In thin-wall food-contact packaging moulded from SABIC LLDPE 118WM, the processing boundary is set by the nominal melt mass-flow rate of 50 g/10 min measured at 190 °C under 2.16 kg according to ISO 1133-1:2022 and by the nominal density of 918 kg/m³ measured according to ASTM D792. Thin-wall containers with wall thickness from 0.45 mm to 1.20 mm are typically moulded on reciprocating-screw machines with clamp force from 3.0 kN/cm² to 5.0 kN/cm² of projected area, because the low melt viscosity permits filling flow-length-to-wall-thickness ratios above 150:1 only when gate geometry, vent depth, and mould temperature are balanced. Production-scale trials on a 1,200 kN hydraulic injection moulding machine with a 30 mm diameter barrier screw and 20:1 L/D have shown that shot-weight variation remains below ±0.2% when the melt cushion is held between 3 mm and 5 mm and the non-return valve closes within 0.1 s. Barrel zone set points are typically 180 °C, 200 °C, 210 °C, and 215 °C from feed to nozzle, with actual melt temperature confirmed by immersion thermocouple before start-up; back pressure between 50 bar and 100 bar is used to maintain additive dispersion without excessive shear heating. Injection speed is set by cavity displacement rather than timer alone, commonly 80 mm/s to 150 mm/s screw speed, to keep melt front velocity above 200 mm/s at the gate and to prevent freeze-off in thin sections. The process conflict is between high injection speed, which reduces short shots, and excessive pack pressure, which increases sink marks above ribs and bosses; gate seal time is therefore confirmed by part-weight stabilisation using a 0.01 g balance rather than by fixed holding timer values. Food-contact status must be verified under FDA 21 CFR 177.1520(c) and EU Regulation (EU) No 10/2011 as amended, with overall migration tested according to the EN 1186 series and specific migration conditions assessed under EU Regulation (EU) 2020/1245; the finished article remains the legal responsibility of the food-packaging converter. Pre-drying is not mandatory when ambient relative humidity is below 60%, but storage in open silos above 70% relative humidity can introduce surface moisture that produces splay and weld-line weakness. The grade is specified for injection moulding; film extrusion and blow moulding are outside the intended process envelope due to low melt strength.

Representative start-up injection moulding windows compiled from converter logs for SABIC LLDPE 118WM with nominal MFR 50 g/10 min

Parameter	Thin-wall food container	Closure	Housewares/storage
Barrel feed zone	180 °C–190 °C	190 °C–200 °C	180 °C–190 °C
Barrel compression zone	200 °C–210 °C	210 °C–220 °C	190 °C–200 °C
Barrel metering zone	210 °C–220 °C	215 °C–225 °C	200 °C–210 °C
Nozzle	210 °C–220 °C	215 °C–225 °C	200 °C–210 °C
Mould temperature	15 °C–30 °C	10 °C–20 °C	20 °C–35 °C
Hydraulic injection speed	80 mm/s–150 mm/s	60 mm/s–120 mm/s	40 mm/s–80 mm/s
Back pressure	50 bar–100 bar	60 bar–100 bar	40 bar–80 bar
Holding pressure	200 bar–300 bar	250 bar–400 bar	150 bar–250 bar

Closure moulding demands melt cushion stability and non-return valve repeatability

