HANWHA EVA 1326 Copolímero de acetato de vinilo de etileno

HANWHA EVA 1326 is a random ethylene-vinyl acetate copolymer supplied as pelletized resin with a nominal vinyl acetate comonomer content of 26 wt%. The material is characterized under ASTM D1238 /ISO 1133-1:2022 at 190 °C and 2.16 kg with a typical melt mass-flow rate of 2.0 g/10 min. Density according to ASTM D1505 /ISO 1183-1:2019 is approximately 0.950 g/cm³. The resin is applied in crosslinked foam, flexible profile extrusion, polymer modification, and hot-melt adhesive formulations where a balance of low-temperature flexibility, polarity, and melt strength is required.

The random distribution of vinyl acetate units lowers crystallinity relative to low-density polyethylene. The CAS registry number is 24937-78-8. Published manufacturer values position EVA 1326 between 15 wt% and 28 wt% VA grades: higher in polarity and elongation than a 15 wt% grade, while retaining lower surface tack and lower adhesive cold flow than a 28 wt% grade.

What Distinguishes the 26 wt% Vinyl Acetate Content from Lower-VA Ethylene Copolymers?

The 26 wt% vinyl acetate content places EVA 1326 above 15 wt% and 18 wt% grades in polarity and low-temperature ductility. In a random copolymer, the acetate side groups disrupt methylene sequence crystallization. The DSC melting endotherm measured per ASTM D3418-15 occurs near 72 °C, compared with approximately 90 °C to 95 °C for a 15 wt% VA grade. The Vicat softening temperature of 45 °C per ASTM D1525-17e1 is lower than that of lower-VA copolymers. This produces a softer article with Shore A hardness of 82, tensile strength at break of 19.6 MPa, and elongation at break of 800 % when tested according to ASTM D638-14 at 50 mm/min. The glass-transition region of this VA range falls below -20 °C; the exact onset varies with measurement rate and residual crystallinity.

Pellet handling requires protection from moisture if storage relative humidity exceeds 60 %. Surface moisture can generate microvoids in extrudate and bubble defects in cast film. Pre-drying at 60 °C to 70 °C for 2 h to 4 h in a desiccant dryer is applied before profile extrusion; hopper temperature remains below 50 °C to prevent pellet sintering. Single-screw extruders with barrier screws and L/D ratios of 24:1 to 30:1 are used for profile and sheet lines, with barrel zones from 120 °C to 180 °C.

When EVA 1326 Is Compounded with Azodicarbonamide and Dicumyl Peroxide for Molded Foam

Molded foam processing with EVA 1326 uses a batch compounding step on a two-roll mill or in an internal mixer at 90 °C to 110 °C. Dicumyl peroxide is added at 0.6 phr to 1.2 phr; azodicarbonamide is added at 2.0 phr to 5.0 phr depending on target density. The peroxide decomposition half-life is approximately 1 h at 137 °C. Azodicarbonamide decomposition onset is 195 °C to 210 °C. Because the cure and blowing exotherms do not overlap completely, zinc oxide or zinc stearate is used as an activator to shift gas evolution toward 150 °C to 170 °C. The compounded sheet is placed in a semi-positive compression mold under 10 MPa to 15 MPa at 170 °C to 180 °C. After crosslinking and gas evolution, a rapid mold-opening step controls expansion ratio and cell size. Published data for this specific configuration is limited; expansion ratios above 1.8× require separate optimization of blowing agent loading and mold venting.

Premature gas evolution in the feed zone is the most common failure mode on two-roll mills. If stock temperature exceeds 120 °C, surface bubbles and pre-crosslinked gel particles appear. Cooling water with inlet temperature below 15 °C is maintained on the rolls to reduce batch-to-batch variation in cell structure. EVA 1326 is selected for foam because the 26 wt% VA content improves blowing-agent solubility and gas retention compared with lower-VA grades, while avoiding the excessive softness and blocking tendency of grades above 28 wt% VA.

Hot-melt adhesive compounding uses EVA 1326 in combination with rosin ester tackifiers and paraffin or Fischer-Tropsch waxes. In a 5 L sigma-blade mixer at 160 °C to 180 °C, the polymer is masticated until a clear melt forms before tackifier addition. The 26 wt% VA content increases compatibility with polar tackifiers and promotes adhesion to aluminium, polyvinyl chloride, and coated paperboard. Melt viscosity of the final adhesive is measured with a Brookfield viscometer per ASTM D3236-15 at 180 °C, with typical packaging formulations in the 1,500 mPa·s to 4,000 mPa·s range. Ring-and-ball softening point per ASTM E28-18 is adjusted by wax type and can be maintained above 85 °C while retaining low-temperature flexibility. Processing should not exceed 220 °C; prolonged residence time above this temperature accelerates deacetylation and releases acetic acid, which corrodes mild steel and degrades adhesion.

The 2.0 g/10 min Melt Index Narrows the Extrusion Window in Cast Film and Sheet Lines

The 2.0 g/10 min melt mass-flow rate is deliberately low enough to maintain melt strength in foam and thick sheet, but it reduces flow length in thin-wall injection molding and raises backpressure in extrusion. On a 90 mm single-screw extruder with an L/D of 30:1, barrel set points are typically 150 °C to 190 °C. Melt temperature at the die is held between 190 °C and 210 °C. A gear pump between screw and die is required for stable gauge control below 0.1 mm thickness variation. Chill roll temperature is maintained at 15 °C to 25 °C to control crystallinity and surface gloss.

Compared with a 6.0 g/10 min or 25 g/10 min EVA grade, EVA 1326 produces higher extruder amperage at the same screw speed and requires wider die gaps because of higher elastic recovery. Users replacing a high-MI grade must reduce production rate or increase melt temperature; otherwise sharkskin or melt fracture can appear at the die lip. The exact onset of flow instabilities depends on die geometry and shear rate; published data for this specific configuration is limited.

Food-contact compliance is assessed under FDA 21 CFR 177.1350 for ethylene-vinyl acetate copolymers, with vinyl acetate content not exceeding 40 wt% and extractives limits as specified. EU Regulation (EU) No 10/2011 applies for plastic materials and articles intended to come into contact with food; users must verify migration limits for the specific application. The product is subject to REACH registration under EC 1907/2006. RoHS Directive 2011/65/EU does not restrict vinyl acetate copolymers as a base polymer but applies to additives and colorants in electrical and electronic equipment. Decomposition above 230 °C releases acetic acid; local exhaust ventilation and corrosion-resistant tooling are required.

Polymer modification with EVA 1326 is used to improve impact resistance and filler wetting in polyolefin compounds. Addition of 5 wt% to 15 wt% EVA 1326 to a linear low-density polyethylene matrix lowers the brittleness temperature and increases tensile elongation. Mixing on a co-rotating twin-screw extruder with L/D 40:1 at 180 °C to 200 °C disperses the EVA phase. The vinyl acetate groups interact with calcium carbonate and talc surfaces, improving filler wetting at loadings above 40 wt%. This practice is generic; exact property changes depend on the base resin and screw configuration.