Jiangsu Dewei YJ-35 is supplied as a ready-mixed peroxide-curable XLPE compound for cable insulation; converter-side additions are limited to colour masterbatches and process aids, not cure agents. For low-voltage distribution cables rated 0.6/1 kV and designed to IEC 60502-1:2021, the compound is extruded directly over stranded copper or aluminium conductors as the primary dielectric layer at nominal wall thicknesses from 0.7 mm to 1.4 mm depending on conductor cross-section. The compound is run at 100 parts by mass; colour masterbatch additions above 2.0 wt% have been observed in batch records to raise the 90°C tan δ of the insulation, so pigment dosing is confined to 0.5–2.0 wt% where phase identification is required. A single-screw extruder with a screw L/D of 24:1 to 30:1 and a compression ratio of 2.5:1 is typical; barrel temperatures from feed to metering are held at 110–120°C, and the die head is maintained at 120°C to avoid premature peroxide decomposition in the screw. Continuous vulcanization follows in a steam or nitrogen tube with a crosslinking zone of 180–200°C; line speed is set by inner-surface cure rather than surface gloss. On high-speed lines, a pressure rise above 15–20% from the stable baseline at the breaker plate is a field indicator of premature gel formation in the screw and requires a zone-temperature reduction of 5°C rather than increased screw speed. The crosslinked insulation layer is rated for 90°C continuous conductor temperature under normal service; the unfilled compound is not inherently flame retardant, so flame propagation tests such as IEC 60332-1-2 apply to the completed cable construction with sheath and bedding, not to the insulation compound alone. The end product is used in building riser cables, industrial feeder cables, and distribution board connections; open-air installation requires an outer sheath because the compound does not supply UV protection.

What Limits Crosslink Density in 35 kV-Class CV Lines When Insulation Wall Thickness Exceeds 4.5 mm?

At wall thicknesses above 4.5 mm, heat transfer into the inner insulation layer becomes the controlling variable; surface crosslinking may be complete while the conductor interface remains undercured. The CV tube profile is typically divided into a pre-heat zone at 170–190°C, a crosslinking zone at 250–320°C, and a cooling section where the cable is quenched to below 60°C before take-up. YJ-35 is used at 100 parts; the peroxide cure package is already incorporated in the compound, and the converter does not modify it. The practical cure-package response in 35 kV-class processing is comparable to formulations containing 1.6 wt% to 2.2 wt% dicumyl peroxide; a heat history that produces an undercure response below 1.4 wt% equivalent has been observed to yield hot-set elongation at 200°C and 0.2 MPa load exceeding the 175% criterion of IEC 60811-507, while an overdrive equivalent above 2.4 wt% has been linked to microvoid formation in thick sections because volatile decomposition products cannot escape before the network locks. Extruder barrel temperatures are held at 110–120°C; a melt temperature above 125°C has caused intermittent surface blemishes and rising melt pressure on CV lines. Degassing after CV is performed at 70–80°C for 24–72 h depending on wall thickness; incomplete degassing has been linked to long-term dielectric loss drift and post-installation shrinkage. Converter additives containing free amine groups must be excluded because they interfere with peroxide decomposition and reduce final crosslink density. The end product is the primary insulation of medium-voltage underground or indoor distribution cables, where partial discharge-free operation is verified by the cable manufacturer under IEC 60502-2:2014 or applicable utility specifications.

Photovoltaic DC cable insulation is specified for 120°C continuous thermal endurance under EN 50618:2014 and IEC 62930:2017. On a co-extrusion line where a semi-conductive conductor shield, XLPE insulation, and crosslinked polyolefin sheath are applied in sequence, YJ-35 is run as the middle dielectric layer at 100 parts by mass, with no filler loading because unfilled crosslinked polyolefin more reliably maintains volume resistivity after humid ageing at 80°C. Insulation wall thickness for conductor sizes from 2.5 mm² to 35 mm² commonly falls between 0.5 mm and 0.8 mm; undercure at the conductor shield interface is detected as an increase in hot-set elongation after 15 min at 200°C and 0.2 MPa, so line speed is set to keep hot-set permanent set below 15% for batch release. The main failure mode on production lines is interfacial roughness between the semi-conductive conductor shield and insulation, which begins as a periodic wave mark on the inner screen and propagates into an eccentric wall during line-speed changes; this is controlled by limiting the melt-temperature difference between the two co-extruders to ±5°C. The compound itself is not formulated as a UV-stable exposed surface; UV resistance is supplied by the outer sheath, not the insulation layer, which is why the insulation remains unpigmented to avoid contamination at the shield interface. End products are module interconnect cables, DC feeder cables from combiner boxes to inverters, and array-to-inverter truncated main cables installed in direct sunlight, where the completed cable must also meet flame propagation requirements under IEC 60332-1-2 and cold bend tests at -40°C under the applicable harmonised standard.

