In blown-film extrusion of light grey refuse sacks and industrial liners produced on single-screw lines with screw L/D between 28:1 and 32:1, LyondellBasell POLYBATCH™ Light Grey LL803366/4 Concentrate Based In LLDPE is gravimetrically metered into a natural LLDPE/LDPE let-down resin at 2.0–3.5 wt%; this addition range normally gives a final film thickness of 45–70 µm with sufficient opacity for light-duty containment. The LLDPE carrier is not an inert pigment paste and can shift the let-down melt-flow rate measured under ISO 1133-1:2022 at 190 °C/2.16 kg; barrel profiles are therefore set from 180–195 °C in the feed zone to 210–220 °C at the die to keep bubble contact and haul-off tension stable. Die gap settings of 1.8–2.2 mm and a blow-up ratio between 2.5:1 and 3.2:1 are used on lines running above 60 m/min, but recycled LDPE fractions with a melt-flow-rate spread above 0.5 g/10 min can destabilise the frost line when the concentrate is added at the upper limit. Screen packs of 80/100/120 mesh downstream of the breaker plate remove agglomerates larger than approximately 150 µm; haze is measured on final film according to ASTM D1003-21, and colour is quantified by ASTM D2244 using D65 illuminant and 10-degree observer geometry. Terminal articles from this processing window include grey refuse sacks, wheelie-bin liners, e-commerce mailer film, and light-duty protection shrouds.

What Processing Windows Govern LL803366/4 Let-Down in Thin-Wall Injection Moulding?

A gravimetric dosing system with shot-to-shot repeatability better than ±0.2% is specified for thin-wall polyolefin parts with nominal wall sections from 0.6 mm to 1.2 mm; melt-flow variation caused by uneven masterbatch feeding appears as short-shot defects and weld-line flow marks before the part reaches the ejection station. LL803366/4 is typically metered at 2.0–4.0 wt% into natural HDPE, LLDPE, or HDPE/LLDPE moulding compounds. Because the concentrate uses an LLDPE carrier, the diluted blend has a slightly lower viscosity than a comparative HDPE-only natural resin; this shift can be logged with ISO 1133-1:2022 at 190 °C/2.16 kg and compared against the natural resin baseline before modifying sprue or gate dimensions. Forced-air drying is not normally required because the LLDPE carrier is non-hygroscopic, but hopper fogging from cold warehouse storage indicates condensed surface moisture and should be eliminated before start-up. Barrel temperatures are normally set between 210 °C and 245 °C, with nozzle temperature held 5–10 °C below the front zone to reduce stringing; hydraulic back pressure between 5 bar and 15 bar is maintained, but dead spots in worn screw tip and check ring regions can produce yellow shift measured as a CIELAB b* increase above 1.5 against the control under ASTM D2244. Pigment dispersion is checked on polished plaques according to ISO 18553, and mould temperature is kept between 20 °C and 40 °C for thin-wall caps and food-service containers. Terminal products include thin-wall caps, closures, stackable totes, and disposable takeaway containers; the light grey masterbatch should not be combined with brass inserts or amine-based antioxidant packages where premature pigment/polymer interaction produces pink-grey discolouration.

Particle-Size Parity Limits Rotational Moulding Use

Rotational moulding of outdoor PE storage tanks and agricultural water butts with wall sections above 4 mm does not accept pelletised LL803366/4 as a direct dry-blend; the pelletised carrier must first be pulverised to pass a 500 µm US Standard 35 mesh screen. Otherwise the pelletised masterbatch segregates from the PE powder, migrates to the inner wall, and produces grey streaks and pinholes at the weld line of the final moulding. The ground masterbatch is introduced at 2.0–4.0 wt% into LLDPE or MDPE powders and mixed in a low-speed helical mixer for 10–20 min; mixing beyond 30 min can create electrostatically bound fines that do not coalesce uniformly. Internal air temperature in the mould is held between 260 °C and 300 °C during the coalescence phase, but light grey colour should not be regarded as a long-term UV stabiliser for PE tanks exposed outdoors; a separate hindered amine light stabiliser and antioxidant masterbatch must be qualified for the intended service life. Published data for this specific pelletised concentrate in food-contact rotomoulded tanks is limited, so final-article migration testing according to EU Regulation (EC) No 10/2011 or FDA 21 CFR 177.1520 is required before such use. Terminal products are grey chemical storage tanks, underground utility chambers, and agricultural water-holding cells.

