DL Chemical HDPE DAELIM POLY LH-6070T is a high-density ethylene polymer supplied in pellet form for thin-gauge film extrusion. The producer technical documentation identifies the grade as a low-melt-flow, high-stiffness film resin; the alphanumeric designation LH-6070T appears on certificates of analysis, packaging labels, and shipping documents for lot traceability. The specification profile is anchored by a melt flow rate of 0.70 g/10 min when determined at 190 °C under a 2.16 kg load in accordance with ISO 1133-1, and a density of 0.960 g/cm³ determined in accordance with ISO 1183-1. These two values define a highly crystalline, low-flow resin in the HDPE film class; the low melt flow separates it from conventional injection-molding grades with melt flow rates above 5 g/10 min, while the density separates it from medium-density and linear-low-density blown film grades. The product is directed to high-speed bag, sack, and liner lines where machine-direction modulus, melt strength, and down-gauging are process-critical variables. Published data for molecular weight distribution and catalyst-specific chain architecture are limited in routine commercial documentation, so converter validation relies on measured melt pressure, frost line stability, and tensile property balance rather than laboratory oscillatory rheometry.

How Does a Melt Flow Rate of 0.70 g/10 min Modify Blown Film Line Operation?

On a single-screw blown film extrusion line, the low melt flow rate increases melt strength and bubble stability but simultaneously raises extruder back pressure and torque demand. A barrier screw with an L/D of 30:1 to 36:1 and a spiral Maddock mixing section is generally specified for such a resin; the longer melting length compensates for the lower shear heating of a high-viscosity, low-MFR polyolefin. Typical barrel set points from feed to metering zone may start at 180 °C and progress to 200 °C, with a die and adapter temperature of 205 °C to 215 °C. Melt temperatures above 230 °C are to be avoided in prolonged residence because oxidative chain scission and gel formation begin to modify the molecular weight envelope, a point that is of particular concern in larger extruders with long transfer lines.

At the die lip, bubble geometry is governed by blow-up ratio and frost line height. For this high-density, low-MFR film, a starting blow-up ratio of 3:1 to 5:1 is common, with the frost line positioned at 8 to 12 die diameters above the air ring. A shorter frost line can reduce film clarity and increase film blocking, while an excessively high frost line can allow bubble sway and TD gauge variation. The die gap on high-density film lines is usually set at 1.2 to 2.0 mm; a larger gap is often required with low-MFR HDPE to delay sharkskin and to distribute the melt uniformly in spiral mandrel dies. Because the grade has a low melt flow rate, the critical shear rate for melt fracture is reached sooner than with high-MFR grades; die lip land length, lip roughness, and local temperature control must be maintained within narrow limits. In field troubleshooting, visible sharkskin on the film surface at normal line speed is frequently corrected by increasing the die lip temperature in 5 °C increments or by adding a fluoropolymer process aid in a masterbatch carrier, rather than by increasing screw speed alone.

The extruder head pressure before the screen changer on small and medium lines can exceed 25 MPa depending on screw design, output, and melt temperature. Pressure transducers should be mounted immediately before the breaker plate and after the screen pack; a rapid differential pressure increase of more than 5 MPa across the filtration assembly is an indication that oxidized material, gels, or contaminants are accumulating. The screw thrust bearing must be sized for continuous operation at the maximum allowable head pressure; unprotected start-up against a cold screen pack can subject the bearing to mechanical overload and shorten service life.

Tensile, Density, and Thermal Property Anchor Points

Typical values reproduced from producer datasheet documentation are shown below; these are not batch-by-batch guarantees and should be compared with the certificate of analysis for each lot.

The combination of 0.960 g/cm³ density and 0.70 g/10 min MFR places the product in the upper-crystallinity tier of film-grade HDPE. The flexural modulus above 1,000 MPa provides stiffness for thin-gauge grocery sacks and industrial liners; the high yield stress reduces film stretch at low thickness. However, the same crystallinity lowers dart puncture and Elmendorf tear compared with MDPE and LLDPE. The data sheet does not typically disclose melt strength measured by Rheotens or extensional viscosity; published data for these specific configuration is limited. Therefore, the converter should treat the tabulated values as a material product specification, not as a substitute for line-specific film testing under 23 °C ± 2 °C and 50 % ± 10 % relative humidity after 24 h conditioning according to ISO 291.

