Copolímero de acetato de vinilo de etileno ELVAX 4031WLG

Photovoltaic encapsulant film lines running ELVAX 4031WLG typically compound the resin by tumble-blending 100 phr pellets with 1.0–1.5 phr tert-butyl peroxy-2-ethylhexyl carbonate, 0.3–0.5 phr vinyltrimethoxysilane, 0.2–0.5 phr of a phosphite-phenol antioxidant blend, and, where a white reflective encapsulant is required, 5–10 phr of a titanium dioxide masterbatch. The grade carries a nominal vinyl acetate content of 40 wt% and a melt flow rate of 3.1 g/10 min under ISO 1133-1:2022 at 190°C and 2.16 kg, placing it in a low-flow, high-polarity class that requires melt-confining screw geometry rather than high-shear homopolymer-grade screws. In a single-screw extruder with 30:1 L/D, barrel temperatures are set from 85°C at the feed throat to 105°C at the metering section, while the flex-lip die and melt pump are maintained at 110–115°C to suppress premature peroxide decomposition. The film is cast onto a polished chill roll at 20–30°C, and gauge is controlled to 400–500 µm before lamination. Hot spots near the die lips generate gel specks that appear as colourless inclusions in the cured module; the defect rate increases when melt residence exceeds 20 min or when the product contains moisture above 0.05 wt%. Pre-drying in a desiccant hopper at 60°C for 4 h is therefore standard in plant environments above 60% RH. Crosslinking occurs during vacuum lamination at 145–150°C for 15–20 min; gel content measured by solvent extraction in boiling xylene under ASTM D2765-16 is targeted at 70–85 wt%. Published data for ELVAX 4031WLG in high-speed photovoltaic encapsulant lines is limited, so the specified peroxide ratio and gel-content window are to be confirmed against lot-specific rheology data before die-lip modifications are approved.

What Hot-Tack Parameters Govern EVA-Rich Sealant Layers in Coextruded Blown Film?

In three-layer blown film structures for laminated pouches and frozen-food bags, ELVAX 4031WLG is let down into the sealant skin at 20–40 wt% with a linear low-density polyethylene carrier. The addition range is limited at the upper end because the high vinyl acetate content raises melt stickiness and the wound roll blocking force increases sharply above 40 wt% EVA when the film is stored above 35°C ambient temperature. The sealant skin is coextruded on a spiral mandrel die with a die gap of 1.5–2.0 mm and a blow-up ratio of 2.2:1 to 2.8:1; melt temperatures are kept between 195°C and 215°C, and purge time at idle is capped at 15 min because stagnant melt releases acetic acid and accelerates die-lip corrosion. Hot-tack force is measured on a laboratory seal tester according to ASTM F1921-18, and seal strength after cooling is measured under ASTM F88/F88M-21. For a 30 wt% EVA sealant web, converters typically require a seal initiation temperature below 85°C at 0.3 MPa seal pressure and 0.5 s dwell, with a seal strength above 2.0 N/15 mm; published data for this exact ELVAX 4031WLG dilution is limited, and the threshold shifts downward with increasing corona treatment level. The final sealant layer must satisfy the overall migration and polymer-specific conditions shown in the compliance table below.

When ATH Loading Exceeds 170 phr in Halogen-Free Jacketing Compounds

In halogen-free sheathing compounds for control and power cables, ELVAX 4031WLG is used as the polymeric wetting phase because the acetate side groups interact with uncoated alumina trihydrate surfaces and permit filler loadings that would otherwise cause brittle failure in low-polarity polyolefins. The manufacturing procedure begins with a co-rotating twin-screw extruder of 44:1 to 52:1 L/D; resin is fed by loss-in-weight at the main throat, while dried alumina trihydrate is side-fed downstream at total loadings between 150 phr and 180 phr per 100 phr resin. Magnesium dihydrate is added at 10–20 phr only when the final cable specification requires a char plateau above 300°C; higher additions reduce tensile elongation below the 150% threshold required by many IEC 60811-series tests. The screw configuration uses distributive mixing elements after the side feeder and a low-pressure die zone, with barrel temperatures from 120°C at intake to 160°C at discharge. Operation above 170°C is avoided because the alumina trihydrate decomposition endotherm becomes measurable and moisture-driven porosity appears in the pellet. The compound is pelleted under water and dried to less than 0.1 wt% moisture before silane grafting or peroxide addition in the cable extrusion stage. Finished sheathing is tested for acid gas generation per IEC 60754-1:2011 and IEC 60754-2:2011, smoke density per IEC 61034-2:2005, and flame spread per IEC 60332-1-2:2015.

