For data center cables, rail transit cables, new energy system cables, and fiber optic cables, the most widely used material in the market today is low smoke zero halogen (LSZH) cable material.
LSZH materials are widely used because they produce low smoke, contain no halogen, are eco-friendly, and have good flame resistance. They have become an important direction in modern cable industry.
Among many performance items, the IEC 60332-3 bunched cable flame test is one of the key standards for checking the flame resistance of LSZH Jacket material.
For cable makers, whether the supplier material can pass the bunched cable test directly affects whether the final cables can be used in building wires, rail transit systems, communication cables, and fiber optic cables.
So, how do LSZH sheath materials pass the IEC 60332-3 bunched cable requirement?
In cable fire accidents, fire does not usually spread along a single cable. It often spreads fast along many cables in trays, shafts, or pipes.
So single cable tests can only show basic flame resistance, while bunched cable tests are closer to real use conditions.
IEC 60332-3 is not a single test. It is a full bunched cable flame test system. It installs many cables in a bundle in a fixed way and applies flame for a period of time. It then checks the flame spread behavior in fire conditions. After the test, the char height must stay within the standard limit to pass.
For LSZH sheath materials, passing IEC 60332-3 means not only good flame resistance, but also the ability to slow down flame spread and reduce fire risk.
The main evaluation items of the IEC 60332 bunched cable test include:
Flame spread height. After the test, the highest point of burned or charred area is measured. It must not exceed the set limit (usually based on 2.5 m or 3.5 m from the bottom of the sample).
After-flame behavior. After removing the flame, check whether it keeps burning, re-ignites, or causes drip ignition.
Char length and damage area. Record the char length of the jacket or insulation layer, melted area, and structure damage.
Dripping behavior. Although IEC 60332-3 is not as strict as CPR systems, it still checks whether burning droplets appear and whether they ignite cotton pads or other cables below.
LSZH sheath materials mainly use polyolefin as base resin, so they are also called LSZH flame retardant polyolefin materials.
Polyolefin has good electrical properties and good weather resistance, but it is a flammable material.
During burning, polyethylene and ethylene copolymers can produce many flammable gases, which help flame spread.
So to pass the bunched cable test, LSZH materials do not rely on base resin alone. They depend on a full flame retardant system design.
Today, LSZH sheath materials widely use aluminum hydroxide and magnesium hydroxide as main flame retardants.
When heated, these inorganic flame retardants absorb a large amount of heat and release crystal water, which reduces the surface temperature of the material. At the same time, the released water vapor dilutes oxygen and flammable gases in the burning zone, slowing down the burning process.
This heat-absorption mechanism is one of the core flame retardant principles of LSZH materials.
In real formulations, the filler content of flame retardants is much higher than normal polyolefin materials. High loading improves flame rating, but it also affects mechanical strength, processing, and surface quality.
For IEC 60332-3 testing, heat absorption alone is often not enough. So the material must also have good char formation ability.
During continuous flame exposure, the char layer formed on the cable surface can block heat and oxygen and prevent fire from spreading inward. So char formation plays an important role in bunched cable performance.
Good LSZH flame retardant polyolefin systems usually form a dense and continuous char layer during burning. This layer reduces thermal decomposition and lowers flammable gas release, improving overall flame resistance.
For large building cables, rail transit cables, and fiber optic cable jackets, the stability of char structure often decides the final test result.
Many cable companies find that even when using the same LSZH sheath material, different cable batches may still show different IEC 60332-3 results.
The reason is not only the material formula but also the processing process.
If there are problems such as uneven dispersion, voids, impurities, or surface defects during extrusion, these areas can become heat concentration points during burning. This will speed up material breakdown and help flame spread.
So, material producers must ensure good dispersion of flame retardants during compounding and extrusion, and also control volatiles, moisture, and impurities to achieve stable flame performance. For fiber optic cable jackets, because the thickness is thin, the processing quality has a stronger effect on final flame behavior.
For cable makers, choosing the right LSZH Jacket material is not only about flame resistance. It also affects production efficiency and product consistency.
Good LSZH flame retardant polyolefin materials must balance flame resistance, mechanical properties, and processing performance to ensure successful IEC 60332-3 test results.
Taking ANGREEN LSZH sheath series as an example, the products use a flame retardant polyolefin system and are suitable for communication cables, fiber optic cables, power cables, rail transit cables, and building wires. The materials have good flame resistance and stable processing performance and can provide solutions based on different cable standards.
Currently, ANGREEN New Materials can provide many LSZH sheath products, including LSZH materials for fiber optic cable jackets, rail transit cable sheath materials that meet EN 50264, power cable sheath materials that meet IEC 60502, LSZH flame retardant sheath materials that meet CPR B1ca, B2ca, Cca, Dca levels under EN 50575, LSZH materials that meet GB/T31247 B1 grade, and LSZH flame retardant polyolefin for communication cables. Based on different bunched cable requirements, flame retardant system design support can be provided to help cables meet IEC 60332-3 Cat.C, Cat.B, and higher levels.
For cable products that require flame resistance, low smoke performance, and long-term reliability, a stable LSZH material system is more effective than simply increasing flame retardant content to achieve stable bunched cable test results.
Q: Where can LSZH sheath materials for fiber optic cables be purchased?
A: ANGREEN provides LSZH sheath solutions for fiber optic cables, communication cables, power cables, building wires, and rail transit cables, and can support different flame rating requirements.
Q: What types of LSZH flame retardant polyolefin cables does ANGREEN provide?
A: ANGREEN LSZH materials can meet IEC60754, IEC60332-1, IEC60332-2, IEC60332-3, IEC60502, EN50575 CPR, GB/T31247, IEC60092, EN50264, EN50306 and other cable standards.
Previous