HDPE Sheet Melt Strength and LLDPE Carrier Dilution Effects

In flat-die sheet extrusion from 0.5 mm to 6 mm thickness, LL803366/4 is metered at 1.5–3.0 wt% into natural HDPE or LLDPE/HDPE blends, and the three-roll stack is operated with middle roll surface temperature 60–90 °C to avoid embossed surface defects. The LLDPE carrier broadens the melting range of the diluted resin, which can reduce melt strength at the die lip; this is observed as edge sag and non-uniform draw after the sheet exits the calendar stack, particularly when die temperature exceeds 200 °C. In polypropylene sheet, the same concentrate is not fully miscible: differential scanning calorimetry on blended samples commonly shows a separate low-temperature melting endotherm from the LLDPE carrier, and flexural modulus tested according to ISO 178 or ASTM D790-17 may fall with increasing masterbatch addition. Let-down above 2.5 wt% in PP should be preceded by a notched impact test and a low-temperature instrumented falling-weight test on the actual part because the dispersed LLDPE phase can act as a stress concentrator at service temperatures below −10 °C. Terminal grey sheet products include industrial dunnage trays, reusable transit sheets, appliance back panels, and thermoformed automobile trunk floor liners.

Under High Line Speeds, Melt-Pressure Oscillation Governs Drip Tube Colour Uniformity

Light grey drip irrigation laterals and HDPE ducts extruded above 30 m/min require a gravimetric feeder with repeatability better than ±0.3%; LL803366/4 is fed into a natural PE80 or PE100 compound at 1.5–3.0 wt%, and the small tube diameter of 12–20 mm plus thin wall leaves a short residence time to homogenise masterbatch streaks. Screw L/D ratios of 24:1 to 30:1 are common on these lines, and pressure transducers ahead of the breaker plate should hold a melt-pressure band within ±10 bar; longer-period oscillations indicate feed surging or a carrier melt-flow mismatch and correspond with longitudinal light/dark grey banding on the extrudate surface. Dispersion is assessed on microtomed cross-sections by ISO 18553. Light grey pigmentation does not replace carbon black for UV blocking; pipes intended for multiyear above-ground solar exposure should be coextruded with a carbon black outer layer or formulated with a separate UV stabiliser masterbatch. For potable water contact, final system compliance with NSF/ANSI 61, AS/NZS 4020, or equivalent national standards must be demonstrated on the finished pipe and fittings. Terminal products are grey drip laterals, grey HDPE ducts, and low-pressure irrigation headers.

When low-voltage power, signal, or instrumentation cable outer jacketing is specified in light grey, the formulation is more demanding than black jacketing because the absence of carbon black removes a natural UV-screening pigment; LL803366/4 is incorporated at 2.0–3.0 wt% only after the jacket compound has been qualified for thermal and UV endurance with a separate stabiliser package. The concentrate is added using a hopper or side gravimetric feeder on a single-screw cable extruder with L/D 24:1–30:1; melt temperatures are normally kept between 160 °C and 210 °C for EVA-rich sheath formulations, and screw speed is trimmed to keep die-head pressure stable because pigment agglomerates can accumulate on breaker plates after runs longer than 8 h. Final jackets are tested for tensile strength and elongation at break before and after thermal ageing according to IEC 60811-501, and the light grey shade is assessed against a customer-approved CIELAB reference using ASTM D2244. LL803366/4 is not recommended for primary insulation layers unless the complete insulation system passes the applicable electrical property tests, because the masterbatch is intended for sheath colouration only. Terminal products include grey sheathing for control cables, instrumentation lines, and low-voltage power distribution cables.