Crosslinked Foam Densities and the Peroxide-Azodicarbonamide Balance

Compression-moulded EVA foams for footwear midsoles use ELVAX 4031WLG at 100 phr with azodicarbonamide at 3.0–5.0 phr, dicumyl peroxide at 0.6–0.9 phr, zinc oxide at 2.5–5.0 phr, stearic acid at 1.0–2.0 phr, and calcium carbonate at 10–20 phr. The resin’s low melt flow rate of 3.1 g/10 min at 190°C under ISO 1133-1:2022 functions as a melt-strength reserve; cell coalescence is less frequent than with high-MI EVA when the gas pressure inside the growing cells exceeds the elongational strength of the melt during mould opening. Mixing is carried out on an open two-roll mill with a front roll temperature of 85–95°C and a friction ratio of 1.15:1. The compounded sheet is cut into preforms and placed into a compression mould at 165–175°C and 150–200 kg/cm² for 8–12 min. The blowing and crosslinking reactions must reach their exothermic peaks nearly simultaneously; a premature peroxide peak causes a dense skin and an underblown core, while a late peroxide peak allows cell collapse and surface cratering. Moving-die rheometry at 170°C is used to confirm a t₉₀ below 8 min. Foam density is verified per ISO 845:2006, compression set per ISO 815-1:2014, and Asker C hardness per JIS K 7312. Typical density after free expansion is in the range 0.12–0.20 g/cm³, with skin density measurably higher than core density; published data for ELVAX 4031WLG in this specific foam formulation is limited, so the blowing-agent and peroxide split should be confirmed on a small-scale press before production.

Solventborne adhesive formulations for film-to-foil lamination dissolve ELVAX 4031WLG in a 70/30 wt% toluene/methyl ethyl ketone blend at 12–18 wt% solids. The dissolution is conducted in a jacketed mixer at 55–60°C for 2–4 h; the low melt index grade requires longer solvation than high-MI EVA, but the resulting solution exhibits higher green strength and creep resistance. After cooling, a hydrogenated rosin ester tackifier is added at 5–10 parts per 100 parts dry resin, and the viscosity is adjusted to 400–800 mPa·s at 25°C using a Brookfield RVT viscometer. The coat weight is controlled at 3–6 g/m² dry on a reverse-roll coater, followed by forced-air drying at 80–90°C. Bond strength is evaluated by T-peel under ASTM D1876-08; foil-to-polypropylene laminations commonly require at least 2.5 N/15 mm. Operational boundaries include solvent flammability under Directive 2010/75/EU and the sensitivity of vinyl acetate to alkaline hydrolysis; amine-cured primers or amine-containing inks can shift the wet adhesive pH and produce viscosity growth during long production runs. Published data for ELVAX 4031WLG in this exact solventborne system is limited, so the viscosity-solids relationship should be measured for every lot before solvent addition is reduced on the coating line.

Bituminous roofing membranes and damping sheets are modified with ELVAX 4031WLG at 6–12 wt% of the total bitumen mass. The EVA pellets are added to oxidized bitumen at 170–180°C in a high-shear rotor-stator mixer; batch residence time is held at 60–90 min because the crystalline ethylene segments need time to melt and disperse into a continuous bitumen-rich phase. Above 12 wt% addition, the compound frequently enters a phase inversion and the viscosity at application temperature rises beyond the pumping range of standard spreader machines, producing uneven heat-welded seams. Softening point is checked under ASTM D36-14, penetration under ASTM D5-20, and low-temperature flexibility under EN 1109:2013. Storage stability is assessed according to EN 13399:2017 at 180°C for 3 days; visible phase separation or a penetration split greater than 10 dmm between top and bottom layers indicates insufficient shear dispersion. Since the grade contains 40 wt% vinyl acetate, prolonged storage above 200°C accelerates acetic acid release and can attack unlined carbon steel tanks; stainless steel or phenolic-lined vessels are specified for closed-loop blending systems.

Injection Moulding Gate Sizing for Low-Melt-Index EVA Blend Components

Injection moulded cable entry seals, pipe gaskets, and vibration-isolation parts are produced from ELVAX 4031WLG blended with 15–25 wt% of an ethylene-propylene rubber or styrenic block copolymer and 5–10 wt% mineral filler. The blend is moulded on a reciprocating-screw injection machine with a clamp force of 120–180 t, a screw L/D of 22:1, and a compression ratio of 2.0:1. Barrel temperatures from feed to nozzle are set at 140°C, 165°C, 175°C, and 185°C, with the hot runner held at 185–190°C. The low melt flow rate of 3.1 g/10 min under ISO 1133-1:2022 imposes a minimum gate diameter of 1.2 mm; smaller gates produce jetting, weld-line weakness, and surface delamination because the long relaxation time of the high-molecular-weight EVA phase prevents molecular re-entanglement before quench. Mould temperatures are controlled between 20°C and 40°C; higher mould temperatures reduce orientation but extend cycle time beyond 60 s. The demoulded article is tested for Shore A hardness under ISO 48-4:2018, tensile strength under ISO 527-2:2012, and compression set under ISO 815-1:2014. A common failure mode on production lines is gas-burning streaks when the screw back pressure is set below 5 bar, resulting in inadequate homogenization of the EVA and rubber phases.