Headquarter
Brühler Straße 60
Basell Polyolefine GmbH – B 100
D-50389 Wesseling
Phone +49 (0) 22 36 / 3 78 59 0
Fax +49 (0) 22 36 / 3 78 59 99
pegon GmbH
The Polymer Source
Siemensstraße 18
D-50374 Erftstadt-Lechenich
T +49 (0) 22 36 / 3 78 59 70
F +49 (0) 22 36 / 3 78 59 99
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![[ Applications ] LUCOBIT resins and their use in wire and cable](http://www.lucobit.de/icoaster/files/cms__applications_lucobit_resins_and_their_use_in_wire_and_cable_.png) |
[ termine und intern ] | INPLASTICS
The use of plastics in the production of wire and cable is known for more than a century. Originally, the field was dominated by elastomers – first natural rubber chemically modified and later on synthetic rubbers. With the arrival of thermoplastics in the 1930s and their widespread use after the second world war, this group of materials also conquered the world of wire and cable and more by more replaced elastomers. The bulk of the thermoplastics used in wire and cable are with PEs and PVCs. The PEs offer excellent insulating ability with moisture and chemical resistance, flexibility, and light weight. Compared to the PEs, the vinyls are heavier, flexible, and are somewhat poorer insulators. Polyethylene belongs to the family of polyolefin resins. It is a simple polymer with repeating CH2CH2 structure. It is an incredibly versatile polymer with almost limitless variety due to copolymerization potential, a wide
density range, and a molecular weight that ranges from low to very high.
Ethylene is copolymerized with many nonolefinic monomers, particularly acrylic esters and vinyl acetate. All of the copolymers involve disruption of the regular, crystallizable polyethylene (PE) homopolymer, and as such they feature reduced yield stresses and moduli with improved low temperature flexibility. LUCOBIT AG offers two types of ethylene butyl acrylate copolymer (EBA): Lucofin® 1400HN and Lucofin® 1400MN.
Lucofin® 1400HN contains 16 % butyl acrylate and has a MFI of 1,4 g/10 min. Lucofin® 1400MN contains 17 % butyl acrylate and has a MFI of 7 g/10 min. The repeat unit of EBA copolymers is shown in Figure 1. At room temperature Lucofin® 1400HN / Lucofin® 1400MN have about the same flexibility as plasticized PVC and four times the flexibility of LDPE. (Fig. 2)
Both grades maintain their rubbery character without the use of plasticizers down to temperatures as low as -70°C. Typical wire and cable formulations include polymer modifications where Lucofin® 1400HN or Lucofin® 1400MN is blended with olefin polymers to yield a blend with a specific modulus, yet with the advantages of EBA’s polarity. The EBA presence promotes -among other advantages- toughness, flexibility, and greater filler acceptance.
Lucofin® 1492 is a Maleic anhydride (MAH) grafted variation of Lucofin® 1400MN. Due to the innovative reactive extrusion technology the extremely polar MAH in Lucofin® 1492 is more active than in comparable competion grades. Consequently, the use of Lucofin® 1492 in only small concentrations (ca. 5 %) in blend with Lucofin® 1400HN or Lucofin® 1400MN allows for highly filled formulations, such as HFFR compounds, with superior mechanical properties.
Viscosity
The viscosity of all thermoplastic melts is non-Newtonian, i.e., the viscosity is a function of the shear rate at which it is tested. For a given polyethylene resin, the relationship between its measured viscosity and the applied shear rate depends on its molecular characteristics. All polyethylene resins are shear thinning.
The general characteristics of the relationship of viscosity to shear rate are shown in Figure 3. Both viscosity and shear rate are plotted on logarithmic scales, reflecting the wide range of values encountered in commercial processes.
The response of the various types of polyethylene resins to increasing shear is a function of their degree of long-chain branching and molecular weight distribution.
Lucofin® 1400HN and Lucofin® 1400MN with their high degree of long-chain branching and broad molecular weight distribution show a shear thinning effect close to that of conventional LDPE. This guarantees a superior processabilty. Opposite to that finding LLDPEs -including plastomers- with their rather linear structure and narrower molecular weight distribution show a shear thinning effect to a much lesser degree. As a result, plastomers have only small processing windows prone to instabilities, such as melt fracture. This means, that Lucofin® resins will run smoothly during wire and cable extrusion.
Melting point and vicat temperature
Figure 4 shows the melting points and the vicat temperatures of Lucofin® 1400HN compared to an EVA with similar comonomer-content and MFI and compared to a plastomer with similar MFI. Both the melting points and the vicat temperatures show the highest values for Lucofin® 1400HN. This is a clear indication for the excellent maximum service temperature during end-usage of Lucofin® 1400 HN based compounds compared to competition grade based compounds. All wire and cable testing procedures involving elevated temperatures are therefore likely to be passed by formulations based on Lucofin® resins. |
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