The polyvinyl chloride insulated wires we use in our daily lives produce toxic gases when they burn, which can be harmful to our bodies.

But flame retardant wires have their own advantages for this situation, with special flame retardant and toxic smoke suppression properties, which are related to their materials.

Flame retardant wire has flame retardant, low smoke generation and toxic smoke suppression properties, except for the required property of 694:1990.

In the event of a fire, ordinary PVC-insulated wire releases smoke and toxic gases that are not only deadly but also impede rescue operations.

Materials for Flame Retardant Wires

The higher the oxygen index of the material used for flame retardant cable, the better the flame retardant performance, but as the oxygen index increases, some of the other properties are lost.

Such as the physical properties of the material and process performance has decreased, difficult to operate, while making the cost of materials increased.

Therefore, the oxygen index should be selected reasonably and appropriately. If the oxygen index of general insulation material reaches 30, the product can pass the test requirement of category C in the standard.

If the sheath material, filling materials are used in flame retardant materials, the product can meet the requirements of Class B and A.

Flame retardant wire and cable materials are mainly divided into halogen-containing flame retardant materials and halogen-free flame retardant materials.

I. Halogen-containing flame retardant materials

Due to the decomposition of hydrogen halide released when burning and heated, the hydrogen halide can capture the active radical HO root, thus delaying the combustion of the material or making the material burn.

Thus, the burning of the material is delayed or extinguished to achieve the purpose of flame retardant.

Commonly used materials include PVC, neoprene, chlorosulfonated polyethylene, ethylene propylene rubber, etc.

① Flame retardant polyvinyl chloride (PVC): Because of its cheap price, good insulation performance and flame retardancy, PVC is widely used in ordinary flame retardant wires and cables.

In order to improve the flame retardancy of PVC, halogen flame retardants (decabromodiphenyl ether), are often added to the formula

(2) chlorinated paraffin waxes and synergistic flame retardants to improve the flame retardancy of PVC.

Ethylene propylene rubber (EPDM): non-polar hydrocarbon, with excellent electrical properties.

high insulation resistance, low dielectric loss, but EPDM is a flammable material.

Must reduce the degree of cross-linking of ethylene propylene rubber, reduce the molecular chain break and the resulting low molecular weight material, in order to improve the flame retardant properties of the material.

As the cross-linking degree of ethylene propylene rubber increases, the oxygen index increases.

For example, adding crosslinking agent DC (P peroxide diisopropylbenzene), crosslinking auxiliary TAIC (triacryloyl cyanurate),

HVA-(2N, N inter-phenylene bimarimide) can make the oxygen index increase by 10-15.

Another method, the addition of inorganic flame retardant filler in ethylene propylene rubber can also make the oxygen index increased.

Generally commonly used fillers are A (lOH) (3) they can release crystalline water at high temperatures, a large amount of heat absorption and achieve flame retardant effect.

But a large number of fillers will make the mechanical and electrical properties of the material decline (such as tensile strength and elongation decline), so the filler can not exceed 150 parts.

In order to obtain better flame retardant performance and maintain high mechanical properties, it is necessary to properly reduce the flame retardant filler and properly increase the other flame retardants.

Second, low smoke and low halogen flame retardant materials

It is mainly for two kinds of materials, PVC and chlorosulfonated polyethylene. The addition of CaCO3 and A(lOH)3 in the formulation of PVC.

Zinc borate and MoO3 can reduce the HCL release and smoke emission of flame retardant polyvinyl chloride

This improves the flame retardancy of the material and reduces the emission of halogen, acid mist and smoke, but may cause a slight decrease in the oxygen index.

When the amount of additives is large, the mechanical and electrical properties of the material will also be reduced.

Third, halogen-free flame retardant materials

Polyolefin is a halogen-free material, consisting of hydrocarbons, decomposing carbon dioxide and water during combustion, without producing obvious smoke and harmful gases.

Polyolefin mainly includes polyethylene (PE), ethylene - vinyl acetate polymer (E-VA).

These materials are not flame retardant by themselves and require the addition of inorganic flame retardants and phosphorus series flame retardants to be processed into practical halogen-free flame retardant materials;

However, due to the lack of polar groups on the molecular chain of non-polar materials with hydrophobic

However, due to the lack of polar groups on the molecular chain of non-polar substances with hydrophobic properties, the affinity performance with inorganic flame retardants is poor, making it difficult to firmly bond.

In order to improve the surface activity of polyolefins, surfactants can be added to the formulation; or polar group containing polymers can be blended with polyolefins.

Thus, the amount of flame retardant filler can be increased to improve the mechanical properties and processing performance of the material, while obtaining better flame retardancy.