In extrusion blow moulding of 20 L to 60 L chemical containers, Arya Sasol MDPE 3820 is processed on shuttle-type blow moulding machines fitted with a grooved-feed extruder of 70–90 mm screw diameter and 24:1 to 30:1 L/D barrier screws. The melt temperature at die entry is held between 195°C and 210°C; operation above 215°C lowers parison hang strength by reducing extensional viscosity, producing wall-thickness thinning in the lower pinch-off region of tall containers. At a nominal melt flow rate of 2.0 g/10 min under ISO 1133-1:2022 and density of 0.938 g/cm³ under ISO 1183-1:2019, the resin provides sufficient melt strength for accumulator-head parison extrusion but is not suitable for high-speed wheel machines where melt fracture and uncontrolled die swell are observed at melt flow rates below 4.0 g/10 min. A parison programmer with at least 20 points is required for containers with height-to-diameter ratios above 2.5:1; die gap modulation between 0.8 mm and 2.5 mm compensates for die swell and gravitational sag. Blow pressure is maintained at 0.6–0.8 MPa and mould cooling water is held at 8–12°C to accelerate solidification of the inner wall. The main technical advantage of this density class is environmental stress crack resistance; when tested under ASTM D1693-21 Condition B in 10% Igepal CO-630 at 50°C, MDPE grades of this density class typically exceed 1000 h F50, while a 0.950 g/cm³ HDPE blow moulding grade may fail between 100 h and 300 h in the same chemical environment. The pinch-off weld is the limiting zone; weld-line ESCR commonly drops to 30–50% of the sheet value, so die temperature and pinch clearance must be set to generate a flash bead at least 1.2 mm thick. Containers intended for UN-certified chemical transport require drop testing at -18°C according to ADR/RID packaging instructions; the low-temperature impact resistance of MDPE 3820 is evaluated on the finished article by drop impact testing under ASTM D2463-15. Published data for this specific container configuration is limited because final performance is governed by mould venting, clamp tonnage, and article geometry.

Does Medium-Density Core-Layer Extrusion Alter Tear Propagation in Heavy-Duty Shipping Sacks?

Coextruded heavy-duty sack film using Arya Sasol MDPE 3820 as the core layer is produced on three-layer blown-film lines with die diameters from 200 mm to 300 mm, die gap 1.2–1.8 mm, and blow-up ratios between 2.0:1 and 2.8:1. The core is normally blended with 10–30 wt% LLDPE C4 or LLDPE C6 to raise dart impact and reduce machine-direction tear anisotropy; the outer layers are LLDPE or LDPE for heat sealing. Film thickness in this application ranges from 60 µm to 120 µm. Melt temperature at the die is set to 200–220°C and the frost-line height is kept at 1.5–2.0 times the die diameter to stabilise the bubble. The influence of the medium-density core on tear propagation is measured by Elmendorf tear testing under ASTM D1922; machine-direction tear in an 80 µm film typically declines by 15–25% relative to an all-LLDPE film of equal gauge, while transverse-direction tear increases, producing tear ratios above 3.0. This shift occurs because the 0.938 g/cm³ core has higher crystallinity and lower elongation at break than the adjacent LLDPE layers. Dart drop impact under ASTM D1709-16A for an 80 µm film is lower than an all-LLDPE equivalent, and the MDPE core contributes primarily to creep resistance and stack-load performance rather than impact. The 1% secant modulus of the film is measured under ASTM D882-18; a 70/30 MDPE/LLDPE core film can exceed 400 MPa in the machine direction, which reduces pallet stack failure. The process boundary is bubble instability when the MDPE core exceeds 40 wt% under blow-up ratios above 2.5:1; internal bubble cooling is then required. Haze values in heavy-gauge film typically exceed 15% under ASTM D1003-21, so this formulation is not used for high-clarity overwrap. Food-contact status is determined on the finished article under EU Regulation No 10/2011 and FDA 21 CFR 177.1520, with the outer layers selected to control migration; MDPE 3820 should not be used as the direct food-contact layer without validation.