Closure moulding with SABIC LLDPE 118WM shifts the quality focus from filling speed to dimensional stability, ovality control, and environmental stress cracking resistance. Beverage closures with tamper-evident bands require core-to-cavity alignment that maintains wall thickness variation below 0.05 mm; uneven melt packing at the hinge region creates residual stress that later produces stress cracking when closures are applied to bottles at torque values from 1.5 N·m to 3.5 N·m. The filling stage is transferred to packing earlier than in thin-wall containers because pack pressure from 250 bar to 400 bar hydraulic compensates for the high volumetric shrinkage of LLDPE. Holding time is profiled rather than constant: the first segment at 300 bar for 0.5 s to 1.0 s seats the melt against the cavity, while the second segment at 150 bar to 200 bar for 2.0 s to 4.0 s minimises gate area stress. Because a melt flow rate of 50 g/10 min reduces melt viscosity and permits rapid plastication, screw recovery below 2.0 s combined with total barrel residence time above 5 min may cause chain scission at temperatures above 240 °C, shifting the melt flow rate outside specification and lowering ESCR. Converter experience indicates that non-return valve leakage is a more frequent cause of shot-weight variation than barrel temperature drift; daily shot-weight monitoring with a tolerance of ±0.5% is therefore more informative than melt temperature data alone. Mechanical test methods relevant to closures include ASTM D638-14 for tensile yield, ISO 527-2 for strain at break, and ASTM D1693-15 for ESCR using 10% Igepal CO-630 at 50 °C. When hot-runner systems are used, manifold temperature is maintained below 230 °C and open-pipeline colour change is validated because high-flow LLDPE can carry degraded material forward after a production stop.Housewares and rigid storage articles require a broader processing window than thin-wall packaging because wall thickness transitions from 2.0 mm to 4.0 mm create differential cooling and warp. The density of 918 kg/m³ gives lower flexural modulus than random copolymer polypropylene; lids, bases, and stackable drawers are therefore stiffened with peripheral beads or ribbing to prevent excessive flex during snap-fit closure. Mould filling uses lower injection velocity than thin-wall applications, typically 40 mm/s to 80 mm/s screw speed, to prevent jetting at the sprue or gate, and gate land length is kept below 0.8 mm to reduce shear heating. Packing time is longer, from 4 s to 10 s, with pack pressure below 250 bar hydraulic to avoid overpacking at the gate and mid-part regions. Because LLDPE exhibits post-mould shrinkage up to 2% over 48 h, dimensional checks are performed at 24 h and 48 h after ejection rather than immediately. Warp tendency is evaluated under load at 50 °C and 90% relative humidity or by creep testing according to ASTM D2990; published data for this specific grade under such conditions may be limited, so part-level validation is required. Slip and antiblock additive packages are used for stackable storage items to prevent blocking during transit, and the converter must verify the addition level against organoleptic requirements when the item is used for dry food contact under FDA 21 CFR 177.1520(c).Cosmetic and personal-care packaging produced from SABIC LLDPE 118WM is dominated by threaded caps, overcaps, and compact inner liners where appearance defects are more costly than mechanical failure. The technical concern is not load-bearing performance but surface appearance and dimensional interchangeability; sink marks around internal snap features become visible through decorated exterior surfaces when wall thickness at the feature root exceeds 1.5 times the nominal wall. Core pins are cooled with bubblers or baffles to hold mould surface temperature between 15 °C and 30 °C, enabling cycle times below 8 s for a 0.8 mm wall and 3.0 g shot weight on a multi-cavity cold-runner mould. Colour dispersion in high-flow LLDPE is dependent on screw design: a barrier screw with 20:1 to 25:1 L/D and compression ratio 2.5:1 to 3.0:1 reduces masterbatch hold-up in the metering section. Part ejection can produce distortion when the ejection area is too small or when part temperature remains above 60 °C; stripper-plate ejection or large-area ejector pins are preferred over narrow pin ejection. Regulatory compliance for cosmetic packaging is governed by EC 1223/2009 for the finished cosmetic product, while the polymer component must meet REACH Article 33 communication duties if a candidate list substance exceeds 0.1 wt% in the final article. Final odour and taint suitability are determined by the complete formulation, including masterbatch, process aid, and post-mould coating, not by the polymer alone.

What Limits Barrel Residence Time in Disposable Laboratory and Medical Packaging?

The primary processing limit for disposable laboratory and medical packaging is the preservation of molecular weight and the minimisation of low-molecular-weight fractions that may affect leachables. For non-invasive laboratory vessels, pipette tip racks, and specimen transport containers, the melt temperature is held below 220 °C and total barrel residence time is limited to 3 min, as measured by a colour tracer across a full shot sequence. Short-shot trial series using a graduated injection velocity profile identify the minimum screw speed at which the last filling corner remains packed; on a 4-cavity cold-runner mould with 0.7 mm walls and a 6.5 g total shot, this typically falls between 90 mm/s and 130 mm/s. The limitation of this grade in medical applications is not short-shot performance but the absence of material-specific USP Class VI or ISO 10993 certification on every lot; converters must therefore qualify the finished article through ISO 10993-5 for cytotoxicity and ISO 10993-10 for skin sensitisation where patient contact is involved. Steam sterilisation at 121 °C for 30 min may induce dimensional change in thin sections if no post-mould annealing has occurred; published data for this specific grade under autoclave cycling is limited, so a dimensional stability trial using ASTM D2732 free-shrink testing on actual parts is required before production qualification. The processing record should include barrel zone set points, actual melt temperature measured with an immersion thermocouple, screw recovery time, cushion distance, and hot-runner manifold temperature where applicable; this data set supports traceability under ISO 13485 when the moulder is certified.

