Copolímero de acetato de vinilo de etileno ELVAX 760

In three-layer coextruded blown-film lines running a sealant web of ELVAX 760, the copolymer’s vinyl acetate content of 9.3 wt%, density of 0.930 g/cm³ (ASTM D1505), and melt index of 2.0 g/10 min (ASTM D1238 /ISO 1133-1:2022, 190 °C/2.16 kg) place the melt within a viscosity region that supports finite bubble stability at die gaps between 0.8 mm and 2.0 mm. The sealant layer is formulated either neat or as a 20–40 wt% ELVAX 760 blend with LDPE/LLDPE; addition below 20 wt% reduces the seal-initiation contribution to the point where the web reverts to polyethylene-like seal behaviour, while loadings above 40 wt% can lower stiffness sufficiently to affect web handling on high-speed pouch converters. In this structure the sealant web thickness is maintained between 5 µm and 15 µm, and the layer is let down with 0.05–0.20 wt% of a migratory slip concentrate and 0.1–0.5 wt% of synthetic silica antiblock to control blocking on rewind. Production-scale runs on three-layer blown-film equipment using a 30:1 L/D extruder with a 45–65 mm screw diameter typically set barrel temperatures from 150 °C in the feed section to 190 °C at the metering zone, with die zones held at 190–220 °C; melt temperatures above 260 °C should be avoided because deacetylation releases acetic acid, which can corrode downstream winders and generate pinhole defects in the web. The food-contact status of the sealant layer is governed by FDA 21 CFR 177.1350 and Commission Regulation (EU) No 10/2011, with overall migration below 10 mg/dm² under the intended contact conditions; REACH compliance is documented under EC No 1907/2006. Seal strength and hot-tack performance are measured on converted pouches according to ASTM F88 and ASTM F1921, and the resulting terminal product classes include frozen-food pouches, sauce sachets, and non-aseptic liquid packaging with polyolefin-based multi-layer structures.

What Controls Neck-In and Adhesion When ELVAX 760 Is Extrusion-Coated onto Aluminium Foil and Paperboard?

ELVAX 760 is applied on extrusion-coating lines with a 90–150 mm single-screw extruder and 30:1 L/D at coating weights of 10–25 g/m² as a heat-seal tie or barrier-adhesion layer on foil and paperboard. The melt is processed at 232–260 °C through a slot die with a die gap of 0.5–0.8 mm and an air gap of 100–250 mm; a chill-roll temperature of 15–25 °C is fixed to quench the web and to limit post-extrusion crystallinity. Neck-in on production-scale lines is controlled by adjusting the deckle from 20–40 mm inside the substrate edge, by limiting draw ratio to 2:1–4:1, and by raising melt temperature in 5 °C increments if draw resonance appears. Adhesion to aluminium foil typically requires in-line corona discharge at 2–4 kW or a polyethyleneimine primer at 0.01–0.05 g/m² dry coating; without surface activation, peel strength on foil can fall below the 2 N/15 mm threshold needed for lidding applications. Formulation for the coating includes 10–20 wt% LDPE to modify melt extensibility and to reduce edge waste, with ELVAX 760 constituting 80–90 wt% of the applied layer; a small addition of 0.02–0.05 wt% antioxidant can be used where long residence times at high temperature are expected. The compliance matrix for this converted-structure application appears in the table below, and terminal product types include aseptic beverage cartons, foil lidding membranes for dairy cups, and microwaveable susceptor laminates for bakery snacks. A process boundary is that melt temperatures above 260 °C initiate deacetylation; at this point the web develops a vinegar-like odour, and the resulting acetic acid can attack chill-roll surfaces and downstream slitter blades.

