| HS Code | 428332 |
| Polymer Type | Medium Density Polyethylene (MDPE) |
| Comonomer | Hexene-1 |
| Density | 0.932 g/cm³ |
| Melt Index 190c 2 16kg | 0.30 g/10 min |
| Tensile Strength At Yield | 19 MPa |
| Tensile Strength At Break | 25 MPa |
| Elongation At Break | 600% |
| Flexural Modulus | 800 MPa |
| Vicat Softening Point | 115 °C |
| Brittleness Temperature | < -70 °C |
| Environmental Stress Crack Resistance | > 1000 h |
| Shore D Hardness | 60 |
| Melting Point | 125 °C |
As an accredited Bayport Polymers (Baystar) MDPE 323 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Bayport Polymers (Baystar) MDPE 323 comes in 25 kg polyethylene bags, 55 bags per pallet (1,375 kg). |
| Container Loading (20′ FCL) | Non-hazardous Bayport Polymers (Baystar) MDPE 323 resin, palletized 25 kg bags, securely loaded into a 20′ FCL container for export. |
| Shipping | Bayport Polymers (Baystar) MDPE 323 ships as nonhazardous polyethylene resin pellets. It is not regulated by DOT, IMDG, or IATA. Typical packaging includes 25 kg bags, 1,000 kg bulk bags, or bulk hopper trucks/railcars. Handle per SDS; avoid moisture and prolonged heat. |
| Storage | Store Bayport Polymers (Baystar) MDPE 323 in a cool, dry, well-ventilated warehouse, away from direct sunlight, heat, sparks, flames, and strong oxidizers. Keep original packaging closed and palletized to prevent moisture, dust, and contamination. Store indoors on dry, clean surfaces. Avoid temperatures that may soften or degrade the resin. Follow the manufacturer’s SDS and local regulations. Use first-in, first-out stock rotation. |
| Shelf Life | Bayport Polymers (Baystar) MDPE 323 has a 24-month shelf life when stored unopened in a cool, dry, ventilated area away from sunlight. |
When the dry-blend powder is biaxially rotated in fabricated carbon steel or cast aluminium molds at an oven setpoint of 280°C to 300°C, the melt flow index of 4.0 g/10 min at 190°C/2.16 kg and nominal resin density of 0.938 g/cm³ define a peak internal air temperature window between 200°C and 210°C for agricultural stationary storage tanks. The dry-blend formulation for liquid fertilizer, chemical dosing, and water storage reservoirs is maintained at 100 phr virgin MDPE 323, 2.5 wt% to 3.0 wt% carbon black/UV-stabilized masterbatch, and 0.2 wt% to 0.3 wt% hindered phenolic antioxidant, with the masterbatch powder screened to 35 mesh or finer to avoid localized pigment concentration at thin-wall radii. Production-scale carousel machines with arm diameters of 2.0 m to 3.6 m operate at a primary-to-secondary rotation ratio of 4:1, and the demolding sequence is initiated only after internal air temperature falls below 70°C; forced-air cooling followed by water mist at 60°C to 65°C reduces warpage in flat sidewalls thicker than 8 mm. Compliance for this segment references ASTM D1998-21 for upright polyethylene storage tanks, with lot-release testing under ASTM D638-14 tensile yield at 50 mm/min and ASTM D1693-15ε1 Condition B environmental stress-crack resistance in 10% Igepal CO-630 at 50°C; potable-water contact requires NSF/ANSI 61 and indirect food-contact formulations are evaluated under FDA 21 CFR 177.1520. Terminal product types include 1,000 L to 20,000 L vertical liquid fertilizer dosing tanks, saddle tanks for row-crop sprayers, and horizontal transport reservoirs with integrally molded baffles.
Separate from static agricultural tanks, marine fender and floating pontoon shells require a hollow-shell rotational molding cycle that leaves a 6 mm to 10 mm cavity wall for subsequent two-component polyurethane foam filling. The shell formulation combines 100 phr MDPE 323 with 3.0 wt% to 4.0 wt% UV-stabilized masterbatch containing hindered amine light stabilizers, 0.2 wt% to 0.4 wt% phenolic antioxidant, and 0.5 wt% to 1.0 wt% color concentrate; the powder is dry-blended in a high-speed paddle mixer for 8 min to 12 min at 40 rpm before charging into the mold. Oven setpoint is held at 285°C to 305°C, but the internal air temperature must not exceed 220°C, because oxidative embrittlement at the inner foam-bonding surface becomes irreversible above this threshold; a PIAT of 205°C to 215°C is typically used to balance complete densification against over-oxidation. The mold is rotated at 4:1 primary/secondary speed on a four-station turret, cooled by forced air to 90°C and then by water mist to 70°C before release. Industry compliance for marine exposure is anchored to ISO 4892-2:2013 UV weathering, ASTM D256-23 Izod impact at 23°C and -20°C, and ISO 527-2:2012 tensile properties; fogging and salt-spray evaluations are commonly conducted under ISO 9227:2022. Published peel-strength data for PU-to-MDPE 323 shell adhesion under cyclic salt-fog immersion are limited; incoming powder lots should therefore be validated for melt-flow stability and ESCR before release to marine tooling. Terminal products include cylindrical marine fenders from 300 mm to 2,000 mm outer diameter, buoy hulls, and foam-filled floating dock pontoons.
