LyondellBasell HDPE L4907WC is a high-density polyethylene extrusion-blow-molding resin supplied as pellet. The grade is positioned as a bimodal medium-to-high molecular weight HDPE for rigid monolayer and multilayer packaging. The nominal density is 0.954 g/cm³ when tested according to ISO 1183-1:2019, and the melt mass-flow rate is 0.70 g/10 min at 190 °C with a 2.16 kg load according to ISO 1133-1:2022. The material is not formulated for sustained hydrostatic pressure pipe service under ISO 9080; its stabilizer package and colorant system are optimized for container blow molding. Compared with injection-molding HDPE grades having melt mass-flow rates above 4.0 g/10 min, L4907WC exhibits lower flow length and higher melt strength, which make it unsuitable for thin-wall injection molding of closures or caps. Compared with single-reactor unimodal HDPE resins of similar melt flow rate, the bimodal molecular weight distribution increases the weight fraction of high-molecular-weight chains; this increases environmental stress crack resistance without a proportional reduction in modulus.

The bimodality of the molecular weight distribution is not quantified by a single lot-release specification. The melt-flow ratio, defined as MFR_21.6/MFR_2.16, provides an indirect measure of shear-thinning. Typical values for this grade class are 15 to 25; published data for this specific configuration is limited. The high-molecular-weight tail raises the zero-shear viscosity and melt strength, while the low-molecular-weight component permits flow at high shear rates in die lips. This separation is not present to the same degree in single-reactor unimodal HDPE.

In continuous shuttle blow-molding lines with extruder diameters between 55 mm and 80 mm and 24:1 L/D barrier screws, the barrel temperature profile is usually set from 170 °C at the feed zone to 205 °C at the metering zone. Head and die temperatures are held at 195 °C to 210 °C; the melt temperature measured at the die exit should not exceed 220 °C. Sustained residence above 230 °C accelerates thermo-oxidative degradation and increases the risk of gels in the parison. Mold temperatures of 10 °C to 20 °C support surface definition and reduce post-mold shrinkage. Parison blow air pressures of 0.4 MPa to 0.8 MPa are typical for 1 L bottles, with the lower range used when the mold has a direct edge-thread detail. The grade does not require pre-drying at normal storage conditions, but regrind with surface moisture above 0.1 wt% should be dried with dry air at 65 °C for 2 h. Processing pressure data from a 60 mm grooved-feed extruder at 45 min⁻¹ indicate head pressures of 18 MPa to 24 MPa; published data for this specific configuration is limited.

The feed section of the extruder should be water-cooled to maintain the pellet conveying zone below 80 °C to prevent premature softening and bridging. Grooved-feed barrels are preferred for high throughput because they increase the pressure generation capacity of the high-molecular-weight fraction. Smooth-bore extruders may require higher screw speeds and can generate excessive melt temperature. For molds with complex handle pinch-off details, the blow air delay should be set to 0.2 s after parison capture to allow the parison to contact the mold bottom without pre-inflation. Excessively early blow air can reduce pinch-off strength and increase the rejection rate at the handle weld line.

What torque and head-pressure signatures distinguish L4907WC from a 0.35 dg/min unimodal HDPE?

A direct substitution trial on a 60 mm grooved-feed extruder with a 24:1 barrier screw showed that L4907WC reaches a screw torque of 65%–80% of motor load at 45 min⁻¹, while a unimodal HDPE of similar melt flow rate may run 5%–10% lower under the same barrel profile. The difference is attributed to the higher high-molecular-weight fraction in the bimodal resin. Die-head pressure is typically 18–24 MPa, and the material exhibits pronounced shear thinning. At a parison length of 20 cm and melt temperature of 200 °C, sag velocity is approximately 0.8–1.2 mm/s; published data for this specific configuration is limited.

When a unimodal HDPE is replaced by L4907WC without tooling adjustment, the die swell tends to increase parison diameter. A die gap increase of 0.2 mm is often required to hold the same parison diameter. At die gaps below 1.2 mm and land-length-to-gap ratios above 15:1, melt fracture can occur at melt temperatures below 190 °C. Circumferential die temperature variation exceeding 3 °C has been observed to induce parison curl and uneven wall thickness in 1 L round bottles. For thin-wall containers with nominal wall thickness below 0.6 mm, melt temperature deviation of ±5 °C changes parison length by approximately 3%; this is a critical processing boundary because it affects top-load ring thickness and pinch-off integrity.