Compounding 5–20 wt% ELVAX 760 into high-density polyethylene on a corotating twin-screw extruder with 40:1 L/D is used to modify the environmental stress-cracking resistance of injection-moulded crates and cold-chain containers. The blend is prepared with barrel temperatures between 180 °C and 230 °C, a screw speed of 300–600 min⁻¹, and a specific energy input below 0.25 kWh/kg to avoid local overheating; the EVA phase distributes in discontinuous domains when cooled at moderate rates. At the lower end of the loading window, 5 wt% is used to improve notched Izod impact retention at −20 °C by approximately 20–40% over unmodified HDPE in published low-VA EVA compounding studies, while loadings toward 20 wt% are selected for deep-freeze service where slow crack growth is the primary failure mode. For polypropylene-based compounds, the preferred loading is 5–10 wt%; above that level the difference in crystallisation temperature between the phases can reduce weld-line strength measured on dual-gate specimens under ASTM D638-14. The downstream production line is injection moulding with clamp force settings from 3,000 kN to 12,000 kN, mould temperatures of 10–40 °C, and back pressure not exceeding 0.8 MPa to prevent screw slippage. Testing of the moulded parts follows ASTM D638-14 for tensile properties, ASTM D256-10 for notched Izod, and ASTM D1693 for environmental stress-cracking resistance under 10% Igepal CO-630; REACH and RoHS declarations are required for export to EU markets. Terminal product classes include stackable distribution crates, cold-chain fish totes, and industrial tote bins with wall-stiffening ribs. Published data specific to ELVAX 760 at all formulation levels is limited; therefore, trade formulation trials on the actual mould geometry remain necessary before tooling is released for mass production.

Wire and Cable Sheathing Compounds Based on 9.3 wt% VA Ethylene-Vinyl Acetate

Halogen-free wire and cable formulations that incorporate ELVAX 760 at 10–30 wt% in an LLDPE base are processed on crosshead extrusion lines with screw diameters of 45–90 mm and 24:1–30:1 L/D, using melt temperatures from 160 °C to 200 °C to avoid premature peroxide decomposition where crosslinking is not intended. The VA term at 9.3 wt% changes the dissipation factor in a range measurable by ASTM D150 at 1 kHz; the low melt index of 2.0 g/10 min supports the draw-down required for thin-wall insulation on copper conductors from 0.5 mm to 2.5 mm core diameter. In filled sheathing compounds, the addition ratio of ELVAX 760 is kept at 10–15 wt% when the aluminium trihydroxide loading reaches 60–65 wt%; above 15 wt% EVA, the compound viscosity at low shear can drop below the level required for pressure extrusion of flame-retardant jackets. The downstream production sequence is cable extrusion on a single-screw extruder with a pressure-regulation crosshead, followed by water trough cooling with a temperature gradient from 80 °C to 20 °C to control jacket shrinkback. Compliance for low-voltage appliance wiring and automotive single-core cables includes IEC 60332-1-2 for flame spread, UL 1581 for physical properties of thermoplastic insulation, REACH EC No 1907/2006, and RoHS 2011/65/EU; for EU construction-product cables, EN 50575 requires declaration of performance under the CPR. Terminal product types comprise low-voltage appliance wires, automotive primary wires, and halogen-free sheathing layers for data and control cables. The operational boundary is the deacetylation ceiling at 260 °C; barrel residence times above 20 min at 230 °C or above should be avoided because acetic acid generation accelerates when the melt index begins to drift upward.

When Profile Die Swell Must Be Controlled in Flexible Tube and Weatherseal Extrusion

During vacuum calibration of flexible profiles made from ELVAX 760 either neat or at 30–70 wt% in LLDPE, the high melt elasticity of the 2.0 g/10 min melt index raises die swell but permits thin wall sections to retain shape after vacuum calibration; the EVA phase forms the continuous matrix above 50 wt% for high-flexibility profiles. The formulation is let down with 0.05–0.15 wt% of a fluoropolymer processing aid where sharkskin appears at shear rates above 500 s⁻¹, and with 0.1–0.3 wt% of an antioxidant for long-run profile extrusion; LDPE-based color concentrates are added at 2–4 wt%. Barrel temperatures in a 45–65 mm single-screw extruder with 24:1 L/D are set at 150–180 °C, while the die and calibrator are maintained at 180–200 °C; vacuum calibration pressure between 0.02 MPa and 0.06 MPa is applied to hold tube ovality below 0.1 mm at line speeds of 10–40 m/min. For flexible industrial tubing, the final wall thickness is typically 0.5–3.0 mm, and the terminal products include pneumatic tubes, wire spiral hose covers, bumper edge profiles, and weatherseals for agricultural equipment cabins. Compliance for non-food industrial profiles is based on REACH EC No 1907/2006 and RoHS 2011/65/EU; where the extrudate is used in electrical-equipment contact, the compound is tested against UL 94 HB or IEC 60695-11-10 for horizontal burn. A processing constraint at the die lip is that moisture absorption from high-humidity storage can produce surface splay and longitudinal microgrooves; if storage above 70% relative humidity is unavoidable, pre-drying at 60 °C for 2 h in a desiccant hopper eliminates the defect without changing the melt index.