When corrugated drainage pipe is extruded without a separate structural foam layer, the medium-density resin contributes to ring stiffness and slow crack growth resistance. Pipe lines for MDPE 3820 use single-screw extruders with 30:1 L/D barrier screws and screen packs of 60/40/20 mesh; melt temperatures are held at 200–220°C and the upper processing limit is set at 240°C under ISO 11357-6. The corrugator runs at 1.5–4.0 m/min depending on diameter; vacuum forming pressure at the corrugation blocks is set between 0.06 MPa and 0.08 MPa. Ring stiffness is certified under ISO 9969; for MDPE pipe, SN4 or SN6 classes are achieved at standardised wall thicknesses depending on outside diameter. Slow crack growth resistance is characterised by the notched pipe test under ISO 13479; MDPE 3820 pipes typically exceed 200 h at 80°C and 4.0 MPa hoop stress, although public data for this specific grade in corrugated pipe is limited and should be confirmed by converter testing. The density of 0.938 g/cm³ is not sufficient for pressure pipe rated PE100, which requires higher hydrostatic strength and a density typically above 0.945 g/cm³ with a bimodal molecular weight distribution; therefore MDPE 3820 is used only in non-pressure drainage, soil-water retention, and cable duct applications. Notched impact resistance after conditioning at -20°C is evaluated under ISO 179-1; corrugated MDPE pipe can sustain impact despite wall-thickness discontinuities if the corrugation geometry is designed with a radius-to-thickness ratio above 2.0.

Injection Moulded Closure Bodies Under Repeated Flexure

Injection moulding of thick-wall industrial closures from MDPE 3820 is limited to shot weights above 50 g because the 2.0 g/10 min MFR under ISO 1133-1:2022 requires higher injection pressures than high-flow HDPE closure grades in the 20 g/10 min class. Machines with clamp force from 150 tonnes to 350 tonnes are used; melt temperature is set at 220–240°C, injection pressure at 90–120 MPa, and mould temperature at 20–40°C. The hinge region of a closure body is the critical zone; hinge flexural endurance is evaluated by repeated flexure testing under internal protocols, and resistance to crack initiation is compared using notched Charpy impact under ISO 179-1. MDPE 3820 is expected to exhibit notched Charpy impact above 20 kJ/m² at 23°C based on the density class; a minimum hinge thickness of 0.4 mm is used in closure designs. The 0.938 g/cm³ density lowers flexural stiffness relative to a 0.952 g/cm³ HDPE; closure strip torque may be lower by 5–10%, and this must be compensated by rib design or increased wall section. Environmental stress crack resistance under ASTM D1693-21 Condition B is the main reason this grade is selected for closures used with detergents, agrochemicals, and swimming-pool chemicals. Mould release additives containing migratory erucamide are restricted below 0.1 wt% because they reduce adhesion for tamper-evident induction liners. Published data for this specific grade in closure moulding is limited; tooling trials are required to establish gate freeze time, flatness after demoulding, and dimensional stability after 48 h annealing at 70°C.

When Flat-Die Sheet Extrusion Requires Weld Integrity Without HDPE Full Stiffness

For flat-die sheet extrusion of chemical tank lining and medium-thickness geomembrane, MDPE 3820 is processed on 90 mm single-screw extruders with barrier screws, screen changers at 80/100/120 mesh, and flat dies with a nominal die gap of 1.0–1.5 times the final sheet thickness. Melt temperature at the die is 220–235°C, chill roll temperature is 40–60°C, and line speed is 3–8 m/min for sheet from 1.0 mm to 2.0 mm. Tensile properties are certified under ISO 527-3; the yield strength of MDPE sheet is lower than HDPE by approximately 15–20%, which may not meet all geomembrane class specifications. The grade is therefore used where weld integrity and chemical resistance are valued over stiffness. Hot-wedge welding trials show that MDPE 3820 sheets in the 1.5 mm thickness range can achieve a seam peel strength above 70% of parent sheet when wedge temperature is 320–360°C and travel speed is 1.0–1.5 m/min, although published data for this specific grade is limited. Tear resistance is assessed under ASTM D1004-21, and chemical resistance is validated by immersion in 10% nitric acid for 28 days with mass change typically below 0.5%. Water vapour transmission rate is lower than LDPE by 30–40% under ASTM E96-22 at 38°C and 90% relative humidity, which supports containment of aqueous solutions. This conversion route is not recommended for sheet thickness below 0.5 mm because edge trim fracture and draw resonance occur at the 2.0 g/10 min MFR.