Lotte Chemical HDPE HIVOREX 6200B is a high-density polyethylene blow molding grade supplied in pellet form for extrusion blow molded rigid packaging. The grade is classified by melt flow rate measured at 190 °C under 2.16 kg in accordance with ASTM D1238 and ISO 1133-1:2022. The published typical value is 0.60 g/10 min, and density is 0.960 g/cm³ under ASTM D1505 and ISO 1183-1. This combination positions the material between fractional-melt HDPE film grades and higher-MFR injection molding grades, and directs its use toward monolayer containers with typical shot mass above 1 kg.

Specification Profile and Standardized Test Methods

The published data sheet values are not specification limits. They are included here as a baseline for material substitution, mold design, and converter qualification. Certificates of analysis should be requested for batch-specific lot data because melt flow rate, density, and additive package can vary within the manufacturer's control window.

The density of 0.960 g/cm³ corresponds to a crystalline volume fraction of approximately 65 % to 70 % when calculated from linear two-phase density values. Higher crystallinity contributes to flexural modulus and top-load strength, but it reduces intrinsic impact toughness and slow crack growth resistance compared with HDPE copolymers of density 0.945 g/cm³ to 0.950 g/cm³. This trade-off is important because the selection of 6200B for a rigid container is a compromise between stacking stiffness and stress-crack performance.

Because the 2.16 kg melt flow rate is collected at low shear, it should not be used as a direct predictor of parison hang time. Capillary rheometry under ISO 11443 at apparent shear rates of 10 s⁻¹, 100 s⁻¹, and 1,000 s⁻¹ is required for die gap calculations and accumulator-head pressure-drop estimates. Molecular weight distribution parameters are not published on the standard data sheet; therefore, extruder screw speed and head pressure alone are insufficient to predict parison sag across batch-to-batch variation.

Why Does 6200B Maintain Parison Stability During Large-Part Accumulator-Head Molding?

The practical processing constraint is the interval between parison extrusion and mold closure. In accumulator-head machines with 24:1 L/D barrier screws and elongated shot sizes, a grade with insufficient melt strength sags at the pinch-off region and creates thin sidewalls. 6200B is formulated with a molecular weight distribution that increases zero-shear viscosity relative to intermediate-MFR blow molding grades, which reduces drawdown over hang times typical of 10 L to 25 L containers. Melt temperature at the die exit should be maintained between 190 °C and 210 °C. At melt temperatures below 185 °C, extensional viscosity at high take-off rates can produce shark-skin surface defects at the die lip. Above 220 °C, oxidative degradation becomes kinetically significant and parison sag increases, forcing wider programmed die gaps.

On a single-station shuttle blow molder equipped with a 90 mm extruder and 24:1 L/D screw, die-head pressure for a 20 L jerry can tool is commonly observed in the 25 MPa to 35 MPa range. Batch-to-batch fluctuation in melt flow rate within the manufacturer's specification window is typically compensated by die gap changes of 0.5 mm to 1.0 mm. Published data for this specific configuration is limited, but these ranges are consistent with accumulator-head operation for HDPE blow molding grades of similar density and MFR. Mold cooling water at 10 °C to 20 °C produces a frozen skin quickly enough to maintain dimensional stability when shot size approaches 4 kg; higher mold temperatures increase cycle time and can cause post-mold shrinkage above 2 % in thick pinch-off areas.

A barrier screw with a Maddock mixing section is recommended over a general-purpose polyethylene screw when throughput exceeds 300 kg/h. The mixing section distributes thermal history and prevents unmelted pellets from entering the accumulator head. Grooved-feed extruders are not required for this grade, and excessive shear heating should be avoided because it lowers the effective melt strength without changing the laboratory MFR. On continuous extrusion shuttle blow molding machines with multiple parison heads, shot-to-shot variation in melt temperature at each head should be maintained within ±5 °C. Temperature differences above this range produce observable differences in parison length and wall distribution, particularly when the shot mass exceeds 2 kg.

In rigid industrial packaging, environmental stress crack resistance is the controlling performance variable for liquid agrochemical, household cleaner, and soap-surfactant formulations. The ASTM D1693 F50 value is a comparative ranking of slow crack growth resistance under a fixed stress and a standard wetting agent. It does not replace finished-container compatibility testing. Stress cracking in HDPE blow moldings initiates preferentially at the pinch-off zone, at mold weld lines, and at sharp handle transitions where process orientation is highest. For a 5 L to 25 L container, the combination of 0.960 g/cm³ density and the specified ESCR range indicates suitability for detergents and water-based industrial cleaners, but not for aromatic or chlorinated solvent systems above 40 °C without fluorination or barrier treatment.

Environmental stress cracking is a physical failure mechanism, not chemical degradation. The aggressive agent plasticizes the amorphous tie-chain regions and reduces resistance to crack propagation. For HDPE, ESC is pronounced with polyethylene glycol ether surfactants, wetting agents, and certain vegetable-oil derivatives. The ASTM D1693 test uses a standard nonylphenoxy poly(ethyleneoxy)ethanol solution as the stress-cracking agent. In finished containers, molded-in stress level is higher at corners, handle attachment points, and pinch-off lines; therefore, the test coupon F50 value should be interpreted as a ranking rather than a guaranteed service life.

