On monolayer blown film lines producing grey heavy-duty sacks, construction sheeting, and temporary weather-protection membranes, the LLDPE carrier of LyondellBasell POLYBATCH™ Lattice Grey 80354U/4 is introduced at 2–4 wt% through a gravimetric hopper loader upstream of the feed throat. The carrier is metered into a single-screw extruder with an L/D ratio of 25:1 to 30:1, a barrier flighted screw, and a spiral mandrel die gap of 1.6–2.4 mm; barrel zones are typically profiled from 160–190°C in the feed section to 210–230°C at the metering section, with melt temperature at the die between 195°C and 230°C. Blow-up ratio is maintained from 2.2:1 to 3.0:1, and the frost-line height is adjusted to control bubble stability; because the concentrate uses an LLDPE carrier, the melt-phase viscosity mismatch in LLDPE-rich film blends is lower than with LDPE-carrier or PP-carrier masterbatches, which reduces the probability of pigment specking and die-lip plate-out. Tensile anisotropy is monitored according to ASTM D882, dart impact by ASTM D1709 Method A, Elmendorf tear by ASTM D1922, and opacity by ASTM D1003. Visual dispersion is checked by counting visible pigment agglomerates over a 1 m² sample under 2000 lux inspection light; agglomerates larger than 50 µm at the film surface indicate inadequate back pressure or a worn screw. No pre-drying is generally required when the package remains sealed, but at relative humidity above 80% the material should be pre-dried in a hopper dryer at 60°C for 2 h to prevent moisture streaks. In high-line-speed applications above 80 m/min, static charge on the pellets can cause feed-throat bridging, so a grounded feed hopper or ionizing air bar is recommended.

Does Gate Freeze Pressure Affect Pigment Aggregate Retention in Thin-Wall Grey Moulding?

In thin-wall grey crate, tote, and automotive interior trim moulding, the concentrate is metered at 1.5–3.0 wt% into a reciprocating-screw injection moulding machine with an 18:1 to 22:1 L/D general-purpose polyolefin screw, a compression ratio of 2.5:1 to 3.0:1, and a non-return valve. Nozzle melt temperature is held between 210°C and 250°C; hydraulic back pressure is set at 0.5–1.2 MPa to maintain pigment dispersion without excessive shear heating. Injection pressure is typically 80–120 MPa, and clamp force is scaled at 0.4–0.6 kN/cm² of projected mould area for thin-wall tools. The critical processing conflict occurs when the gate freezes before the packing phase fully decays: the carrier-rich phase continues to orient through the gate while pigment aggregates become frozen near the flow front, producing gate blush and grey streaking parallel to flow. This defect is reduced by increasing gate diameter, extending hold pressure, or reducing the letdown to 2 wt% rather than increasing melt temperature without control. Mechanical properties of the grey moulding are verified by ISO 527-2 or ASTM D638-14 for tensile strength and elongation, ISO 179-1 for notched Charpy impact, and ISO 178 for flexural modulus. Because the LLDPE carrier is not the base resin of polypropylene matrices, addition above 3 wt% in PP homo- or copolymer parts may reduce rigidity and alter gloss; published data for this specific configuration is limited, so multi-shift trials with falling-dart impact and weld-line tensile bars are required before locking the formulation. The masterbatch melt mass-flow rate should be recorded per ISO 1133-1:2022 at 190°C/2.16 kg; a carrier MFI far below the dilution resin can demand back pressure above 1.2 MPa or a mixing screw to avoid pigment agglomerates larger than 30 µm in the cavity.

Compliance verification for grey polyolefin articles using an LLDPE-carrier masterbatch is application-specific; the absence of a standard from the following matrix does not imply suitability. The converter is responsible for final article testing under the intended use conditions.

Extrusion blow moulding of grey HDPE industrial pails and agricultural chemical containers uses the concentrate at 2–3 wt% because the LLDPE carrier raises low-shear viscosity relative to HDPE, which changes parison swell and hang time. Accumulator-head machines with 24:1 L/D extruders and diverging die gaps of 1.5–3.0 mm are generally serviceable at melt temperatures between 190°C and 220°C; continuous shuttle machines may require more frequent die-lip wipe cycles because LLDPE fractions can accumulate at the die land and produce longitudinal grey die lines. The grey pigmentation does not replace the need for internal chemical resistance validation: containers used with aggressive liquid formulations are tested according to ASTM D543 or ISO 22088-1, and environmental stress crack resistance is measured by ASTM D1693 Condition B. Tensile yield at the pinch-off weld is checked by ISO 527-2; a drop in weld strength above 3 wt% masterbatch indicates that the LLDPE carrier is locally increasing the crystal orientation at the pinch-off zone. The concentrate should not be considered an ESCR improver; carbon-grey pigment systems can mask surface stress whitening but do not prevent crack growth. Published data for this specific configuration is limited, so blow-moulded containers for dangerous goods packaging require additional drop testing under ASTM D5276 and stack testing before use.

