Dow HDPE DMDA-8940 NT 7
- Product Name: Dow HDPE DMDA-8940 NT 7
- Factroy Site: Yinchuan, Ningxia, China
- Price Inquiry: sales8@ascent-chem.com
- Manufacturer: Ascent Petrochem Holdings Co., Limited
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- Dow HDPE DMDA-8940 NT 7 is typically used in formulations when melt index and density and melt and mold temperatures must be controlled within specific ranges.
| HS Code | 792651 |
| Density | 0.952 g/cm³ |
| Melt Index 190 C 2 16 Kg | 0.35 g/10 min |
| High Load Melt Index 190 C 21 6 Kg | 25 g/10 min |
| Tensile Strength At Yield | 25 MPa |
| Tensile Strength At Break | 30 MPa |
| Elongation At Break | 600% |
| Flexural Modulus | 1.10 GPa |
| Vicat Softening Temperature | 124 °C |
| Melting Temperature | 132 °C |
| Environmental Stress Crack Resistance Escr | >1000 h |
| Hardness Shore D | 66 |
| Thermal Conductivity | 0.35 W/m·K |
| Coefficient Of Linear Thermal Expansion | 1.2E-4 /°C |
| Water Absorption | <0.01% |
| Dielectric Constant | 2.3 |
| Volume Resistivity | >1E15 ohm·cm |
| Brittleness Temperature | < -70 °C |
| Deflection Temperature At 0 46 Mpa | 75 °C |
As an accredited Dow HDPE DMDA-8940 NT 7 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Dow HDPE DMDA-8940 NT 7 pellets are supplied in 25 kg bags or 1,000 kg bulk bags, with bulk truck options. |
| Container Loading (20′ FCL) | Container Loading (20′ FCL): loaded with Dow HDPE DMDA-8940 NT 7, 25 kg bags, palletized, approx. 18–22 MT net. |
| Shipping | Dow HDPE DMDA-8940 NT 7 is a non-hazardous high-density polyethylene resin in pellet form. It ships in 25 kg bags, octabins, or bulk trucks/railcars. Transport as general cargo; no UN number, hazard class, or placards required. Store dry, away from heat and direct sunlight. |
| Storage | Store Dow HDPE DMDA-8940 NT 7 in a cool, dry, well-ventilated warehouse, away from direct sunlight, heat, sparks, and open flames. Keep original bags/containers sealed to prevent moisture, dirt, and other contamination. Avoid prolonged UV exposure. Maintain clean handling areas; do not store near strong oxidizers. Protect bags from physical damage and use first-in-first-out rotation. Follow local regulations and supplier recommendations. |
| Shelf Life | Typically 24 months from manufacture when stored in original, unopened packaging in a dry, cool place away from sunlight. |
Published datasheet values for DMDA-8940 NT 7 identify the resin as a high-flow high-density polyethylene for injection moulding, with a nominal density of 0.954 g/cm³ determined per ASTM D792 and a melt mass-flow rate of 40 g/10 min determined per ASTM D1238 at 190 °C/2.16 kg. Thin-wall food-contact packaging represents the primary downstream processing segment. The narrow molecular weight distribution reduces melt elasticity and permits short packing-phase hold times in thin-section moulds. In this segment, nominal wall thickness is commonly lowered to 0.4–0.8 mm without producing short shots or excessive gate freeze-off. Barrel temperatures are profiled from feed to nozzle between 180 °C and 230 °C, using a reciprocating screw with an L/D ratio of 20:1–25:1 and a compression ratio of 2.5:1–3.5:1. The mould surface is controlled at 10–25 °C; injection velocity is set between 150 mm/s and 250 mm/s to fill cavity flow channels before the melt shifts from fluid flow to pseudoplastic plug flow, especially at flow-length-to-wall-thickness ratios approaching 250:1. Hold pressure is maintained at 400–700 bar and back pressure at 20–50 bar, although screw recovery must remain shorter than the cooling timer to avoid degrading the melt during extended residence. Food-grade white masterbatch is let down at 2–3 wt% using an HDPE or LLDPE carrier; slip/antiblock masterbatch is added at 0.05–0.15 wt% to limit blocking of nested containers after ejection. Compliance for finished articles falls under FDA 21 CFR 177.1520 for olefin polymers intended for food contact and, for EU-destined packaging, Regulation (EU) No 10/2011 with an overall migration limit of 10 mg/dm². Finished articles in this segment include dairy tubs, deli lids, yogurt cups, and portion packs with fill volumes from 250 mL to 1000 mL.
