Feeding HDPE COM70HF1 into a high-speed injection moulding cell for thin-wall beverage closures requires control of shear-sensitive flow behaviour at filling velocities that routinely exceed 200 mm/s in the runner system. The barrel profile is set between 180 °C at the feed throat and 230 °C at the nozzle, while the hot runner manifold is held within ±5 °C of the nozzle set point to prevent premature gate freeze. Gates are dimensioned with land lengths below 0.8 mm and are placed in sub-surface or edge configurations to limit pressure drop during the pack phase. Injection velocity is increased until the flow front fills the tamper-evident band without jetting, which on multicavity closures is normally confirmed by short-shot progression at 10% increments. Hold pressure is maintained until cavity pressure transducers show a clear decay inflection indicating gate freeze. Mould temperature is controlled at 10–30 °C with turbulent water channels and monitored at each cavity wall. Dimensional stability is assessed after 24 h ambient conditioning using ISO 294-4, with shrinkage for thin-wall HDPE closures typically in the 1.5–2.5% range. Finished closures are tested for drop impact according to ASTM D2463-15, and closure retention or strip torque is measured on application-specific capping heads. Food-contact status is verified under FDA 21 CFR 177.1520(c) and EU No 10/2011, with overall migration determined by EN 1186-1. When slip and anti-block masterbatches are used at 1–3 wt%, coefficient of friction is checked against ISO 8295 because erucamide migration can alter cap decoration and downstream capping torque.

On production-scale closure lines, cavity-to-cavity fill imbalance exceeding 5% by shot weight has been correlated with ovality drift above the tolerance of high-speed capping equipment. Gate freeze must be confirmed by cavity pressure transducer decay rather than timer-only hold settings, because barrel lot changes can shift solidification time by more than 0.3 s on thin-wall rims. The screw should have a compression ratio of 2.5:1 to 3.0:1 and an L/D ratio of 20:1 to 25:1, with a non-return valve seal inspected at scheduled intervals to avoid shot-weight variation. Pre-drying is not normally required if sealed packaging is handled, but storage at relative humidity above 60% can introduce surface moisture sufficient to cause splay in thin sections. Material cleaned from purges should not be re-introduced into food-contact closures unless the re-grind fraction is controlled and migration re-tested under EN 1186-1.

What Defines the Extrusion Blow Moulding Window for Small Rigid Containers?

For small containers under 1 L, COM70HF1 can be processed on a shuttle blow moulder with a continuous extrusion head, but the operating window is narrower than for a dedicated blow-moulding HDPE because the melt flow behaviour increases parison sag. Melt temperature is held in the lower portion of the HDPE envelope, normally 180–200 °C, to preserve adequate melt strength during parison hang time. The extruder is specified with an L/D ratio of 24:1 to 30:1 and a barrier-type screw, which stabilises output against die pressure variation. Parison programming is not optional; a wall-thickness programmer is required to compensate for flare at the tail and thinning at the neck. The die gap is adjusted for a blow-up ratio that keeps container sidewall stress within measurable limits. Mould closing speed is set to avoid excessive pinch-off tailing, and the flash pocket is vented to prevent air entrapment at the parting line. Blow pressure is applied at 0.6–0.8 MPa through calibrated needle blow pins, followed by post-mould cooling in a sizing fixture for neck and handle regions. For household chemical containers, environmental stress-crack resistance is evaluated under ASTM D1693, Condition A or B, with the specific F50 acceptance criterion set by the brand owner. Grade-specific published data for COM70HF1 in extrusion blow moulding is available from the producer’s technical service, but line validation remains required because parison sag depends on melt temperature, shot size, and die gap together rather than on melt index alone.

Thermoformed Thin-Gauge Sheet: Plug-Assist Sequencing and Cooling

Sheet extrusion at 0.3–1.0 mm gauge demands a flat die with automatic gauge control keeping thickness within ±3% across the web. Melt temperature at the die is maintained at 200–220 °C, and the sheet is polished on a three-roll stack with roll temperatures of 60–90 °C to balance surface gloss and residual stress. The reheated sheet enters a form-cut-in-place thermoformer where the lower surface temperature is set just above the crystalline melting temperature; the grade-specific peak melting point is determined by ISO 11357-3 differential scanning calorimetry. Plug-assist speed, plug depth, and plug delay are set as a coordinated sequence to avoid base-thickness thinning below 60% of the starting sheet gauge. Plug material is syntactic foam or P20 steel with independent temperature control, and plug surface texture is specified to avoid sticking without the use of external release agents that could compromise food-contact compliance. Vacuum and air pressure are sequenced only after the plug has displaced the sheet into the cavity, preventing early cooling against the plug. Residual moisture in the sheet above 0.02% causes bubble defects during heating; pre-drying is required when storage humidity exceeds 60% RH. For fatty food applications, compliance under EU No 10/2011 requires migration testing with simulant D2 according to EN 1186-1, and the thermoformed article should be trimmed with die cutting that compensates for anisotropic sidewall shrinkage.