When a Grey Cap Layer Replaces Carbon Black in Coextruded Sheet for Thermoforming

Where a grey cap layer is extruded over a black-filled core in coextruded sheet for automotive interior trim, industrial housing, or reusable dunnage, the masterbatch is metered into the cap-layer extruder at 3–5 wt%. The cap layer is maintained at 8–12% of total sheet thickness; this band keeps the grey tone stable without allowing the carbon-grey pigment loading to reduce cap-layer elongation more than the core. The cap-layer extruder is typically a 30:1 L/D single-screw machine with a gear pump and a screen pack of 40/60 mesh, with melt temperature between 210°C and 240°C. Viscosity matching is the limiting factor: if the LLDPE-carrier cap layer runs against a polypropylene core, the viscosity ratio at 100 s⁻¹ should not exceed approximately 2.5:1; published data for this specific configuration is limited, so coextrusion feedblock pressure traces and line-speed sweeps are used to detect incipient interfacial instability before lock-in. Thermoforming behaviour is measured by sheet tensile elongation per ISO 527-2, multiaxial impact per ISO 6603-2, heat deflection temperature per ISO 75-2, and surface gloss after forming per ASTM D523. Because carbon-grey cap layers absorb infrared energy differently than unfilled layers, the sheet surface temperature is monitored by infrared pyrometry at 170–200°C before the forming station; overheated cap layers above 200°C show reduced grey uniformity and an increased tendency to delaminate at the core interface. The concentrate should not be combined with amine-based additive masterbatches in the same cap-layer hopper because acid-base interaction can destabilize the pigment dispersion and produce plate-out on polishing rolls.

Rotational moulding of grey LLDPE tanks, bins, agricultural hoppers, and outdoor enclosures requires the pelletized concentrate to be pulverized or supplied as a micropellet with a particle-size distribution matching the 35-mesh (500 µm) base powder. When dry-blended prior to charging, the carrier particles must pass a 35-mesh screen at ≥98%; oversized carrier particles melt late in the cycle and leave pigment-rich dots at the inner surface, especially in deep ribs and sharp corner radii below 3 mm. Peak internal air temperature in the oven is usually 200–240°C, and the part wall thickness is commonly 3–6 mm. The mould rotation ratio is set at 4:1 primary-to-secondary axis for most tanks, and initial air cooling at 10–15°C/min followed by water mist cooling controls pigment migration in the melt pool and minimizes warpage at the parting line. At addition levels above 2 wt%, the dry blend should be evaluated for bulk density and dry-flow angle; static charge increases agglomeration when ambient relative humidity is below 30%, so ground hoppers and antistatic feed tubes are specified. Mechanical performance is measured by ASTM D638-14 for tensile properties, ASTM D1998 for polyethylene tanks, and ASTM D1693 for environmental stress crack resistance. Because rotomoulding uses no shear, the masterbatch pigment system must be pre-dispersed in the carrier; any pigment agglomerates remaining in the carrier survive the low-shear melt pool and appear as surface specks. Published data for this specific grey concentrate in rotomoulding-grade LLDPE is limited, so the first production lot should be screened for low-temperature impact by ARM low-temperature impact test methods and for pinholes by a 10 kV spark tester on hollow parts.

Wire Jacketing: Screen-Pack Loading, UV Screening, and Carbon-Grey Tone Control

In LLDPE-based wire and cable jacketing, the grey concentrate is added at 2–5 wt% to a compounding or direct-sheathing line using a 24:1–30:1 L/D barrier screw, gear pump, and screen pack of 60/80/100 mesh. Melt temperature at the crosshead die is maintained between 180°C and 220°C; above 220°C, carbon-grey oxidation can shift the jacket tone brown and reduce UV screening efficiency. The grey pigment system acts as a partial UV screening agent when carbon black is present, but the finished jacket requires weathering validation by IEC 60811-4-1 or ASTM D4329, with colour retention measured by ASTM D2244. Surface smoothness is inspected at 10× magnification; pigment agglomerates above 50 µm are unacceptable because they create stress concentration points during repeated bending tests conducted per IEC 60811-1-4. The screen pack is positioned after the gear pump to protect the breaker plate from carbon-grey agglomerates; an increase in pressure drop across the screen pack of more than 20% during a shift indicates pigment or gel accumulation and requires screen replacement. For low-smoke halogen-free jacketing formulations, the addition of an LLDPE-carrier grey masterbatch must be checked against IEC 60754-1 and IEC 60754-2 for acid gas evolution and pH/conductivity; carbon-grey concentrates that pass standard PE jacketing requirements may not be suitable for halogen-free compounds because the pigment system can alter char formation. The material should not be exposed to open flame during hopper cleaning; carbon-black-containing concentrates can form conductive dust layers in poorly grounded conveying systems.