HANWHA EVA 2815

Hanwha EVA 2815 is compounded into hot-melt adhesive systems on a co-rotating twin-screw extruder with an L/D 40:1 barrel configuration and vacuum venting at −0.08 MPa. The nominal vinyl acetate content of 28 wt% introduces sufficient polarity for tackifier compatibility while the melt flow index of 15 g/10 min at 190 °C/2.16 kg according to ASTM D1238 maintains fluidity during slot-die coating. Barrel temperatures are profiled from 120 °C at the feed throat to 160 °C at the die, with screw speeds in the 250–350 rpm range and residence times normally below 10 min. Typical compounding recipes contain 30–40 phr of EVA 2815, 35–50 phr of a C5/C9 aromatic-modified tackifier with softening point between 95 °C and 115 °C, 5–20 phr of microcrystalline wax, and 0.5–1.0 phr of a hindered phenolic antioxidant. The antioxidant is first dispersed in the molten wax phase to avoid localized over-concentration in the feed zone. Viscosity of the finished adhesive at 180 °C is commonly measured with a Brookfield Thermosel; typical industrial formulations fall between 2,500 mPa·s and 5,500 mPa·s depending on wax type and tackifier softening point. The task-defined grade is processed through hot-melt application equipment, including gear-pump-driven slot-die heads with shim gaps of 0.2–0.5 mm, onto corona-treated polyethylene or coated paperboard. Open time is adjusted by wax melting range and add level; higher microcrystalline wax fractions above 15 phr shorten open time below 5 s on 20 °C substrates, while lower fractions extend positioning time. Bonded assemblies are evaluated by ASTM D1876 T-peel and ASTM D4498 shear adhesion failure temperature. Process control limits include keeping the melt temperature below 200 °C for more than 30 min to prevent measurable acetic acid evolution from vinyl acetate pendant groups, and vent-port fouling must be monitored because low-molecular-weight tackifier fractions can carry over under high vacuum. Published data for this exact formulation configuration is limited, but the relationship between vinyl acetate content and polar substrate adhesion is well established in hot-melt compounding practice.

Does Blowing Agent Decomposition Align with the Crystallite Melting Endotherm of EVA 2815?

In crosslinked footwear midsole production, Hanwha EVA 2815 is masticated on a two-roll mill at 105–115 °C before dicumyl peroxide is added downstream. The grade is selected in this application because the 28 wt% vinyl acetate content suppresses crystallinity and lowers the peak melting endotherm into the 70–75 °C range when measured by differential scanning calorimetry at 10 K/min under ISO 11357-1 conditions. This thermal characteristic creates a working window in which the polymer can be filled with azodicarbonamide blowing agent, zinc oxide activator, and stearic acid lubricant without premature gas evolution. A typical midsole formulation contains 100 phr EVA 2815, 0.5–1.0 phr dicumyl peroxide, 2.5–4.0 phr azodicarbonamide, 1.0–2.0 phr zinc oxide, and 0.5 phr stearic acid. After mixing, the plaque is crosslinked and foamed in a compression press at 155–165 °C for 7–10 min, during which peroxide decomposition and blowing agent decomposition overlap. The critical processing boundary is scorch at the mixing stage: dump temperatures above 120 °C initiate measurable dicumyl peroxide decomposition, producing local gel particles that appear as hard specks in finished midsoles. Therefore, two-roll mill rolls are cored with tempered water and batch weight is selected to avoid temperature overshoot above 115 °C.

