Ateva 3325ACX EVA Copolymer Resin,33% VA,43 MI,Low Gel,Insulation Shield Grade

Compounding of a peroxide-curable bonded semiconductive insulation shield for medium-voltage XLPE power cable begins with melt homogenization of Ateva 3325ACX with conductive carbon black, phenolic antioxidant, and processing aid. The 33 wt% vinyl acetate content lowers crystallite size and permits carbon black wetting at shear rates generated in a co-rotating twin-screw extruder with L/D 44:1 or L/D 48:1; the 43 g/10 min melt index, measured under ISO 1133-1:2022 at 190°C and 2.16 kg, reduces specific mechanical energy input compared with low-melt-index EVA grades. Starting-point formulations for a bonded insulation shield place the EVA base at 55–65 wt%, acetylene black or extra-conductive furnace black at 30–38 wt%, dicumyl peroxide at 1.5–2.0 wt%, and polymerized 1,2-dihydro-2,2,4-trimethylquinoline at 0.5–1.0 wt%. Low gel content is critical because gel particles in the shield layer form surface protrusions that become electrical stress concentrators at the insulation-shield interface; therefore barrel temperatures are held below 120°C, since the one-hour half-life temperature of dicumyl peroxide is approximately 135°C and localized overheating in high-shear kneading blocks can initiate premature crosslinking. After pelletizing, the compound is extruded as the outer semiconductive screen in a three-layer crosshead on a catenary continuous vulcanization line. The shield extruder melt temperature at the head is held at 105–115°C, the cure tube is operated at 250–350°C, and line speed for 6–36 kV cables ranges from 20 m/min to 60 m/min depending on conductor cross-section and insulation wall thickness. The finished product types are single-core and three-core medium-voltage distribution cables, underground feeder cables, and wind farm array cables conforming to IEC 60502-2:2014 or ICEA S-93-639/NEMA WC 74. Semiconductive shield volume resistivity after thermal ageing is measured per ISO 3915:1999 or ASTM D4496-21, with production targets commonly held within 1 Ω·cm to 1,000 Ω·cm. If the resin is exposed to relative humidity above 60%, pre-drying at 60–70°C for 4 h is required before compounding because moisture interferes with peroxide efficiency and can create voids at the insulation-shield boundary.

What Compounding Adjustments Control Peel Force in Strippable Insulation Shields at 12–36 kV?

Where cable jointers must remove the outer semiconductive shield without leaving carbon residue on the XLPE surface, the compound is shifted toward reduced adhesion. Starting-point strippable formulations using Ateva 3325ACX place the EVA base at 50–60 wt%, conductive furnace black at 35–40 wt%, dicumyl peroxide at 1.0–1.5 wt%, and an adhesion-modifying co-resin at 2–5 wt%; phenolic antioxidant is added at 0.3–0.8 wt%. Carbon black selection affects peel force independently of loading: high-structure furnace grades create stronger mechanical interlocking at the interface, while lower-structure grades and surface-modified conductive blacks permit controlled release. Compounding is performed on a co-rotating twin-screw extruder with L/D 40:1 or higher and low-specific-energy screw profiles, keeping melt temperature below 115°C so peroxide remains unreacted. The resulting pellets are coextruded onto the XLPE insulation in a three-layer line; strippability is evaluated on finished cable after dry cure and accelerated ageing, because plaque measurements do not reproduce the interfacial thermal history. Construction compliance is assessed under IEC 60502-2:2014, which requires semiconductive screens to be removable without damage to the insulation; material acceptance may reference ASTM D3004-22 for extruded semiconductive shield compounds and ICEA S-93-639/NEMA WC 74 for utility-grade cable systems. Production-line observations show peel force increases when the lower cure tube temperature exceeds 280°C or when line speed falls below 15 m/min, producing over-cure at the interface. Terminal cable products are 12–36 kV medium-voltage cables for wind farm collector circuits and utility distribution feeders where splice preparation time and joint reliability are critical. Replacement of phenolic antioxidant with amine-based antiozonant is not recommended because secondary amines can quench peroxide radicals and alter cure density.

