LyondellBasell HDPE H5112 is a high-molecular-weight high-density polyethylene resin supplied for extrusion and extrusion-blow moulding applications where melt strength, environmental stress crack resistance and long-term hydrostatic integrity control service life. The grade is produced as a natural pellet with a nominal density of 0.951 g/cm³ measured according to ISO 1183-1:2019 and a nominal melt flow rate of 0.12 g/10 min under 190 °C/2.16 kg using ISO 1133-1:2022. These values are supplier-published nominal values for the unfilled natural grade; black or coloured concentrates alter density and additive loading and require lot-specific certificates. The stabiliser package permits short-term processing at melt temperatures up to 220 °C, but residence times above 45 min at maximum barrel settings can initiate chain scission, gel formation and a measurable upward drift in melt flow rate. Nominal data should not be treated as a specification; the certificate of analysis controls lot release and should be consulted for the actual batch.

The following nominal property profile is drawn from supplier technical literature for natural HDPE H5112. Values are not specifications and may shift with lot, pigmentation and regrind content.

How Do the Rheological Properties of H5112 Translate to Screw and Die Design?

Because H5112 has a high weight-average molecular weight, its melt exhibits pronounced shear thinning. On a capillary rheometer at 190 °C, apparent viscosity from 10 s⁻¹ to 100 s⁻¹ typically decreases by more than an order of magnitude. Single-screw extrusion therefore requires a grooved-feed section and a screw with L/D ≥ 24:1 to convey the pellets and build head pressure. Barrel temperatures of 180–210 °C and die temperatures of 190–220 °C are used, while melt temperatures above 220 °C increase oxidation risk unless nitrogen blanketing is maintained in the hopper. During start-up, the screw should be rotated at 5–10 rpm until melt appears at the die, then increased to production speed over 15–20 min to prevent overtorque. On extruders with L/D 30:1, barrier screws with a Maddock mixing section are used to disperse stabilisers and colour masterbatch; distributive mixing is more important than dispersive mixing because the natural grade contains no pigments or glass fibres. Head pressures in blow moulding dies typically range from 20 MPa to 35 MPa; dies with a pressure drop below 15 MPa may produce poor helical weld-line healing and surface streaks.

Die swell in blow moulding is controlled by divergence ratios of 2.0:1 to 3.5:1; smaller die gaps increase shear stress and may induce sharkskin at linear extrusion speeds above 1.0 m/min. Fluoropolymer processing aids at 200–400 mg/kg are used to shift the melt fracture threshold. On accumulator-head machines, parison programming with wall-thickness settings from 2 mm to 8 mm compensates for swell and sag. At low output rates below 20 kg/h, melt fracture may be absent, but small-diameter parisons at high take-off speeds can develop surface roughness unless die land temperatures are raised or processing aid is added.

Compliance statements for H5112 are not uniform across all supply regions and colour packages. The unfilled grade is typically evaluated under the food-contact requirements of FDA 21 CFR 177.1520 and the Union List of EU Regulation 10/2011; however, migration testing according to the EN 1186 series must be performed on the finished article rather than the pellet. For drinking-water contact, a formulation-specific certification such as NSF/ANSI 61 is required. Heavy-metal restrictions under RoHS Directive 2011/65/EU are met by the natural unfilled product only when no heavy-metal pigment masterbatch is added. REACH compliance under Regulation (EC) No 1907/2006 requires that each monomer and additive be registered for the intended European market. Published data for this specific configuration is limited for certain pigment masterbatches, so converters should obtain a compliance declaration from the masterbatch supplier rather than assume that the base resin alone confers regulatory clearance.

Environmental Stress Crack Resistance and Chemical Exposure Boundaries

HDPE H5112 is differentiated from conventional unimodal HDPE resins by its environmental stress crack resistance measured under ASTM D1693, Condition B, in 10 % Igepal CO-630 at 50 °C. The failure time is sensitive to mould temperature, residual stress and wall thickness. In high-molecular-weight extrusion grades of this density class, failure times above 1000 h are common, but published data for this specific configuration is limited for thick-walled parts above 6 mm. The slow crack growth mechanism is controlled by tie-molecule concentration and lamellar thickness distribution; the molecular architecture of H5112 is designed to increase tie-chain density relative to a lower-molecular-weight HDPE at equivalent density. At constant density, reducing melt flow rate from 0.30 g/10 min to 0.12 g/10 min typically increases environmental stress crack resistance, but also increases melt viscosity and reduces mass flow at a fixed screw speed.