Top-load and stacking performance are governed by flexural modulus, wall thickness distribution, and container geometry. At a flexural modulus of 1,200 MPa under ASTM D790, 6200B provides a stiffer container than HDPE grades with density of 0.945 g/cm³ to 0.950 g/cm³. The trade-off is a reduction in molded-in impact toughness and stress-crack resistance when compared with medium-density polyethylene or lower-density HDPE copolymers. This is the primary reason the grade is not automatically interchangeable with lower-density blow molding grades in sealed chemical packaging.

When High-Density Polyethylene Grades Are Substituted in Rigid Packaging

HIVOREX 6200B differs from higher-MFR HDPE blow molding grades in three measurable areas: parison hang time, environmental stress crack resistance, and flexural stiffness. A grade with MFR above 1.0 g/10 min may fill a 2.5 L bottle with shorter cycle time, but the lower molecular weight fraction typically reduces ASTM D1693 F50 values and narrows the processing window for heavy shot masses above 1 kg. Conversely, a fractional-melt HDPE with MFR below 0.2 g/10 min may offer higher ESCR but generates higher head pressure and requires a lower screw speed to avoid excessive melt temperature. 6200B is therefore placed as a rigid packaging grade for shot masses from 1 kg to 8 kg, where both parison stability and stress-crack resistance are required.

Comparisons with HDPE film grades are made under different rheological conditions. Film grade high-molecular-weight HDPE is often characterized by high-load melt flow rate at 21.6 kg under ISO 1133-1 condition G. The 2.16 kg MFR of 6200B is not directly equivalent because the molecular weight distributions address different extensional flow requirements: thin-film bubble stability versus large-part parison stability. A film grade can exhibit high melt strength in biaxial stretching but does not necessarily offer the same die swell, pinch-off integrity, and wall thickness control required in accumulation-head blow molding.

Within the Lotte Chemical HDPE line, the numerical grade designation should not be interpreted as a fractional melt index sequence. The 5000-series blow molding grades are generally positioned for smaller containers and faster cycles, while the 6000-series products address larger shot mass and improved resistance to aggressive fill goods. Published data for direct 5200B versus 6200B substitution is limited; converter trials on 2.5 L bottles show that 6200B may require a wider programmed die gap to compensate for higher melt viscosity but delivers higher top-load retention after prolonged contact with surfactant-based liquids. These differences require re-qualification of drop impact, closure torque retention, and ESCR before any substitution is made on a qualified production line.

For food-contact applications, the neat resin falls under olefin polymer provisions of FDA 21 CFR §177.1520 and EU Regulation No 10/2011. Finished article compliance is not determined by resin type alone; the converter must validate overall migration and specific migration limits under the intended temperature and simulant conditions. The overall migration limit for plastic food-contact materials under EU Regulation No 10/2011 is 10 mg/dm². Industrial chemical packaging classified under UN Model Regulations Chapter 6.1 requires drop testing of filled containers at 1.2 m for packing group II and 0.8 m for packing group III. The resin data sheet cannot substitute for these finished-container qualifications. REACH SVHC status and RoHS Directive 2011/65/EU conformance should be confirmed through the grade-specific product stewardship declaration and batch compliance certificate.

Material Substitution Boundaries

Processing and handling limits are defined by moisture absorption, thermal oxidative stability, and chemical exposure. Pellets stored at relative humidity above 60 % can accumulate surface moisture; visible condensation on cold pellets introduced into the feed throat may produce splay or internal voids in thick-walled parisons. If surface moisture is present, desiccant drying at 80 °C for 2 h to 4 h is recommended before processing. The resin is not hygroscopic in the same sense as polyamide or polycarbonate, so routine drying is unnecessary when storage is dry and the hopper temperature is above dew point.

Melt residence time at high temperature must be controlled. Continuous operation above 220 °C for more than 15 min increases the risk of oxidative chain scission and gel formation. In production stops, the extruder should be purged with a lower-MFR HDPE transition material and the die head should be cooled if the interruption exceeds 10 min. Use of oxidative recycling streams, broad-spectrum peroxides, or high levels of unsaturated migratory plasticizers is not recommended without re-qualification because these additives can shift ESCR and generate odor. The grade is also not intended for injection molding; the low MFR at 2.16 kg can cause short shots and weld-line weakness in injection molded parts unless the machine provides sufficient injection pressure and melt temperature above 220 °C.

Chemical exposure boundaries apply to the finished container rather than the pellet. Strong oxidizers, concentrated mineral acids above 60 °C, aromatic hydrocarbons, and chlorinated solvents should be evaluated by immersion studies on molded plaques or bottles under ASTM D543 or ISO 175. Published data for this specific grade under all chemical classes is limited, and no single HDPE provides universal barrier performance. Fluorination or barrier-layer coextrusion may be required for oxygen-sensitive or permeation-limited materials.