HANWHA EVA 2815 Copolímero de acetato de etileno e vinil

Hanwha EVA 2815 is an ethylene-vinyl acetate copolymer grade with a nominal vinyl acetate content of 28 wt% and a melt mass-flow rate of 15 g/10 min determined at 190 °C under 2.16 kg load in accordance with ASTM D1238-20 or ISO 1133-1:2022. The grade coding denotes the vinyl acetate level and the melt-flow class. Density measured at 23 °C by ASTM D792-20 is approximately 0.950 g/cm³. The polymer is supplied as translucent pellets for flexible compounding, hot-melt adhesive systems, and low-temperature impact modification. In comparison with ethylene-vinyl acetate copolymers containing 14–18 wt% vinyl acetate, the 28 wt% level lowers crystallinity and crystalline melting point while raising polarity; the effect on adhesion is evaluated by ASTM D1876-08(2015) peel testing on aluminum, corona-treated polyester, and polyamide. The product is not a direct substitute for metallocene polyolefin elastomers or for lower VA extrusion grades; selection is driven by the need for solventless polar adhesion, low flexural modulus, and moderate melt viscosity in a single feedstock.

For melt processing, a single-screw extruder with a barrier screw and L/D of 24:1 to 30:1 is commonly used. Barrel setpoints from feed throat to die are typically 130–180 °C, and the melt temperature is held below 200 °C to limit acetic acid evolution. Pellets do not normally require pre-drying when stored in sealed bags below 40 °C and ambient relative humidity below 60%; when surface moisture or condensation is observed, drying at 60–70 °C for 4–6 h in a desiccant dryer with a dew point of −30 °C is applied. Production-scale compounding of tackifier, wax, or filler masterbatches is carried out on co-rotating intermeshing twin-screw extruders with L/D 40:1 and moderate shear screw elements; excessive shear at high barrel temperatures can initiate chain scission and acid odor. Injection molding of the neat copolymer uses barrel temperatures of 150–190 °C, mold temperatures of 20–40 °C, and moderate injection speed to avoid jetting and surface flow marks.

How Does the 28 wt% Vinyl Acetate Level Alter Performance Boundaries?

Thermal analysis of an EVA 2815-class copolymer under ASTM D3418-21 typically shows a broad melting endotherm with a peak from 70 °C to 76 °C and a glass transition temperature in the range of −30 °C to −25 °C. The crystalline fraction is reduced to approximately 15–20% by DSC heat-of-fusion calculations, compared with roughly 25–35% for lower vinyl acetate grades. The lower crystallinity reduces room-temperature flexural modulus into the range of 20–40 MPa when measured by ASTM D790-17, while tensile stress at break measured on ASTM D638-14 Type IV specimens is generally 10–15 MPa with elongation of 750–900%. Hardness measured by ASTM D2240-21 is typically 78–82 Shore A. The Vicat softening temperature by ASTM D1525-17 is normally 45–55 °C, which restricts continuous load-bearing service to below 80 °C. The higher vinyl acetate content also increases polarity, which improves wetting of aluminum foil, corona-treated polyethylene, and polyester films in hot-melt lamination. The trade-off is reduced resistance to nonpolar solvents and increased water-vapor transmission relative to lower VA grades; transmission data require formulation-specific testing under ASTM E96/E96M-22 or equivalent.

Physical Property Benchmarks Under ASTM D638 and D1238 Conditions

The following values represent the typical property envelope for a 28 wt% vinyl acetate /15 g/10 min melt-flow EVA and are not specification limits. Batch-to-batch variation is normal, and finished-compound properties depend on additive loading.

Hot-melt adhesive compounding with EVA 2815 is performed in jacketed sigma-blade or vertical mixers at 160–180 °C under a nitrogen blanket. The copolymer is added to a molten hydrogenated rosin ester or C5/C9 hydrocarbon tackifier at 30–50 phr; paraffin or microcrystalline wax at 10–30 phr lowers viscosity and controls open time, while a hindered phenolic antioxidant at 0.5–1.0 phr is included. Viscosity stability is monitored with a Brookfield Thermosel at 180 °C using ASTM D4499-20 as a heat-stability framework; an increase of more than 20% over 72 h is typically interpreted as inadequate stabilization or excessive processing temperature. The 15 g/10 min melt-flow class provides higher cohesive strength than higher MI grades at equivalent tackifier loading; shear adhesion failure temperature and peel values are measured by ASTM D4498-07(2013) and ASTM D1876-08(2015). Open time and set time are not assignable to the base polymer alone; they are controlled by tackifier type, wax melt point, and add-on weight. Published data for a specific final adhesive formulation based on this grade is limited outside supplier application literature.

