SABIC LLDPE 122WJ is a butene-comonomer linear low density polyethylene produced by gas-phase polymerization and supplied as cylindrical pellets. The base resin is specified at a nominal melt flow rate of 2.0 g/10 min when measured at 190°C/2.16 kg according to ISO 1133-1:2022, and a nominal density of 0.922 g/cm³ according to ISO 1183-1:2019. The product is intended for blown film converting lines where intermediate melt flow, bubble stability, and film toughness must be balanced. Primary application classes include heavy-duty sacks, carrier bags, industrial liners, and agricultural film. The comonomer chemistry and molecular weight distribution differ from high-pressure low density polyethylene and from metallocene-catalysed ethylene-alpha-olefin copolymers; the consequence is a specific balance of elongational viscosity, seal initiation temperature, and optical haze. The additive package is proprietary and must be confirmed against the certificate of analysis, because slip and antiblock loadings directly influence coefficient of friction, blocking behaviour, and print adhesion. The molecular architecture of 122WJ introduces ethyl branches along the polyethylene backbone. The short-chain branching distribution of a Ziegler-Natta gas-phase LLDPE is broader than that of a metallocene-catalysed grade; therefore, the resin contains chains with low comonomer incorporation and chains with higher incorporation. This distribution affects thermal behaviour: the melting peak is broad, and the seal initiation temperature is higher than for a homogeneously branched C6 copolymer of the same density. The weight-average molecular weight and molecular weight distribution are not routinely published in product literature; however, the measured melt flow rate of 2.0 g/10 min per ISO 1133-1:2022 indicates an intermediate viscosity that supports both adequate extruder throughput and bubble stability. The absence of long-chain branching relative to high-pressure LDPE reduces strain-hardening in the melt, lowering bubble stability and requiring frost-line control at high blow-up ratios.

Which Extrusion and Rheology Parameters Govern 122WJ Processing?

In blown film production, 122WJ is run at an extruder melt temperature between 190°C and 215°C. A die gap of 1.5 mm to 2.5 mm is used to maintain wall shear stress below the melt fracture threshold; when melt fracture appears as sharkskin at high output, polymer processing aid is added at 400–800 ppm. Blow-up ratio is controlled at 2.0:1 to 3.0:1, with frost-line height adjusted to keep the film bubble below the crystallization onset temperature until biaxial orientation is complete. On a production-scale single-screw extruder with screw L/D of 25:1 to 30:1, barrel zone settings start at 150–170°C near the feed throat and rise to 200–210°C in the metering zone. The die lip temperature is maintained within ±2°C of setpoint to prevent gauge variation. The maximum attainable output on a given line is not fixed solely by screw torque. For 122WJ, bubble instability and melt fracture are the limiting defects at high screw speed. On a 45 mm extruder with smooth-bore feed and 24:1 L/D, a stable output of 35–45 kg/h may be obtained at a melt temperature of 205°C; higher output generally requires a grooved-feed extruder or a barrier screw with dedicated mixing sections. Internal bubble cooling extends the output window by removing heat from the film and reducing frost-line height. If the line has no internal bubble cooling, the maximum blow-up ratio should be kept below 3.0:1 to avoid bubble breathing and gauge variation. No pre-drying is required under normal indoor storage; if pellet condensation occurs after cold outdoor storage, a desiccant hopper at 60°C for 2 h is sufficient. Melt temperatures above 220°C with residence times exceeding 5 min should be avoided because oxidative chain scission can generate gel defects and reduce dart impact. Quality control for incoming resin should include melt flow rate per ISO 1133-1:2022, density per ISO 1183-1:2019, and visual pellet contamination inspection. Moisture content should be below 0.05% by Karl Fischer titration if the resin has been exposed to humid air; standard polyethylene is not hygroscopic, but surface condensation can introduce water into the feed throat and create surface defects. Bulk handling equipment should avoid long transfer distances that generate fines; fines above 0.5% by weight can accumulate at the hopper throat and cause feed instabilities.

Mechanical, Thermal, and Optical Property Envelope

The typical values in Table 1 are measured on 50 µm blown film produced at a blow-up ratio of 2.5:1 and a die gap of 1.6 mm. They are manufacturer-published typical data and do not replace lot-specific certificate of analysis values.

Table 1: Typical resin and film property data

Property	Test method	Unit	Typical value
Melt flow rate	ISO 1133-1:2022	g/10 min	2.0
Density	ISO 1183-1:2019	g/cm³	0.922
Tensile stress at yield MD/TD	ISO 527-3:2018	MPa	11 / 11
Tensile strain at break MD/TD	ISO 527-3:2018	%	650 / 750
Dart impact F50	ISO 7765-1:2004	g	110
Elmendorf tear MD/TD	ISO 6383-2:1983	g	60 / 110
Haze	ASTM D1003-13	%	12
Gloss at 45°	ISO 2813:2014	GU	50
Vicat softening point A50	ISO 306:2022	°C	100
Melting peak temperature	ISO 11357-3:2018	°C	108
Seal initiation temperature	ASTM F1921-12 Method B	°C	105

