Braskem HDPE HC7260LS-L is a high-density polyethylene blow moulding resin supplied as pellets. Current technical data sheets list a nominal density of 0.954 g/cm³ per ASTM D792 and a melt flow index of 0.30 g/10 min at 190°C/2.16 kg per ASTM D1238. The grade is specified for extrusion blow moulding of rigid containers in which environmental stress crack resistance, parison melt strength, and cap-torque retention are primary engineering requirements. Typical lot-release values include tensile yield strength of 26 MPa per ASTM D638, elongation at break above 600%, flexural modulus of 1,200 MPa per ASTM D790, and Vicat softening temperature of 126°C per ASTM D1525. Published data for certain application-specific configurations is limited; converter trials are required to establish mould shrinkage, stacking strength, and environmental stress crack resistance on the finished article. The grade is generally not intended for pipe extrusion, film casting, or thin-wall injection moulding.

What separates HC7260LS-L from higher-flow HDPE blow moulding grades?

The melt flow index of 0.30 g/10 min deliberately restricts melt-phase chain mobility. Compared with HDPE blow moulding resins having melt flow indices above 0.60 g/10 min, HC7260LS-L retains higher parison sag resistance and permits longer parison lengths before mould closure. The trade-off is lower throughput per screw revolution and higher extruder backpressure. On a 60 mm single-screw extruder with 25:1 L/D and a barrier screw, head pressure can enter the range of 18–25 MPa at screw speeds above 60 rpm, depending on die gap and melt temperature. Compared with injection moulding HDPE grades having melt flow indices above 5 g/10 min, HC7260LS-L is unsuitable for thin-wall injection moulding because the low melt flow index produces high filling pressure and an elevated risk of short shots below 2 mm wall thickness. The property differences originate from the molecular architecture of the grade: a higher average molecular mass and a broader molecular mass distribution increase entanglement density and slow crack growth resistance, but they also reduce melt-phase mobility.

Material handling for HC7260LS-L follows standard HDPE practice. The resin is not hygroscopic in the manner of polyamides or polyesters. However, condensation on cold pellets taken from outdoor storage can introduce enough surface moisture to disrupt extrusion. When pellet temperature is below the dew point of the surrounding plant air, condensation occurs. Transfer lines should be grounded to prevent static charge accumulation, and pellet temperature should be allowed to equilibrate to 20–25°C before opening the feed hopper. Pre-drying is not normally required for sealed pellets stored below 60% relative humidity. If storage exceeds 80% RH for more than 24 h, surface moisture can produce splay and reduce pinch-off weld strength. When wet resin is suspected, a desiccant dryer at 75–80°C for 2–3 h is commonly used.

Parison swell, die gap, and clamp force limitations in HC7260LS-L extrusion blow moulding

Extrudate swell and parison stability are governed by die geometry, melt temperature, and shear history. Land length-to-gap ratios below 10:1 generally produce non-uniform swell and wall-thickness variation in HC7260LS-L. Melt temperature above 205°C reduces melt strength and can produce parison drop-off at lengths above 150 mm. Below 185°C, surface melt fracture and die lines tend to increase. Blow air pressure is normally set at 0.6–0.8 MPa. Clamp force requirements for blow moulds are lower than for injection moulding; a 2 L container mould may require 150–250 kN depending on parting-line area and blowing pressure. Pinch-off weld strength depends on mould closing speed. Closing speeds below 200 mm/s often produce weak weld lines because the parison edge cools before full compression. On production lines, barrel zone temperatures are typically set between 170°C and 190°C, with head temperature at 185–200°C and die temperature at 190–205°C. Die gap settings of 0.8–1.2 mm are used for containers from 500 mL to 20 L, with blow-up ratios between 2.0:1 and 3.5:1. Mould cooling water between 10°C and 25°C is maintained to prevent sink marks and reduce warpage after demoulding.

