Versalis S.p.A.

Versalis S.p.A. is specified as a multi-line product range covering high-pressure low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ethylene-vinyl acetate copolymers (EVA), general purpose and high-impact polystyrene (GPPS/HIPS), expandable polystyrene (EPS), and solution- and emulsion-polymerized elastomers. Model designations within the range include Riblene for LDPE, Flexirene and Clearflex for LLDPE and EVA, Edistir for styrenics, Extir for expandable polystyrene, Europrene for styrene-butadiene rubbers, and Intene for polybutadiene. Typical LDPE film extrusion grades show density values between 0.918 g/cm³ and 0.925 g/cm³ when tested according to ISO 1183-1:2019; melt flow rate measured at 190°C/2.16 kg under ISO 1133-1:2022 spans 0.2 g/10 min to 70 g/10 min across extrusion coating and thin-wall moulding grades. The selection of co-monomer—butene, hexene, or octene—distinguishes LLDPE sub-ranges by tear strength, dart impact, and seal initiation temperature rather than by density alone. Styrenic grades are differentiated by gel content, rubber particle size, and pentane loading; elastomer grades are differentiated by bound styrene, vinyl content, and Mooney viscosity. Food-contact listings for olefin-based grades align with FDA 21 CFR 177.1520 and Commission Regulation (EU) No 10/2011, while general compliance is documented under REACH Regulation (EC) No 1907/2006.

What Differentiates High-Pressure Tubular LDPE From Autoclave Grades in the Versalis S.p.A. Portfolio?

The two high-pressure LDPE process routes generate dissimilar molecular architectures even when density and melt flow rate values overlap. Tubular-reactor grades are produced at pressures of 200–350 MPa and peak temperatures between 280°C and 340°C; the short residence-time profile yields a narrower molecular weight distribution and lower long-chain branching frequency than autoclave grades. Autoclave-reactor grades, typically polymerized at 100–200 MPa, exhibit broader molecular weight distribution and higher long-chain branching density, which improves neck-in control and adhesion in extrusion coating. Downstream, this difference appears as a trade-off between optical clarity and melt elasticity. Tubular grades tend to produce lower haze in blown film, with values assessed under ASTM D1003-21, while autoclave grades provide stable draw at coating line speeds above 200 m/min. Coextruded structures should not be re-qualified without reassessing seal initiation temperature and hot-tack force, because the long-chain branching architecture alters elongational viscosity and heat-seal behaviour. In adhesive lamination, autoclave grades with higher melt elasticity can reduce edge weave on high-speed slitter-winders but may require higher chill-roll contact uniformity.

In injection moulding cells with clamp force between 80 t and 150 t, high-flow LDPE and LLDPE grades with melt flow rate values of 20–70 g/10 min are typically selected for thin-wall lids and tubs, while lower-flow grades at 4–10 g/10 min are retained for closures and squeezeable packaging where stress-crack resistance is prioritized. Melt temperatures are maintained at 180–240°C for neat polyolefin grades, and mould temperatures are held between 20°C and 40°C to balance cycle time against visual surface defects. Drying is not required for unfilled polyethylene at ambient relative humidity below 60%; moisture-condensed regrind, however, should be re-dried at 60–70°C for 2–4 h to prevent surface splay. Tensile yield strength and elongation at break are verified under ISO 527-2:2012 or ASTM D638-14, while flexural modulus is measured according to ISO 178:2019. Shrinkage for semi-crystalline polyethylene can range from 1.5% to 2.5% in the flow direction, requiring tooling compensation that differs from amorphous styrenic parts. Injection speed profiling is critical with high-flow grades because shear-thinning behaviour at apparent shear rates above 1,000 s⁻¹ can produce jetting if gate velocity is not controlled.

Film Extrusion Grades Demand Narrow Molecular Weight Distribution Control

In blown film towers running three-layer lines, narrow molecular weight distribution is the primary control variable for bubble stability and gauge uniformity. Die gaps between 1.6 mm and 2.8 mm, blow-up ratios of 2.0:1 to 3.5:1, and frost-line heights from 4D to 8D are common operating conditions; grades with broad distribution can tolerate lower melt temperatures but may generate higher gel counts and poorer dart impact. The addition of 10–30 wt% LLDPE into LDPE film improves tear strength measured by ASTM D1922-15 but increases extruder motor load on single-screw extruders with 25:1 L/D to 30:1 L/D. Melt fracture can be suppressed by raising the temperature profile at the die from 190°C to 205°C or by using a fluoropolymer processing aid, but the latter may affect seal strength if used above 0.1 wt%. In cast film lines using wider die gaps and higher melt temperatures, retained orientation is reduced; property balance is therefore specification-driven rather than generic.

For extrusion coating, autoclave LDPE grades with low melt flow rate values of 4–7 g/10 min are generally preferred because their melt elasticity reduces neck-in and edge instability. The melt is delivered through a T-slot die with a die gap of 0.6–1.0 mm and drawn onto paper, board, or aluminium foil at coating speeds up to 300 m/min in some lines; however, published data for specific line-speed thresholds is limited because adhesion depends on substrate surface energy, corona discharge level, and chill-roll finish. Adhesion is measured by peel tests such as ASTM D1876 or ISO 8510-1, with values reported in N/15 mm or N/25 mm depending on the converting specification. The same autoclave LDPE grades used in extrusion coating should not be assumed suitable for low-haze film because the molecular architecture that supports draw also raises haze under high blow-up ratio conditions.

