Ningxia Baofeng Energy HDPE DMDA8008 is a high-density polyethylene blow-moulding grade supplied as white pellets. The material is positioned for continuous-extrusion and reciprocating-screw blow moulding of small-to-medium containers, where a melt flow rate near 0.8 g/10 min and a nominal density near 0.956 g/cm³ provide a measured balance between parison melt strength, die swell, and extrusion output. Lot release documentation typically references ISO 1183-1:2019 for density and ISO 1133-1:2022 condition 190 °C/2.16 kg for melt flow rate. Unlike high-MFR injection-moulding HDPE grades, DMDA8008 retains higher molecular weight, which increases environmental stress cracking resistance and melt elasticity while reducing spiral-flow length. The resin is employed in dairy bottles, cosmetic containers, pharmaceutical bottles, and small industrial chemical containers. Published data for this specific configuration is limited to the producer’s technical certificate and converter trials; lot-specific certificates of analysis should govern incoming inspection. The material is not a polypropylene random copolymer; density and stiffness are higher, but clarity is lower.

Physical Property Envelope and Test Methods

The property envelope in the following table represents typical release metrics reported for DMDA8008. These values are not design minima. Batch-to-batch variation can occur within the producer’s specification limits, and specimen preparation, cooling rate, and test temperature exert measurable influence on mechanical data. Tensile and flexural values are determined on conditioned specimens; notched Charpy impact is sensitive to specimen thickness and moulding history. For design purposes, the target application should be validated on finished containers under the actual wall thickness and service temperature.

The melt flow rate is measured at low shear stress and does not fully describe the shear-thinning behaviour in a blow-moulding die. Capillary rheometry, if required, should be performed according to ISO 11443:2021 over shear rates from 100 s⁻¹ to 1,000 s⁻¹ to establish lot-to-lot viscosity consistency. ESCR failure time is strongly influenced by notch quality and stress-relieving conditions; therefore, ASTM D1693-15 values should be compared only within the same laboratory and specimen preparation protocol. Melting point is not a single value for HDPE; differential scanning calorimetry according to ISO 11357-3:2018 typically shows a peak melting temperature near 132 °C for densities in this range. Crystallization temperature and degree of crystallinity depend on cooling rate; fast cooling in thin bottle walls lowers density and stiffness while improving impact, while slow cooling in thick sections increases crystallinity and shrink potential.

Continuous-extrusion blow-moulding trials commonly evaluate DMDA8008 at melt temperatures between 170 °C and 190 °C. On shuttle machines producing 500 mL to 5 L bottles, die head temperatures above 195 °C produce observable parison sag, resulting in thicker bottom walls and reduced top-load consistency. The resin’s ESCR performance under ASTM D1693-15 condition B is especially relevant for surfactant-based household chemical packaging; it is less informative for hot-fill applications because oxidative degradation and creep become controlling failure mechanisms. When wall thickness distribution is controlled, the grade provides sufficient stiffness for self-standing containers without requiring a separate stiffening layer. Multi-layer co-extrusion lines using an HDPE outer layer and EVOH barrier must verify that the die swell of DMDA8008 does not displace the barrier layer; published data for this specific configuration is limited.

How Does the Melt Flow Rate Affect Continuous Extrusion Blow Moulding?

At 0.8 g/10 min, the melt flow rate of DMDA8008 is selected to minimize parison sag under its own weight. The melt viscosity is sufficiently high to maintain parison integrity during long drop times on shuttle machines, but flow resistance is not so high that extrusion output is severely restricted. Typical blowing lines use grooved-feed single-screw extruders with screw diameters from 60 mm to 75 mm and L/D ratios from 24:1 to 30:1. In a continuous extrusion head, the die land shear rate typically falls between 100 s⁻¹ and 500 s⁻¹, where the resin exhibits shear thinning. Barrel zone settings of 170 °C to 190 °C and head/die settings of 175 °C to 185 °C are common starting conditions. Raising melt temperature above 190 °C reduces melt strength and increases die-swell variability; lowering below 170 °C raises melt pressure and may produce melt fracture at high output. Die swell is not a linear function of melt flow rate; it is governed by molecular weight distribution, molar mass tail, and die geometry. DMDA8008’s typical MFR of 0.8 g/10 min indicates only the low-shear viscosity at 190 °C; capillary rheometry is required to predict die swell quantitatively.

The grade is usually run without pre-drying when packaging is intact and storage relative humidity is below 60 %. If hopper residence time exceeds 4 h under humid conditions, surface moisture can generate splay and bubbles in the parison; a desiccant hopper dryer at 80 °C for 4 h is used only when visual defects are observed. Extruder screw design affects melt temperature uniformity. Barrier screws with mixing sections are preferred because DMDA8008 has a relatively narrow processing window under high output. If a standard three-stage screw is used, head pressure should be monitored between 20 MPa and 35 MPa; higher pressures indicate insufficient heating or a blocked screen pack. Screen pack mesh sizes of 40/60/80 are common. Melt temperature measured by an immersion thermocouple at the die entry should be compared with setpoint; differences greater than 5 °C indicate poor shear heating control.

