a more sensitive indicator of molecular weight distribution than melt-flow index; a shift of more than 20% from the reference lot indicates a change in long-chain branching or comonomer distribution that may not be visible in single-point melt-flow testing. Torque-rheometer data at 60 rpm and 170 °C show a fusion time of 1–2 min and an equilibrium torque of 8–12 N·m for the neat resin in a 350 cm³ mixing head. These measurements are used to establish incoming raw-material consistency before compounding with peroxide or blowing-agent masterbatches.

When EVA 1319 Replaces EVA 1317 in Hot-Melt Adhesive Compounding

In hot-melt adhesive formulations based on EVA, rosin ester tackifier, and paraffin wax, substitution of EVA 1317 with EVA 1319 changes the apparent viscosity at 180 °C in a manner that is larger than the numeric melt-flow index difference alone suggests. The apparent viscosity is measured with a rotational viscometer under ASTM D3236-88 using a 27 spindle at 5 rpm; formulation shear rates during roll coating can exceed 1000 s⁻¹, where the shear-thinning exponent of the EVA phase controls the viscosity drop. Because EVA 1319 has a shorter average relaxation time than EVA 1317, it reduces stringing during high-speed packaging lines but also shortens open time by 5–10% on corrugated board at 25 °C, depending on wax loading.

Adhesive peel adhesion is evaluated under ASTM D1876-08 T-peel geometry on untreated polyethylene film; a drop in T-peel force of more than 15% after formula substitution indicates inadequate chain entanglement at the bond interface. For freezer-grade labels, EVA 1319 alone may not provide sufficient low-temperature flexibility; a higher vinyl acetate content or a lower melting point EVA grade is required. The grade is compatible with hydrocarbon tackifiers and ester-functional tackifiers, but it should not be formulated with amine-catalyzed epoxy modifiers, which interfere with thermal stabilizers and increase char formation in the adhesive pot.

Compared with a higher vinyl acetate grade such as a 28 wt% EVA at equivalent melt flow index, EVA 1319 exhibits a higher crystalline melting peak and lower surface tack. This distinction is significant in footwear foam, where excessive surface tack causes blocking of freshly expanded sheet and reduces automatic cutting yields. In adhesive applications, EVA 1319 provides lower adhesion to unprimed polyethylene but better heat resistance than higher-vinyl-acetate grades when blended with high-softening-point rosin esters. The grade is not suitable for applications requiring transparency at high vinyl acetate contents; haze increases as the vinyl acetate level falls and crystallite size increases.

Production-scale foaming trials on EVA 1319 have shown that foam density is more sensitive to blowing-agent decomposition pressure than to melt-flow index when the mold cavity is not fully filled. A 5 °C increase in cure temperature can reduce cured foam density from 0.20 g/cm³ to 0.17 g/cm³, but the same temperature increase also raises the gel-content gradient between the skin and core. In a 300 mm × 300 mm × 10 mm plaque molded at 165 °C, a density gradient of 0.02 g/cm³ between the center and edge has been recorded by water-displacement testing under ISO 1183-1:2019. This gradient is corrected by increasing the mold clamp pressure rather than by changing the blowing-agent level.

Compliance documentation for EVA 1319 is lot-specific and includes a REACH registration number issued under Regulation (EC) No 1907/2006, as well as a supplier statement for the European Union Directive 2011/65/EU RoHS recast. The RoHS statement confirms that the resin does not contain lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, or polybrominated diphenyl ethers above 0.1 wt% for lead, mercury, hexavalent chromium, PBB, and PBDE, and above 0.01 wt% for cadmium in a homogeneous material. For food-contact uses, the processor is responsible for verifying the finished article under the relevant national law; ethylene-vinyl acetate copolymer falls within 21 CFR 177.1350 when the specified extraction and end-use conditions are met, but EVA 1319 may be supplied in a non-food-contact stabilization package depending on the lot.

Storage below 40 °C and away from direct sunlight is required to limit thermal deacetylation. Direct contact with copper or copper alloys at processing temperatures above 180 °C should be avoided because copper ions catalyze oxidative chain scission. Bags should be resealed after use; once exposed to high-humidity air above 60% relative humidity, the product must be dried before melt processing. The processor should not rely on a single melt-flow index value for lot acceptance; a capillary rheometry check over 100–1000 s⁻¹ at 190 °C is recommended for critical foam and adhesive batches.