PetroChina Daqing HDPE DGDB 6097

PetroChina Daqing HDPE DGDB 6097 is a high-density polyethylene resin supplied by Daqing Petrochemical Company within the PetroChina portfolio. The grade is classified as a high-molecular-weight film extrusion resin and is normally delivered as white pellets. It is converted primarily on air-cooled blown film lines and, in selected sheet applications, on cast or polishing stack lines where high melt strength is required. The resin is not classified as a pipe compound or as a conventional injection-moulding grade, and substitution into those processes without pilot validation is not recommended. The published application envelope includes refuse sacks, carrier bags, liners, freezer packaging, and thin-gauge sacks in which downgauging and bending stiffness are process-relevant.

The following typical property set is drawn from producer technical bulletins and is not a substitute for a lot-specific certificate of analysis. Values obtained on compression-moulded plaques may differ from values obtained on finished film because film orientation, frost-line height, blow-up ratio, and gauge variation influence the final mechanical response.

Dart impact resistance, Elmendorf tear strength, and environmental stress cracking resistance are not fixed universal values for this resin. They are dependent on film thickness, orientation balance, additive package, and conversion parameters. Where a specification requires those values, the producer should be asked for the current technical data sheet and the converter should generate film samples under the intended line conditions.

How Does DGDB 6097 Behave Under Blown Film Extrusion Conditions?

On monolayer blown film lines, the grade is typically processed with a screw length-to-diameter ratio of 25:1 to 30:1 and a barrier or high-shear mixing section. Grooved feed sections are commonly employed to stabilize solids conveying at the low melt-index end of the high-density polyethylene range. Screen packs are usually built in the 60/80/100 mesh configuration, but backpressure must be monitored because the high-molecular-weight fraction raises head pressure quickly when screen blockage begins. Melt pressure at the breaker plate is to be maintained within the barrel and adapter pressure rating; on lines with restrictive screens, values above 25 MPa can indicate a need for screen replacement.

The melt-temperature window is generally set between 200 °C and 220 °C. Operation below 195 °C increases extrusion pressure and raises the risk of sharkskin, melt fracture, and uneven film gauge. Operation above 230 °C for extended hold times accelerates thermo-oxidative degradation, visible as gel defects, odour, and reduced dart impact strength. A temperature spread across the die of not more than 5 °C is recommended for uniform bubble stability. Die gaps from 0.8 mm to 1.2 mm are appropriate for most tube diameters. Below 0.8 mm, die-lip deposit formation and melt fracture become more frequent; above 1.2 mm, the bubble becomes more difficult to stabilize because the film retains heat and the frost-line position shifts upward.

A high-stalk bubble configuration is preferred over a low-stalk or pocket configuration because the grade’s melt strength supports an extended stalk. The blow-up ratio is typically set between 3:1 and 5:1, with the frost-line height held at 5 to 8 die diameters. Excessively high frost-line height reduces transverse direction orientation and produces a film with lower dart impact resistance and higher splitiness. Excessively low frost-line height chills the film before adequate orientation is developed and can reduce tensile yield stress in the machine direction. Output rate must be balanced against bubble stability rather than driven only by screw speed; when output is increased without proportional cooling air adjustment, bubble flutter and gauge variation increase. Internal bubble cooling, where available, expands the stable output range but requires a higher air-exchange capacity and close monitoring of frost-line position.

During extended runs, die-lip deposit is a known bottleneck. The deposit rate increases when melt temperature exceeds 225 °C or when the line is operated at high output with inadequate die-lip air cooling. Purging between campaigns is usually performed with a lower-viscosity polyethylene, but abrupt transitions from high-molecular-weight high-density polyethylene to a low-viscosity purge can cause screw slip if the feed section is not kept full. Gradual purge transitions and hopper-level control are standard on production-scale lines to avoid feed starvation and bubble collapse.

When converted into 25 µm monolayer film on an air-cooled high-stalk line, the resin develops a balance of high bending stiffness and moderate puncture resistance. Film tensile properties should be measured according to ISO 527-3 or ASTM D882 rather than ISO 527-2, because the oriented film sample differs from the compression-moulded plaque. Dart impact resistance is normally measured under ASTM D1709 Method A for thin film below 30 µm; results between production lots can shift by more than 15 g when the frost-line height or film gauge is not held constant. Tear resistance measured under ISO 6383-2 is lower than that of linear low-density polyethylene at equal thickness, but the high-density polyethylene film shows higher tensile yield stress and a lower water-vapour transmission rate under ASTM F1249 or ISO 15106-2. The moisture barrier advantage is thickness-dependent and must be compared at equal gauge rather than as an absolute material property.

