Low smoke zero halogen

Material classification for cable jacketing

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Low smoke zero halogen or low smoke free of halogen (LSZH or LSOH or LS0H or LSFH or OHLS or ZHFR) is a material classification typically used for cable jacketing in the wire and cable industry. LSZH cable jacketing is composed of thermoplastic or thermoset compounds that emit limited smoke and no halogen when exposed to high sources of heat.[1]

Description

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The first commercial thermoplastic LSZH material for cable jacketing was invented by Richard Skipper in and patented by Raychem Corporation.[2] This invention resolved the challenge of incorporating sufficient inorganic filler, aluminium trihydrate (ALTH), into an appropriate thermoplastic matrix to suppress the fire and allow a char to be formed, which reduced emission of poisonous carbon gases and also smoke and carbon particles, whilst maintaining electrical insulation properties and physical properties required by the end application. The preferred inorganic filler to achieve flame retardation continues to be aluminium trihydrate (ALTH). In the event of a fire this material undergoes an endothermic chemical reaction

2Al(OH)3 &#; Al2O3 + 3H2O (180 °C)

that absorbs heat energy and releases steam when the compound reaches a certain temperature. It is critical that the decomposition of the polymer(s) used to carry the filler happens at approximately the same temperature. The steam disrupts combustion of the evolved gases and helps form a char layer that protects the remaining material and traps particulates. The high level of filler required (&#; 60%) also replaces the base polymer reducing the total amount of fuel available for combustion.

Low smoke zero halogen cable considerably reduces the amount of toxic and corrosive gas emitted during combustion. When burned, a low-smoke zero halogen cable emits a less optically dense smoke that releases at a lower rate. During a fire, a low-smoke cable is desirable because it reduces the amount and density of the smoke, which makes exiting a space easier for occupants as well as increases the safety of firefighting operations. This type of material is typically used in poorly ventilated areas such as aircraft, rail carriages, tanks, subsea and offshore installations, submarines or ships. It is also used extensively in the rail industry, wherever high voltage or track signal wires must be run into and through tunnel systems. The nuclear industry is another area where LSZH cables have been and will be used in the future. Major cable manufacturers have been producing LSZH cables for nuclear facilities since the early s. Construction of new nuclear plants will almost certainly involve extensive use of LSZH cable. This will reduce the chance of toxic gases accumulating in those areas where personnel are working and the lack of corrosive gases where there are computer controlled systems will reduce the possibility of wires being damaged by fire resulting in a short circuit fault.

Since the s, the wire and cable industry has been using low-smoke, low-halogen materials in a number of applications. The introduction of a thermoplastic LSZH extended its use to accessories such as heat shrink tubing, labelling and fixtures. The objective was to create a wire and cable jacketing system that was not only flame retardant but also did not generate dense, obscuring smoke and less toxic or corrosive gases. In the military field its introduction was accelerated after following the dense black smoke emitted from HMS Sheffield after being hit by an Exocet missile in the Falklands War. Several fires, such as the King's Cross fire in London that killed 31 people in London's underground in , increased the awareness of the contribution that wire and cable jacketing makes in a fire. As a result, there has been an increased use of LSZH cables. With an increase in the amount of cable found in residential, commercial and industrial applications in recent years, there is a greater fuel load in the event of a fire and LSZH systems have a major role to play in protecting the public.

Several standards describe the processes used for measuring smoke output during combustion. For military applications Def Stan 02&#;711 in the UK and ASTM E662 in the US which are both based on an ASTM STP No. 422 pages 166&#;204, modified by AMTE, Portsmouth in the UK[3] and superseded by E662 in the US. During these tests a specified material sample is standardised and then exposed to a radiant heat source; the optical density of the smoke given off is photometrically measured.[clarification needed] There are various means of measuring optical density: peak smoke release rate, total smoke released, and smoke density at various points and durations during the test. Results must be below a certain value and the material must pass the burn test in order for the material to be labelled as low smoke.

These tests are conducted under laboratory conditions and cannot claim to replicate the range of conditions expected in a real fire scenario. However they do provide a measure by which the potential smoke emission of materials can be assessed and dangerous materials identified before proceeding to further testing of preferred materials, if deemed necessary.

References

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1. ^MSS Fibre Glossary of Terms
2. ^

   United States Patent

3. ^

   A new approach to testing materials in the NBS smoke chamber, A. Routley and R. Skipper Fire and Materials Volume 4, Issue 2 June Pages 98&#;103

Model: SHD01-H-02

SUNUA, established in October , is a leader in the high polymer material industry, specializing in premium cable compounds like Low Smoke Zero Halogen (LSOH/LSZH) and flame-retardant polyethylene. We adhere to strict standards, including ISO and ISO, ensuring top quality from raw material procurement to delivery. Our professional laboratory complies with EU RoHS and REACH regulations, maintaining rigorous quality control. With 19 new invention patents and a network of over 500 global manufacturers, including Hengtong Group and Japan Furukawa Electric, we are recognized for our exceptional quality and service. Committed to innovation and customer satisfaction, SUNUA continues to develop advanced cable solutions that meet diverse industry needs.