Against lower-viscosity HDPE blow moulding grades with melt flow indices near 0.45 g/10 min, HC7260LS-L demonstrates higher environmental stress crack resistance. Published product data list F50 values above 600 h under ASTM D1693 using 10% Igepal CO-630, whereas conventional blow moulding grades often fall between 50 h and 200 h under the same condition. The difference is relevant for containers holding surfactants, agrochemicals, and alkaline cleaning fluids. The same molecular features that raise ESCR also reduce extrusion throughput; converters should not expect the output of an HDPE grade with melt flow index above 1.0 g/10 min. In HDPE slow crack growth, tie molecules bridging adjacent lamellae are the principal structural features resisting crack propagation. Higher molecular mass fractions increase tie molecule density, which in turn extends F50 time. Moulded-in stress from aggressive die gaps or insufficient cooling can reduce that advantage.

Mechanical property comparisons for HC7260LS-L and a reference blow moulding grade

Regrind addition on single-layer blow moulding lines is generally limited to 30 wt%. Higher regrind fractions raise viscosity heterogeneity and reduce ESCR because of chain scission from multiple heat histories. When regrind above 30 wt% is used, lot-by-lot testing to ASTM D1693 and ASTM D1238 is recommended to detect melt-flow drift and crack resistance loss. The resin should not be blended with high levels of linear low-density polyethylene above 20 wt% unless the resulting melt strength and top-load performance are explicitly evaluated on the target container. Chemical resistance follows general HDPE behavior: HC7260LS-L is suitable for many acids, bases, and alcohol-based products at ambient temperature, but it is not a barrier to aromatic hydrocarbons, chlorinated solvents, or strongly oxidizing media. Containers intended for aggressive solvents require specific permeation and stress crack testing on the finished article.

If ESCR performance is specified, which test condition controls the result?

Under ASTM D1693, the test condition governs the stress crack ranking. Condition A uses 10% Igepal CO-630 at 50°C; condition B uses 100% Igepal. For high-ESCR grades such as HC7260LS-L, condition A may not separate formulations within short test durations, so condition B is sometimes used to force failure. F50 values above 600 h under condition A indicate suitability for surfactant and detergent packaging, but F50 is a statistical value. Moulded-in stress, cooling rate, and notch severity in the finished container can reduce actual service life below the plaque-derived F50 result. Processors should therefore evaluate finished bottles under ASTM D2561 or a container-specific cap-torque and panel-load test standard rather than relying solely on compression-moulded plaques.

When organoleptic performance and food-contact compliance are required

For food-contact uses, converter documentation commonly references FDA 21 CFR 177.1520 for olefin polymers. That citation covers the base polymer but not the finished article; migration testing remains the converter’s responsibility under end-use conditions. European Union compliance is assessed under EU Regulation 10/2011, with an overall migration limit of 10 mg/dm² for plastic materials in contact with food. REACH documentation for HC7260LS-L generally states that substances of very high concern are not present above 0.1% w/w, subject to supplier declaration. RoHS compliance is not inherently applicable to HDPE packaging but is documented when electrical and electronic equipment parts are moulded.

On multi-cavity blow moulding lines, cavity-to-cavity weight variation should be held below ±1.5% to maintain ESCR and top-load performance. Flash thickness at the parting line is typically controlled between 0.05 mm and 0.15 mm. Mould venting below 0.01 mm depth is required to prevent air entrapment and pinholes. Melt temperature should be monitored with an immersion probe; values above 215°C can increase odour carryover and reduce ESCR, while values below 180°C can overload the extruder drive and produce melt fracture. The 126°C Vicat softening temperature imposes a hot-fill ceiling. For hot-fill applications above 90°C, container distortion may occur unless wall thickness and cooling are adjusted. Finished containers intended for outdoor exposure require ultraviolet stabilization through a carbon black masterbatch or a suitable hindered amine light stabilizer package; natural HC7260LS-L is not a UV-resistant grade.