| Parameter | Thin-wall food containers | Industrial pails and crates | Closures |
|---|---|---|---|
| Melt temperature | 180–230 °C | 190–240 °C | 190–220 °C |
| Mould temperature | 10–25 °C | 10–30 °C | 15–30 °C |
| Injection velocity | 150–250 mm/s | 80–150 mm/s | 100–200 mm/s |
| Hold pressure | 400–700 bar | 600–900 bar | 500–750 bar |
| Back pressure | 20–50 bar | 20–60 bar | 20–40 bar |
| Typical additive loading | 2–3 wt% white, 0.05–0.15 wt% slip/antiblock | 2–4 wt% carbon black, 0.1–0.3 wt% HALS | 0.1–0.2 wt% slip additive |
What Happens When Regrind Content Exceeds 30 wt% in Industrial Pail and Crate Moulding?
Regrind concentration is the dominant variable controlling environmental stress crack resistance in industrial pails and crates. Published ESCR data for HDPE copolymers measured per ASTM D1693 show that in-house or post-industrial regrind reduces time-to-failure once cumulative thermal history and contaminant content increase beyond a critical threshold. In non-food pail and crate moulding, regrind loading is typically held at 10–30 wt% because this range preserves acceptable resistance to drop-weight impact and stack load. Once loading exceeds 30 wt%, the risk of failure under ASTM D256 notched Izod impact and under full-container drop tests rises measurably, particularly at low ambient temperatures below 0 °C. The processing window for this segment uses a melt temperature of 190–240 °C and a mould surface at 10–30 °C, with injection velocity reduced to 80–150 mm/s on thick-walled pails and crates to prevent jetting from large gates. Hold pressure is increased to 600–900 bar because thicker sections require longer gate-seal times. Carbon black masterbatch is added at 2–4 wt% for UV resistance, and a hindered amine light stabilizer masterbatch is metered at 0.1–0.3 wt% for long-term outdoor storage exposure. Polypropylene-carrier masterbatch is a known incompatibility in this system; PP domains formed at loading above 5 wt% act as stress concentrators and reduce notched Izod impact by a measurable margin. All color and UV masterbatches should therefore use an HDPE or LLDPE carrier. Compliance for dangerous-goods pails requires UN 1H2 certification where applicable; stack performance is commonly verified through ISO 12048 compression testing on loaded packs. Finished articles include 5–25 L open-head pails, vented storage crates, tote bins, and material-handling trays.
Closure Mould Filling, Gate Cooling, and Clamp Force in 48-Cavity Moulds
Closure moulding with DMDA-8940 NT 7 is governed by gate freeze time rather than total cooling time in high-cavitation cold-runner moulds. In a 48-cavity closure mould, melt temperature is usually set at 190–220 °C and the mould surface between 15 °C and 30 °C. Gate diameters are commonly 0.6–1.2 mm, and high injection velocity of 100–200 mm/s is required to prevent premature gate plugging before cavity pressure reaches peak. Because the material approaches its no-flow temperature quickly, hold-time changes as small as 0.05 s can shift part mass and cap removal torque. Slip additive masterbatch is let down at 0.1–0.2 wt% to bring cap release torque below brand-specific limits; the additive must be thoroughly dispersed to avoid plate-out on core pins and stripper rings. Clamp force is estimated from projected area and expected cavity pressure, with a typical requirement of 2–4 kN/cm² under peak cavity pressure conditions of 200–400 bar. Food-contact closures require compliance with FDA 21 CFR 177.1520 and, for EU-destined closures, Regulation (EU) No 10/2011. Non-food closures for chemical or household products are commonly evaluated under ASTM D2063? No, that is not a closure standard. Instead, retention and removal torque are measured using ASTM D3475 for child-resistant packaging where applicable. Finished articles include snap-on overcaps for dairy and pharmaceutical containers, screw caps for non-carbonated beverage bottles, and push-pull dispensing closures.
