Lotte Chemical HDPE HIVOREX 5305E

Lotte Chemical HIVOREX 5305E is a high-density polyethylene injection moulding grade identified by melt mass-flow rate and density boundaries. Published manufacturer data list a melt mass-flow rate of 5.0 g/10 min at 190 °C/2.16 kg under ASTM D1238-20 and a nominal density of 0.953 g/cm3 under ASTM D792-20. The grade is positioned for short-cycle injection moulding of packaging closures, caps, crates, pails and engineered industrial components in which stiffness, impact resistance and cavity-fill velocity must be balanced. On production-scale reciprocating-screw machines with clamp force between 120 t and 180 t, the material exhibits stable screw recovery and ejection behaviour when the thermal and pressure limits described below are maintained. Published data for the exact molecular weight distribution, polydispersity index and crystallization half-time of this grade are limited; those characteristics are inferred indirectly from density, viscosity, mould shrinkage and dynamic mechanical response on moulded plaques.

Rheological Response and Shear Stability in Injection Moulding

The melt mass-flow rate of 5.0 g/10 min places HIVOREX 5305E between low-flow extrusion blow-moulding HDPE and high-flow thin-wall injection HDPE. Capillary rheometry under ASTM D3835 reveals pseudoplastic shear-thinning behaviour: apparent viscosity decreases by approximately one order of magnitude as apparent shear rate increases from 10 s⁻¹ to 1000 s⁻¹ at 210 °C. This response supports multi-cavity filling without the excessively narrow processing window associated with some metallocene HDPE grades. Complete viscosity curves for the commercial stabilised formulation are not fully published; processors are therefore advised to generate capillary data before designing hot-runner systems or specifying gate dimensions. In barrel-temperature profiles from 190 °C to 240 °C, melt-pressure stability is generally acceptable. Prolonged residence above 15 min at temperatures above 240 °C is associated with increased screw torque variability and upward drift in melt pressure due to thermo-oxidative chain extension. The failure mode appears on reciprocating-screw machines as a gradual increase in cushion-position variance and inconsistent switchover weight.

Injection-moulding conditions documented for HDPE grades in this melt-flow class include melt temperatures between 220 °C and 250 °C, mould surface temperatures of 15 °C to 40 °C, and specific injection pressures of 80–110 MPa. For packaging closures with wall thickness from 1.0 mm to 2.5 mm, gate freeze-off occurs more rapidly than with HDPE grades below 2.0 g/10 min, but hot-runner venting must maintain land depths of 0.02–0.03 mm to avoid gas-burn defects at valve-gate tips. Clamp force calculations for a 16-cavity cap mould with projected area of 0.02 m² per cavity indicate a required clamp force of 100–140 t at the lower end of the injection pressure range. Shrink porosity near thick bosses is observed when melt temperature exceeds 250 °C and hold pressure drops below 60 MPa; increasing gate diameter and delaying pack-to-hold transfer reduce the defect. Published data for this specific tool configuration are limited; the parameters are derived from standard HDPE injection-moulding practice rather than from a supplier-validated design-of-experiment.

Where Does HIVOREX 5305E Differ from Extrusion and Blow Moulding HDPE Grades?

The primary measurable distinction is melt mass-flow rate. Extrusion blow-moulding HDPE grades in the same density band typically carry MFR values below 1.0 g/10 min and therefore possess higher zero-shear viscosity and greater parison melt strength. HIVOREX 5305E is not intended for parison hang-time-limited extrusion processes; at 5.0 g/10 min, the low melt strength can produce parison sag and non-uniform wall thickness in continuous extrusion blow moulding. In comparison with high-flow HDPE grades above 20 g/10 min, HIVOREX 5305E generally exhibits higher notched Izod impact strength and higher environmental stress-crack resistance because the average molecular weight is larger. Environmental stress-cracking resistance, when measured under ASTM D1693 Condition B in 10 % Igepal CO-630 at 50 °C, is frequently a more discriminating selection criterion than MFR alone for detergent and aggressive liquid packaging. Published data for the exact ESCR value of this grade in public literature are limited; comparative ranking should be verified on moulded plaques, not pellet samples, because moulded-in orientation influences crack initiation.

Table 1 summarizes representative physical properties reported in materials databases and supplier technical documentation for HIVOREX 5305E. The values are typical ranges, not absolute incoming inspection limits; lot-to-lot variation, specimen preparation and conditioning protocol influence mechanical results. Mechanical property comparisons should use identical crosshead speed, gauge length and conditioning time. The density and MFR values are identity-defining; stiffness and impact values are a function of crystallinity, orientation and wall thickness.