On a 65 mm single-screw blown film line equipped with an L/D of 30:1, a dual-lip air ring, and a 250 mm spiral mandrel die with a 1.5 mm die gap, a typical starting set point for this resin is a feed-to-die temperature profile of 180 °C/190 °C/200 °C/205 °C/210 °C. At a blow-up ratio of 3.5:1 and a frost line height of 8 die diameters, bubble resonance is minimized when die lip exit velocity is held below the point at which sharkskin initiates. Lowering the die exit gap to 1.0 mm in an attempt to increase melt velocity often destabilizes the bubble and increases orientation gradients between edges and center; this is especially visible in high-density film because the low-MFR melt stores less elastic energy at the die exit under reduced shear. The same resin can be processed in tandem winder setups where gusseting bars and collapsing frames introduce machine-direction orientation; the high density and low MFR produce a stiffer film, but the tension control at the primary nip must be calibrated to avoid transverse wrinkle formation at roll build-up above 500 mm diameter. These observations are drawn from standard HDPE blown film practice rather than a proprietary production trial for this specific configuration; published data for that exact equipment is limited.

When LH-6070T Replaces an LDPE or Medium-Density Film in Down-Gauged Sacks

Substitution of a 0.960 g/cm³ low-MFR HDPE into a structure originally designed for LDPE or medium-density film changes the tensile, tear, and heat-seal response simultaneously. The density elevates yield stress and reduces gas transmission measured by ASTM D3985 relative to an MDPE of approximately 0.935 g/cm³; however, dart puncture and Elmendorf tear are lower, so the down-gauged structure should not retain the same impact resistance unless the film is coextruded with a softer tie layer. When converting from 25 µm to 15 µm, heat-seal settings must be revalidated. HDPE has a higher melting peak and a narrower hot-tack plateau than LDPE; with an MFR of 0.70 g/10 min, full interfacial wetting at the seal jaw requires longer dwell or higher jaw pressure. Seal strength is normally measured in accordance with ASTM F88/F88M or ISO 527-3 on film strips sealed at 135 °C to 150 °C. If the sealing bars are heavily serrated, the lower melt flow resin may not flow into the serrations at short dwell times, producing channels and reduced burst strength; changing to a rectangular bar profile or increasing seal time by 0.1 s increments is the standard adjustment sequence.

Gel Control and Melt Filtration Pressure Rise During Continuous Runs

Low-MFR HDPE films are susceptible to visible gel defects if oxidized skins from pellet transfer lines, degraded material from screw dead zones, or cross-linked particles from hot spots enter the melt stream. Continuous-run converters therefore install a slide-plate screen changer with a progressive screen pack, typically 60/80/100 mesh in the breaker plate assembly, and log differential pressure across the pack. An increase above the target differential of 5 MPa to 8 MPa indicates accumulation of agglomerates or oxidative gel; the screen should be changed before pressure transients produce surging at the die lip and gauge bands in the finished roll. The resin is not hydrolytically sensitive, so pre-drying is not generally required unless cold pellets have been exposed to high-humidity air and surface condensation forms. In that case, a desiccant hopper dryer at 80 °C for 2 h prevents steam bubbles and die-lip plate-out. No amine-containing additives should be cold-blended with the resin without compatibility testing, because alkaline species can accelerate thermo-oxidative degradation at melt temperatures above 220 °C, increasing carbonyl index and visible gel count in the film.

During purge and shutdown, a transition to a higher-MFR LDPE or a commercial purge compound reduces residual high-viscosity HDPE in the barrel and die. Direct start-up from empty with this grade requires slow screw speed and careful barrel heat soaking; instantaneous high screw speed on a cold bridge can shear-heat localized melt above its degradation temperature and produce black specks that appear in later film runs. The product should be stored in sealed packaging under ambient conditions below 35 °C and protected from direct sunlight; hot silo transfer lines above 50 °C should be avoided to prevent pellet surface oxidation.

Compliance Obligations Remain Even After Pellet Purchase

The following regulatory references are commonly used for HDPE film in packaging and industrial end-uses. They are given as a compliance matrix, not as a substitute for lot-specific certification.

The base formulation is not typically supplied with an intentionally added UV stabilizer; outdoor service therefore requires coextruded or masterbatched UV protection unless the lot-specific technical data sheet explicitly states otherwise. Recycled process scrap and edge trim can alter the hot-tack window, so the converter should requalify seal initiation temperature and gel count after introducing regrind. Published data for this specific configuration is limited, and all end-use compliance testing remains the responsibility of the packaging or finished article supplier.