About
Product
Service
News
Contact Us
CN

News

Professional manufacturer and service provider specializing in the production and sales of wires and cables and accessories

Company News

Trends

Causes of uneven and bulged cable insulation surface (II)

Release time：

2023-02-13

source：

network

The common two-step silane crosslinked polyethylene is prepared by grafting silane with PE to produce crosslinkable PE (material A for short). In order to accelerate its crosslinking reaction, a masterbatch containing catalyst (material B for short) is prepared, and then materials A and B are uniformly mixed in a certain proportion. After extrusion molding, they are crosslinked in warm water. The main causes of insulation core quality problems caused by material stability are:

3. Material stability

(1) The components of cross-linked polyethylene insulating material are mixed unevenly. Because material A contains cross-linking agent and a small amount of antioxidants, if the antioxidants are not stirred evenly during the production process, the more concentrated antioxidants will be heated and vaporized after the insulating material is extruded by the extruder at high temperature, forming bulges in the insulating layer;

(2) The cross-linked polyethylene insulating material is improperly stored. The silane cross-linked polyethylene material will be crosslinked slowly at room temperature even if no catalyst is added. This is because the material contains a small amount of water (about 50 × 10-4%). If it is high temperature and wet during storage, the surface of extruded insulating layer will be not smooth. Recommended product: flame-retardant cable

4. Cooling process

In addition to the factors of extrusion temperature, extrusion speed, cross-linking speed and material stability, the cooling process after extrusion of crosslinked polyethylene from the die also has the following factors that may cause the surface quality problems of the insulation core:

(1) There are bubbles on the surface of the cable. When the cable enters the water, if there are bubbles on its surface, there will be "small pits" after cooling at this location. This is because the bubbles wrap the air on the insulation surface, and the cooling speed of the part covered by the bubbles is slower than that of the part in contact with the water. The reason why bubbles adhere to the cable surface is generally that the circulating water for cooling enters the water tank at a high speed and the water flow is fast. The high speed water flow brings air into the water, and part of the air attaches to the cable surface, forming bubbles;

(2) Before entering the cooling water, there are water droplets splashing on the cable surface. The part in contact with the water is cooled and contracted first, while the part in contact with the air is still at high temperature. Due to the difference in cooling speed, the surface of the insulated wire core is uneven.

Causes of uneven and bulged cable insulation surface (I)

How to select heat-resistant wires and cables

Causes of uneven and bulged cable insulation surface (I)

How to select heat-resistant wires and cables