Dow HDPE DMDA-8910 NT 7
- Product Name: Dow HDPE DMDA-8910 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-8910 NT 7 is typically used in formulations when melt flow index and density and melt temperature and die pressure must be controlled within specific ranges.
| HS Code | 840182 |
| Density | 0.952 g/cm³ |
| Melt Index | 0.10 g/10 min (190°C/2.16 kg) |
| Tensile Strength At Yield | 26 MPa |
| Tensile Strength At Break | 30 MPa |
| Elongation At Break | >600% |
| Flexural Modulus | 1100 MPa |
| Vicat Softening Point | 124°C |
| Melting Point | 130°C |
| Environmental Stress Crack Resistance | >1000 h |
| Hardness | 60 Shore D |
| Thermal Conductivity | 0.4 W/m·K |
| Coefficient Of Linear Thermal Expansion | 1.2E-4 /°C |
| Specific Heat | 1.9 kJ/kg·°C |
| Water Absorption | <0.01% |
| Dielectric Constant | 2.3 |
| Volume Resistivity | >1E16 ohm·cm |
As an accredited Dow HDPE DMDA-8910 NT 7 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Dow HDPE DMDA-8910 NT 7 is typically supplied in 25 kg polyethylene bags, with 55 bags per pallet. |
| Container Loading (20′ FCL) | 20′ FCL loading of Dow HDPE DMDA-8910 NT 7 in 25 kg bags on pallets, fully secured for ocean freight. |
| Shipping | Dow HDPE DMDA-8910 NT 7 is a non-hazardous polyethylene resin. It is not classified as dangerous goods for transport. Ship in sealed original bags or octabins, protected from moisture, sunlight, heat, and contamination. Store in a cool, dry, ventilated area. Follow the SDS and local shipping regulations. |
| Storage | Store Dow HDPE DMDA-8910 NT 7 in a cool, dry, well-ventilated warehouse, preferably in original sealed bags or containers. Keep away from direct sunlight, heat, ignition sources, and strong oxidizers. Prevent moisture, dust, and contamination. Keep containers closed when not in use. Use proper grounding to avoid static buildup. Follow the manufacturer’s SDS and local regulations. Store at ambient temperature. |
| Shelf Life | Dow HDPE DMDA-8910 NT 7 has no defined shelf life if stored cool, dry, clean, and away from direct sunlight. |
Continuous-extrusion blow molding lines producing UN-certified tight-head drums from Dow HDPE DMDA-8910 NT 7 typically operate with barrel temperatures profiled from 170°C at the feed throat to 210°C at the accumulator head, while parison programming splits the 200 L drum parison into 12–20 axial segments to compensate for gravitational sag. The nominal resin density of 0.954 g/cm³ and melt flow rate of 0.95 g/10 min at 190°C/2.16 kg according to ISO 1133-1:2022 permit melt temperatures at the lower boundary of the HDPE blow molding window, reducing thermal degradation during color masterbatch dispersion and preserving the environmental stress crack resistance required by ASTM D1693-21 when containers are filled with polar industrial solvents. Compliance for 20–30 L jerricans and 120–200 L tight-head drums is governed by the UN Recommendations on the Transport of Dangerous Goods, Model Regulations, Chapter 6.1, including design-type drop tests at −18°C after 24 h conditioning, leakproofness tests at 20–30 kPa internal air pressure, hydrostatic internal pressure tests, and stacking tests at 40°C for 28 days; U.S. specifications under 49 CFR Part 178 for non-bulk packagings apply for domestic shipment. In industrial chemical packaging formulation, 1.5–3.0 wt% carbon black masterbatch is added where outdoor storage exposes containers to UV radiation, 0.5–2.0 wt% antistatic masterbatch is used for containers holding flammable solvents with flash points below 60°C, and fluoropolymer processing aid is dosed at 0.05–0.20 wt% to eliminate melt fracture at parison extrusion rates above 120 mm/s. Regrind from trimmed flash and rejected containers is maintained between 20 wt% and 35 wt% on the basis of lot-to-lot ASTM D1693-21 Condition B validation; the upper regrind boundary is reduced when the container is destined for oxidative chemicals because reprocessing shifts molar mass distribution and accelerates slow crack growth at the pinch-off heel. Downstream production uses accumulator-head machines with 80–110 mm grooved-feed extruders at L/D ratios of 24:1 to 30:1; mold cooling water is held at 12–18°C, blow air pressure at 0.7–0.9 MPa, and demolding occurs only after internal mold surface temperature falls below 45°C to avoid pinch-off tail curl and part-line thinning. Terminal product types include 20 L and 25 L jerricans, 120 L and 200 L tight-head drums, and open-head pails fitted with gasketed lids, all of which are leak-tested at 20 kPa internal pressure for 5–10 s on the production line.
