Two-Part Polyurethane Cable Joint Sealant for Reliable High-Voltage Insulation

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Every high-voltage cable joint is a small piece of real estate carrying an outsized share of the risk. Moisture reaches the insulation screen, tracking starts, partial discharge builds, and a joint that was supposed to last decades becomes a fault report. The sealant poured into the joint shell is what stands between those two outcomes. Hunan Shangyu Waterproof Material Co., Ltd. manufactures exactly that layer: a two-component polyurethane sealant system engineered for high-voltage cable joints and cable accessories, supplied as separate Part A and Part B components and cured on site at ambient temperature.

What the SY Sealant System Is

The SY range is a two-part, cold-applied polyurethane system. Part A is a buff, light-yellow sticky liquid built on polyether polyol with diphenylmethane diisocyanate, plasticizer and fire retardant. Part B is a black sticky liquid formulated with MOCA, tar asphalt, plasticizer, insulating compound and fire retardant. The two components are supplied in separate sealed pails and are combined on site at a documented 2:1 ratio (Part B into Part A), stirred until uniform, then poured or injected into the protective shell of the joint. Once in place, the mixture cures at normal ambient temperature into a rubber-elastic polymer that fills voids, bonds to the surrounding surfaces and seals the joint against water ingress.

No heating equipment, no open flame and no solvent handling are required. That matters in a trench, in a substation compound or on a tower: the installation team carries less equipment, works faster, and removes a whole category of hot-work risk from the job.

Performance You Can Specify Against

The standard grade is produced to enterprise standard Q31/0120000518C001-2017, and the flame-retardant grade to Q31/0120000518C002-2017. Published technical values for the standard grade include:

Hardness: Shore A 50 ± 10 | Elongation at break: ≥ 200% | Tensile strength: ≥ 1.2 MPa
Water absorption (50 °C, 24 h): ≤ 4% | Volume resistivity: 1.0 × 10¹² Ω·cm
Breakdown voltage: ≥ 20 kV/mm | Impermeability (0.3 MPa, 30 min): no penetration
Pourable time at 30 °C: ≥ 10 min | Surface dry time at 30 °C: ≤ 180 min

In practice, the numbers translate into three things buyers care about. The high elongation and moderate Shore A hardness let the cured rubber absorb thermal expansion, cable movement and mechanical shock without cracking or pulling away from the shell. The volume resistivity and breakdown voltage figures support use in medium- and high-voltage joint bodies where dielectric strength cannot be compromised. And the impermeability result at 0.3 MPa confirms the cured material holds a water seal under pressure rather than merely resisting surface moisture.

The Flame-Retardant Grade

For joints inside cabinets, tunnels, stations and other confined or fire-sensitive locations, the SY flame-retardant grade adds fire retardant loading to both components and is formulated without solvent. Key values include hardness Shore A 50 ± 5, elongation ≥ 200%, tensile strength ≥ 1.5 MPa, solids content ≥ 96%, volume resistivity 1.0 × 10¹² Ω·cm, breakdown voltage ≥ 15 kV/mm, a surface dry time of ≤ 12 hours, and low-temperature flexibility tested at −20 °C with no cracking. Impermeability at 0.3 MPa for 30 minutes again shows no penetration.

Both grades are classified as non-dangerous goods: stable, non-flammable and non-explosive, and therefore transportable as ordinary cargo. For importers, that simplifies freight booking and documentation compared with solvent-based or hazardous-classified alternatives.

Where the Material Is Used

The system is designed around the real duty cycle of cable accessories rather than a laboratory coupon. Typical applications include:

Power cable joints — straight joints, transition joints and repair joints in distribution and transmission networks, where the sealant fills the joint shell and excludes groundwater.
Terminations and accessories — sealing and potting around cable lugs, stress cones and accessory interfaces.
Substation and switchgear work — flame-retardant grade for enclosed locations where a non-flammable cured material is preferred.
Renewable and industrial networks — collector systems at wind and solar farms, plus plant cabling in steel mills, mines and chemical facilities where vibration and damp conditions are normal.
Harsh climates — the formulation work was aimed at climate ranges from cold northern winters to hot, humid coastal and desert conditions, so the same product line can serve projects across several regions.

Installation Discipline

The material is straightforward, but it rewards discipline. The joint area must be dry before pouring. Part A and Part B must be stirred evenly and thoroughly after combination, then poured through the injection port into the protective shell. Any unused Part A must be resealed immediately, because the component cures on contact with atmospheric moisture and an open pail will skin over and become unusable. Work areas should be well ventilated, and gloves and eye protection should be worn; personnel with known isocyanate sensitivity should not handle the components. Pails should be stored unopened in a cool, well-ventilated warehouse, protected from direct sun and rain.

The Company Behind the Product

Hunan Shangyu Waterproof Material Co., Ltd. was established in October 2018 in the Liling Economic Development Zone, Hunan, following relocation from Shanghai, where the team had built its experience in cable joint sealing materials. The company's registered business scope covers production, processing and sales of building waterproof materials, waterproof engineering contracting, general freight, metal products, and the processing and sale of cable sealants — a combination that keeps application know-how close to the formulation bench.

Product development draws on design concepts from established Japanese, American and German brands, adapted through years of domestic production experience and matched to individual customer requirements. The company currently supplies cable accessory manufacturers and utilities, with a customer base reported to include Changlan Cable Accessories, Qingdao Hanhe Cable, Yongjin Electric Power, Ankuang Technology, ZTT and Woer Heat-Shrinkable Material, among dozens of listed companies. Products have been exported to the United States, India, Ukraine, Saudi Arabia and countries across Africa. Drum labeling references GB/T 19001-2016 / ISO 9001:2015 quality management conformity, and each batch is inspected before dispatch.

Drums are lithographed with the Shang Yu mark and the product designation, packed for export handling and stacked for consolidated shipments. Part A and Part B are shipped as matched sets so that installation teams always receive balanced quantities of both components.

Why Buyers Work With Shangyu

For cable accessory OEMs, the value is a sealant that can be specified by standard number and verified against published values, with consistent batch behavior from one container to the next. For distributors, it is a non-dangerous-goods product that ships on ordinary terms, stores without special handling, and covers both standard and flame-retardant demand from a single supplier. For utilities and contractors, it is a cold-applied system that installs without heat and cures into a rubber-elastic seal engineered to hold water out of the joint for the long term.

Talk to Us About Your Next Project

Whether you are sourcing sealant for a joint production line, stocking cable accessory consumables for a regional market, or evaluating a replacement for a current supplier, Shangyu can review your application conditions and recommend the appropriate grade. Tell us your voltage class, joint type, climate and packing requirements, and we will respond with product documentation and a quotation.

Company: Hunan Shangyu Waterproof Material Co., Ltd.
Address: Beside Guoci Road, Liling Economic Development Zone, Hunan, China
Postal code: 412200
Contact: Huang Sandi
Phone: 13386069160
Landline / Fax: 0731-22971118
Email: 249150783@qq.com
Website: http://www.shangyu-waterproof.com/