Crosslink density of the expanded part is controlled through gel content after xylene extraction per ASTM D2765-16, with industrial midsoles typically falling between 70% and 85% gel. Foam density is then measured by displacement and normally ranges from 0.15 g/cm³ to 0.20 g/cm³ depending on azodicarbonamide loading and press cure pressure. Compression set under ASTM D395 Method B at 50 °C/6 h is used as a release criterion because lower gel levels produce higher set values and visible crease retention after flexural fatigue. The exothermic cure reaction can create center-to-skin density gradients when part thickness exceeds 20 mm, a problem addressed by stepping cure temperature from 150 °C to 165 °C over the first 4 min. Additionally, the vinyl acetate content of EVA 2815 increases gas permeability relative to low-VA EVA grades, which shortens the diffusion path for CO₂ and N₂ generated by azodicarbonamide decomposition; this accelerates cell growth but also raises sensitivity to demoulding pressure drop. Mould opening speed is therefore reduced below 5 mm/s to prevent post-expansion defects such as internal splits.

In low-voltage cable jacket formulations, Hanwha EVA 2815 is used as a polar modifier rather than a sole base polymer, generally at 20–40 phr blended with low-density polyethylene or linear low-density polyethylene. The vinyl acetate copolymer raises filler incorporation capacity for aluminium trihydrate and magnesium dihydrate, which are required to meet flame-retardant targets in halogen-free sheathing compounds. A twin-screw extruder with a 44:1 L/D barrel and co-rotating intermeshing screws is used, with barrel temperatures from 140 °C to 170 °C and a melt temperature limit of 180 °C to prevent filler-driven local overheating. The molten compound is pelletized through a die-face cutter; water temperature is held at 40–60 °C because excessively cold water can crack the filled strands at the die face. Flame-retardant jacket compounds using EVA 2815 are screened for limiting oxygen index, heat ageing, and vertical flame behaviour before cable-scale trials.

In this application the principal incompatibility is retained moisture in mineral fillers, which reacts with vinyl acetate under extrusion conditions and produces surface defects if the filler is not pre-dried to below 0.1 wt% moisture. Vent-port vacuum must remain above −0.07 MPa to withdraw evolved water and low-molecular-weight volatiles. Batch-to-batch variance is controlled by sieve analysis of the filler and by monitoring barrel torque; excursions above 85% of extruder motor rating indicate filler dispersion failure that can tear the jacket surface during high-speed extrusion. The use of EVA 2815 additionally lowers cold-temperature brittleness of the jacket; finished formulations are typically evaluated for low-temperature impact at −25 °C or −40 °C depending on the installation specification, using test methods under IEC 60811-504. In halogen-free jacketing, published data for this specific EVA 2815 blend ratio is limited at the production scale, so pilot-scale runs are used to confirm flame performance before full cable extrusion.

When EVA 2815 Is Selected as a Melt-Miscible Modifier in Cast Film Heat-Seal Layers

Heat-seal initiation temperature decreases as vinyl acetate content increases, and a 28 wt% vinyl acetate grade such as Hanwha EVA 2815 is blended into metallocene linear low-density polyethylene at 20–30 wt% to produce lower seal initiation values in multilayer cast film structures. The blend is extruded through a cast film die with a lip gap of 0.3–0.5 mm and chilled-roll temperature of 15–25 °C, with melt temperature held between 180 °C and 210 °C. The 15 g/10 min melt flow index of EVA 2815 reduces blend viscosity and improves web draw uniformity, but the higher vinyl acetate content also increases die lip deposit formation over extended runs. Seal strength is measured by ASTM F88 with a dwell time of 0.5–1.0 s and pressure of 2.0–3.0 bar; seal initiation temperatures for such blends are commonly observed in the 85–95 °C range. Hot tack is evaluated by ASTM F1921 to ensure the seal resists opening before solidification on vertical-form-fill-seal lines.

The processing boundary in this application is the limit of thermal stability of EVA 2815 at high cast film temperatures. Extended hold-up at die temperatures above 220 °C leads to gel formation and optical haze in the sealant layer. Purging after a production campaign uses low-density polyethylene at barrel temperatures of 190–210 °C until the melt stream is clear. Because cast film quality depends on chill-roll surface finish, contamination from vinyl acetate decomposition products is controlled by regular cleaning with non-abrasive solvents and by maintaining backpressure below 200 bar. The final film is generally incorporated into a laminate structure with coex layers, and the sealant layer thickness is specified between 10 µm and 30 µm depending on seal strength and package heaviness.