What ESCR Thresholds Govern Detergent Bottle Production When Surfactant Loads Exceed 10% Nonionic Content?
Detergent bottle converters running multi-cavity shuttle blow molding machines observe a measurable decline in ASTM D1693-21 Condition B ESCR when the packaged formula contains branched alcohol ethoxylates above 10 wt%; stress cracking initiates at the pinch-off heel and propagates along the part line under top-load warehousing conditions of 25–35°C and 60–80% relative humidity. The bottle body in this sector is not classified as dangerous goods packaging, so compliance is anchored to mechanical performance tests rather than UN design-type testing: ASTM D638-14 for tensile yield strength, ASTM D790-17 for flexural modulus, ASTM D2561-17 for internal pressure creep of blow-molded containers, and ISO 8317:2015 where child-resistant closures are used as a secondary assembly. Formulation at the converting stage adds 0.5–3.0 wt% color masterbatch carried in a high-density polyethylene base, 0.5–1.5 wt% slip/antiblock masterbatch with erucamide or oleamide active content of 1–2% to control film-to-film friction in conveying, and 0.03–0.15 wt% fluoropolymer processing aid to suppress melt fracture at high shear rates near the die land. Regrind from flash and startup scrap is introduced at 25–40 wt%, but the upper boundary must be reduced to 15–20 wt% when the destination product is a bleach bottle because residual metal ions and oxidized regrind accelerate autoxidation; the lower regrind boundary remains mandatory when peroxide-based disinfectants exceed 5 wt% active chlorine. Downstream production on continuous rotary or shuttle machines uses a melt temperature of 185–210°C, a mold temperature of 8–15°C, and blow air at 0.55–0.75 MPa; drop impact resistance at −20°C is maintained by controlling parison wall thickness to 0.7–1.2 mm for 1 L bottles and 0.9–1.6 mm for 5 L bottles. Terminal product types include 500 mL, 750 mL, 1 L, 2 L, and 5 L laundry detergent bottles, dish soap bottles, and bleach containers; the bleach packaging requires titanium dioxide or carbon black pigment loadings of 1.0–2.0 wt% to block UV-induced autoxidation in the sidewall.