When DMDA8008 Replaces Traditional HDPE Blow Moulding Grades

Substitution studies generally compare DMDA8008 with HDPE blow-moulding grades of similar density and different melt index, including resins in the 0.3 g/10 min and 1.2 g/10 min classes. The 0.8 g/10 min grade occupies an intermediate processing zone: lower-MFR resins can provide greater melt strength and ESCR but require higher screw torque and may reduce output; higher-MFR resins allow faster cycling but increase parison sag and reduce ESCR. Compared with injection-moulding HDPE grades in the 4 g/10 min to 20 g/10 min range, DMDA8008 shows higher notched Charpy impact and ESCR, but lower spiral-flow length and higher die pressure. It is not suitable for thin-wall injection moulding; bottle wall thicknesses above 0.4 mm are more realistic.

The difference in ESCR is not solely a function of MFR. The molecular weight distribution and comonomer placement in DMDA8008 create a higher concentration of tie-chain segments bridging crystalline lamellae. At the nominal density of 0.956 g/cm³, the resin retains sufficient crystalline fraction for stiffness; density increases above 0.960 g/cm³ typically raise flexural modulus but reduce slow crack growth resistance because fewer tie chains remain in the amorphous phase. A notched specimen in 10 % Igepal CO-630 at 50 °C fails by environmental stress cracking when the applied stress exceeds the craze strength of the amorphous tie-chain network. DMDA8008 is positioned in the lower-MFR portion of the blow-moulding range to preserve these tie chains. Orientation effects in the bottle wall are not captured by the isotropic compression-moulded specimen used in ASTM D1693-15; therefore, bottle-level ESCR testing should be performed on finished containers. When compared with polypropylene random copolymer blow-moulding grades, DMDA8008 has higher density and lower transparency, while ESCR in detergent and surfactant packaging is generally superior. Published data for direct substitution on multi-layer co-extrusion lines is limited.

Food-contact compliance for DMDA8008 is typically assessed under FDA 21 CFR 177.1520 for olefin polymers and European Commission Regulation EU 10/2011 with an overall migration limit of 10 mg/dm² for plastic materials. The grade may also be listed under REACH and is generally considered compliant with RoHS Directive 2011/65/EU for restricted substances, but converters must verify lot-specific certificates and migration test results for the finished container. The stabilization package should not be assumed identical to other suppliers; therefore, formulation-specific food-contact conditions such as simulant type, time, and temperature must be taken from the producer’s declaration of compliance. The resin contains no intentionally added heavy metals. It is incompatible with strong oxidizing agents and should not be stored in direct contact with copper or copper alloys at processing temperatures because of accelerated thermo-oxidative degradation.

Storage, Drying and Thermal Stability Limits

Pellets are supplied in 25 kg bags or bulk containers. Storage should be in a dry, closed area below 40 °C and away from UV radiation because the resin contains limited UV stabilizer unless specifically compounded. Although HDPE is not hygroscopic, surface condensation can occur when cold pellets are transferred into a warm processing hall; a minimum 24 h tempering period is recommended for bulk containers moved from outdoor storage. Thermal stability limits are derived from melt-processing conditions: the melt should not remain at 220 °C for extended periods, and emergency shutdowns should be purged within 15 min to limit chain scission or crosslinking. Prolonged residence time at high temperature can produce gel particles, yellowing, and off-odour in finished bottles. The recommended hopper capacity should match extrusion rate to avoid bridging; pellet bridging is rare but possible at hopper outlet temperatures above 60 °C because of surface softening.

Regrind from clean blow-moulding scrap can be added at up to 20 wt% without significant loss of ESCR, provided the regrind has not undergone more than 3 heat cycles. Higher regrind fractions require in-house ESCR testing under ASTM D1693-15 because each heat history shifts the molecular weight distribution and antioxidant consumption. Published data for this specific configuration is limited for regrind fractions above 20 wt%.

On accumulator-head blow moulding machines, barrel and head volumes are larger; therefore, residence time must be reduced when using DMDA8008. At 180 °C melt temperature, the recommended maximum continuous residence time is 30 min; above 200 °C, purge every 15 min to avoid gel contamination. Die gap adjustment should be verified with parison length measurements because the melt strength of this grade allows a slightly wider die gap than high-MFR grades without losing parison integrity. Weld-line strength of bottle handles is improved by increasing clamp time and maintaining mould temperature above 10 °C; mould temperatures below 5 °C can produce brittle weld lines and surface cold marks. For multi-cavity moulds, balancing flow channels is more critical than with lower-viscosity HDPE grades because higher melt pressure amplifies cavity-to-cavity wall thickness differences. All incoming lots should be tested for melt flow rate and density before release to the blow-moulding floor; deviations outside the certificate range require reprocessing control or lot segregation.