HANWHA EVA 1316

Compounding lines that convert HANWHA EVA 1316 into crosslinked closed-cell foam for sports shoe midsoles and sheet underlays select this grade for its nominal vinyl acetate content of 16 wt% and its melt flow index of 1.8 g/10 min measured at 190°C under 2.16kg by ASTM D1238. The acetate side groups reduce polyethylene crystallinity to a degree that permits homogeneous peroxide crosslinking, while the moderate molecular weight distribution maintains enough melt strength for controlled bubble expansion when the blank is heated under pressure and then released. Production-scale two-roll mills band the compound at 90–100°C before adding azodicarbonamide at 2.0–4.0phr, dicumyl peroxide at 0.6–1.2phr, zinc oxide at 1.0–2.5phr, and zinc stearate at 0.5–1.0phr. The decomposition kinetics of dicumyl peroxide define the lower cure limit, with a 1min half-life near 171°C, while azodicarbonamide gas evolution becomes rapid above 200°C; the press plateau is therefore held at 165–175°C for 8–12min for blanks of 10–12mm thickness. A processing deviation of more than ±5°C from the optimized plateau creates either insufficient crosslinking with high compression set or premature gas release that collapses the cell structure before the polymer matrix can retain expansion.

Density in midsole foams is typically controlled from 0.12g/cm³ to 0.25g/cm³ according to ISO 845; athletic sheet goods may fall below 0.08g/cm³. Hardness values measured under ASTM D2240 Shore A or Asker C follow the density curve, generally between 25 and 45. Tensile strength determined by ASTM D638 at 500mm/min falls in the 1.0–3.0MPa range, with elongation at break between 150% and 350%. Tear strength by ASTM D624 Die C is 2.0–8.0kN/m. Compression set tested by ASTM D395 Method B for 6h at 50°C under 50% compression should remain at 20–40% for crosslinked EVA; higher values indicate under-crosslinking or over-blowing that thins cell walls. Dimensional stability after die cutting is monitored as shrinkage after 24h at 70°C, and values above 3% are generally rejected for contour-machined midsoles because subsequent side-wall distortion prevents accurate periphery bonding during lasting.

When Halogen-Free Sheathing Compounds Are Extended with Magnesium Hydroxide

In low-smoke halogen-free cable sheathing, EVA 1316 is compounded with precipitated magnesium dihydroxide at 120–180phr, or with a mixed filler system of magnesium dihydroxide and aluminium trihydroxide at total loadings of 150–200phr. The 16wt% vinyl acetate content supplies sufficient polar sites for filler wetting, but the relatively low melt flow index of 1.8g/10 min forces compounding on a co-rotating twin-screw extruder with L/D of at least 40:1. Barrel temperatures are typically profiled from 120°C at the feed throat to 150°C at the die, and screw speed is limited to 250–350rpm to avoid excessive shear heating. Predrying is mandatory at 70°C for 4h when storage RH exceeds 60%; moisture retained above 0.05% promotes acetic acid formation and increases melt fracture at the die lip. Without adequate venting, the resulting porosity also reduces sheathing tensile strength and creates surface defects detectable by IEC 60811-501 visual inspection.

Mechanical performance after extrusion depends heavily on silane coupling. Trimethoxyvinylsilane at 0.5–1.0phr is added in a side feeder or through pre-treated filler to reduce interfacial slip and preserve tensile strength. Without a coupling agent, tensile strength per IEC 60811-501 can drop below 9MPa after 168h at 135°C; silane-treated compounds often retain 10MPa or higher. Elongation at break is to remain above 150% for sheathing installed in tight bend radii. Because EVA 1316 has lower vinyl acetate content than the 18–28wt% grades commonly used in LSZH compounds, filler loadings beyond 180phr reduce melt strength and increase die pressure; plant formulations frequently blend 10–20wt% of a higher-VA EVA to restore elongation and surface smoothness while maintaining the required flame retardance.