| Downstream application sector | Regrind allowance | Masterbatch loading window | Processing aid / functional additive | Primary compliance anchor |
|---|---|---|---|---|
| Industrial UN-certified jerricans and tight-head drums | 20–35 wt% | 1.5–3.0 wt% carbon black; 0.5–2.0 wt% antistat | 0.05–0.20 wt% PPA | UN Model Regulations Chapter 6.1 |
| Household detergent and bleach bottles | 25–40 wt%; 15–20 wt% for bleach | 0.5–3.0 wt% color; 1.0–2.0 wt% TiO₂/CB | 0.03–0.15 wt% PPA; 0.5–1.5 wt% slip/antiblock | ASTM D1693-21 |
| Agricultural chemical containers | ≤15 wt% | 2.0–4.0 wt% carbon black; 0.5–1.0 wt% antistat | 0.5–2.0% fluorine post-treatment | UN Chapter 6.1 + 40 CFR Part 165 |
| Food contact water and dairy bottles | 20–25 wt% in-house scrap | 0.5–2.0 wt% approved food-contact colorant | No PPA unless approved by EU 10/2011 | 21 CFR 177.1520(c) |
| Lubricant and automotive fluid bottles | 25–35 wt% | 1.0–3.0 wt% color; 0.5–1.5 wt% antistat | 0.02–0.08 wt% PPA | ASTM D2561-17 |
In agricultural chemical packaging, the interaction between carbon black dispersion and environmental stress crack resistance determines whether a 5 L jug survives a 1.2 m drop at 23°C after 45 days of warehouse storage. The container body is regulated under the same UN Model Regulations Chapter 6.1 design-type test regime as industrial jerricans, but additional obligations apply: US EPA 40 CFR Part 165 container design and residue removal requirements for agricultural pesticide containers, and the FAO/WHO Guidelines on Management Options for Empty Pesticide Containers for triple-rinse residue limits. Weathering resistance is evaluated by ASTM D2565-16 xenon-arc exposure, and drop impact resistance by ASTM D5276-19; published data for the specific fluorination and carbon black combination in DMDA-8910 NT 7 is limited for multi-year outdoor exposure, so converters validate via accelerated xenon testing at 2500 h with retention of 80% elongation at break. Formulation windows for agricultural chemical containers are narrower than for industrial packaging: carbon black masterbatch is added at 2.0–4.0 wt%, UV stabilizer masterbatch at 1.0–2.0 wt% where carbon black is visually undesirable, and antistatic masterbatch at 0.5–1.0 wt% to reduce dust attraction and volatile residue adhesion. Regrind usage is capped at 15 wt% because batch-to-batch traceability and contamination risk outweigh the cost benefit, and post-consumer agricultural container material is not reincorporated under normal landscape production protocols. Downstream production often uses single-station or double-station shuttle blow molding machines with 60–80 mm extruders, parison programming with 8–15 points, and post-mold fluorination in a separate chamber at fluorine concentrations of 0.5–2.0% in nitrogen for 5–30 min to create a surface barrier to solvent permeation; wall thickness distribution is monitored by ultrasonic gauging at 12 positions per container, with minimum wall thickness no less than 0.8 mm for 5 L containers and 1.2 mm for 20 L containers. Terminal product types include 1 L, 2 L, 2.5 L, 5 L, 10 L, and 20 L high-density polyethylene agrochemical bottles, measuring chambers, and closure hoods, all of which undergo leakproofness testing at 20–30 kPa and drop testing per ASTM D5276-19 at 1.2 m on conditioned containers.
Food Contact Bottles for Ambient-Fill Water and Dairy Products: Migration Control and Organoleptic Thresholds
Ambient-fill water and dairy bottles manufactured from HDPE DMDA-8910 NT 7 are subject to a dual regulatory burden when the lot-specific food-contact certification is in force: FDA 21 CFR 177.1520(c) for olefin polymers in contact with food and European Commission Regulation (EU) No 10/2011 Annex I with an overall migration limit of 10 mg/dm² for plastic food contact articles. Where high-fat dairy liquids are packaged, the organoleptic threshold is evaluated by ISO 13302:2003 sensory analysis for packaging-related off-flavors; published data for this specific resin in high-fat milk packaging is limited, so converters run site-specific sensory panels after 72 h at 40°C contact. Formulation addition ratios for food contact production exclude heavy-metal pigments; approved titanium dioxide or food-contact colorant masterbatch is used at 0.5–2.0 wt%, and only masterbatches whose carrier resin is an olefin polymer listed under the relevant positive list are used. In-house regrind from trimmed flash and rejected bottles may be reincorporated at 20–25 wt% when it comes exclusively from food-contact production of the same grade, but post-consumer recycled resin is not added unless it has a formal food-contact no-objection letter from the relevant authority. Downstream production uses reciprocating screw blow molding machines with melt temperatures of 190–215°C, mold cooling water at 5–10°C, and blow air at 0.60–0.75 MPa; pre-drying is not required below 60% relative humidity, but granulate stored at RH > 70% is dried at 70–80°C for 2–4 h to prevent surface splay and odor carryover. Terminal product types include 1 gal and 2.5 gal water jugs, 1 L milk bottles, 500 mL and 1 L edible oil bottles, and 250–500 mL juice bottles, with closure thread dimensions inspected by no-go gauges to avoid leakage at 20 kPa top-load compression.
