CHN Energy Baotou (Shenhua Baotou) HDPE DMDA-9520 is a high-density polyethylene resin produced on a gas-phase polymerization asset at the Baotou coal-to-olefins complex in Inner Mongolia. The grade designation encodes nominal density 0.952 g/cm³ and nominal melt mass-flow rate 0.20 g/10 min when tested under ISO 1183-1 and ISO 1133-1 (190 °C, 2.16 kg), respectively. This combination places DMDA-9520 in the medium-molecular-weight, medium-density HDPE film segment, where bubble stability and stiffness are balanced against dart impact and tear resistance. The product is supplied as pelletized resin with antioxidant stabilisation; slip and antiblock additives are not necessarily present in the base grade and are usually introduced by converter masterbatch additions.

What distinguishes DMDA-9520 from high-fluid injection and blow moulding HDPE grades on the same site?

When compared with DMDA-8920, a high-flow injection moulding grade assigned a nominal MFR of 20 g/10 min (ISO 1133-1), DMDA-9520 exhibits an MFR lower by approximately 100-fold. The low MFR corresponds to longer chain relaxation times, higher extensional viscosity and greater melt strength, all of which stabilise the blown film bubble under transverse draw. DMDA-8920 is unsuitable for blown film operations at comparable die gaps because its low melt strength promotes bubble sag and thickness variability; it is instead processed in short-cycle injection moulding machines with clamp forces typically above 800 kN. Conversely, DMDA-9520 is not intended for injection moulding; the high melt viscosity restricts flow into thin-wall moulds and increases injection pressure requirements. Blow moulding grades such as DMDA-8007 are positioned at higher density for bottle and container top-load performance; DMDA-9520 is optimised for film rather than parison hang strength and die swell control. The molecular architecture that supports a stable film bubble is therefore different from the narrow molecular weight distribution required for injection moulding or the die swell consistency required for blow moulding.

The specification framework for DMDA-9520 is anchored to the producer technical datasheet and lot-specific certificate of analysis. Table 1 lists the nominal property data most frequently used for incoming resin inspection. Detailed mechanical and optical film properties are not tabulated because published data for this specific configuration is limited; tensile yield stress, elongation at break, dart drop impact strength, Elmendorf tear resistance and haze must be established at the converter on a pilot line or production trial using the intended film thickness, blow-up ratio, frostline height and additive package. Reliance on values from other HDPE film grades with similar density and MFR is not a substitute for lot-specific verification because catalyst residues, comonomer distribution and molecular weight distribution can shift film properties even at identical density and MFR. Incoming resin inspection should include melt index verification to ISO 1133-1, density by gradient column or gas pycnometer per ISO 1183-1, and visual pellet inspection for black specks and angel hair. Moisture content by ISO 15512 should remain below 0.05 wt% for film extrusion.

Processing Behavior on High-Density Polyethylene Blown Film Lines

On conventional blown film lines equipped with single-screw extruders of 40–70 mm screw diameter and 24:1–30:1 L/D ratio, DMDA-9520 requires sufficient barrel heating and motor torque due to its 0.20 g/10 min MFR. Recommended melt temperature range is 190–210 °C, with die temperature 200–210 °C; exceeding 230 °C may initiate oxidative degradation, detected as yellowing, gel formation and the development of fish-eye defects in film. Die gap settings from 0.8–1.2 mm and blow-up ratios from 3:1–5:1 are typical for gauge control. Internal bubble cooling is advisable for high-output campaigns because low-MFR HDPE generates a stiff, stable bubble but high melt temperature may limit output; throughput is constrained by extruder drive load and melt pressure before the screen changer. Pressure screening with 100–120 mesh packs is used to remove unmelts and gels. Start-up with a high-MFR HDPE purge grade is recommended to remove barrel residence material and to reduce start-up gel contamination.

Screw design matters. A barrier screw with Maddock mixing section and compression ratio 3.0:1–3.5:1 is preferred over a general-purpose PE screw for low-MFR HDPE. Grooved feed sections are not required for conventional PE extruders but improve output per rpm in high-throughput lines. Melt temperature is best measured with an immersion probe at the die adaptor; contact thermocouples in the barrel may underreport by 5–10 °C. Operators should set rear barrel temperature at 160–180 °C, compression section at 180–200 °C, metering section at 190–210 °C and die head at 200–210 °C. Sudden temperature drops below 170 °C in the adaptor cause melt fracture and bubble instability.