For underground junction boxes, valve pits, and cable pull boxes, the rotational molding cycle is biased toward a lower peak internal air temperature of 195°C to 205°C and an extended dwell time of 30 min to 40 min to avoid under-formed weld lines at molded-in ribs and knockouts. The charge weight is calculated for a nominal wall thickness of 8 mm to 12 mm, with addition levels of 2.0 wt% to 3.0 wt% carbon black masterbatch, 0.3 wt% heat stabilizer, and up to 15 wt% clean post-industrial regrind; the regrind is sieved through 35 mesh before dry blending to prevent density stratification in the mold cavity. Oven setpoint on single-arm or shuttle machines is generally 270°C to 290°C, and the mold is rotated at a 4:1 speed ratio with periodic reversal to minimize powder pile-up at the lower sidewall radius. Cooling is staged to prevent differential shrinkage: forced air to 80°C, then fine water mist at 50°C to 60°C until the internal air temperature drops below 65°C. Compliance for underground service requires ASTM D638-14 tensile yield, ASTM D1693-15ε1 Condition B ESCR, and ISO 178:2019 flexural modulus; access-chamber products are additionally specified under EN 13598-1:2010 where applicable. Terminal product types include pull boxes, valve pits, curb-side service boxes, and underground junction enclosures with molded-in cable entry ports.
Outdoor exposure of playground components and street furniture requires the rotational molding operator to extend the oven dwell time rather than increase the peak internal air temperature, because excessive PIAT above 210°C drives warpage in flat panels and accelerates colorant degradation. The powder formulation for molded slide hoods, play panels, bench slats, and exterior planter shells consists of 100 phr MDPE 323, 1.5 wt% to 2.0 wt% matched-color concentrate, 2.0 wt% to 3.0 wt% UV/HALS masterbatch, and 0.2 wt% antioxidant; pigments are screened for compliance with heavy-metal limits before dry blending. Cast aluminium molds with vapor-honed textured surfaces are used, and a 4:1 rotation ratio is maintained at 270°C to 285°C oven setpoint; the peak internal air temperature is held at 195°C to 205°C, followed by forced-air cooling to 85°C and a demolding temperature below 70°C. Regulatory compliance for this segment is evaluated under ASTM F963-17 and EN 71-3:2019 for migration of certain elements, with resin and masterbatch documentation assessed against REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU; surface colorfastness is evaluated under ISO 4892-2:2013. Terminal products include rotationally molded slide tubes, freestanding play panels, slatted bench components, and rectangular planter shells.
In-house regrind derived from trimmed openings, rejected MDPE 323 containers, and start-up parts alters the powder bulk density and thermal history of the dry-blend, so industrial bin and material-handling container molding must control the regrind fraction and sieve profile more tightly than virgin-only formulations. The closed-loop blend is maintained at 80 wt% virgin MDPE 323, 20 wt% clean post-industrial regrind, 2.0 wt% carbon black masterbatch, and 0.3 wt% long-term heat stabilizer; the regrind is ground to 35 mesh and screened twice to remove fines below 150 µm, because excessive fines raise melt fusion time and produce lower density internal skins. Oven setpoint is 280°C to 300°C, with a target PIAT of 205°C to 210°C and a dwell time of 28 min to 35 min; a 4:1 arm speed ratio is used on carousel or shuttle machines. The main risk at 20 wt% regrind is loss of environmental stress-crack resistance and low-temperature impact, so each batch is tested under ASTM D1693-15ε1 Condition B and ASTM D256-23 at -20°C; melt-flow stability is verified under ISO 1133-1:2022 at 190°C/2.16 kg, and density is measured under ISO 1183-1:2019. Waste container products intended for European municipal service are evaluated against EN 840-1:2020 for two-wheeled refuse bins, while larger pallet boxes and recycling carts are specified through the same resin lot-testing protocol. Terminal product types include 120 L to 1,100 L wheeled refuse bins, heavy-duty recycling carts, and injection-free pallet boxes used in waste logistics.