When Extrusion Blow Molding Lines Reincorporate Up to 35% In-House Regrind for Lubricant Bottle Production
Lubricant bottle production on high-output rotary machines exposes the polymer melt to a different shear history than accumulator-head drum lines, and the reincorporation of up to 35 wt% in-house regrind becomes feasible only when the regrind fraction is sieved below 6 mm and blended before the extruder feed throat rather than side-fed downstream. The bottle body must pass ASTM D2561-17 constant internal pressure ESCR testing and ASTM D1693-21 Condition C for oil-in-water emulsion stress cracking because motor oil bottles experience prolonged contact with mineral oil additives and aliphatic hydrocarbons during warehouse cycling at 30–45°C. Compliance anchors for this sector are largely mechanical rather than transport-based: ISO 16770:2004 full notch creep testing for slow crack growth resistance, ASTM D638-14 for tensile yield strength at 50 mm/min, and ASTM D2990-17 for creep and creep-rupture under static load. Formulation for oil and automotive fluid packaging uses 1.0–3.0 wt% color masterbatch, 0.5–1.5 wt% antistatic masterbatch where the filling line requires dust-free surfaces, and 0.02–0.08 wt% fluoropolymer processing aid to maintain stable die-lip pressure at high output; regrind is controlled at 25–35 wt%, with the upper boundary rejected when the in-house scrap contains labels, stickers, or adhesive residues because adhesive migration acts as a stress-crack accelerator. Downstream production uses continuous rotary blow molding with 10–30 stations, melt temperatures of 190–215°C, mold temperatures of 10–20°C, and blow air at 0.65–0.85 MPa; wall thickness for 1 L quart bottles is maintained at 0.8–1.4 mm, and the handle pinch-off weld is validated by burst pressure testing above 50 kPa. Terminal product types include 1 L motor oil bottles, 5 L engine oil jugs, transmission fluid bottles, coolant containers, and windshield washer fluid containers, all with tamper-evident neck finishes tested for removal torque between 1.0 N·m and 2.5 N·m.
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- Dow HDPE DMDA-8910 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-8910 NT 7 is an injection moulding grade of high-density polyethylene supplied as natural, pelletised resin. The product is defined by a nominal melt mass-flow rate of 10 g/10 min at 190 °C under 2.16 kg load in accordance with ISO 1133-1:2022, and by a nominal density of 0.954 g/cm³ in accordance with ISO 1183-1:2019. These two values place the resin in a flow–density envelope that separates it from lower-fluid, higher-density HDPE injection moulding grades such as DMDA-8007 NT 7 and from higher-fluid grades such as DMDA-8920 NT 7. The 0.954 g/cm³ density provides lower melt viscosity than 0.963 g/cm³ HDPE while retaining enough crystalline fraction to deliver moulded-part stiffness in thin-wall rigid packaging and closures.
The linear polyethylene architecture limits shear-thinning relative to broad-molecular-weight HDPE grades. This means that process adjustments relying on high shear rates to reduce viscosity are less effective for DMDA-8910 NT 7 than for high-MFR injection moulding grades. Injection moulders using hot runners should also account for the grade’s relatively low melt elasticity, which reduces die swell but can increase the tendency toward gate blush or splay when the gate diameter is below 50% of the nominal wall thickness. A gate diameter of 0.8–1.2 mm is typical for containers with wall thicknesses between 0.6 mm and 1.2 mm, and moulding trials should confirm gate freeze time by short-shot analysis or thermocouple placement in the gate.