In chemically blown and peroxide-cured foam, EVA 2815 is compounded with azodicarbonamide at 1.0–3.0 phr, zinc oxide at 0.5–1.5 phr, and dicumyl peroxide as the crosslinking initiator. The peroxide 1 min half-life temperature of 171 °C sets the lower boundary of the cure plateau, while azodicarbonamide decomposition around 200–210 °C requires careful ramping to synchronize gas evolution with melt strength. The high vinyl acetate content lowers crystallinity, allowing lower-density expansion and higher resilience than lower VA grades; density and resilience are evaluated by ASTM D792-20 and ASTM D2632-15(2019). The melt temperature window is narrow; twin-roll mill and internal mixer production has shown that deviations of ±5 °C around the setpoint can produce surface blisters or density variation. Blowing agent residues and acetic acid traces can corrode unplated steel molds; chrome plating or stainless steel tooling is preferred. Because the grade is not inherently crosslinkable without peroxide, cure kinetics must be revalidated if the peroxide type or coagent package is changed; the cure curve is commonly measured by moving-die rheometer at 170–180 °C with torque increase as the cure indicator. Published data for this specific configuration is limited to general EVA foam practice.

In halogen-free flame-retardant compounds for wire and cable, EVA 2815 is often selected as the base polymer because the vinyl acetate group improves filler wetting at high aluminum trihydrate or magnesium hydroxide loadings of 150–200 phr. Compounding is carried out on a co-rotating twin-screw extruder with L/D 40:1, using side feeding for the mineral filler to avoid excessive torque on the main feed. Melt temperature is kept below 180 °C to prevent premature filler dehydroxylation and acid decomposition. Mechanical properties after extrusion are evaluated by ASTM D638-14, and hot-set elongation under load by IEC 60811-507; formulations typically require silane coupling agents at 0.5–2.0 phr to maintain elongation after aging. The 15 g/10 min melt-flow grade provides higher melt strength during tubing extrusion than a 40 g/10 min VA grade, as measured by a Rosand or Göttfert Rheotens at 180 °C, but it increases torque and requires a barrel temperature profile with a flat 140–170 °C zone before the die. Published data for this specific formulation configuration is limited; pilot-scale trials are required.

When Lower VA or Higher MI Grades Are Substituted in Production

Substituting a lower vinyl acetate grade with the same melt-flow rate, for example 18 wt% VA, raises the crystalline melting peak, increases hardness and tensile strength, and improves heat resistance in adhesives and films. However, it reduces adhesion to polar substrates and lowers low-temperature flexibility; peel adhesion measured by ASTM D1876-08(2015) or ASTM D903-98(2017) on corona-treated polyester and aluminum often falls unless tackifier loading is increased. Substituting a higher melt-flow grade, such as 28 wt% VA with a melt mass-flow rate above 40 g/10 min, reduces melt viscosity and improves wet-out on rough or fibrous substrates but decreases melt strength and green strength. In injection-molded closures or footwear components, the higher MI grade fills thin walls at lower pressure, whereas EVA 2815 requires higher injection pressure and may exhibit melt fracture at fast injection speeds. The 15 g/10 min melt-flow class is therefore positioned for applications where melt strength, cohesive strength, and moderate viscosity are more important than thin-wall filling. In blown film, the lower MI improves bubble stability but may require die gaps at the upper end of typical 0.8–1.5 mm settings.

Against ethylene methyl acrylate copolymers of similar comonomer content, EVA 2815 shows higher polarity and generally lower thermal stability because of the acetate side group. In extruded profiles, the EMA grade may retain flexibility at lower temperatures, while the EVA grade gives higher green strength in hot-melt systems and better adhesion to polar foils. Against ethylene butyl acrylate or metallocene polyolefin elastomers, the 28 wt% vinyl acetate grade exhibits higher surface polarity and better compatibility with rosin ester tackifiers but lower heat-aging resistance and greater moisture permeability. The choice between these polymer families is typically made after comparing peel adhesion by ASTM D1876-08(2015), low-temperature flex crack by ASTM D1052-09(2019), and melt viscosity on a capillary rheometer at 180 °C.

When the final article requires food-contact status, the base polymer may be evaluated against FDA 21 CFR 177.1350 or EU Regulation (EU) No 10/2011 for the specific food type, temperature, and contact duration. Compliance of the formulated compound is not automatic; migrating tackifiers, waxes, antioxidants, and processing aids must be considered. For industrial applications, the unmodified polymer is typically outside the restricted substances categories of REACH and RoHS Directive 2011/65/EU, but finished-article certification requires full composition review. In storage, sealed bags should be kept below 40 °C and away from direct sunlight; the expected shelf life is typically 12 months from production. Opened bags should be consumed promptly because surface condensation in humid environments introduces moisture that can cause splay in extrusion and pinholes in cast film. The grade is incompatible with strong oxidizing acids, chlorinated solvents at elevated temperature, and acid-sensitive additives; prolonged exposure above 200 °C generates acetic acid and can corrode unplated steel equipment.

Typical production failures associated with EVA 2815 are moisture splay from inadequately dried pellets, melt fracture from excessive screw speed or low die temperature, acid odor from extended hold times above 200 °C, and surface tack or blocking in pellet handling when storage temperatures exceed 40 °C. Each failure mode is mitigated by controlling the specific equipment parameter—dew point, screw speed, barrel temperature profile, and warehouse temperature—rather than by reformulating the base polymer. If a persistent processing defect remains after these controls are implemented, a different melt-flow grade or vinyl acetate level should be selected. Material change-over in a production extruder requires purging with a lower melt-flow polyethylene or purging compound at 160–180 °C to remove residual EVA from stagnant zones before shutdown.