The combination of 28 wt% vinyl acetate and 15 g/10 min melt flow in Hanwha EVA 2815 corresponds to an encapsulation-grade rheology window used in photovoltaic module lamination. Before film extrusion, the raw EVA is compounded with a silane coupling agent such as vinyltrimethoxysilane at 0.3–0.8 phr, a peroxide crosslinker at 0.5–1.0 phr, a UV absorber, and a hindered amine light stabilizer. The compounded material is extruded through a flat die and calendered into film thicknesses of 0.4–0.6 mm. During module lamination, the EVA sheet is placed between glass and backsheet and processed in a vacuum laminator at 145–155 °C for 10–20 min, during which peroxide decomposition reaches sufficient conversion to produce gel contents above 80%. Gel content is determined by xylene extraction per ASTM D2765, and lamination adhesion is checked by IEC 61215 sequences for peel and damp-heat ageing.

In this application moisture control is the dominant process variable. EVA encapsulant film is stored below 50% RH and warmed before lamination only to remove residual surface humidity; absorbed moisture accelerates adhesion loss and increases bubble formation during the vacuum cycle. The lamination chamber pressure profile is typically stepped from evacuation below 10 mbar to a press phase at 900–1,000 mbar to permit trapped air removal before crosslinking closes the film surface. The vinyl acetate content of EVA 2815 also influences free-acetic-acid potential during long-term damp-heat exposure; therefore module-level tests under IEC 61215 damp-heat conditions at 85 °C/85% RH for 1,000 h are used to screen encapsulant stability. Specific data for EVA 2815 in commercial photovoltaic encapsulant certification is limited in published literature, so converter-scale trials remain necessary to establish glass adhesion after damp-heat ageing and to validate the chosen stabilizer package.

Low-Odor Carbon Black Masterbatch Carrier Functions in Polyolefin Packaging

In masterbatch compounding, Hanwha EVA 2815 is let down at 3–5 wt% in final packaging film and serves as a wetting resin for carbon black before dispersion into polyethylene carrier resins. The vinyl acetate groups adsorb onto polar carbon black surfaces and reduce agglomerate persistence, while the 15 g/10 min melt flow permits effective distributive mixing in a high-shear internal mixer. Masterbatch production uses a co-rotating twin-screw extruder with barrel temperatures between 140 °C and 180 °C and a screw speed of 400–600 rpm to generate dispersive shear. Carbon black loading in the masterbatch is commonly 40–50% by weight, and pressure filtration testing per DIN 53775 is used to quantify unmixed aggregates. The limitation in this use is that EVA 2815 should not be exposed to prolonged residence time above 180 °C; thermal degradation produces acetic acid that can corrode downstream film die lips and odour in the final package.

Injection moulding trials using a 120-tonne clamping force machine and a general-purpose screw with 20:1 L/D ratio require barrel temperatures from 160 °C to 185 °C for Hanwha EVA 2815. The melt is injected into flexible closure and gasket moulds with shot weights configured to keep cushion above 3 mm and screw recovery consistent. The high vinyl acetate content lowers crystallinity and reduces shrinkage to the 1.5–2.5% range depending on part thickness, but it also increases cycle time because the soft solidified surface can stick to mould cores. Mould temperature is held below 40 °C, and release is assisted by non-silicone external release agents. Parts produced from EVA 2815 are flexible at low temperature and are tested for Shore hardness per ISO 868 or ASTM D2240. If the material is left in the barrel at melt temperature for more than 20 min, the next shot may contain yellowed streaks from acetate decomposition, so the machine is purged with high-density polyethylene before shutdown. Published processing data for this specific grade in injection moulding is limited, but the relationship between 28 wt% vinyl acetate content and mould release behaviour is consistent with general EVA copolymer practice.