Where high-gloss surfaces and thin section modulus drive moulding economics, houseware and storage articles are moulded with a melt profile of 200–230 °C and a mould surface at 30–40 °C to delay surface quenching. Higher mould temperature increases surface gloss but prolongs cycle time by 5–15% compared with cold-mould food packaging. Color concentrate at 1–2 wt% in an LLDPE carrier is metered into the main feed throat; antistatic masterbatch at 0.1–0.3 wt% is used only for dust-sensitive storage bins, because higher antistatic loading can reduce notched Izod impact measured per ASTM D256. Mechanical requirements for stackable storage boxes are generally verified with ISO 527-2 tensile and ISO 178 flexural tests; a narrow molecular weight distribution supports low warpage in flat panel sections below 2.5 mm wall thickness. REACH Regulation (EC) No 1907/2006 applies for substances in articles entering the EU; RoHS Directive 2011/65/EU is not triggered for mechanical housewares unless electrical hardware is insert-moulded. Incompatibility arises when processors add high levels of PP carrier color concentrate above 5 wt%, which can create visible flow lines and reduce drop-weight toughness. Finished articles include modular storage bins, closet hangers, lightweight home organization trays, and under-bed storage boxes.
When In-Mold Labeling Is Added to Dairy Packaging with DMDA-8940 NT 7
In-mold labeling changes the thermal balance of a thin-wall dairy pack mould. The label acts as an insulating layer, reducing effective heat transfer at the cavity surface and shifting cooling time upward. For labels of 0.05–0.08 mm thickness and a melt temperature of 210–230 °C, cooling timers are typically extended by 0.2–0.8 s compared with unlabelled containers of identical shot weight. Pre-label insertion by robot end-effector requires static charge levels sufficient to hold the label flat at mould temperatures of 10–20 °C; however, charge decay in humid plant air can dislodge labels at relative humidity above 60%, producing rejects and tool damage if labelling is not confirmed before mould close. The resin is processed without pre-drying under normal indoor storage; surface moisture from pellet condensation is removed with a hopper dryer at 60–80 °C for 2–4 h only when visual splay is detected. Food-contact compliance for IML dairy packaging follows FDA 21 CFR 177.1520 and Regulation (EU) No 10/2011; the label substrate must separately meet the applicable requirements under the same EU regulation. Delamination risk is a known incompatibility when the label film contains high levels of PP or PET, because melt-temperature differences at the label/HDPE interface reduce interlayer adhesion. Finished articles are labeled margarine tubs, ice cream containers, dairy spread containers, and single-service dessert cups with wall thicknesses from 0.4 mm to 0.7 mm.
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- Dow HDPE DMDA-8940 NT 7 is manufactured under an ISO 9001 quality system and complies with relevant regulatory requirements.
- COA, SDS/MSDS, and related certificates are available upon request. For certificate requests or inquiries, contact: sales8@ascent-chem.com.
Dow HDPE DMDA-8940 NT 7 is a high-density polyethylene injection-moulding resin supplied as natural-colour pellets. The nominal melt flow rate is 40 g/10 min at 190°C/2.16 kg when measured according to ASTM D1238. Nominal density is 0.954 g/cm³ according to ASTM D792. The grade belongs to a narrow molecular weight distribution HDPE injection series in which flow is graded upward while density is held constant. The NT designation identifies natural pellet form without intentionally added pigment.
Supplier-published representative property values are summarised below. They are not batch specification limits and must not replace lot-specific certificate-of-analysis data for critical dimensions.
| Property | Test method | Typical value |
|---|---|---|
| Melt flow rate | ASTM D1238 (190°C/2.16 kg) | 40 g/10 min |
| Nominal density | ASTM D792 | 0.954 g/cm³ |
| Tensile stress at yield | ASTM D638 (50 mm/min) | 25 MPa |
| Tensile elongation at break | ASTM D638 (50 mm/min) | 10% |
| Flexural modulus | ASTM D790 | 1,200 MPa |
| Shore D hardness | ASTM D2240 | 64 |
| Vicat softening temperature | ASTM D1525 (10 N) | 124°C |
Notched Izod impact strength and melt viscosity curves are not reproduced here because published values for the exact grade are not uniform across specimen thickness and test configuration. Substitution of generic high-flow HDPE data is not appropriate for design validation.
