Elvax 760 EVA Copolymer Resin,Wire & Cable,Adhesives & Sealants Grade

Halogen-free low-voltage cable jacket compounds are processed on co-rotating twin-screw extruders with the feed throat cooled to 40–50°C. Elvax 760 is metered at 20–30 wt% alongside linear low-density polyethylene and magnesium hydroxide. The copolymer contains 9.3 wt% vinyl acetate. Polar acetate dipoles interact with magnesium hydroxide surfaces and reduce filler agglomeration. The compound is pre-dried in a desiccant dryer at 60°C for 4 h when ambient relative humidity exceeds 60%. Residual moisture below 0.08 wt% avoids microvoid formation during cable jacket extrusion. A production-scale 44:1 L/D twin-screw unit shows increased melt pressure before the die when magnesium hydroxide moisture content rises above 0.4 wt%. The finished sheath compound must pass vertical flame propagation, acid gas, and smoke density tests. The test matrix includes IEC 60332-1-2:2015, IEC 60754-2:2011, and IEC 61034-2:2005. Magnesium hydroxide dehydrates near 340°C. Aluminum trihydrate dehydrates between 180°C and 220°C. In compounds containing both fillers, the lower dehydration temperature of aluminum trihydrate limits the processing window. Tensile strength retention after aging for 168 h at 100°C is assessed per ISO 527-2:2012. On twin-screw lines operated above 400 rpm, torque spikes occur at the first kneading block if filler loading exceeds 60 wt%. The screw configuration must include forwarding elements upstream of the main kneading section. Underwater pelletizing is preferred to strand pelletizing because the melt remains low-viscosity at die temperature and strand breakage increases below 170°C.

Qualification testing of a halogen-free sheath compound is performed before cable type testing. The matrix below lists the standards applied to the compound rather than the final cable.

Why Is the Melt Temperature Ceiling for Elvax 760 Set at 190°C in Twin-Screw Compounding?

Once melt temperature exceeds 190°C, deacetylation of the vinyl acetate comonomer becomes measurable and acetic acid evolution accelerates as the melt approaches 230°C. Thermogravimetric analysis under nitrogen at 10 K/min per ISO 11358-1:2022 shows a multi-step mass loss in which acetic acid elimination precedes main-chain hydrocarbon degradation. Acetic acid contributes to gas acidity, pH drop, and corrosion of downstream metal surfaces. In wire and cable compounds, the acid component is penalized by IEC 60754-2:2011. Barrel set temperatures on a 44:1 L/D co-rotating twin-screw extruder are therefore configured at 150°C in the feed zone, 170–180°C in the middle zones, and 175°C at the die. Shear heating from the 2.0 g/10 min melt flow rate raises actual melt temperature by 15–20°C. At screw speeds above 400 rpm, melt temperature can reach 195–205°C. Oil-cooled barrel zones are adjusted to hold melt temperature below 190°C. Torque limit is set at 85% of gearbox rating. If the torque limiter is triggered repeatedly, the production rate is reduced instead of increasing barrel temperature. This operational boundary prevents acidic degradation during long campaigns. The screw configuration uses forwarding elements before the main kneading block to avoid excessive shear heating. A production trial with a 52:1 L/D machine showed that melt temperature overshoot was 18°C higher at 600 rpm than at 350 rpm for an identical barrel profile. The compound is pelletized underwater at a water temperature below 40°C to prevent pellet blocking. The pellets are then dried to below 0.08 wt% moisture before shipment.

In medium-voltage cable designs, conductor shield compounds require carbon black loadings sufficient to create a semiconductive layer between the copper conductor and the crosslinkable polyethylene insulation. Elvax 760 is used as a dispersion aid because the 9.3 wt% vinyl acetate polar group reduces carbon black agglomeration. A conductor shield may contain 25–35 wt% furnace black, 40–55 wt% Elvax 760, and 10–25 wt% higher-VA EVA or ethylene-butyl acrylate. The compound is mixed on a twin-screw extruder with downstream carbon black side feeding. Premature carbon black addition in the main throat causes dusting and poor dispersion. Dispersion quality is checked by optical microscopy. Surface roughness after co-extrusion is controlled by passing the melt through a 60/100/60 mesh screen pack. Triple-head extrusion lines use a 60 mm conductor shield extruder, a 90 mm insulation extruder, and a 120 mm insulation shield extruder. Melt temperature at the conductor shield die is maintained at 180–185°C to avoid premature peroxide crosslinking in the adjacent XLPE insulation. Volume resistivity is measured with a four-point probe according to ASTM D4496-21. The strippability of the insulation shield is adjusted by blending Elvax 760 with higher-VA EVA. Higher Elvax 760 content increases strip force because the lower acetate concentration reduces interfacial polarity against the XLPE insulation. Run times above 12 h on a 90 mm extruder can produce carbon black agglomerates if screw cooling is inadequate. The semiconductive compound must remain thermally stable during long co-extrusion runs. Carbon black dispersion failure appears as surface protrusions under a 15× optical comparator. Those protrusions create local field enhancement in the cable insulation and are rejected before vulcanization.