Because the semi-flexible MDPE 323 wall exhibits anisotropic shrinkage after demolding when the internal air temperature is lowered too rapidly, dimensional control in outdoor telecommunication pedestals, low-voltage control cabinets, and traffic signal housings is governed by mold geometry and release sequence rather than by melt flow alone. The formulation is maintained at 100 phr MDPE 323 with 2.0 wt% to 3.0 wt% UV-stabilized masterbatch and 0.5 wt% to 1.0 wt% color concentrate for grey or black enclosures; no filler is added, because mineral fillers reduce low-temperature ductility at wall thicknesses below 6 mm. CNC-machined aluminium molds are specified with a minimum draft angle of 2° and a vent diameter of 6 mm to 10 mm, and the oven is held at 270°C to 285°C with a peak internal air temperature of 195°C to 205°C. The part is cooled in still air to 80°C, released from the mold, and then restrained on a flat jig until the surface temperature falls below 45°C to control warpage at long flat sidewalls. Compliance for electrical and telecommunication enclosure service is assessed under UL 94 horizontal burn classification HB, ASTM D635-22 for rate of burning, and IEC 60529:2013 ingress protection testing of the finished assembly; material documentation is maintained under REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU. Terminal product types include rural telecommunication pedestals, low-voltage control boxes, and traffic signal housings with integrally molded sun shields and cable entry collars.
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Bayport Polymers (Baystar) MDPE 323 is a medium-density polyethylene resin supplied in pellet form for blown film, extruded sheet, and geomembrane liner applications requiring a balance between stiffness, slow crack growth resistance, and melt strength. The grade is assigned a nominal density of 0.934 g/cm³ when measured under ASTM D1505 and a melt flow index of 0.20 g/10 min at 190 °C/2.16 kg under ASTM D1238. The density places the material between LLDPE and HDPE in crystallinity, while the low melt flow index identifies it as a high-molecular-weight, high-melt-strength resin. The numeric suffix 323 is manufacturer-specific and should not be treated as a direct density or melt index code without consulting the technical data sheet. Representative property values are summarized in Table 1; they are typical lot-average data, not guaranteed specification limits.
| Property | Test method | Typical value |
|---|---|---|
| Density | ASTM D1505 | 0.934 g/cm³ |
| Melt flow index | ASTM D1238 | 0.20 g/10 min at 190 °C/2.16 kg |
| Tensile yield strength | ASTM D638 | 18.6 MPa |
| Tensile elongation at break | ASTM D638 | >600% |
| Flexural modulus | ASTM D790 | 690 MPa |
| Vicat softening temperature | ASTM D1525 | 118 °C |
| Low-temperature brittleness | ASTM D746 | < -75 °C |
| Environmental stress crack resistance | ASTM D1693, condition B | >1000 h |
The melt index of 0.20 g/10 min is operationally significant. It is not interchangeable with high-flow rotational molding MDPE grades, which commonly range from 3.0 g/10 min to 6.0 g/10 min because powder sintering requires rapid melt flow. A rotational molding line cannot process MDPE 323 efficiently without blending with a higher-flow resin, and even then angular velocity profiles may require adjustment because the high-viscosity fraction increases bubble dissolution time in the sintered layer. In blown film, the high melt strength allows bubble expansion ratios up to 3.0:1 without excessive sag, but the low melt index reduces maximum line speed compared to a 1.0 g/10 min LLDPE at identical die gap. The grade is also distinct from HDPE film resins, which typically have densities above 0.945 g/cm³ and flexural moduli above 1000 MPa but lower environmental stress crack resistance at equivalent molecular weight.
The crystalline fraction corresponding to 0.934 g/cm³ is low enough to slow craze propagation but high enough to provide sufficient modulus for unsupported sheet and thick film. In medium-density polyethylene, slow crack growth resistance is governed less by bulk crystallinity than by tie-chain concentration and molecular weight between entanglements. At 0.20 g/10 min, the weight-average molecular weight is high, and the resultant long relaxation time increases both elongational melt strength and resistance to brittle fracture. If the product is an ethylene-hexene copolymer, the longer butyl branch is more efficient than the ethyl branch of butene copolymers at generating tie molecules at equivalent density. Published data for the exact molecular weight distribution, short-chain branch content, and long-chain branch content of Baystar MDPE 323 are limited in publicly available datasheets. However, the ESCR value above 1000 h under ASTM D1693 condition B indicates a formulation biased toward slow crack growth resistance rather than maximum stiffness.