The ESCR difference is the most significant product-selection factor. A standard unimodal HDPE with equivalent density and melt flow rate may exhibit ESCR values below 100 h under ASTM D1693 condition B, while L4907WC is specified to exceed 600 h. The improved ESCR allows the use of the grade in containers for household and industrial chemicals where stress cracking at the pinch-off weld or handle pinch points is a failure mode. The tradeoff is a slightly lower flow path and a higher die swell, so injection-molding conversion is not recommended.

Top-load rigidity is controlled by density and wall thickness. A 1 L bottle with a 0.6 mm wall thickness produced from L4907WC typically shows top-load yield above 200 N, while an unimodal HDPE of equal density and wall thickness may be 10%–15% lower because of differences in molecular orientation during parison stretching. Published data for this specific configuration is limited.

Low-temperature impact in containers produced from L4907WC is governed by the high-molecular-weight fraction. Container drop tests at -20 °C on 1 L bottles with 0.6 mm wall thickness typically pass fill-and-drop criteria from 1.2 m when the pinch-off seam is aligned properly. Misalignment of the blow pin or mold misalignment exceeding 0.1 mm creates a stress concentration that can reduce the drop impact by more than 50%.

When accumulator-head machines replace reciprocating screw systems for 10 L containers

Accumulator-head conversion of L4907WC from a 0.4 dg/min HDPE requires a longer parison drop time because the 0.70 g/10 min melt has lower zero-shear viscosity. On a 2.5 L accumulator head, a shot-volume deviation of 1.5% can produce wall-thickness variation of 0.15 mm in the pinch-off region. The recommended blow-up ratio is between 2:1 and 4:1; ratios above 4:1 reduce weld-line strength in the flash pocket and may produce pinholes at the gate. For 10 L industrial bottles, the mold close speed should be controlled to avoid pinch-off tearing; hydraulic pressure settings below 10 MPa may produce incomplete pinching with this grade. Published data for every accumulator-head geometry is limited; therefore, tool-specific validation is required.

The melt temperature at the accumulator exit should be held within 190 °C to 205 °C. Above 205 °C, parison sag can create uneven side-wall thickness in 10 L containers with a height-to-width ratio above 2.5:1. Below 190 °C, the die-head pressure rises and the risk of melt fracture increases at thin die lips. In operations using up to 30 wt% dry regrind from flash and trim, the regrind should be added at the feed throat and the screw speed should be limited to 40 min⁻¹ to avoid melt-temperature overshoot. The grade is compatible with standard high-density polyethylene regrind on the same machine, but mixing with polypropylene or incompatible barrier layers must be avoided.

For food-contact applications, compliance for LyondellBasell HDPE L4907WC is to be confirmed against the formulation and colorant package used at the converter. The base olefin polymer is subject to FDA 21 CFR 177.1520 and Commission Regulation (EU) No 10/2011, as amended, when the finished container is evaluated under the applicable migration conditions. Overall migration testing under Commission Regulation (EU) No 10/2011 uses food simulant and test conditions assigned to the intended food type; the overall migration limit is 10 mg/dm². Under REACH, the grade is not expected to contain Substances of Very High Concern above 0.1% w/w on the Candidate List in effect at the datasheet date. RoHS 2011/65/EU is not relevant to packaging unless the final article is part of electrical and electronic equipment.

The stabilizer system of L4907WC is formulated for container conversion and short-term thermal exposure. Sustained contact with strong oxidizing acids at temperatures above 40 °C should be avoided, and aromatic hydrocarbon solvents can reduce ESCR by plasticizing the high-molecular-weight fraction. The material is not intended for outdoor weathering beyond incidental exposure; multi-year UV weathering performance is not supported by the stated stabilizer package. Pre-drying is not required for original pellets, but if surface condensation occurs at relative humidity above 80%, dry-air drying at 65 °C for 2 h is recommended.