Silane moisture-cured insulation shield compounds based on Ateva 3325ACX employ a different cure chemistry in which vinyltrimethoxysilane or vinyltriethoxysilane is grafted onto the EVA chain with a minor peroxide initiator dose. The starting-point formulation places the EVA base at 55–65 wt%, conductive carbon black at 30–40 wt%, silane at 1.0–2.0 wt%, peroxide initiator at 0.1–0.3 wt%, dibutyltin dilaurate catalyst at 0.05–0.15 wt%, and phenolic antioxidant at 0.2–0.5 wt%. The compound is prepared on a co-rotating twin-screw extruder with high-shear screw elements to distribute silane uniformly, with melt temperature maintained below 130°C to avoid premature silane condensation and gel formation. After pelletizing, the compound is coextruded as the insulation shield layer in a triple-head extrusion line, and the cable is passed through a water bath at 70–95°C or stored under controlled humidity for 4–8 h depending on conductor size and insulation wall thickness. The absence of a high-temperature catenary cure tube permits faster line start-up and lower energy demand. Compliance is evaluated under IEC 60502-1:2021 for 0.6/1 kV distribution cables or IEC 60502-2:2014 for 3.6/6–20.3/35 kV designs where a crosslinked shield is specified. Hot-set elongation is tested per IEC 60811-507:2012, with standard pass criteria generally set below 175% elongation under load and 15% maximum permanent set. Terminal product types include low-voltage aerial bundled cables, utility service cables, and medium-voltage distribution feeders where moisture-curing infrastructure is available. Carbon black adsorbs both moisture and organotin catalyst, so masterbatch blending must be completed in closed feeders; pellets exposed to ambient humidity above 50% require pre-drying at 60°C for 4 h before extrusion.

When Trailing Cable Flexural Fatigue Demands a Low-Gel Semiconductive Shield

Trailing, reeling, and continuous miner cables used in mining and tunnelling impose repeated flexural strain on the semiconductive insulation shield. For this family, Ateva 3325ACX is blended with EPDM at an EVA/EPDM ratio from 70/30 to 50/50 wt% to retain low-temperature flexibility while maintaining carbon black dispersion and electrical stability. The full compound includes the EVA/EPDM base at 55–70 wt%, conductive furnace black at 30–40 wt%, dicumyl peroxide or a co-peroxide system at 1.5–2.5 wt%, phenolic antioxidant at 0.5–1.0 wt%, and process oil at 2–5 wt%. Mixing is performed in an internal mixer with a two-stage cycle: first-stage dump temperature is kept at 110–125°C to incorporate carbon black, and peroxide is added on a second-stage mill at 80–90°C to avoid scorch. The compound is then extruded as a shield onto EPR or XLPE insulation on a continuous vulcanization line or calendered for specific reel cable constructions. Low gel content is particularly important because gel particles generate surface roughness that concentrates dust and may initiate flexural cracking in dynamic service. Compliance for mining and portable power cables is commonly assessed against ICEA S-75-381/NEMA WC 58 and AS/NZS 1802:2012 where applicable; shield resistivity is tested per ASTM D4496-21, and tensile properties after thermal ageing per ASTM D638-14. Finished product types include 0.6/1 kV to 6.6/7.2 kV trailing cables, continuous miner cables, dragline cables, and pump cables. Halogenated flame retardants are excluded where low-smoke performance is required; phosphate ester flame retardants can interfere with peroxide cure and require reformulation. Pre-drying of the EVA pellets at 60–70°C for 4–6 h is mandatory before mixing in humid production environments.

Carbon Black Masterbatch Carrier for Wire and Cable Semicon Systems

When Ateva 3325ACX is used as a carrier resin for conductive carbon black masterbatches intended for let-down into semiconductive cable compounds, the 33 wt% vinyl acetate and 43 g/10 min melt index permit carbon black loading at 35–45 wt% in the masterbatch while maintaining pellet uniformity and rapid wetting. The carrier EVA occupies 55–65 wt% of the masterbatch, with processing aid at 1–3 wt% and antioxidant at 0.2–0.6 wt%. Masterbatch production is carried out on co-rotating twin-screw extruders with L/D 44:1 or L/D 48:1 and high-shear screw elements; melt temperature is kept below 140°C because no peroxide is present in the carrier system. The resulting masterbatch is let down at 10–20 wt% into final semiconductive shield compounds. Compliance is linked to the finished cable standards rather than the masterbatch itself; masterbatch quality is controlled by ASTM D4496-21 for resistivity on a compression-molded plaque and ASTM D638-14 for tensile yield. Published production-scale data specific to this exact grade in masterbatch carrier applications remains limited; industrial starting points are therefore reported as ranges rather than fixed recipes. Finished product types are conductive masterbatch pellets for medium-voltage shield compounds, silane-curable shield compounds, and mining cable semicon layers. Storage limitations are similar to the final compounds: sealed packaging and pre-drying at 60°C for 4 h are required if the resin has been exposed to ambient humidity above 50%.