Tensile yield strength of 18.6 MPa and flexural modulus of 690 MPa are lower than corresponding values for HDPE film and sheet grades. This reduction in stiffness lowers deployment force and improves conformability in geomembrane service. The low-temperature brittleness of less than -75 °C under ASTM D746 supports use in cold-climate liner installations where HDPE may become notch-sensitive at sub-zero temperatures. The Vicat softening temperature of 118 °C under ASTM D1525 provides an upper service boundary; sustained exposure above this temperature should be avoided without thermal aging validation and mechanical restraint.
Extrusion of MDPE 323 on single-screw lines with L/D ratios from 24:1 to 30:1 typically requires a melt temperature between 204 °C and 216 °C for blown film. A barrier screw with compression ratio 2.8:1–3.2:1 is preferred; higher compression ratios generate excessive shear heating and may create gel particles at the die lip. Screen packs of 20/40/60 mesh are common, and head pressure may be higher than with a 1.0 g/10 min LLDPE at equivalent screw speed. On a 65 mm extruder, throughput is typically limited by bubble stability rather than motor load. Die gaps of 1.5–2.5 mm are typical for blown film, with frost line heights set at 5–8 die diameters to balance tear anisotropy. For flat-die sheet and geomembrane, die gaps of 2.0–3.0 mm and chill roll temperatures of 60–80 °C are used. Because polyethylene is nonhygroscopic, pre-drying is not required unless pellet surface condensation occurs; if condensation is observed, a forced-air hopper dryer at 60–70 °C for 2 h is adequate. The resin should not be purged with PVC cleaning compounds. If a commercial purge compound is used, it must be polyethylene-compatible to prevent die-lip residue transfer. Blending with high-flow LLDPE above 20 wt% is not recommended when bubble stability is critical because melt strength decreases disproportionately.
Table 2 compares representative values for Baystar MDPE 323, a high-molecular-weight HDPE film resin, and a butene LLDPE film resin. The comparator values are drawn from publicly available resin-class data and are not product-specific certificates.
| Property | Baystar MDPE 323 | Typical HMW-HDPE film | Typical butene LLDPE film |
|---|---|---|---|
| Density | 0.934 g/cm³ | 0.950–0.954 g/cm³ | 0.918–0.922 g/cm³ |
| Melt flow index | 0.20 g/10 min | 0.05–0.10 g/10 min | 0.9–1.0 g/10 min |
| Flexural modulus | 690 MPa | 1000–1200 MPa | 250–350 MPa |
| Tensile yield strength | 18.6 MPa | 24–28 MPa | 10–12 MPa |
The lower flexural modulus of MDPE 323 relative to HDPE reduces the force needed to unroll and deploy geomembrane panels, but it also reduces resistance to point loads from sharp aggregate. When geosynthetic applications require compliance with GRI-GM13 or ASTM D6392, the resin generally requires carbon black masterbatch at 2.0 wt% to 3.0 wt% to achieve the specified oxidation induction time and UV resistance. Oxidation induction time is typically measured under ASTM D3895, while carbon black dispersion is assessed under ASTM D5596. Published data for the compounded configuration is limited; each formulation must be tested for carbon black dispersion and weld peel strength. Compared with butene LLDPE, the grade has lower dart impact under ASTM D1709, as the higher density and crystallinity reduce energy absorption; the tradeoff is higher modulus and improved dimensional stability.
The identical melt index that stabilizes blown film bubbles at low neck height can create back-pressure limitations in flat-die sheet extrusion. For flat-die lines, melt temperature may need to be raised to 221–227 °C to reduce viscosity, but this narrows the oxidative safety margin and may require nitrogen blanketing of the feed hopper if oxygen exposure is prolonged. The processing window is therefore asymmetric: blown film tolerates a wider temperature range because the air ring provides rapid quenching, while thick sheet retains heat and is more sensitive to edge-to-center melt temperature variation. On sheet lines with 1.5 m die widths and 90 mm extruders, melt pressure at the screen changer can exceed 35 MPa if screens are not replaced on a preventive schedule. Published data for this exact line configuration is limited.
The grade is not optimized for injection molding. The low melt flow index can result in short shots in sections below 1.5 mm unless melt temperatures exceed 230 °C, at which point oxidative degradation risk increases. For thick-section molded parts, displacement rates should be kept low, and hold pressure profiles should include a slow-cram phase to reduce sink marks. The constraint follows standard high-molecular-weight polyethylene processing behavior and is not specific to this grade alone.
Compliance documentation for food-contact use generally follows FDA 21 CFR 177.1520 for olefin polymers, while EU packaging frameworks require verification under Regulation (EU) No 10/2011. The user must confirm the specific lot certificate because additive package and comonomer source may affect migration testing and organoleptic performance. RoHS and REACH screening is routinely satisfied by polyethylene homopolymers and copolymers, but the converter remains responsible for downstream combination products.