For blown film operations where EVA 1316 is blended with low-density polyethylene at 10–30wt%, the grade modifies dart impact strength and lowers heat-seal initiation temperature while increasing haze. Bubble stability is the limiting processing factor because the 1.8g/10 min melt flow index and 0.938g/cm³ density produce lower melt strength than fractional-MI LDPE; processors therefore use die gaps of 1.8–2.5mm and maintain blow-up ratios below 2.5:1. Dart impact per ASTM D1709 Method A on 50µm film containing 20wt% EVA 1316 is generally higher by 15–30% relative to the neat LDPE control, while seal initiation per ASTM F2029 shifts downward by 8–12°C. Optical clarity measured by ASTM D1003 deteriorates with increasing vinyl acetate content, so transparent overwrap structures limit EVA 1316 to 10wt% or below; for heavy-duty sacks and frozen-food films the higher loading is selected to win puncture resistance and low-temperature ductility.

On monolayer blown film lines, screw temperature profiles below 170°C are used to suppress gel formation; the maximum melt temperature at the die is 210°C for blends, and residence time at temperature should not exceed 15min. The melt pressure before the screen pack rises by 10–20% relative to LDPE because of the higher viscosity of EVA 1316, and extruder drives sized for the base LDPE may require derating throughput by 5–10% to avoid over-torque. Published data for this specific configuration is limited in public literature, but the operational boundary is well established by film converting trials that measure gel counts and melt-pressure variation as leading indicators of bubble instability.

What Limits Draw-Down Stability in Extrusion Lamination with EVA 1316?

Extrusion lamination lines running EVA 1316 as a tie layer or sealant web require melt temperatures at the die of 240–280°C because lower temperatures produce insufficient adhesion to aluminium foil and primed polyester. The maximum safe melt temperature is 285°C; above this limit acetic acid evolution is measurable and crosslinked gels can form in the die lip. Draw-down ratios of 20:1 to 40:1 are achievable when the melt is extruded through a coat-hanger die with a die gap of 0.8–1.2mm and the substrate is pre-treated with polyethyleneimine primer at 0.05–0.10g/m². Peel strength on foil at 15µm coating thickness, measured by ASTM F904, typically falls between 2.0 and 4.0N/15 mm. Neck-in is controlled by blending with LDPE at 30–50wt%, although the blend reduces oxygen barrier and flavour retention relative to pure EVA sealant layers.

The screw configuration for lamination grade EVA 1316 should use a barrier screw with L/D of 30:1 and a compression ratio between 2.5:1 and 3.0:1. In multi-layer coextrusion structures with aluminium foil, the melt curtain is cooled on a chill roll held at 15–20°C; roll speed differential and air knife settings are adjusted to prevent melt curtain flutter that creates transverse gauge bands. Thickness variation is evaluated gravimetrically per ASTM D4321 or by beta gauge, and coating weight is maintained at ±5% of target to ensure peel adhesion consistency across the web width.

Masterbatch Carrier Resin Rheology and Carbon Black Dispersive Loading

Masterbatch producers select EVA 1316 as a carrier for carbon black and organic pigment concentrates destined for polyolefin film and injection molding because the 16wt% vinyl acetate content improves pigment wetting compared with neat LDPE, while the 1.8g/10 min melt flow index matches many let-down resins without causing melt-fracture in film grade dilution. In twin-screw masterbatch compounding, carbon black loadings of 40–50wt% are feasible if the extruder has an L/D of 48:1 and a mixing section with kneading blocks arranged for high dispersive shear. The melt temperature should be limited to 220°C at the die to prevent oxidative gel formation; a vacuum vent at -0.08MPa removes moisture and low-volatility oligomers. Let-down ratios of 2–5% are standard in film, and filter pressure rise per EN 13900-5 can be used to rank dispersion quality; pressure rise below 0.5MPa/min is typically considered acceptable for film-grade black masterbatch.

EVA 1316 is not suitable as a carrier for high-melt-flow spunbond nonwoven masterbatch because its viscosity is too high for uniform dispersion at high let-down ratios exceeding 1% in high-MFR polypropylene. In that application, a higher-MFR EVA or an acrylic-based carrier would be required to avoid undispersed pigment agglomerates and spinneret clogging. For polyolefin film and injection molding concentrates, however, the polarity and melt stability of EVA 1316 support a wider processing window than unmodified LDPE carrier resins.