When thin-walled closures and caps require fast cavity filling

When wall thickness drops below 1.5 mm in caps and thin-wall closures, HIVOREX 5305E allows lower melt temperature than low-flow HDPE. Melt temperatures of 220 °C to 230 °C are frequently sufficient for flow lengths below 100 mm; reduced melt enthalpy lowers cooling time and improves gate-freeze consistency in high-cavitation tools. Closure torque retention after repeated opening cycles depends on creep and stress relaxation in the lid bridge and annulus. Creep compliance should be measured under ASTM D2990 or ISO 899-1:2017 because short-term tensile data do not predict long-term sealing force. Production lines using hot-runner valve-gate systems observe that gate vestige height in 1.2 mm-thick closures remains below 0.15 mm when valve-pin retraction is delayed by 0.2–0.4 s after hold-pressure completion. Published data for this specific grade in valve-gated closure applications are limited; tool trials on production-scale equipment are required to confirm these values.

Assessing Weld-Line Strength and Gate Location Effects

Weld-line strength in multicavity closures and containers is controlled by melt temperature, hold pressure and gate location. In reinforced crates and pails, flow fronts meeting at ribs and bosses produce knit lines; HDPE yield strength at the weld line is typically lower than the bulk value, and the reduction is measured using tensile specimens and ASTM D638-14. For HIVOREX 5305E, maintaining melt temperature above 220 °C and hold pressure above 60 MPa reduces the visual prominence of weld lines, but complete elimination is not possible when opposing flow fronts meet at low temperature. Gate sequencing with valve gates can reposition the weld line into low-stress regions; this is particularly relevant for pressure-containing closures and tamper-evident bands in which a weak knit line can initiate stress cracking. Published data on weld-line efficiency for HIVOREX 5305E are limited; processors should evaluate weld-line tensile strength using moulded plaques with dual end gates before final tool approval.

Pigment masterbatches based on low-MI LLDPE carriers can shift the apparent MFR of the mixture and alter solidification behaviour. When a 3 wt% white titanium dioxide masterbatch is added, density increases by approximately 0.01 g/cm3 and mould shrinkage may decrease by 0.1–0.2 %; this is measurable by ASTM D955-20. Such changes are within normal grade variability but can affect cap dimensions in tight-tolerance closures. Carbon black masterbatch at 2 wt% can improve ultraviolet weathering, but UV stabilisation must be verified by ASTM D4329-21 or ISO 4892-2:2013; published data for this grade with UV-stabilised pigmentation are limited. Incompatible masterbatch carriers can increase melt-pressure variation and cause splay, especially when drying is inadequate. Processors should verify the masterbatch carrier resin before use in high-speed cap moulding.

Thermal excursions above 250 °C cause measurable impact loss

High-density polyethylene is not hygroscopic; under dry indoor storage the moisture content remains below 0.01 % and pre-drying is unnecessary for natural resin. If regrind or polar pigment masterbatch is added at high humidity above 60 % RH, surface splay and internal voids may occur; drying in a dehumidifying hopper dryer at 80 °C for 2 hours is recommended. The processing window is governed by two failure modes. Melt temperature below 190 °C can produce high frozen-in orientation, gate-stringing and poor surface replication. Sustained melt temperature above 250 °C triggers thermo-oxidative degradation, evidenced by yellowing, plate-out on mould vents and loss of notched Izod impact as measured by ASTM D256-23. The allowable residence time at 240 °C should not exceed 10–15 min; longer hold periods increase the risk of gel particles and crosslinked domains in the melt stream. Avoid amine-based light stabilisers and certain hindered amine compounds because they can interact with acidic catalyst residues, causing discoloration and mould plate-out. The base stabiliser package is typically phenolic and phosphite; reformulation with amines is not recommended without pilot-scale verification.

Regulatory positioning for food-contact applications is a central selection criterion. The base polymer may be formulated to support compliance with FDA 21 CFR 177.1520 for olefin polymers used in contact with food, but the converter must verify the specific end-use condition, including food type and temperature. For the European market, compliance with EU Regulation 10/2011 requires that the final article meet the overall migration limit and any specific migration limits applicable to additives and monomers; the supplier’s formulation disclosure is necessary. Industrial documentation typically indicates alignment with REACH Annex XVII restrictions and RoHS Directive 2011/65/EU when the grade is used in electrical and electronic equipment. Medical-grade claims are not included in the published data; no ISO 10993 testing is implied. Use in pharmaceutical packaging requires separate validation.

In industrial container applications such as stackable crates, pails and tote boxes, moulded HIVOREX 5305E articles are subjected to stacking loads, low-temperature handling, and contact with detergents or oils. The selection of this grade over lower-MFR HDPE is justified where cycle time and melt distribution in steel moulds outweigh the higher ESCR of slower-flow grades. For stackable crates with nominal wall thickness above 2.0 mm, sink marks at reinforcing ribs are controlled by maintaining pack pressure above 50 MPa and using rib-to-wall thickness ratios below 0.6. Low-temperature impact resistance should be evaluated at -30 °C using ASTM D256-23 or ISO 179-1:2023 because the glass transition of HDPE is below typical freezer storage temperatures, but moulded-in stress can reduce impact resistance. Cleaning with aggressive surfactants requires ESCR testing under ASTM D1693; published comparative data for this specific grade in such aggressive media are limited, and lot-specific validation is required before use in detergent pails or agricultural chemical containers.