Wire and cable compounds

As European standards agencies have been updating their specifications to harmonize with European Union codes, one significant document to emerge has been that covering the insulation of single-core unsheathed electrical cables European Harmonization Document HD 22.9, published by CENELAC. 

In a fire, conventional PVC-based cables tend to produce black smoke and acid gas, arising from the use of plasticizers in the compound, and the presence of 

XU chuniad pivjH rtk s (liS EN M)H 11) Minimum tensile strength Minimum clongtiUon at break Hciit-iificdproiurtles (liS HN 60S /1  

Tensile strength maximum variation Klongation at break maximum variation Hiah-ti mpmitiirc properties (BS EN60811) I ressure test at 1 ()() C maximum penetration Hot set test at 2()0°C 30C, mechanical stress 0,20 N mm -Maximum elongation Maximum permanent elongation 

50 mm minimum 60% maximum 0.5% maximum 4.3 pH minimum lOpSmm maximum 

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Stabilizers. Lead stabilizers, particularly tribasic lead sulfate, is commonly used in plasticized wire and cable compounds because of its good nonconducting electrical properties (122). 

BeU Laboratories studied wire and cable compounds made of PVC or other halogen-based compounds vs halogen-free compounds and found that neither type of material presented a clearcut advantage in a fire, and that the halogenated compounds sometimes outperformed the nonhalogenated products in terms of creating less corrosion (193). 

Samples are normally exposed in a vertical orientation. If samples melt and drip, the heat can be redirected, by means of a system of aluminum foil mirrors, towards a horizontal sample. Many of the materials used for the series of experiments reported here melted excessively, away from the flame. Therefore, vertical burns were impossible for them, without distorting the data. All the materials investigated in the OSU RHR calorimeter, with the exception of the experimental flexible vinyl wire and cable compound, were, thus, exposed horizontally. 

Akron, Oh., ACS Rubber Division, 2004, Paper 19, pp.10, ISSN 1547-1977, 28cm, 012 NEED FOR LOW LEAD WIRE AND CABLE COMPOUNDS... 

Elexar Shellf linear EB wire and cable compounds... 

Cone calorimetry according to the ASTM E1354138 or ISO 5660139 standards are commonly used in the laboratory to screen flammability of materials by measuring heat release characteristics of the compound.116140 This device is similar to FPA but does not have the versatility of FPA. The cone calorimeter can determine the ignitability, heat release rates, effective heat of combustion, visible smoke, and C02 and CO development of cable materials. This test has been used extensively for wire and cable material evaluation. The microscale combustion calorimeter (MCC), also known as pyrolysis combustion flow calorimeter (PCFC), was recently introduced to the industry for screening heat release characteristics of FR materials.141142 This device only requires milligram quantities of test specimen to measure the heat release capacity (maximum heat release potential). Cone calorimetry and MCC have been used in product development for flammability screening of wire and cable compounds.118... 

Correlations were also established between UL 94, LOI, MCC, and cone calorimetry for both halogenated and nonhalogenated FR wire and cable compounds.149 The study (Figure 26.5) indicated that LOI has poor correlation with MCC parameters due to different flame combustion mechanisms in the LOI (incomplete combustion) and the MCC (forced complete combustion) tests. This correlation was improved by taking into account the burning efficiencies (i.e., combustion and heat transfer efficiencies) of the polymer compounds.150... 

FIGURE 26.5 Relationships between LOI and HRC for pure polymers and FR compounds. (From Lin, T.S. et al., Correlations between microscale combustion calorimetry and conventional flammability tests for flame retardant wire and cable compounds, in Proceedings of 56th International Wire and Cable Symposium, 2007, pp. 176-185.) The LOI-HRC relationship for pure polymers is obtained from the literature. (From Lyon, R.E. and Janssens, M.L., Polymer flammability, Final Report DOT/FAA/AR-05/14 May, 2005.)... 

As one can see from the above discussion, establishing correlation between bench-scale flammability and cable flame tests is a difficult task because of complicated chemical and physical processes involved in the burning and combustion of polymer materials and cables. Much research is still needed to understand fundamental processes governing the flaming combustion of wire and cable compounds in actual cable designs and cable bundles in a given environment. 

Hirschler, M.M. and Grand, A.F., Comparison of the smoke toxicity of four vinyl wire and cable compounds using different test methods Fire Mater., 1993, 17, 79-90. 

Cogen, J.M., Jow, J., Lin, T.S., and Whaley, P.D., New approaches to halogen free polyolefin flame retardant wire and cable compounds, in Proceedings of the 52nd IWCS/Focus International Wire Cable Symposium, Philadelphia, PA, 2003, pp. 102-107. 

Kaolin or clay, its more common name, is a naturally occurring mineral with the chemical formula Al Si, 0, (OH)5. It has a plate-like structure, and is refined and treated for specific uses, the largest of which is the paper industry. Metakaolin, produced by the dehydroxylation of kaolin, is often used to improve the electrical properties of PVC wire and cable compounds. At loadings of about 30 weight percent of the resin in a wire and cable PVC formulation, a doubling of the volume resistivity can be achieved. 

Among Ihe most commercially prevalent of these alloys is the PVC-NBR blends, the properties of which approach those of thermoplastic elastomers. Since nitiile elastomers are well established in conventional elastomer applications such as hoses, belts, and calendared goods, these alloys are found in many of the same fabricated products. NBR s are available in a variety of molecular weights, gel levels, comonomer rahos, and in physical forms ranging from powders to crumb rubber to slabs or bales of rubber. Alloys of these polymers are commonly found in automotive dashboard skins, wire and cable compounds, water and fuel hoses, and oil resistant boots and outerwear, among others (83). 

Formulations for Flame Resistant Wire and Cable Compound (157) ... 

Another company making moves in this field is MA Hanna, the US-based compoimder now part of PolyOne. Cable compounds became their first market-oriented product group, following an expansion of their German-based unit Melos Carl Bosch in Melle. This increased production of ECCOH brand of low smoke and zero halogen (LSOH) compounds was first made at Enviro Cable Compounds based in Oslo, Norway, another subsidiary. The company is possibly the leader in wire and cable compounds, after the in-house compounding of the cable makers themselves. 

CyberShield, Wire and cable compounds. Cybertech Polymers... 

Ester lubricants ate based frequently on pentaerythritol. The mixed mono- and distearate ester blend is particularly useful in wire and cable compounds for improving output and providing a smooth surface without bloom. It is often used in combination with low-MW PE wax in high-speed extmsions. Some use has also been made in rigid PVC profile extmsions, for similar reasons. The latter application has also seen use of pentaerythritol tetrastearate, a lubricant of somewhat lower cost than the mono/diblend. The tetrastearate is, however, more external in rigid PVC and thus more prone to bloom or deposit. 

Ross Wax No. 130, No. 145 and No. 165 are fully refined, high melting point petroleum waxes. They are widely used in the formulating of PVC and electrical wire and cable compounds, as well as other applications which require a lubricant which is effective in small quantities without danger of exudation. 

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