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Every high-voltage cable joint is a promise the grid has to keep for decades. Buried under a city street, threaded through a substation, or suspended inside a wind tower, that joint has one non-negotiable job: keep moisture out and keep the electrical field stable. Splice bodies, stress cones, conductor lugs and armor hardware all inherit their reliability from the seal that surrounds them. Hunan Shangyu Waterproof Material Co., Ltd. manufactures the material that makes that seal hold — a two-component polyurethane sealant developed specifically for high-voltage cable joints and cable accessory assemblies.
A Two-Component System Built for Cable Accessories
SY-Sealant of High-Volt Cables is supplied as a matched A and B pair. Part A is a buff-colored, sticky, thick liquid built on polyether polyols and diphenylmethane diisocyanate, with plasticizer and fire retardant blended in. Part B is a black, sticky, thick liquid carrying MOCA, coal tar asphalt, plasticizer, insulating compound and fire retardant. The two components are combined at a 2:1 volume ratio (B into A), stirred until uniform, and poured through the injection port into the cable protective shell. At normal ambient temperature the mixture cures into a rubber-like high-polymer elastomer that insulates and seals the joint from the inside out.
There is no heat, no open flame and no solvent in the process. The system is designed for cold application, which keeps installation work safe and convenient on site and removes the fire risk that comes with hot-pour compounds and torch work.
Product Advantages That Matter on Site and in Service
Cold application, safe handling. Installation is carried out at normal temperature. Field crews mix and pour, and the working environment only needs to be dry — a real advantage in compact trenches, cable chambers and tower bases where hot work permits are difficult to obtain.
High elongation, high strength. The cured elastomer delivers elongation at break of 200% or more with tensile strength of at least 1.20 MPa for Part A and 1.5 MPa for Part B. That combination lets the seal absorb thermal expansion, cable movement and mechanical shock without cracking or pulling away from the joint body.
Cold and heat resistance, lasting durability. The formulation is built to resist aging across the temperature swings that cable accessories face in service. Part B is rated to remain crack-free after low-temperature exposure, so the material performs in climates ranging from cold northern winters to hot, humid coastal and desert conditions.
Electrical insulation. Volume resistivity is specified at 1.0×10^10 ohm·cm. Dielectric breakdown strength reaches 20 kV/mm or higher for Part A and 15 kV/mm or higher for Part B, matching the electrical demands of high-voltage joint insulation.
Moisture and water blocking. The cured compound shows no penetration under a 0.3 MPa water pressure test held for 30 minutes. Water absorption is held to 4% or lower. For an underground or submerged joint, this is the property that decides whether the accessory survives its design life.
Flame-retardant grade available. Alongside the standard SY product, Shangyu supplies a flame-retardant version of the high-voltage cable joint sealant, formulated with the same cold-application process and the same elongation, heat resistance and aging profile.
Technical Profile at a Glance
Both products are manufactured to published enterprise standards — Q31/0120000518C001-2017 for the standard grade and Q31/0120000518C002-2017 for the flame-retardant grade — and the production system operates under the GB/T 19001-2016 / ISO 9001:2015 quality management framework marked on every pail.
Key figures buyers can plan around: Shore A hardness 50±10 for Part A and 50±5 for Part B; non-volatile content of 96% or higher in Part B; surface drying time within 12 hours; and a tack-free time within 180 minutes for Part A. Product literature lists a 12-month shelf life from the date of production when stored in a cool, well-ventilated warehouse, away from direct sunlight and rain. The material is classified as non-dangerous, stable, non-flammable and non-explosive, and can be transported as ordinary goods — a practical point for distributors managing freight and customs documentation.
Where the Material Performs
Shangyu sealant is used wherever a high-voltage cable joint must be insulated, encapsulated and protected against water ingress. Typical applications include power cable intermediate joints and terminations, prefabricated and cold-shrink cable accessory assemblies, transition joints between different cable types, cable joints in ring main units and switchgear enclosures, and sealing work in substations, tunnels, offshore and coastal installations. Because the material cures in place and conforms to the geometry of the shell, it fills voids that pre-formed parts cannot reach.
Installation discipline is simple but critical: mix thoroughly until the A and B components are uniform, keep the joint area dry during application, and reseal any unused Part A immediately so it does not cure in the container.
Manufacturing Capability and Partner Network
Hunan Shangyu Waterproof Material Co., Ltd. is a specialist manufacturer of high-voltage cable joint sealant, combining production, sales and research and development in one company. The business was established in October 2018 in the Liling Economic Development Zone, Hunan, after relocating from Shanghai, and operates with a registered capital of RMB 10 million. Drawing on years of experience in high-voltage cable joint sealing materials, the company studied the design concepts of well-known Japanese, American and German brands and adapted them to the practical requirements of individual customers — including the demand for products that hold up across widely differing regional climates.
That work has earned the trust of cable accessory manufacturers and utilities. The company currently supplies dozens of listed companies, among them Changlan Electric, Hanhe Cable, Yongjin Electric Power, Ankao Technology, Zhongtian Technology and Woer Heat-Shrinkable Material. Finished products are exported to the United States, India, Ukraine, Saudi Arabia and countries across Africa.
What Cable Accessory Buyers Should Evaluate
The global shift toward underground distribution, renewable energy connections and grid reinforcement is pushing demand for cable accessories that can be installed faster and last longer. Buyers comparing sealants should look past the price per pail and check four things: whether the material is genuinely cold-applied, whether the elongation and tensile figures support the movement expected in the joint, whether water-blocking performance is documented under pressure, and whether the supplier can hold consistent quality across repeat orders. Shangyu addresses each of these through published standards, batch-level quality control under an ISO 9001 framework, and a formulation developed over years of direct cooperation with cable accessory producers.
Partner With Hunan Shangyu
Whether you manufacture cable accessories, distribute electrical materials, or specify sealing compounds for utility projects, Hunan Shangyu Waterproof Material Co., Ltd. welcomes the opportunity to discuss your requirements, provide product documentation and supply samples for evaluation. The company's approach is summed up in its own operating principle: survive by quality, develop by efficiency.
Contact details
Company: Hunan Shangyu Waterproof Material Co., Ltd.
Address: Beside Guoci Road, Liling Economic Development Zone, Hunan, China
Postal code: 412200
Contact: Mr. Huang Sandi
Mobile: 13386069160
Tel / Fax: 0731-22971118
Email: 249150783@qq.com
Website: http://www.shangyu-waterproof.com/
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