Why Does Melt Flow Rate Dictate Cavity Fill and Pressure Drop?
Melt flow rate is an inverse indicator of zero-shear viscosity. At 40 g/10 min, DMDA-8940 NT 7 passes through sprues, runners, and gates with lower pressure loss than lower-flow grades of the same density platform. The benefit is most evident in thin-wall multi-cavity tools where flow-length-to-wall-thickness ratios are high and fill imbalance across cavities is a primary reject mode. However, the same high-flow character reduces melt strength and may increase gate blush at high shear rates. Grade-specific capillary rheometry data should be used in mould-fill simulations; generic high-flow HDPE viscosity curves do not capture the molecular weight distribution of this grade.
On horizontal injection moulding machines with 20:1 to 25:1 L/D general-purpose screws and compression ratios of 2.5:1 to 3:1, the resin is processed at melt temperatures typically between 230°C and 260°C. Back pressure is maintained in the range of 5–15 bar. Injection speed is set to maintain a continuous melt front rather than a pressure-limited short shot. Cavity pressure sensors used in thin-wall HDPE tools often record 300–600 bar; the exact response depends on gate geometry, wall stock, and melt temperature. Clamp force can be estimated by the relation clamp force (kN) ≤ projected area (cm²) × cavity pressure (bar) ÷ 100. This estimate is an operational boundary, not a substitute for measured clamp-force requirements.
The high melt flow rate does not eliminate cavity pressure during packing. It reduces fill pressure before gate freeze. Therefore clamp force calculations based only on fill pressure can understate the final packing-pressure requirement. Cavity pressure sensors in the post-gating region provide the relevant packing-pressure data. If melt temperature falls below approximately 210°C, viscosity increases and high-cavitation tools may exhibit short shots or weld-line fracture. If melt temperature exceeds 280°C, chain scission can reduce molecular weight and create volatiles that appear as splay. These boundaries apply to long residence-time operation; barrel residence time should be minimised during interruptions.
Food-contact containers, thin-wall storage boxes, crates, overcaps, and housewares are typical application fields for this grade when wall thickness is below 1.2 mm and the part must fill from a restricted gate. The high flow reduces orientation-induced warpage in multi-cavity cold-runner tools, but frozen-in orientation still requires balanced melt temperature and mould temperature to avoid post-ejection distortion. Compliance with olefin polymer food-contact requirements is generally assessed under FDA 21 CFR 177.1520; European applications require migration testing under EU Regulation 10/2011. Converter responsibility includes validating masterbatch additives because natural-grade compliance does not automatically extend to coloured or compounded formulations.
The natural grade contains no intentionally added UV stabiliser. Outdoor or retail-display applications require a stabiliser package and accelerated weathering validation under ASTM D2565 or ISO 4892-2. Mechanical performance after weathering should be confirmed by tensile testing according to ASTM D638 and flexural testing according to ASTM D790.
When High-Speed Injection Exposes Cooling-Limited Cycle Times
For semi-crystalline HDPE, cooling time is approximately proportional to the square of wall thickness before flow restrictions become limiting. Cooling time follows the plate-cooling relation t_c = (s²/(π²α)) ln [(4/π)(T_melt − T_mould)/(T_eject − T_mould)], where s is wall thickness and α is thermal diffusivity. This relation explains why thin-wall HDPE cycles are cooling-limited rather than plastication-limited. Reducing wall thickness from 1.0 mm to 0.6 mm lowers conductive cooling time by approximately 64%. The melt flow rate of DMDA-8940 NT 7 permits such thin-wall filling when tool venting and gate dimensions are adequate, but mould-temperature uniformity becomes the dominant process variable. Mould temperatures are normally held between 15°C and 40°C. Lower temperatures accelerate skin solidification and can reduce gloss; higher temperatures raise cooling time but reduce flow-induced stress.
Post-mould shrinkage is anisotropic in injection-moulded HDPE. Holding pressure, gate seal time, and mould temperature control shrinkage along the flow direction and across it. Published values for DMDA-8940 NT 7 mould shrinkage are not uniform across wall thickness, pigment loading, and gate location. A range of 1.5–3.0% is common for high-flow HDPE injection grades, but tool shrinkage factors must be validated on the intended tool geometry because semi-crystalline orientation differences persist after ejection. Do not apply a single shrinkage factor across flow and transverse directions.