High-Temperature Hot Melt Adhesive for Edgebanding and Profile Wrapping

Because edgebanding and profile wrapping line speeds can exceed 60 m/min, hot melt formulations incorporating Elvax 760 are mixed in sigma-blade or turbine mixers under nitrogen at 170–180°C. Elvax 760 is not the sole base polymer. The 9.3 wt% vinyl acetate content keeps crystallinity high. The crystalline melting peak of 99°C contributes to a higher set point and reduced cold flow compared with 28% VA EVA grades. In a typical edgebanding formulation, Elvax 760 is added at 10–20 parts by weight per hundred resin. A 28% VA EVA grade provides adhesion to PVC edgebanding. The tackifier is a hydrogenated C9 resin at 35–45 parts by weight. Fischer-Tropsch wax at 5–10 parts by weight controls viscosity and set speed. Viscosity at 180°C is measured on a Brookfield Thermosel viscometer using ASTM D3236-15. The presence of low-MI Elvax 760 increases Brookfield viscosity compared with formulations using 400-grade EVA. Slot die coaters apply the adhesive at 180–200°C. The molten adhesive film must remain tacky for only 1–3 s before the edgeband is pressed onto the panel. The final bond is conditioned for 24 h at 23°C. Heat resistance is evaluated under a 500 g static load in a forced-air oven at 70°C. The low VA content of Elvax 760 contributes to creep resistance. A formulation containing more than 25 parts by weight Elvax 760 shows reduced adhesion to polar surfaces because the acetate group concentration is insufficient. The adhesive may peel from the PVC edgebanding in a 180° peel test. This limitation is managed by keeping the ratio of high-VA EVA to Elvax 760 above 1.5:1. The equipment operator monitors batch viscosity at the end of mixing. Viscosity drift above 10% of the target value indicates oxidative degradation or incomplete tackifier dispersion. The batch is then sampled for softening point and color measurement before transfer to the coating line. The softening point is measured by ring-and-ball method per ASTM E28-18.

When Intumescent Systems Replace Metal Hydroxides in Thin-Wall Cable Insulation

At total intumescent loadings of 25–35 wt%, thin-wall automotive wiring compounds use ammonium polyphosphate, pentaerythritol, and melamine as the fire-retardant package. Elvax 760 acts as the char-forming polyolefin. The compound is processed below 190°C. Ammonium polyphosphate begins to release ammonia at 250°C. The temperature gap between safe EVA processing and ammonium polyphosphate decomposition is therefore only 60°C. A twin-screw extruder with a 40:1 L/D configuration and low-shear screw design is used. The melt temperature is monitored with an infrared sensor at the die. If melt temperature exceeds 195°C, surface roughness increases and char formation becomes nonuniform. The compounded pellets are dried to 0.05 wt% moisture. Thin-wall insulation of 0.2 mm thickness is extruded on a 45 mm single-screw wire coating line. The line speed is reduced compared with metal hydroxide-filled compounds. The melt strength of Elvax 760 at 2.0 g/10 min melt index is sufficient for thin-wall draw-down but not for high-speed tubing lines. Flame performance is evaluated by cone calorimetry under ISO 5660-1:2015 at 35 kW/m². Oxygen index is measured by ISO 4589-2:2017. The char residue is inspected for intumescence. The pH and conductivity of fire gases are measured by IEC 60754-2:2011. Published comparative data for Elvax 760-specific intumescent compounds is limited. The char height and residual mass must be validated on the actual wire construction because the copper conductor acts as a heat sink. This heat sink effect reduces the intumescent char formation in thin-wall construction. The compound must be stored sealed. Exposure to high humidity hydrolyzes ammonium polyphosphate and reduces the oxygen index by progressive acid release. The use of amine-based additives is avoided because they accelerate deacetylation and darken the material during residence time at 180°C.

Solvent-borne heat-seal lacquers for aluminum lidding foils are produced by dissolving Elvax 760 in a 60:40 toluene/methyl ethyl ketone blend at 15–20 wt% solids. Dissolution takes place in jacketed stainless steel vessels at 60°C with low-shear agitation. The low VA content reduces solution viscosity relative to high-VA EVA grades. The lacquer is applied to lidding foil by reverse gravure coating at 150 m/min. Drying oven zones are set at 60°C, 80°C, and 100°C. Residual solvent is measured below 2 mg/m² before the foil is rewound. The heat seal is activated at 110–130°C against polypropylene or PVC thermoformed trays. Seal strength is measured on a 25 mm strip at 300 mm/min jaw speed according to ASTM F88/F88M-21. The crystalline melting peak of 99°C controls the minimum seal activation temperature. Seal strengths above 5 N/25 mm are typically achieved when the coating weight is 3–4 g/m². The lacquer pot life is limited by moisture uptake. The solution must be stored under nitrogen. If ambient relative humidity exceeds 60%, water absorption into the MEK/toluene blend causes phase separation. The lacquer can be crosslinked with an isocyanate hardener. Amine-based additives must be avoided because they accelerate deacetylation and darken the solution. This solvent-borne route is used where coextrusion coating is not available. The viscosity is checked with a #3 Zahn cup at 25°C, and the target is 22–28 s. The coating line is stopped if the measured viscosity exceeds 32 s because excessive viscosity changes the gravure transfer volume and produces seal-strength variation across the web.