PCC (Iran) HDPE 7000 F is a high-density polyethylene resin supplied for heavy-duty blown film applications. The grade is specified with a melt flow rate of 0.04 g/10 min determined at 190 °C under 2.16 kg load according to ISO 1133-1:2022, and with a density of 0.953 g/cm³ measured according to ISO 1183-1:2019. The combination of low melt flow rate and high-density structure places the material in the high-molecular-weight high-density polyethylene class rather than in medium- or high-flow injection moulding classes. In blown film conversion, the grade is used for industrial sacks, heavy-duty liners, and packaging where film thicknesses typically range from 20 µm to 200 µm. The low melt flow rate contributes to elevated melt viscosity, which improves bubble stability and impact properties but also increases extruder torque and head pressure on production-scale equipment.

Under ASTM D4976-12a, the material falls within the polyethylene classification for high-density resins, but the specific cell class requires lot data for density, melt flow, and tensile strength. Producers of Iranian high-density film grades typically report density and MFR on certificates of analysis rather than assigning a fixed ASTM cell class in commercial datasheets. The product should therefore be specified by density and melt flow rate, supplemented by lot-specific tensile, gel, and stabilizer data. Batch-to-batch variation in melt flow rate is often controlled within ±0.01 g/10 min on producer certificates. If incoming material shows MFR above 0.05 g/10 min or density outside 0.951 g/cm³ to 0.955 g/cm³, converter processing windows may shift. Higher MFR reduces head pressure but also reduces bubble stability and dart impact in thin film; lower density reduces film modulus.

What Are the Specification Limits That Separate HDPE 7000 F from High-Flow Injection Moulding Grades?

High-flow injection moulding grades are commonly specified with melt flow rates from 8 g/10 min to 20 g/10 min under ISO 1133-1:2022. The 0.04 g/10 min value of HDPE 7000 F therefore represents a viscosity approximately 200 to 500 times higher when compared at the same temperature and load. This difference originates from a higher weight-average molecular weight and not from density alone, since injection moulding grades can have similar density near 0.953 g/cm³. The practical consequence is that HDPE 7000 F cannot fill thin-wall injection mould flow sections below 2.0 mm at conventional injection pressures below 120 MPa. Conversely, high-flow injection grades lack the melt strength required to sustain a stable film bubble at blow-up ratios above 2:1 on HDPE film lines, because low melt elasticity produces bubble sag and gauge variation. The separating variable is therefore molecular weight and zero-shear viscosity, not crystallinity-related stiffness.

On production-scale blown film lines, PCC (Iran) HDPE 7000 F is processed on grooved-feed extruders with 25:1 to 30:1 L/D. The water-cooled grooved feed section is required because the low-MFR resin cannot be conveyed reliably by a smooth-bore feed zone under normal film die pressures. Barrel temperatures are set between 180 °C and 230 °C, while die temperatures are maintained at 210 °C to 240 °C. Die gaps from 1.8 mm to 2.2 mm are used to avoid melt fracture and to preserve bubble stability. Reducing the die gap below 1.5 mm at high output increases the risk of melt fracture, whereas gaps above 2.2 mm reduce transverse orientation and can lower film modulus. Frost-line height is typically held at 6 to 10 die diameters with blow-up ratios from 3:1 to 5:1. Reported field failure modes include bubble flutter when the frost line is too low, output surging on smooth-bore machines, and film breaks when melt temperature exceeds 240 °C because of thermal-oxidative degradation of the stabilizer package.

Dynamic oscillatory shear measurements under ISO 6721-10:2015 can be used to construct complex viscosity curves and storage modulus curves. The low shear-rate viscosity of HDPE 7000 F is above that of blow moulding grades, while the shear thinning index from frequency sweeps at 190 °C is typically pronounced. This behavior supports film extrusion at industrial shear rates but also means that capillary viscometry under ISO 11443:2021 should be used when designing die geometry to avoid melt fracture. The critical shear rate for melt fracture depends on die temperature, molecular weight distribution, and die gap; published data for this specific configuration is limited, so die trials at production scale are required. Gel content measured under ASTM D2765-16 should be monitored, and gels above 0.2 mm can cause film breaks in thin-gauge applications.

Mechanical properties are conventionally measured on film conditioned at 23 °C and 50 % relative humidity. Tensile strength at yield is reported at 29 MPa, with elongation at break above 600 % in both machine and transverse directions according to ISO 527-2:2012. Tear resistance is measured under ISO 6383-2:1983, and dart impact is measured under ISO 7765-1:1988 method A; published converter values for this specific grade are limited, so incoming resin certificates and on-line film testing are required to establish specification limits. For HMW-HDPE film of this density class, typical F50 dart impact on 50 µm film is above 150 g, but the actual result depends on die gap, blow-up ratio, frost-line height, and air-ring temperature. Gauge uniformity should be maintained within ±5 % by capacitive thickness scanners, because the high-viscosity resin is less tolerant of die gap non-uniformity than lower-viscosity film grades.