What Process Limitations Govern Thin-Wall Food-Packaging Moulding?
In production-scale injection moulding, DMDA-8910 NT 7 is typically processed on reciprocating-screw machines with general-purpose polyolefin screws having L/D ratios between 20:1 and 24:1 and compression ratios between 2.5:1 and 3.0:1. The feed throat should be kept below 40 °C to prevent pellet bridging. Barrel temperatures from 180 °C in the feed zone to 230 °C at the nozzle are common, with the nozzle maintained at 220–240 °C. The melt should not be held above 260 °C for more than 15 min, because high-flow HDPE is susceptible to thermo-oxidative chain scission. Published residence-time studies on HDPE with melt flow rates of 10–20 g/10 min report melt-flow shifts of 3–8% after 30 min at 240 °C when oxygen is not excluded; these shifts are often invisible in part appearance but alter cavity pressure and warp direction.
Mould temperature is controlled at 20–40 °C using turbulent water channels. A 10 g/10 min melt transmits cavity pressure with less line loss than lower-flow HDPE, making the grade suitable for thin-wall geometries from 0.6 mm to 2.0 mm. However, linear HDPE crystallises rapidly, and gate freeze can occur before full hold-pressure compensation in sub-millimetre walls. To maintain hold-pressure effectiveness, gate diameter should not fall below 50% of the part wall thickness, and hold-pressure time should be established by measurement of the part-weight plateau as a function of gate seal time. In multi-cavity tools, runner balancing is required to keep cavity-to-cavity weight variation below 0.15% of shot mass; otherwise, post-mould shrinkage variation can produce dimensional non-conformance in lids and closures.
Typical conversion routes for DMDA-8910 NT 7 are injection moulding only; the grade is not recommended for pipe extrusion, blow moulding, or blown film because the 10 g/10 min melt flow rate reduces melt strength and tubular bubble stability. Documented end uses in public technical literature and supplier application notes include rigid housewares, thin-wall food containers, overcaps and closures, toys, and industrial laboratory articles where clarity is not required. In these applications, the grade’s medium density reduces sink marks and improves dimensional recovery compared with higher-flow HDPE when parts are ejected at temperatures above 80 °C. Mould designers should specify a draft angle of at least 0.5° on cores and cavities for textured surfaces; smooth surfaces can tolerate 0.25°, but ejection force rises sharply below these values. Ejector pins should be located on ribs and bosses to avoid localised stress whitening in visible surfaces.
For snap-fit or living hinge features, the material’s narrow molecular weight distribution reduces stress-cracking sensitivity relative to broad-distribution HDPE, but posts and hinges should be radiused to at least 0.5 mm to avoid notch embrittlement at low temperature. Published data for cyclic closure at -20 °C on similar-density HDPE injection moulding grades indicate that hinge life depends more on gate placement and molecular orientation than on melt index alone. If the hinge is gated along its length, flow-induced orientation increases fold resistance; if gated across the hinge, premature splitting can occur. These findings are transferable to DMDA-8910 NT 7 only after in-house validation on the final tool geometry.
When High-Cavitation Tools Demand Flow Length Without Density Loss
Compared with DMDA-8920 NT 7, which has a nominal melt mass-flow rate of 20 g/10 min and the same 0.954 g/cm³ density, DMDA-8910 NT 7 occupies a lower-flow, higher-toughness position. The difference in flow length is not strictly proportional to melt index because HDPE viscosity is shear-rate dependent. At the shear rates typical of thin-wall filling, a 10 g/10 min grade may require 10–20% higher injection pressure than a 20 g/10 min grade in identical geometry. In exchange, the lower-MFR material generally shows better notched impact and environmental stress-cracking resistance because the higher average molecular weight increases tie-molecule density. Processors switching from DMDA-8920 NT 7 to DMDA-8910 NT 7 should reassess maximum hydraulic pressure, clamp force, and gate size; direct substitution without increasing gate diameter can produce short shots in thin-wall regions or visible flow lines at the end of fill.
