[ schedules and in-house ] | INPLASTICS
For years PVC is one of the most used widely materials in many plastic items as well as in Wire & Cables. During the last decade a strong pressure evolved to move from PVC to Halogen Free Flame Retardant (HFFR) compounds for environmental, economical and safety reasons. In the event of fire PVC develops dark smoke and toxic/corrosive emissions, dangerous for human beings and industrial installations. Specifications for the newly developed HFFR products were established to cover the severe legislation favoring an extended use of HFFR vs. PVC. This trend is even further boosted when the copper price rises quickly as during this period of time, because the price gap between PVC and HFFR compound is minimized compared to the overall cost of the cable.
Market overview
The worldwide market of Low Voltage Industrial Cables, up to 1 kV, and Building Wire, up to 750V, is higher than 25 billion €. For this family of cables with its many applications flexibility and flame retardancy are key requirements as defined both in specifications and in local standards. The general design of a cable includes the copper conductor and a compound for
• insulation
| - | silane crosslinked PE for 1kV cable, 90°C as rated temperature
| | - | flexible PVC for 750V cable, 70°C as rated temperature
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• jacketing
| - | flexible PVC or HFFR compounds.
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Although PVC compounds currently still represent the majority in this market because of the good cost/performance ratio, PE based compounds show double digit growth rates. When the consumption increases over 3000-5000 tons/year, most cable manufacturers are going to become vertically integrated, including the facilities for making their own compounds.
Technical overview
The major challenge in replacing flexible PVC is to develop an HFFR compound with the following characteristics:
• fitting the technical requirements, specifically with respect to mechanical properties and flame retardancy,
• good processability, both during the compounding and extrusion
• cost competitive
In order to fulfill the above mentioned items, different technical solutions have been identified in the technical literature. The polymer is selected within the family of low crystalline polymers to improve the flexibility and the possibility to introduce a large amount of inorganic fillers in order to achieve the HFFR performance. A typical HFFR formulation contains 30 % - 35 % polymer, 60 % - 65 % filler and a few percent additives, including a grafted polymer to enhance bonding between the polymer matrix and the inorganic fillers. Purely polyolefinic polymers like m-PE plastomers are interesting but lack price competitiveness. Ethylene Vinyl Acetate (EVA) copolymers are widely used in many commercially available HFFR compounds, often in combination with aluminium trihydrate (ATH) as a filler. However, this EVA/ATH combination has a strong limitation in production, because of the low decomposition temperature of ATH (typically 180°C) resulting in low output, both in compounding and extrusion.
The use of magnesium dihydrate (MDH) as a filler allows to reach higher temperatures during processing (i.e. > 280°C according to the different commercial grades). Precipitated MDH is suited for the more demanding HFFR compounds, whereas the extremely price competitive grinded MDH derived from the natural mineral brucite is mainly used in commodity HFFR compounds.The combination EVA/MDH cannot fully exhaust the increasing output of polymer/MDHcompounds because EVA starts to decompose at ca. 220°C into corrosive by-products. Conversely, the use of EBA/MDH compounds with ethylene butyl acrylate (EBA) copolymers perfectly suited for high filler uptake due to their polar nature and low crystallinity and having decomposition temperatures > 300 °C allows to fully realize the maximum output. At the same time EBA/MDH compoundsare much more price competitive than plastomer/ MDH compounds due to the price advantage of EBAs towards plastomers.
LUCOBIT AG offers two types of ethylene butyl acrylate copolymers (Lucofin® 1400HN and Lucofin® 1400MN) and a Maleic anhydride (MAH) grafted variation of Lucofin® 1400MN (Lucofin® 1492). Wire and cable manufacturers and wire and cable compounders, respectively, already use these products in HFFR compounds, especially in combination with MDH.
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![[ Applications ] Replacement of PVC by
HFFR compounds in Wire & Cables](http://www.lucobit.de/icoaster/files/cms__applications_replacement_of_pvc_by_hffr_compounds_in_wire_cables__2.png)