Automotive Thin-Wall Primary Wire Subjected to ISO 6722 Long-Term Heat Aging

Automotive harness constructions exploit the crosslinked network to maintain wall integrity at continuous conductor temperatures up to 125°C with short-term excursions to 150°C depending on vehicle zone and classification class under ISO 6722-1:2011. YJ-35 is used at 100 parts; for non-flame-rated signal wires the formulation remains unfilled so volume resistivity remains above 10¹⁴ Ω·m, while flame-rated SAE J1128 variants require cable-level certification rather than a simple filler addition because filler dispersion stability affects dielectric strength at thin walls. High-speed extrusion of 0.20–0.40 mm walls requires a crosshead with self-centring tip and draw-down ratio below 2.0 to keep eccentricity within harness limits; die-head temperature is held at 115–120°C and line speed is constrained by CV tube residence time rather than extruder output. The principal thin-wall start-up failure is a periodic concentricity drift caused by conductor vibration entering the crosshead; this is corrected by increasing back-tension control or fitting an upstream accumulator. The end product is used in engine compartment sensor leads, battery harness signal wires, door and tailgate looms, and cabin wiring where abrasion is managed by tape, conduit, or harness routing rather than by the insulation material itself.

When YJ-35 Is Extruded as the Inner Insulation Layer in Shielded EV High-Voltage Cable Constructions

In shielded high-voltage cables for electric vehicle power distribution, the insulation layer is subjected to partial discharge stress under inverter-driven pulse-width modulation; constructions intended for 600 V to 1500 V DC bus voltages use YJ-35 as the unfilled dielectric between a semi-conductive conductor shield and an extruded semi-conductive insulation screen. The compound is used at 100 parts; if polarity identification requires a coloured insulation layer, a non-conductive colour masterbatch is limited to below 1.5 wt% to avoid reducing breakdown voltage in finished-cable testing. Co-extrusion demands matched melt viscosities between the semi-conductive shield layers and the insulation; a melt-index difference above 2–3 g/10 min has been observed to generate interfacial waviness that lowers partial discharge inception voltage on production trials. The equipment is a co-extrusion line feeding a CV tube, with the insulation extruder screw L/D at 24:1 to 30:1 and barrel temperatures of 110–120°C; after CV, the cable is degassed at 70°C for 48 h to remove peroxide by-products that would otherwise migrate and blister the outer sheath. Published data for YJ-35 under long-term inverter pulse ageing is limited; qualification is therefore conducted at cable level under ISO 19642-1:2019, LV 216-1, or the vehicle manufacturer’s component specification, with partial discharge inception and extinction voltage evaluated before and after bending and thermal cycling. End products are battery-to-inverter links, on-board charger cables, and DC fast-charge harness sections inside the vehicle.

Low-level analogue and digital fieldbus circuits in process automation require insulation with stable dielectric properties after humidity cycling; YJ-35 is applied as a continuous insulation layer at wall thicknesses from 0.25 mm to 0.60 mm. The compound is processed neat at 100 parts; direct pigmentation of the full insulation cross-section is avoided because humidity ageing of pigmented XLPE can lower insulation resistance in installed fieldbus runs, so colour identification is achieved by a thin co-extruded colour stripe or numbered surface print. Constructions are designed to EN 50288-7:2005 for instrumentation cables, with flame performance evaluated at the completed-cable level under IEC 60332-1-2. In multi-wire extrusion, lane-to-lane melt pressure variation is controlled within ±5 bar; higher variation produces eccentric walls and capacitance scatter between adjacent twisted pairs, which becomes critical for digital fieldbus transmission. Undercure in thin walls is detected indirectly when hot-set permanent set exceeds 15% after 15 min at 200°C and 0.2 MPa under IEC 60811-507. The end product is used in sensor and actuator cables, process automation trunk cables, and vibration-resistant machine wiring in manufacturing cells.