What is the difference between low-smoke halogen-free wires and flame-retardant wires?

　　Low-smoke halogen-free wires and flame-retardant wires are two types of wires with different characteristics. The main differences are reflected in materials, combustion characteristics, environmental performance and application scenarios. The following is a detailed comparison:

　　1. Definition and materials

　　Low smoke halogen-free wires:

　　Definition: The insulating layer does not contain halogen (F/Cl/Br/I/At) and heavy metals such as lead, cadmium, chromium, and mercury, and does not produce toxic substances such as hydrogen halide and carbon monoxide during combustion. It is a high-safety and environmentally friendly wire.

　　Material: Halogen-free polymer (such as cross-linked polyethylene XLPE), inorganic flame retardants such as aluminum hydroxide/magnesium are added.

　　Flame retardant wires:

　　Definition: By adding a flame retardant (halogen-containing or halogen-free), the wire is flame-retardant, that is, the flame spread is limited after the fire source is withdrawn.

　　Material:

　　Halogen-containing flame retardant materials: such as polyvinyl chloride (PVC), neoprene rubber, etc., release hydrogen halide flame retardant when burned.

　　Halogen-free flame retardant materials: such as polyolefins (PE, EVA), phosphorus series flame retardants need to be added.

　　2. Combustion characteristics

　　Low smoke halogen-free wires:

　　Smoke volume: The amount of smoke during combustion is extremely low, with a light transmittance of ≥ 60%, ensuring visibility in a fire.

　　Toxicity: No toxic gases such as halogens are released, only a small amount of water mist is generated.

　　Flame retardancy: It has the ability to self-extinguish, but the flame retardant rating may be lower than that of halogen-containing flame retardant wires.

　　Flame retardant wires:

　　Flame retardant grades: divided into categories A, B, and C (GB/T 18380.3), with Class A having the strongest flame retardant performance.

　　Halogen-containing flame retardant wires: Good flame retardancy, but release toxic gases (such as HCl) when burned.

　　Halogen-free flame retardant wires: slightly less flame retardant, but low smoke content and non-toxic.

　　3. Environmental performance

　　Low smoke halogen-free wires:

　　Advantages: no halogen, low smoke, low toxicity, in line with environmental standards (such as ROHS), harmless to the environment and human body.

　　Application limitations: high cost, mainly used in places with high environmental requirements.

　　Flame retardant wires:

　　Halogen-containing flame retardant wires: poor environmental protection, generating toxic gases when burned.

　　Halogen-free flame retardant wires: Environmental protection is close to low-smoke halogen-free wires, but other flame retardants may be added.

　　4. Application scenarios

　　Low smoke halogen-free wires:

　　Mandatory scenarios: crowded public places (e.g. subways, airports, hospitals, schools).

　　Recommended scenarios: high-rise buildings, communication base stations, nuclear power plants, and other places with high safety requirements.

　　Flame retardant wires:

　　Ordinary flame retardant wires: homes, offices, and other general places.

　　High flame retardant wires: commercial buildings, industrial environments (e.g. chemical plants, oil platforms).

　　5. Industry standards

　　Low smoke halogen-free wires:

　　Halogen content: chlorine ≤ 50mg/g, bromine ≤ 10mg/g.

　　Combustion products: pH ≥ 4.3, conductivity ≤ 10 μS/mm (corrosion evaluation).

　　Light transmittance: smoke light transmittance ≥ 60%.

　　Flame retardant wires:

　　Flame retardant grade: GB/T 19666-2019 (A/B/C class), IEC 60332.

　　Test method: single vertical combustion, bundle combustion test.

　　summarize

　　Selection suggestion:

　　Preference is given to low-smoke halogen-free wires: public buildings, confined spaces, hospitals and schools, etc.

　　Flame retardant wires are suitable for general household or industrial environments (depending on the flame retardant grade).