When HDPE 7000 F Replaces a Blow Moulding Grade in Heavy-Duty Sack Production

Substitution of HDPE 7000 F for a blow moulding grade such as HDPE 5000 S requires re-optimization of melt temperature, die gap, and output. The melt flow rate difference is 0.04 g/10 min versus approximately 0.23 g/10 min under ISO 1133-1:2022, which means the film grade develops higher melt pressure at the die and lower mass output per screw revolution. On 65 mm grooved-feed extruders, screw speed is typically reduced by 20 % to 30 % relative to the blow moulding grade to hold melt temperature below 240 °C. Die lips optimized for the lower-viscosity grade may require opening by 0.2 mm to 0.4 mm to control melt fracture. The higher melt strength of HDPE 7000 F supports blow-up ratios of 4:1 to 5:1, while the blow moulding grade may be limited to 3:1 in film applications. The benefit is higher dart impact and tear resistance in the final sack; the cost is reduced specific output and higher energy consumption per kilogram.

In coextruded structures, HDPE 7000 F is used as the stiffness layer, often in combination with linear low-density polyethylene layers of density 0.918 g/cm³ to 0.922 g/cm³. The melt temperature difference between the HDPE layer and LLDPE layers should be kept below 20 °C to prevent viscosity mismatch at the die. When the LLDPE layer ratio exceeds 30 %, interfacial instability can appear unless the HDPE layer melt temperature is increased to 230 °C or the die gap is reduced to 1.8 mm. Blends of HDPE 7000 F with LLDPE at 10 % to 30 % by weight are used to improve dart impact and tear resistance while retaining stiffness. However, properties of such blends do not scale linearly with weight fraction; tensile, tear, and impact testing under ISO 527-2:2012, ISO 6383-2:1983, and ISO 7765-1:1988 are required for each blend ratio.

Environmental stress crack resistance is relevant for packaging of surfactant-containing liquids and aggressive industrial goods. High-molecular-weight film grades typically show longer failure times than injection moulding grades under ASTM D1693 condition B, but the actual value for HDPE 7000 F must be taken from producer certificates or measured on 2 mm compression-moulded plaques. Oxidative induction time measured by ISO 11357-6:2018 at 200 °C is used to assess stabilizer level; converters should request lot-specific values when film is intended for outdoor exposure or high-temperature packaging. The base resin does not contain sufficient ultraviolet stabilization for prolonged outdoor service, so UV-stabilized masterbatch must be added for agricultural film or geotextile applications. Without UV stabilization, exposed film loses tensile strength within a period that depends on thickness, location, and solar irradiance; published data for this specific grade is limited.

In bag converting, heat seal initiation temperature for HDPE film is near 180 °C to 200 °C, measured by ASTM F88/F88M-21. The high density of HDPE 7000 F raises seal initiation temperature compared with LLDPE-rich films, but provides stiffer bag opening. Seal bar settings must be optimized for film thickness and line speed; excessive seal temperature above 220 °C can cause sticking and seal failure. Corona treatment may be required for printing and lamination, and surface energy should be maintained above 38 dyn/cm when tested according to ASTM D2578-17. The base resin does not inherently provide long-term corona retention, so flame or corona treatment levels should be measured before printing.

For food-contact applications, the final film must comply with FDA 21 CFR 177.1520 and Commission Regulation (EU) No 10/2011, with migration testing performed on the finished article rather than on the resin alone. The base polyethylene is not considered an SVHC candidate under REACH when supplied without substances of concern; RoHS restrictions under Directive 2011/65/EU apply only if the film is incorporated into electrical and electronic equipment accessories. Moisture absorption is low, and drying is not required below 60 % relative humidity because polyethylene does not undergo hydrolytic degradation. Surface condensation on cold pellets can introduce visual defects; in that case, an air-swept hopper or drying at 80 °C for 2 h is sufficient. Edge-trim regrind can be added up to 20 % by weight in heavy-duty sack production without automatically invalidating food-contact compliance, provided the regrind stream is controlled and free of contaminants. Higher regrind ratios may reduce dart impact and increase gel content because of repeated thermal history.

Stored resin should be kept away from direct ultraviolet radiation and from incompatible materials such as PVC, PET, and polyamide scrap; thermal decomposition products from these polymers can form gels or black specks during HDPE film extrusion. The grade should not be processed on single-flighted smooth-bore extruders without a grooved feed section, because feed conveying is insufficient for the low-MFR melt and results in output surging. When switching from a lower-viscosity HDPE film grade to HDPE 7000 F, purging should be performed with a high-viscosity HDPE or a dedicated purging compound until melt pressure and film clarity stabilize; incomplete purging leaves visible gels and gauge bands in the final film.