Borealis BorStar MDPE ME6052 is a ready-to-use black medium-density polyethylene jacketing compound manufactured by the Borstar bimodal process. The published density is 0.945 g/cm³ per ISO 1183-1:2019, and the melt flow rate is 0.9 g/10 min at 190 °C/2.16 kg per ISO 1133-1:2022. The carbon black content is 2.5 wt% when measured by ASTM D1603. The compound is supplied as cylindrical pellets and is intended for extrusion into outer jackets and sheaths of energy, telecommunications, and coaxial cables. The following scoped application sections address only cable-sheathing segments where MDPE jacketing is industrially practiced. Unsupported use in pipe coating, blow molding, or rotational molding is excluded because the grade’s melt strength and additive package are not specified for those conversion methods.

Where Does Shrinkback Control Set the Processing Window in Fiber Optic Outer Jackets?

In fiber optic duct and aerial cables, the outer jacket is extruded over aramid yarns or water-blocking tape, and the primary failure mode during hot splicing or aerial thermal cycling is longitudinal jacket shrinkback that exposes gel-filled core elements. The extrusion operation must therefore suppress frozen-in molecular orientation. On a 25:1 L/D single-screw extruder with a barrier screw and a die head pressure of 180–260 bar, the barrel profile is set from 160 °C at the feed zone to 210 °C at the metering zone, with die temperature held at 210 °C. Cable core preheat at 60–70 °C is applied before the crosshead to reduce quench shock. The first cooling trough is held at 40–50 °C; the second trough is held at 20–25 °C. The compound is fed at 100% as supplied; no additional carbon black concentrate or antioxidant masterbatch is used because the product already contains a UV-stabilized carbon black package. If the extruder backpressure exceeds 280 bar, up to 1.5 wt% of a fluoropolymer processing aid may be added, but such an additive must not displace carbon black dispersion and is subject to jacket shrinkback retesting under IEC 60794-1-2:2017. The finished product is the black outer jacket of outside plant fiber optic duct and aerial cables, with wall thickness of 0.8–1.5 mm. Shrinkback acceptance follows Telcordia GR-20-CORE, and the material’s ESCR >1000 h under ASTM D1693 with 10% Igepal contributes to crack resistance in repeatedly flexed drop loops. The jacket is not designed for indoor LSZH applications because it does not meet IEC 60332-1 flame-spread requirements; such sites require a halogen-free formulation.

Medium-voltage distribution cable outer sheathing uses the compound as the outermost protective layer over copper tape or wire screens on XLPE-insulated cores. The sheath is extruded on a 90–120 mm single-screw line operating at a melt temperature of 200–220 °C. The core assembly is preheated to 70 °C to improve polymer-to-screen adhesion without inducing screen-braid displacement. Wall thickness is set according to IEC 60502-2:2014 sheath tables, commonly between 1.6 mm and 2.5 mm for distribution-class voltages up to 33 kV. The material is metered at 100% as supplied; no carbon black masterbatch is top-fed. When a hardness reduction below 58 Shore D per ISO 868 is requested, up to 10 wt% of a compatible LLDPE can be dry-blended, but this shifts the environmental stress crack resistance downward and must be validated against ASTM D1693 before qualification. Routine sheath tests include tensile strength and elongation at break under IEC 60811-501, with the product’s published tensile strength near 21 MPa and elongation at break near 800% under ISO 527-2. The final article is the outer sheath of medium-voltage power distribution cable installed in buried, duct, and cable tray networks. Because the jacket contains carbon black but no flame-retardant filler, its use is limited to installations where cable flame propagation tests such as IEC 60332-3 are not required; indoor high-rise or tunnel risers typically require LSZH materials.

Copper Outside Plant Drop Cable Sheathing Against Environmental Stress Cracking

Copper telecommunication drop cables installed in ducts, lashed to poles, or buried in rocky soil require a sheath with high slow-crack-growth resistance under constant bending and contact with wet soils. The jacket is extruded over an aluminum-polyethylene laminate shield using a pressure-tooling crosshead at a melt temperature of 205–215 °C. The cable core is preheated to 50–60 °C, and the cooling trough is configured with a 35–45 °C first zone and a 20–25 °C second zone to avoid surface stress cracking. The formulation is 100% BorStar MDPE ME6052 as supplied; no reprocessed jacket scrap is recommended above 5 wt% because the resultant melt fracture and gloss defects can increase moisture ingress. The terminal product is the black outer sheath of copper outside plant cable per ANSI/ICEA S-84-608, with thickness from 1.0 mm to 2.0 mm. The environmental stress crack resistance of the compound, cited above 1000 h under ASTM D1693, supports qualification to Telcordia GR-421-CORE where the sheath is subjected to cyclic loading at pole attachment points. A limitation arises in wet-burial applications containing high concentrations of phenolic disinfectants; although the MDPE hydrocarbon barrier is adequate for normal soil, specific chemical resistance should be verified by immersion testing per ISO 175.

In coaxial RF drop cable extrusion, a thin polyethylene jacket is applied over the soldered or welded aluminum outer conductor. The line is run at speeds up to 150 m/min, with a pressure-tooling crosshead and a die land length selected to maintain a draw-down ratio below 2.5:1; higher draw-down raises surface orientation and contributes to jacket splitting at connector crimp zones. The material is fed at 100% as supplied; no pigment or carbon black adjustment is needed because the product’s 2.5 wt% carbon black content under ASTM D1603 provides sufficient UV resistance for outdoor drop cable. The jacket thickness is 0.8–1.2 mm and is verified against EN 50117-1:2018 for coaxial communication cables; North American qualification follows SCTE IPS-SP-100. The terminal product is the outdoor black jacket of CATV drop cable and broadband subscriber cable. Process limitations include the need to maintain melt temperature below 230 °C to prevent thermal degradation of the antioxidant package and carbon black agglomerate formation that produces pinholes visible under high-voltage spark testing at 50 Hz.

When Low-Voltage Service Entrance Cables Require UV-Weathering and Abrasion Resistance

Low-voltage service entrance and overhead service drop cables use a black polyethylene jacket over XLPE or PVC-insulated conductors to withstand sunlight, rain, and branch abrasion. The jacket is extruded on a 65–90 mm single-screw extruder at a melt temperature of 195–210 °C. The core assembly is preheated to 60 °C. The compound is used at 100% as supplied; no lubricant masterbatch is added because the surface friction of the as-extruded carbon black-filled MDPE is within normal duct-pulling limits. The terminal product is a low-voltage service entrance cable jacket conforming to HD 626 S2 or national service drop standards. Thickness is typically 1.0–1.6 mm. Outdoor weathering is verified by ISO 4892-2 UV exposure and hardness retention under ISO 868. The compound’s brittleness temperature near -76 °C under ASTM D746 ensures that jacket cracking does not occur during winter installation at subzero temperatures; however, at temperatures below -40 °C, cable-bending radius should be increased to avoid localized stress whitening.