Processors replacing neat polystyrene with Versalis S.p.A. high-impact grades encounter a two-phase morphology in which rubber particle size and gel content control impact strength. High-impact polystyrene grades typically contain polybutadiene domains of 0.5–4.0 µm, with rubber phase volume 5–15% depending on gloss and toughness targets. Notched Izod impact measured according to ISO 180:2019 can range from 6 kJ/m² to 14 kJ/m² across the high-impact range, while generic GPPS values fall below 2 kJ/m². Melt processing is performed at 200–250°C; prolonged residence above 260°C accelerates rubber-phase degradation and darkening. Drying is recommended when surface moisture exceeds 0.1 wt%, usually at 70–80°C for 2 h. Unlike ABS, the HIPS products do not contain acrylonitrile and therefore exhibit lower chemical resistance to aromatic solvents; this limits use in aggressive cleaning environments despite comparable notched impact values. Flow direction and cross-flow shrinkage differ by 0.1–0.4%, requiring gate placement and hold-pressure adjustment in multicavity tools.

Solution-Polymerized Styrene-Butadiene Rubber and High-Cis Polybutadiene in Tyre Tread Compounds

Solution SBR grades within the Europrene range are specified by bound styrene content of 20–27 wt%, vinyl content between 15% and 55%, and Mooney viscosity ML(1+4) at 100°C of 40–70 MU measured according to ISO 289-1:2018. High-cis polybutadiene grades, typically with cis-1,4 content above 96%, are used as a secondary rubber to improve abrasion resistance and fatigue crack growth. Mixing in a tangential or intermeshing internal mixer uses first-stage dump temperatures of 150–170°C to disperse silica and carbon black; curatives are added during a second stage below 110°C to avoid scorch. Cure kinetics are monitored with a rotorless curemeter under ISO 6502, with optimum cure time defined by the T₉₀ torque rise. Compared with emulsion SBR grades, solution SBR offers lower extractables and more precise vinyl control but generally requires higher shear and tighter temperature control during mixing; zinc-free or reduced-zinc formulations may require re-optimization of the silanization time due to changes in silane coupling kinetics. For extruded profiles and injection-moulded technical rubber goods, the same solution SBR can be diluted with natural rubber or emulsion SBR to reduce compound cost, but at the expense of wet-grip and rolling-resistance indicators.

Expandable polystyrene grades in the Extir line are saturated with pentane at 5–7 wt% and are processed in batch or continuous pre-expanders using steam at 100–120°C. The pre-expanded beads are aged for 6–24 h before moulding to stabilise internal vacuum and residual pentane; block mould pressures are set between 0.8 bar and 1.4 bar depending on density target. Final foam density is controlled from 15 kg/m³ to 40 kg/m³ for packaging and insulation grades, with compressive strength measured under ISO 844:2014 and thermal conductivity under ISO 8301:1991. Differences from extruded polystyrene foam arise from the bead-fusion structure and lower closed-cell orientation; published data for specific fire-retardant package behaviour is limited because performance depends on the blowing agent blend and the selected brominated flame retardant. Storage above 30°C accelerates pentane loss and can shift pre-expansion density.

When Vinyl Acetate Co-monomer Content Exceeds 18 wt% in EVA Copolymer Processing

EVA copolymer grades in the Clearflex range are produced with vinyl acetate contents from 4 wt% to 28 wt%; above 18 wt% vinyl acetate, crystallinity and melting range decline, while adhesion to polar substrates and compatibility with tackifier resins increase. Hot-melt adhesives and extrusion coating require accurate VA determination by ASTM D5594 or FTIR, because even 1 wt% variation in VA can shift heat-seal strength by measurable margins. Processing on single-screw extruders with 24:1 L/D to 30:1 L/D uses barrel temperatures of 90–140°C for high-VA grades, and melt temperatures should remain below 200°C to limit acetic acid evolution. Corrosion-resistant screw and die materials are required when processing high-VA grades; standard nitrided steel may show surface attack after prolonged runs. Unlike acid copolymers, EVA does not provide direct adhesion to aluminium foil without primer or corona treatment; this distinction is critical in multilayer flexible packaging where foil peel strength is specified under ASTM D1876. High-VA grades also show lower Shore hardness, with values dropping below 70 A when VA content exceeds 25 wt% under ISO 48-4, which alters seal-bar release behaviour.

Because the Versalis S.p.A. product range spans non-polar polyolefins, amorphous styrenics, and unsaturated elastomers, storage and handling boundaries are product-specific. Polyethylene and polystyrene should be protected from UV exposure and stored below 40°C away from oxidising agents; EVA grades should be kept in sealed packaging at relative humidity below 60% to prevent surface moisture uptake. Elastomer bales contain stabilizer packages and should be used within the certified shelf life to avoid antioxidant bloom. Incompatibility limits include combination of high-VA EVA with certain phenolic antioxidants at high loadings, and exposure of unsaturated rubber to copper or manganese ions that can accelerate oxidative degradation. Regulatory documentation must be confirmed grade-by-grade; olefin-based food-contact grades may be listed under FDA 21 CFR 177.1520 and Commission Regulation (EU) No 10/2011, but styrenic and elastomer grades are not automatically food-compliant. Electrical and electronic applications should be checked against RoHS Directive 2011/65/EU where brominated flame-retardant grades are considered. Published data for specific bio-based or recycled-content versions within the product family is limited; each lot should be qualified using the relevant ISO 1133-1:2022, ISO 1183-1:2019, and application-specific performance standards.