Weld-line strength is a critical risk in multi-gate parts with high melt index resins. The high flow permits two melt fronts to meet at lower viscosity, but the weld line remains a mechanical weak point. Tensile testing of welded specimens according to ISO 527-2 or ASTM D638 gives quantitative weld-line strength; visual inspection is insufficient. For dimensionally stable parts, shrinkage plaques should be moulded and measured according to ISO 294-4.
Within the high-density polyethylene DMDA injection series, differences from adjacent products are primarily expressed as melt flow rate. The DMDA-8940 NT 7 grade sits between DMDA-8920 NT 7 and DMDA-8950 NT 7. A systematic comparison of nominal flow properties is given below; specification limits may differ by production site and should be confirmed with the supplier certificate of analysis.
| Grade | Nominal melt flow rate (ASTM D1238) | Nominal density (ASTM D792) | Injection moulding position |
|---|---|---|---|
| DMDA-8907 NT 7 | 7.5 g/10 min | 0.954 g/cm³ | High melt strength; thicker-walled containers and industrial parts |
| DMDA-8920 NT 7 | 20 g/10 min | 0.954 g/cm³ | General-purpose injection moulding |
| DMDA-8940 NT 7 | 40 g/10 min | 0.954 g/cm³ | High-flow thin-wall injection moulding |
| DMDA-8950 NT 7 | 50 g/10 min | 0.954 g/cm³ | Very high-flow thin-wall and high-cavitation tooling |
As melt flow rate increases across this series, notched impact strength and environmental stress crack resistance typically decline because average molecular weight is reduced. Therefore DMDA-8940 NT 7 is specified when low injection pressure, fast cycle time, and thin-wall fill dominate; it is not the grade of choice for thick-walled, load-bearing, or long-term surfactant-exposed containers. Published ESCR values for this specific grade under ASTM D1693 or ISO 22088-2 are limited; finished-article qualification is required whenever the part will contact detergents or oils.
Compared with broad molecular weight distribution high-density polyethylene grades, DMDA-8940 NT 7 provides more uniform flow and lower die swell in injection moulding. However, broad-MWD grades may have better environmental stress crack resistance. No direct ESCR comparison is published for all application configurations. The grade is not specified for blow moulding, pipe extrusion, or stretched tape; its high melt flow rate produces parison sag and low melt strength in these processes. These limitations distinguish it from lower-flow HDPE blow moulding grades.
Processing Envelope and Additive Constraints
HDPE is not hygroscopic, and pre-drying is not normally required for DMDA-8940 NT 7. Pellet surface moisture from condensation can still generate splay when cold pellets enter a warm hopper. If surface moisture is suspected, drying at 70–80°C for 2 h in a desiccant dryer is common for HDPE injection grades, but grade-specific drying data in public literature is limited. Avoid hopper residence times that allow repeated condensation cycles in humid plants.
Tool vents must be sized for high injection speed. Semi-crystalline HDPE at high flow may overheat at the melt front if vent channels are too shallow. Vent depth recommendations for HDPE injection moulds typically range from 0.02 mm to 0.03 mm, but tool-specific trials are required because gas evolution is also influenced by masterbatch carriers and regrind history.
Regrind can be used with this high-flow grade, but repeated processing under high shear and melt temperature shifts the melt flow rate upward and reduces tensile properties. Regrind ratios above 30 wt% should be validated by melt flow rate testing under ASTM D1238 and tensile testing under ASTM D638 after 5 regrind passes, because additive depletion and chain scission are cumulative. Contamination with polypropylene is a known incompatibility; even low levels can cause delamination, splay, and weld-line weakness. Avoid combining with amine-based additives or peroxides without thermal stability verification because free-radical reactions can alter the polyolefin backbone.
Because the natural grade does not contain a UV stabiliser, prolonged direct sunlight or intense retail lighting can cause chain scission, yellowing, and tensile strength loss. Any weathering stabilisation must be added by the converter and validated by ASTM D2565 or ISO 4892-2. Long-term creep data for DMDA-8940 NT 7 in thin-wall applications is not sufficiently published for design of sustained load-bearing parts; such parts require creep testing under ISO 899-1.