The primary application envelope for DMDA-9520 is high-stiffness blown film for industrial liners, carrier bags, heavy packaging and agricultural mulch. Films produced from the resin at 15–80 µm thickness exhibit the directional mechanical asymmetry typical of HDPE film: machine-direction tensile strength is governed by draw ratio and frostline height, while transverse-direction properties depend on blow-up ratio. Film property measurements should follow ISO 527-3 for tensile stress–strain, ISO 6383-2 for Elmendorf tear resistance and ISO 7765-1 for dart drop impact, with conditioning at 23 °C/50 % RH for 48 h. Thickness variation must be kept below ±5 % around target because low-MFR HDPE film shows pronounced tear directionality; heavy-gauge liners may be assessed under ASTM D1709 when North American specifications apply. Moisture vapour transmission rate can be compared under ISO 15106-3 at 38 °C/90 % RH, where HDPE films with density in the 0.950–0.960 g/cm³ range generally fall below LLDPE by a factor of 2–3, though exact values vary with crystallinity, orientation and thickness.

When surface properties must be altered, converter masterbatches are preferred over changing the base resin. For low coefficient of friction and antistatic film, erucamide or stearyl erucamide masterbatch is dosed at 0.5–1.0 wt%, while synthetic silica antiblock is added at 0.5–2.0 wt% for film-to-film separation at high blocking tendency. These additives must be predispersed in a polyethylene carrier compatible with HDPE; incompatible carriers can generate gels and die-lip deposit. If carbon black masterbatch is used for UV-stabilised agricultural film, loading of 2–3 wt% carbon black with a hindered amine light stabiliser package can be evaluated under ISO 4892-2 test methods, but the specific loading must be validated for the target service time.

When film stiffness must be balanced against puncture and tear

Selection of DMDA-9520 over lower-density LLDPE is justified when film modulus and water vapour barrier are the controlling requirements. Its density of 0.952 g/cm³ places it below blow moulding HDPE grades at 0.958 g/cm³, thereby retaining greater dart impact and lower seal initiation temperature than higher-crystallinity HDPE. However, high-density polyethylene film is not the appropriate choice where high dart impact at freezer temperatures or high Elmendorf tear resistance is mandatory; hexene or octene LLDPE grades with density 0.918–0.925 g/cm³ outperform DMDA-9520 in these tests. In applications requiring ESCR and top-load, blow moulding HDPE grades are preferred. Converters should not assume that density alone determines performance: comonomer type, molecular weight distribution and catalyst residues also shift impact and tear, and published data for DMDA-9520 in these areas is limited.

Sealing behaviour also differs. HDPE films have higher seal initiation temperature than LLDPE and a narrower sealing window; DMDA-9520 should be sealed at jaw temperatures from 130–160 °C on hot-bar sealers, depending on film thickness and seal dwell time. At thicknesses above 50 µm, thermal transfer limits the sealing speed, and ultrasonic sealing may be necessary. The coefficient of friction is highly additive-dependent; untreated HDPE film typically exhibits kinetic coefficient of friction 0.4–0.6 against stainless steel under ISO 8295, but slip additives can reduce this to 0.1–0.2.

Regrind derived from edge trim and start-up film can be incorporated into DMDA-9520 at 10–20 wt% on high-output lines without automatic gauge control loss when the regrind is clean and free of additive masterbatch residues. Higher levels can increase melt pressure variability and gel counts due to repeated thermal history. The resin does not require pre-drying when stored in closed silos at ambient conditions; however, if pellets are moved from cold storage to a warm, high-humidity production hall, surface condensation can occur, and a hopper dryer at 60 °C for 1–2 h is recommended. Avoid blending DMDA-9520 with polar barrier polymers such as EVOH or polyamide without a tie resin, because interfacial adhesion in coextruded film is insufficient. If barrier films are produced, use an anhydride-modified polyolefin tie layer between HDPE and EVOH/PA. For food-contact use, the resin should be evaluated under FDA 21 CFR 177.1520 and EU Regulation 10/2011, with migration testing on the final film structure; the producer’s regulatory certificate must confirm compliance for the specific lot.

Production-scale conversion experience shows that die lip deposit formation during long runs is influenced by low-MFR HDPE and additive masterbatch interactions. Periodic die lip cleaning every 8–12 h may be necessary when running high levels of silica antiblock masterbatch; air knives in the bubble collapsing frame reduce blocking at high frostline heights. On cast film lines, DMDA-9520 is generally not recommended because the low MFR can produce elevated melt temperatures and die build-up; blown film remains the proven platform. For extrusion coating, the high viscosity is also outside the typical processing window of high-line-speed coating lines, where melt ducts and dies are configured for melt indices above 5 g/10 min.