The film property data are dependent on processing conditions. At a given density and melt flow rate, higher blow-up ratio increases transverse orientation and raises Elmendorf tear in the transverse direction while reducing machine-direction tear. Frost-line height influences crystallinity; a lower frost-line height quenches the film rapidly, reducing haze but also reducing dart impact. Therefore, the converter should generate an internal property map rather than rely solely on datasheet values. Lot-to-lot variability in melt flow rate is typically controlled within ±0.2 g/10 min, and density within ±0.001 g/cm³; these tolerances are not specification limits unless stated on the certificate of analysis. Compared with high-pressure LDPE at equivalent melt index, 122WJ has a linear backbone that raises tensile strain at break and puncture resistance but increases shear heating during extrusion. Against a lower-density C4-LLDPE of 0.918 g/cm³, the 0.922 g/cm³ density of 122WJ increases secant modulus and reduces oxygen permeability per unit thickness, while the higher density narrows the dart impact and low-temperature toughness window. Against metallocene-catalysed C6 or C8 grades, the broad short-chain branching distribution of a Ziegler-Natta butene LLDPE lowers hot-tack strength and optical homogeneity. Published data for direct comparison between 122WJ and metallocene octene grades is limited. In practice, 122WJ is selected where a stiffness-driven film construction is required and where the converting line does not require the ultra-high dart impact of octene mLLDPE. When replacing a standard LDPE in a heavy-duty sack, thickness may be revalidated by dart impact testing per ISO 7765-1:2004 rather than assumed from density ratio alone. Against high-density polyethylene film grades with density 0.941–0.965 g/cm³, 122WJ has lower modulus and higher tear-propagation resistance, making it less suitable for applications requiring high tensile stiffness but more suitable for puncture-resistant liners. Against ethylene-vinyl acetate copolymer films, 122WJ lacks the polar acetate group, which changes dielectric properties and seal initiation behaviour; it also has lower water vapour transmission rate at equivalent thickness.

When 122WJ Replaces High-Pressure LDPE in Heavy-Duty Sack Film

On a 55 mm single-screw blown film line with a 120 mm spiral mandrel die and 1.6 mm die gap, substitution of LDPE with 122WJ typically increases die pressure because of the linear molecular architecture. Extruder barrel zones are set with a profile of 150°C at the feed zone, 180°C in the compression zone, and 200°C in the metering zone, with die zones maintained at 200–210°C. Screw speed is increased until melt temperature reaches 210°C; the maximum stable output is often limited by bubble instability rather than extruder torque. Die pressure should be monitored at the screen pack and breaker plate. If screen-pack differential pressure exceeds 80 bar, the screen pack is changed to prevent gel development. For a 50 µm film, the heat-seal jaw temperature is initially set at 120–125°C and then adjusted using a seal curve generated according to ASTM F1921-12 Method B. Because the seal initiation temperature of the grade is approximately 105°C, dwell time can be reduced by 0.2–0.4 s relative to LDPE at equivalent jaw temperature. Film produced on this equipment at 50 µm is re-validated for dart impact per ISO 7765-1:2004 and Elmendorf tear per ISO 6383-2:1983, because gauge reduction from LDPE requires confirmation on the actual converting line. On form-fill-seal packaging equipment, seal strength curves for 122WJ should be generated according to ASTM F88/F88M-21 at the target film thickness and sealing pressure. Published comparative data for this specific grade on high-speed vertical form-fill-seal lines is limited. Hot-tack testing may be performed according to ASTM F1921-12 Method B; the broad melting distribution of Ziegler-Natta butene LLDPE generally requires longer cooling time before load transfer than metallocene grades. Food-contact suitability of 122WJ is governed by base resin compliance with US FDA 21 CFR 177.1520 and EU 10/2011; end-use migration testing under the finished film thickness and food simulant conditions remains the converter’s responsibility. The grade is manufactured under ISO 9001:2015; REACH registration under EC 1907/2006 and RoHS 2011/65/EU are addressed in the product safety datasheet. Specific heavy metal migration should be verified by IEC 62321 series methods where required by supply chain agreements.

Table 2: Regulatory compliance checklist matrix

Standard / Regulation	Scope	Verification status
US FDA 21 CFR 177.1520	Olefin polymers in food-contact articles	Base resin compliance; finished film migration testing required
EU 10/2011	Plastic materials and articles intended for food contact	Overall migration limit 10 mg/dm²; specific migration limits per Annex I
EC 1907/2006	REACH registration	Substance registered; SVHC content below 0.1% w/w expected
2011/65/EU	RoHS restricted substances	Tested by screening per IEC 62321 series
ISO 9001:2015	Quality management system	Manufacturing site certified

During high-output conversion, winding tension should be kept below the yield stress of the film to prevent permanent strain; for 50 µm film, winding hardness is set at 75–85 Shore O to avoid roll blocking. Warehousing at temperatures above 35°C may accelerate migration of slip additives, reducing coefficient of friction after aging; film stored for more than 30 days should be checked for COF according to ISO 8295:1995 before use on automatic bag machinery. The resin is incompatible with pro-oxidant masterbatches intended for landfill-degradable films because accelerated oxidative breakdown compromises the mechanical property envelope. Do not combine 122WJ with amine-based antifog concentrates unless pre-tested; amine additives can interact with component residues and shift colour or odour in high-temperature extrusion. After shutdown, the barrel should be purged with a low-melt-index LDPE or purging compound to displace 122WJ and prevent carbonized resin from contaminating subsequent film lots. The use of reclaimed film scrap from 122WJ is possible up to 20% by weight without significant loss of dart impact, provided the scrap is dry and free of print ink; higher scrap fractions should be validated for gel count and film optical properties.