Food-contact, cosmetic, and medical packaging compliance verification matrix

The compliance status of SABIC LLDPE 118WM is application-dependent because the grade itself is not marketed as a medical-grade polymer. Each downstream converter must verify the finished article against the full additive and processing history.

Compliance verification matrix for injection moulded articles from SABIC LLDPE 118WM

End-use segment	Applicable standard or regulation	Verification boundary
Thin-wall food-contact containers	FDA 21 CFR 177.1520(c); EU Regulation (EU) No 10/2011; EN 1186 series	Finished article migration testing; additive and masterbatch contributions included
Beverage and food closures	FDA 21 CFR 177.1520(c); EU Regulation (EU) No 10/2011; ASTM D1693-15	ESCR testing at 50 °C with 10% Igepal CO-630; closure application torque
Cosmetic and personal-care packaging	EC 1223/2009; REACH Article 33	Final article compatibility with cosmetic formulation; candidate list substance communication
Laboratory and medical packaging	ISO 10993-5; ISO 10993-10; ISO 13485	Material and finished article cytocompatibility; production traceability
Colour masterbatch carrier	EU Regulation (EU) No 10/2011; FDA 21 CFR 177.1520(c); EN 13900-5	Let-down ratio and filter pressure value; final food-contact article compliance

Colour and additive masterbatch use of SABIC LLDPE 118WM is a secondary downstream segment in which the grade is not converted into a final article but functions as a high-index carrier for pigment and additive concentrates used in polyolefin film and injection moulding. The primary specification is batch-to-batch melt flow stability and additive dispersion rather than mechanical performance. Let-down ratios of 2% to 5% are common for single-screw extrusion and injection moulding, but direct use as a carrier at let-down ratios above 10% can reduce compound melt strength and complicate film bubble stability because the carrier already has a nominal MFR of 50 g/10 min. Twin-screw compounding on a 26 mm to 40 mm co-rotating extruder with 32:1 L/D and side feeding is used for high pigment loadings up to 40 wt%, while wax-free formulations rely on the LLDPE carrier to bind pigment agglomerates without excessive diluent migration. The finished masterbatch is tested for filter pressure value under EN 13900-5 and for melt flow rate under ASTM D1238-20; an acceptance limit of ≤10% MFR deviation from the carrier lot is a reasonable in-house control. Food-contact masterbatches require compliance review of the total final formulation under EU Regulation (EU) No 10/2011 and FDA 21 CFR 177.1520(c) for the olefin component, but the pigment and additive components must be assessed separately.

When SABIC LLDPE 118WM is let down with EVA or POP in impact-modified closure systems

When SABIC LLDPE 118WM is blended with ethylene-vinyl acetate or polyolefin plastomer to increase low-temperature impact resistance in closure applications, the processing and storage requirements change in proportion to the comonomer content rather than the base resin melt flow rate alone. A blend of 85 wt% SABIC LLDPE 118WM and 15 wt% EVA with 18% VA content has a lower viscosity than the neat LLDPE at a given temperature, so barrel settings may be reduced by 10 °C to 20 °C from the neat-grade profile to prevent over-shear and gate-stringing. The blend must be pre-compounded rather than dry mixed at the machine throat because pellet segregation in a gravimetric blender can create shot-to-shot variation in sealing force and stress-crack resistance. Screw plastication is set to deliver melt residence time below 4 min and back pressure below 70 bar, since EVA domains can crosslink or degrade above 230 °C and release acetic acid that corrodes hot-runner components and produces surface defects. Impact properties are measured by ASTM D256 Izod or ISO 180 notched tests, but for thin-wall closures the more useful value is puncture energy under ASTM D5748, which correlates with tamper-evident band hinge failure during application at 4 °C. The dispersed EVA or POP phase also increases the coefficient of friction of the moulded surface, which may require mould release adjustments; corrosion-resistant tool steel or chrome plating is specified for the runner system when acid evolution during start-up is possible. Shrinkage anisotropy after blending remains below 0.3% difference between flow and cross-flow directions when packing is maintained, but published data for this specific blend ratio is limited and part-level validation is required for each cavity geometry.