As we all know, cable performance is determined by the oxygen index of the material it uses, and the higher the oxygen index, the better the flame retardant performance of the flame retardant cable. But at the same time will lose some of the other performance, increase the difficulty of operation and material costs.
The insulating materials used in flame retardant cables are mainly halogen-free flame retardant materials and halogen-containing flame retardant materials:
1, halogen-free flame retardant materials
Polyolefin is a halogen-free material consisting of hydrocarbons that break down carbon dioxide and water when burned, without producing significant fumes and harmful gases. Polyolefin mainly includes polyethylene (PE), ethylene acetate polymer (E-VA). These materials themselves do not have flame retardancy, the need to add inorganic flame retardants and phosphorus series flame retardants, in order to process into a practical halogen-free flame retardant materials, but because the molecular chain of non-polar substances lack of polar groups with hydrophobicity, and inorganic flame retardant affinity performance is poor, difficult to firmly combine. In order to improve the surface activity of polyolefin, surfactants can be added to the formulation, or polymers containing polar groups should be mixed in polyolefin, so as to improve the dosage of flame retardant fillers, improve the mechanical properties and processing properties of materials, and obtain better flame retardancy.
2, low smoke and low halogen flame retardant materials
Mainly for PVC and chlorosulfonated polyethylene materials. Add CaCO3 and A (LOH) 3 to the formulation of polyvinyl chloride. Zinc borate and MoO3 can reduce the HCL release and smoke content of flame-retardant polyvinyl chloride, thereby improving the flame retardancy of materials and reducing the emissions of halogen, acid mist and smoke, but may lead to a slight decrease in the oxygen index. When the amount of additives is large, it will also reduce the mechanical properties and electrical properties of the material.
3, halogen-containing flame retardant materials
Because of the decomposition and release of halogenated hydrogen when the combustion is heated, halogenated hydrogen can capture the active free radical ho root, so that the combustion of the material is delayed or extinguished, to achieve the purpose of flame retardant. Commonly used are PVC, neoprene, chlorosulfonated polyethylene, ethylene propylene rubber and other materials.
(1) Flame retardant polyvinyl chloride (PVC): Because of the cheap price of PVC, good insulation performance, good flame retardancy, is widely used in ordinary flame-retardant wire and cable. In order to improve the flame retardancy of PVC, Halogen flame retardants (10 brominated diphenyl ethers), chlorinated paraffins and efficiency flame retardants are often added to the formulation to improve the flame retardancy of polyvinyl chloride.
(2) Ethylene propylene Rubber (EPDM): Non-polar hydrocarbons, with excellent electrical properties, high insulation resistance, small media loss, but ethylene propylene rubber is flammable materials, it is necessary to reduce the cross-linking degree of ethylene propylene rubber, reduce the molecular chain disconnection caused by low molecular weight substances, in order to improve the flame retardant properties of the material. With the increase of the crosslinking degree of ethylene propylene rubber, the oxygen index increased. For example, the addition of a binder DC (p peroxide) to the formula, crosslinking auxiliaries taic (propylene cyanoacrylate), HVA (2N, n-benzene) can make the oxygen index increase the 10~15. Another method, the addition of inorganic flame retardant filler in ethylene propylene rubber can also increase the oxygen index. Generally commonly used fillers are a (LOH) 3, they can release crystalline water at high temperatures, a large amount of heat absorption to achieve flame retardant effect. However, a large number of fillers can reduce the mechanical and electrical properties of the material (such as decreased tensile strength and elongation). Therefore, the filler cannot exceed 150 copies. In order to achieve better flame retardant properties and maintain high mechanical properties, flame retardant fillers must be appropriately reduced and other flame retardants should be appropriately added.
Guangzhou Kehong sold heat shrinkage pipe, wire and cable, marking tube, heat shrinkage cable accessories, insulation wire and other products are in line with the relevant flame retardant environmental protection standards, UL, RoHS and other related certification.