 

1.Low Smoke ZERO Halogen LSZH Compound

Low Smoke ZERO Halogen Compound is based on polyolefin and contains special halogen-free flame retardants and smoke suppressants, which are processed by precise mixing with unique formulas.

 

2.Features:

- This flame retardant system has excellent zero halogen flame retardancy.

- When the plastic cable sheathing structure is designed reasonably, it can pass the A/B/C type combustion test and meet the light transmittance requirements.

- When burning, no halogen acid gas is released, the amount of toxic and corrosive gas is tiny, and the smoke concentration is shallow.

- This zero halogen flame retardant compound has excellent resistance to environmental stress cracking and good extrusion processability.

- We can also provide anti-termite, anti-rodent, and UV-resistant properties according to customer requirements.

 

3. Implementing standards: GB/T-, YD/T, IEC-359-

 

4. Uses

The SHD01-H-02 series of Low Smoke ZERO Halogen Compound not only have excellent low-smoke halogen-free flame retardant properties, but also have excellent extrusion processing properties. It can be extruded on an ordinary PVC extruder. As long as the cooling device is normal, the extrusion processing speed can be accelerated. The performance of the cable compound is better than similar products. The cable compound is suitable for occasions with high flame retardant requirements and low secondary hazards, such as: subways, ships, power stations, high -rise buildings, program-controlled switch rooms, computer rooms and various crowded public places. Suitable for optical cable and wire core working temperature 90 &#; low smoke halogen free flame retardant cable sheath. The cable compound is guaranteed to pass various beam burning tests and light transmittance tests.

 

5. Extrusion process

The drying temperature is 65°C and the drying time is at least 2 hours. It is advisable for the hot material to enter the extruder. It can be extruded by L/D18-25 extruder. When the screw compression is relatively low, the output is larger. Each zone of the extruder must have a cooling control system, and the melt temperature should not exceed 180 °C. Since the difference between the actual temperature of the melt and the indicated value of the temperature control table varies with the type of extruder, each user should select a suitable temperature according to the specific conditions of the extruder used. The following temperatures can be used as a reference for commissioning:

barrel position

zone 1

zone 2

zone 3

zone 4

nose and mode

Temperature(&#;)

125±5

135±5

145±5

155±5

160±5

Note: If the aluminum-plastic composite inner bag&#;damp proof fails, it should be dried before use. The drying temperature should be 65&#; and the drying time should be at least 2 hours. It is better for hot material to enter and leave the extruder.The machine head can be without a filter screen, or a filter screen below 60 mesh can be used; the mold can be extruded or tube type.

 

6. Packaging, transportation and storage

Packing: N.W: 25kg/kg bags with inner bag of aluminum-plastic composite vacuum moisture-proof bag and outer packing being made of kraft paper composite bag or woven bag.

Transportation and storage: It should not be exposed to the sun and rain during transport. It should be stored in a clean, cool, dry and ventilated warehouse. It should be handled with care.

 

7. Shelf life : 6 months

 

8. Physical and mechanical properties

Project name

Units

SHD01-H-02

Normal value

Typical Value

Density

g/cm³

&#;&#;

1.45

Hardness (Shore D1S)

 

&#;&#;

58

Tensile strength

MPa

&#;10.0

12.5

Elongation at break

%

&#;160

215

Want more information on lszh compound? Feel free to contact us.

Heat aging in air oven (100&#;×168h)

 

 

 

Aging Tensile Strength

MPa

&#;10.0

11.3

Rate of change in tensile strength

%

Max ±30

+15

Elongation at break after aging

%

&#;120

175

Change rate of elongation at break

%

Max ±30

-9.5

Environmental stress cracking resistance

h

&#;96

pass

Heat stress cracking

h

&#;96

pass

Low temperature impact embrittlement temperature

&#;

-25&#;

pass

Volume resistivity at 20&#;

Ω.m

&#;1.0×

3.1×

Dielectric Strength

MV/m

&#;18

37

Oxygen Index

 

&#;30

38.5

Smoke density is flaming

 

&#;100

84

Flameless

 

&#;350

340

Halogen acid gas release amount

mg/g

&#;5

0

PH value

 

&#;4.3

6.0

Conductivity

µS/mm

&#;10

0.3

Toxicity index

 

&#;5

0.5

 

For more information about Low Smoke Zero Halogen Materials, click on the link to contact our product specialists.