Conversely, replacing DMDA-8910 NT 7 with higher-flow HDPE may reduce cycle time but can lower part impact strength and increase the risk of sink marks because the material remains above the solidification temperature for a longer period. The density of 0.954 g/cm³ is deliberately lower than high-density grades such as DMDA-8007 NT 7 at 0.963 g/cm³, providing better flow and impact while reducing flexural modulus. When stiffness is the primary design requirement, the higher-density DMDA-8007 NT 7 grade may be considered, but its lower MFR raises cavity pressure and may require a larger machine clamp force for the same projected area. Selection therefore hinges on whether the part is stiffness-limited or toughness-limited. DMDA-8910 NT 7 is not the optimal choice for maximising either property alone, but it supplies a moderate-flow, moderate-density processing point that reduces total conversion cost in rigid packaging requiring both adequate fill and impact resistance.
Comparative Flow and Density Across Dow HDPE Injection Moulding Grades
The following table lists nominal values compiled from public supplier documentation and should not be interpreted as a specification. Melt flow rate is measured at 190 °C with 2.16 kg load per ISO 1133-1:2022; density is measured per ISO 1183-1:2019.
| Grade | Nominal melt mass-flow rate | Nominal density | Typical processing consequence |
|---|---|---|---|
| DMDA-8007 NT 7 | 8.0 g/10 min | 0.963 g/cm³ | Higher cavity pressure required; elevated flexural stiffness; reduced notched impact relative to DMDA-8910 NT 7. |
| DMDA-8910 NT 7 | 10.0 g/10 min | 0.954 g/cm³ | Intermediate flow for thin-wall closures and housewares; lower pressure than 0.963 g/cm³ grades. |
| DMDA-8920 NT 7 | 20.0 g/10 min | 0.954 g/cm³ | Longer flow length and shorter cycles; reduced melt strength and impact relative to DMDA-8910 NT 7. |
| DMDA-8965 NT 7 | 65.0 g/10 min | 0.954 g/cm³ | Very high fluidity for thin-walled lids and containers; requires gate design to minimise jetting. |
The differences among these grades are primarily due to molecular weight distribution and not density alone. The 0.954 g/cm³ products share similar crystalline fraction and therefore similar chemical resistance, but their melt rheology diverges significantly across the MFR range. A processor selecting among them should compare not only nominal MFR and density but also coefficient of linear thermal expansion and mould shrinkage values at the intended part thickness. Shrinkage in HDPE injection moulding is not isotropic; flow-direction shrinkage is generally lower than transverse-direction shrinkage when orientation is high. For DMDA-8910 NT 7, toolmakers often use an average linear shrinkage allowance of 2.0–2.5% for mould design, adjusted upward for free-standing flat parts and downward for parts with dense ribbing. Flatness in container bases is improved by reducing gate area rather than by increasing hold time, because the central flow region solidifies last and acts as a sink.
Navigating Food-Contact and REACH Compliance Documentation
Compliance for DMDA-8910 NT 7 is application-specific. The base resin may be cited under FDA 21 CFR 177.1520 for olefin polymers in repeated-use or single-use food-contact articles, but the final article must comply with extractive limits for the intended food simulant. EU Regulation 10/2011 requires verification of overall migration, which for general food contact is limited to 10 mg/dm² of food-contact surface area; food-simulant selection and contact time/temperature must match the intended use. The grade’s natural pellet form contains no carbon black or heavy-metal pigments; however, the final compound, masterbatch, or recycled content may introduce substances requiring separate evaluation.