In masterbatch production, HDPE COM70HF1 functions as a carrier resin for pigment and additive systems that are let down at 2–5% in the final moulding or extrusion resin. Compounding is performed on a co-rotating twin-screw extruder with an L/D ratio of 40:1 to 44:1 and screw diameters of 25–75 mm depending on line scale. Pigments and mineral additives are introduced through side feeders located after the polymer melting zone, while liquid dispersants and antioxidants are added through injection lances at 0.5–1.5 wt%. Melt temperature is controlled within 200–230 °C and monitored by an infrared melt probe, with vacuum devolatilisation applied at −0.08 MPa to strip residual moisture and low-molecular-weight volatiles. The melt strand is cooled in water at 20–40 °C and pelletised to a uniform length of 2.5–3.5 mm to prevent feeding stratification in downstream dilute-phase blenders. Dispersion quality is inspected by filter pressure rise and by optical microscopy on pressed films, because pigment agglomerates above 10 µm can create film or fibre defects at low let-down ratios. Thermal stability of the compounded carrier is checked by melt flow rate retention after multiple extrusion passes according to ISO 1133-1:2022. A masterbatch based on COM70HF1 cannot automatically inherit the food-contact status of the base resin; every additive formulation must be re-evaluated under EU No 10/2011 and FDA 21 CFR 177.1520 through migration testing of the final article.

When COM70HF1 Replaces Conventional HDPE in Monofilament Extrusion

Monofilament extrusion of HDPE COM70HF1 is limited to diameters above 0.20 mm because the grade’s high-flow behaviour reduces the maximum continuous draw ratio before melt fracture or filament break-up. The line consists of a single-screw extruder with a metering section length of at least 8D, a spinning head with screen pack filtration, a water quench tank at 30–40 °C, a first godet stand, a heated drawing oven, a second godet stand, and an online diameter gauge. Melt temperature is set between 190 °C and 220 °C, and the quench bath temperature is adjusted to control crystalline orientation before drawing. The first godet speed is typically set at 10–25 m/min, while the second godet speed is adjusted to produce a draw ratio of 6:1 to 8:1; however, published data for COM70HF1 in this specific configuration is limited, and the exact draw ratio must be established by line trials. Annealing in a hot-air or water bath at 80–100 °C reduces free shrinkage and stabilises the oriented structure. Tensile strength is measured according to ISO 2062 or ASTM D2256, and knot strength is determined separately because high-flow HDPE can show lower knot efficiency than grades designed for monofilament. For netting and brush applications, elongation at break is normally maintained above 15%, but the acceptable range depends on the end-use standard and the drawing ratio selected.

Compression Moulding Is Applied to Prototype Liners and Thick-Wall Parts

Compression moulding is applied when short runs or thick-walled parts require low residual stress and the absence of gate or weld-line weaknesses. COM70HF1 is charged as powder or pellets into a matched metal mould mounted in a hydraulic press. Mould temperature is maintained at 170–190 °C, and clamp pressure is applied at 2–5 MPa on the projected part area. The press closes in multiple stages, with slow closing below 50 mm/s for the final 5 mm of stroke to allow trapped air to escape. Breathing cycles may be introduced at 30 s intervals to vent volatiles and reduce void formation in thick sections. Cooling under pressure is continued until the core temperature falls below 60 °C, because ejection above this temperature can cause post-mould warpage. Dimensional stability is measured after 48 h relaxation according to ISO 279, and cooling rates above 10 °C/min are avoided in sections thicker than 10 mm to minimise internal voids. This route is suitable for prototype liners, thick-walled machine guards, and moulded plates where compression moulded consistency under ISO 293 is required for material qualification. For industrial parts placed on the EU market, REACH Article 33 of Regulation (EC) No 1907/2006 requires SVHC content to remain below 0.1% w/w per article unless specific communication obligations are triggered.