Chemical exposure is service-dependent. The resin withstands dilute mineral acids, alkalis, saline solutions, detergents and agricultural emulsions at temperatures up to 40 °C; sustained contact with strong oxidising acids above 40 °C, chlorinated solvents, aromatic hydrocarbons, or brake fluids can lead to swelling, crack nucleation and loss of top-load strength. Swelling and property retention should be tested according to ISO 175:2010. For pressurised containers, long-term hydrostatic strength follows ISO 9080:2022 regression methodology; the upper design temperature for continuous pressure service is normally 60 °C, with derating above 60 °C because creep rupture resistance decreases sharply.

In industrial blow moulding, H5112 is processed on shuttle and rotary wheel machines with clamp forces from 150 kN to 1,200 kN depending on container volume. Accumulator heads with spiral or radial groove mandrels are set at 190–215 °C. Blow air pressure of 0.6–0.8 MPa and mould temperatures of 10–25 °C are used to control surface gloss and cycle time. The high melt strength permits continuous extrusion of large drums and intermediate bulk containers with net weight up to 25 kg, though the upper limit is governed by clamp stroke, accumulator capacity and cooling time rather than by the resin alone. Regrind ratios are commonly held below 20 % for food-contact containers unless the regrind is generated in-house and the masterbatch is compliant; post-consumer recyclate is not recommended without a documented challenge test and migration assessment. On production lines with a gravimetric blender, additive masterbatch addition is controlled to ±0.1 wt% to limit shifts in environmental stress crack resistance. Converters monitor parison length with a camera system; a length change of more than 5 % at constant accumulator stroke indicates a change in melt strength or incoming lot. Head pressure fluctuation of ±2 MPa during a cycle may identify poor homogenisation or bridging in the feed throat.

When HDPE H5112 Is Compared With Unimodal 0.952-Density Blow Moulding Resins

Compared with a 0.950–0.952 g/cm³ unimodal HDPE with a melt flow rate of 0.30–0.45 g/10 min, H5112's lower nominal MFR of 0.12 g/10 min increases parison melt strength and die swell but reduces mass flow at a fixed screw speed. Processors may need to reduce screw speed by 15–25 % or increase barrel temperatures by 10–15 °C to maintain head pressure. In drop-impact testing at -20 °C according to ASTM D2463, high-molecular-weight HDPE containers typically fail in a ductile mode at wall thicknesses above 1.5 mm, whereas lower-molecular-weight grades may show brittle fracture at the same nominal density. Top-load strength under ISO 12048 is also improved by the higher molecular weight, but corner weld lines in handle sections can remain weak if the mould temperature is below 12 °C.

The comparison is best made on three process variables: melt flow rate, die swell ratio and environmental stress crack resistance at constant density. A unimodal grade with MFR 0.35 g/10 min will fill thin handle sections at lower head pressure but exhibits lower ESCR under ASTM D1693 Condition B. H5112's higher molecular weight gives parison hang strength, enabling consistent wall thickness in large drums at melt temperatures above 190 °C, but it may produce melt fracture at lower shear rates than a broader-molecular-weight-grade unless processing aids are used. The narrow melt flow control to ±0.02 g/10 min helps converters maintain container top-load performance but may require precompounding of regrind to prevent viscosity segregation.

At moisture uptake above 0.05 % by weight, pre-drying at 80 °C for 2–4 h in a desiccant dryer is advisable to prevent surface splay and hydrolysis of the stabiliser system. The resin should not be processed with copper-based colourants or certain phenolic/amine combinations because interactions can accelerate oxidative degradation; compatibility of additive packages must be verified by oxidative induction time testing according to ISO 11357-6:2018. Processing above 220 °C without oxygen exclusion increases the melt flow rate and lowers environmental stress crack resistance. The lower continuous service temperature is limited by ductile-to-brittle transition; containers exposed to -20 °C should be evaluated by drop-impact testing at the minimum wall thickness. Lot-to-lot variability in melt flow rate is typically controlled to ±0.02 g/10 min by the supplier, but converters should monitor head pressure and parison length at each silo change.