Melt-Strength Limitations and Molecular-Weight Boundaries in Film Converting

The low melt mass-flow rate of 0.80 g/10 min at 190 °C and 2.16 kg indicates a high average molecular weight. The resulting melt viscosity supports tall bubble configurations and thin-gauge processing, but it also limits the grade’s suitability for fine monofilament, injection moulding, and thin-wall extrusion processes requiring rapid melt flow. The ratio of high-load melt index to standard melt-flow rate is a better indicator of molecular weight distribution than the standard 2.16 kg value alone. Published producer data for the high-load value and the melt-flow ratio of DGDB 6097 should be obtained when comparing the grade against alternative high-molecular-weight high-density polyethylene film resins.

Blending with linear low-density polyethylene is sometimes performed to improve dart impact and tear strength. Addition levels from 20 wt% to 30 wt% of linear low-density polyethylene lower melt strength and can destabilize a high-stalk bubble; converters typically compensate by reducing the blow-up ratio by 1:1 to 1.5:1 and lowering the frost-line height. Melt-phase mixing is generally adequate in a properly designed barrier screw, but optical clarity may decline if the two polymers do not form a miscible melt. For applications requiring a clear outer layer, coextrusion is preferred over blending because haze is not introduced into the outer layer. The grade should not be combined with low-molecular-weight waxes or oxidized recycle streams at high loading; those additives reduce melt strength disproportionately and can increase die-lip deposit formation.

Pre-drying is not normally required when the pellets are stored under dry indoor conditions and the hopper temperature is maintained above the dew point. If the relative humidity around the hopper exceeds 60% or surface condensation is observed, pre-drying at 80 °C for 2 h is a conservative starting condition. Prolonged storage above 50 °C or direct ultraviolet exposure accelerates oxidation and can shift melt-flow stability. The resin should not be kept in outdoor silos where day-night condensation creates intermittent moisture intake.

When the Grade Is Compared Against 5000S, 6200B, and Linear-Low-Density Polyethylene

Comparisons between DGDB 6097 and PetroChina Daqing 5000S show that both resins occupy a similar density range, but 5000S is specified for monofilament, rope, and netting rather than thin film. In 5000S, the molecular architecture is optimized for drawing and orientation; DGDB 6097 does not draw down into fine monofilament without high melt tension that complicates die-start and filament cooling. The difference appears more clearly in processing than in the standard melt-flow-rate specification, because a single 2.16 kg melt-flow value does not capture the high-stalk bubble stability required for film conversion.

Against Daqing 6200B, a blow-moulding grade, the film resin shows a different die-swell pattern and parison sag behaviour. Blow-moulding resins are selected for sag resistance and controlled wall-thickness distribution in a closed mould; DGDB 6097 is not supplied for those parison requirements. On a blow-moulding head, the film grade may show excessive die swell under high shear and may not deliver uniform parison length when the accumulator head is filled. Conversely, 6200B is not an automatic drop-in replacement for DGDB 6097 on a blown film line because the bubble stability and frost-line behaviour differ, and tear strength at thin gauge can be lower than expected.

When compared with a linear low-density polyethylene such as DFDA-7042, DGDB 6097 has higher density, higher flexural modulus, higher tensile yield stress, and lower elongation at break. Linear low-density polyethylene provides higher dart impact and Elmendorf tear resistance at equal thickness, while DGDB 6097 provides greater stiffness and a lower water-vapour transmission rate. In coextruded structures, the high-density polyethylene layer is often placed near the inside or outside of the film for stiffness and moisture resistance, while the linear low-density polyethylene layer supplies tear and impact strength. The two resins are not direct substitutes because their melt-strength characteristics and film-property profiles are governed by different comonomer distributions and molecular weight distributions.

For food-contact applications, converters must obtain the producer’s specific food-contact statement. The base high-density polyethylene polymer may be evaluated under 21 CFR 177.1520 for certain United States applications and under Regulation (EU) No 10/2011 for European Union applications, but additive and processing aids in a finished film are the converter’s responsibility. The resin is not assumed to be a medical-grade material, and no biocompatibility assessment under ISO 10993 should be inferred without a written grade-specific declaration. Electrical and electronic component users must verify compliance with RoHS Directive 2011/65/EU for restricted substances and with applicable REACH obligations for the finished article.

In aggressive detergent and surfactant packaging, environmental stress cracking resistance should be measured under ASTM D1693 on the finished bottle or film, not on a generic plaque, because processing orientation and wall thickness control the final result. The resin should not be used in direct contact with strong oxidizing acids, aromatic solvents, or chlorinated hydrocarbons without chemical-resistance testing on the finished container. High-density polyethylene has adequate moisture resistance but poor oxygen barrier; if oxygen-sensitive goods are packaged with DGDB 6097, a barrier layer or additive system must be introduced by coextrusion or coating rather than by relying on the high-density polyethylene phase alone.