REACH compliance is documented through the supplier’s safety data sheet and should be assessed against the Candidate List of substances of very high concern in force at the time of import or use. RoHS Directive 2011/65/EU restrictive substances are not expected in unfilled natural polyethylene above the maximum concentration values, but moulded parts with colorants, coatings, or electroplating must be tested under the harmonised standards. Packaging and packaging waste Directive 94/62/EC requires that packaging articles sold in the EU meet limits for lead, cadmium, mercury, and hexavalent chromium. These regulatory frameworks do not replace end-product testing; they define the starting point for a compliance dossier.
| Regulatory or standards domain | Relevant criterion or method | Reference |
|---|---|---|
| U.S. food-contact resin clearance | Olefin polymer compliance for food-contact articles; extraction testing required for final article | FDA 21 CFR 177.1520 |
| EU food-contact plastics | Overall migration limit and specific migration of substances; simulant testing | EU Regulation 10/2011 |
| EU REACH | SVHC screening, safety data sheet information, registration obligations | EC 1907/2006 |
| EU RoHS | Restricted substances in electrical and electronic equipment | Directive 2011/65/EU |
| EU packaging waste | Heavy-metal concentration limits for packaging components | Directive 94/62/EC |
Pellets should be stored in sealed original packaging below 50 °C and protected from ultraviolet radiation. Cold storage followed by transfer to a warm processing hall can produce surface condensation; if moisture content exceeds 0.05% by weight, hopper drying at 70–80 °C for 2–3 h using dry air is required. The material is not inherently hygroscopic, but surface moisture on pellets can cause splay and feeding instability. The additive package is proprietary; confirmation of amine-based stabiliser content should be obtained from the supplier before blending with acid-functional polymers or peroxide masterbatches, because acid residues can accelerate thermo-oxidative degradation and shift melt flow rate. The grade is not intended for long-term hot-water service above 60 °C without part-level validation of mechanical property retention and antioxidant migration.
Published Mechanical-Property Benchmarks for Lot Acceptance
Lot release certificates for DMDA-8910 NT 7 typically include melt flow rate and density as primary control parameters. Mechanical property values in public datasheets are reported as typical, not as specification limits. For injection-moulded plaques, tensile yield stress under ISO 527-2 is commonly reported between 25 MPa and 28 MPa, flexural modulus under ISO 178 between 1,200 MPa and 1,500 MPa, and notched Charpy impact under ISO 179-1 at 23 °C between 5 kJ/m² and 12 kJ/m². Heat deflection temperature under ISO 75-2 method B at 0.45 MPa is typically reported between 70 °C and 85 °C. Vicat softening temperature under ISO 306 method A50 is typically above 120 °C. These ranges reflect plaque preparation and conditioning, and they should not be used directly for design without conversion to design allowables based on the final part geometry and service environment.
Environmental stress-cracking resistance is also a relevant property for closures in contact with detergents or aggressive liquids. Published data for this specific grade in surfactant-based ESCR tests may be limited; generic HDPE data indicate that ESCR improves with decreasing melt index when resin density and comonomer content are held constant. Therefore, DMDA-8910 NT 7 should be expected to show lower ESCR than a 5.0 g/10 min HDPE of similar density but higher ESCR than a 20 g/10 min grade. For closure applications, full notched constant tensile load testing per ASTM D1693 or ISO 22088 is required to establish performance under the specific detergent or oil system.
Regrind incorporation from sprues and runners should be controlled through closed-loop weight monitoring. A virgin-rich mix containing up to 20–30% clean in-house regrind is common for rigid packaging; beyond 30%, cumulative heat history can broaden molecular weight distribution and shift melt flow rate by more than 10%. This shift may reduce cavity pressure and part mass, particularly in tools with narrow processing windows. The use of regrind should be suspended for parts exposed to food-contact testing, as the recycled fraction may not be covered by the original resin clearance unless explicitly demonstrated. For thin-wall moulding, regrind particle size should be matched to virgin pellets to avoid segregation in the hopper and inconsistent plastication. If melt pressure drifts outside the validated range, melt flow rate should be checked per ISO 1133-1:2022 and the regrind fraction reduced until the process returns to the qualified centreline.
