What is the chemical composition of LSZH?

The application of cable in life is more and more extensive, in increasing Highrise buildings, using increasing cable, and common cable does not have fire resistance, once Highrise buildings or public place presence of fire, the cable of burning will produce a large amount of hazardous and noxious substances, become people's killer, the flame resistant cable that adopts mica tape to be wound around needs multiple wraps in process of production, due to the restriction of processing condition, often easily cause seam lap place to occur defect, mica tape embrittlement after burning, easily come off, cause fire-resistant weak effect, being difficult to provides safety control for people.

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Summary of the invention

Technical problem to be solved by this invention is to provide that a kind of flame retardant properties is good, with low cost, ratio of briquetting is high, uses the formula of safe material, i.e. a kind of formula of low-smoke halogen-free cable line sheath material.

Technical problem to be solved by this invention realizes by the following technical solutions:

A formula for low-smoke halogen-free cable line sheath material, this formula comprises EVA, PE, aluminium hydroxide, magnesium hydroxide, oxidation inhibitor, coupling agent, silicone masterbatch, lubricant, compatilizer, black masterbatch, the shared mass percent of described each component is as follows:

The shared best in quality per-cent of described each component is as follows:

The performance of described each component and effect are as follows:

EVA: i.e. ethylene-vinyl acetate copolymer, owing to having introduced Vinyl Acetate Monomer in ethylene-vinyl acetate copolymer molecular chain, thereby reduce high-crystallinity, improve snappiness, shock resistance, filler intermiscibility and heat seal performance.

PE: i.e. polyethylene, because of polyethylene nonpolarity, so there is the electrical property excellence that dielectric loss is low, dielectric strength is large.

Aluminium hydroxide: aluminium hydroxide can not only be fire-retardant as fire retardant, and can prevent from being fuming, do not produce dropping, do not produce toxic gas.

Magnesium hydroxide: magnesium hydroxide is a kind of novel filled-type fire retardant, during by decomposes, discharge in conjunction with water, absorb a large amount of latent heat, reduce synthetic materials that it the fills surface temperature in flame, there is the polymer unwinds of inhibition and produced inflammable gas is carried out to cooling effect.Decomposing the magnesium oxide generating is again good refractory materials, also can help to improve the fire resistance of synthetic materials, and the water vapour that it is emitted simultaneously also can be used as a kind of smoke suppressant.

Oxidation inhibitor: in the time that it only exists on a small quantity in polymeric system, just can delay or suppress the carrying out of polymkeric substance oxidising process, thereby stop the aging of polymkeric substance and extend its work-ing life, " anti-aging agent " is otherwise known as.

Coupling agent: in plastics compounding, improve a kind of plastics additive of the interface performance of synthetic resins and inorganic filler or strongthener.Claim again surface-modifying agent.It can reduce the viscosity of molten synthetic resin in plastic working process, improves the dispersity of weighting agent to improve processing characteristics, and then makes goods obtain good surface quality and machinery, heat and electrical property.

Silicone masterbatch: in silicone masterbatch, content of siloxane is higher, the viscosity of material is just larger, is more not easy to disperse during for plastics.The content of siloxanes and molecular weight do anti-wear agent compared with Gao Shike and use.

Lubricant: internal lubricant and polymkeric substance have good consistency, it plays a part to reduce force of cohesion between polymer molecule in polymkeric substance inside, thereby improves the internal friction heat-dissipating of plastic melt and the mobility of melt.

Compatilizer: compatilizer increases the consistency of two kinds of polymkeric substance, makes it bonding force between two kinds of polymkeric substance and increases, and forms stable structure, makes disperse phase and external phase even, i.e. compatibilized.Why compatilizer can make the polymer-compatible of two kinds of different in kinds, is because have the cause that can carry out with two kinds of polymkeric substance respectively physics or chemically combined group in its molecule.

Black masterbatch: black masterbatch is the most frequently used a kind of Masterbatch in plastic cement processing, by a high proportion of pigment or additive and thermoplastic resin, the plastic colorant forming through good distribution, its selected resin has good wet and dissemination to tinting material, and be colored material and there is good consistency.

The invention has the beneficial effects as follows: the present invention have flame retardant properties good, manufacture simple, ratio of briquetting is high, do not produce the advantages such as pollutent after calcination; improve the quality of cable sheath material; flame retardant of plastic performance, wear resisting property and ageing resistance are improved; protect the healthy of environment and people, the use of the modern life preferably.

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Material classification for cable jacketing

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

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

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

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