white paper Electron-beam crosslinking technology Edition 2013

Page 3 white paper Electron-beam crosslinking technology Content Introduction 4 History 4 Polymer material 5 Effect of electron-beam crosslinking 5 Equipment for electron-beam crosslinking 6 High voltage generator 7 Electron accelerator 7 Scanning system and window 8 Product handling system 8 Control system 8 Radiation shielding and personnel safety system 9 Process optimisation by three dimensional computer simulation 10 Accelerator 10 Handling 10 Applications of electron-beam crosslinked cables 11 Other applications of electron-beams 12 Properties of electron-beam crosslinked wires and cables...

Page 4 white paper Electron-beam crosslinking technology Introduction Modern product development requires technically advanced solutions. Wire and cable products are no exception. The environments where speciality cables are installed are hot, sometimes also very cold, chemically aggressive and mechanically challenging. The standard polymers used for cable insulations and sheaths rapidly reach the limits of their capabilities An attractive solution for these challenging applications is the crosslinking of standard polymers. The crosslinking process improves the properties of these materials to...

Page 5 white paper Electron-beam crosslinking technology Polymer material Electron-beam and chemical (continous vulcanisation or silane) crosslinking of standard polymer material lifts the performance of low cost material on levels which are prevailed by engineering or even by high performance polymer materials. In principle polymer material can be classified by three categories: standard materials (like PVC, PE, PP), engineering polymers (PA; POM; PMMA; OC) and high performance polymers (like PPS, PEEK, LCP). The standard polymer materials are used in large amount and the price is low, the high...

Page 6 white paper Electron-beam crosslinking technology Equipment for electron-beam crosslinking In electron-beam crosslinking the electrons are generated by a hot filament and then accelerated in a vacuum chamber by a high voltage. At the end of the vacuum chamber there is a thin titanium foil which the electrons pass through onto the product. Typical values of the high voltage for wire and cable are between 500 kV and 3 MV. Higher and lower voltages are used for other applications. The product is passed through the beam of electrons in a variety of ways to allow optimisation of the process....

Page 7 white paper Electron-beam crosslinking technology high voltage generator The design of the high voltage generator tends to depend on the energy (high voltage level) that the machine operates at. Lower energy machines tend to be based on fairly conventional transformer rectifier combinations operating at power line frequencies. As the energy increases higher frequencies are used in conjunction with capacitor coupling. These systems are available from various manufacturers in sizes up to 5 MV and 250 kW. high voltage generator electron accelerator The electron accelerator consists of an...

Page 8 white paper Electron-beam crosslinking technology Scanning system and window To allow the electron-beam to leave the vacuum and reach the product a thin (10s µm) titanium foil window is used. Some of the electron energy is lost to the foil so it is typically cooled with high velocity air. The electronbeam as generated has a typical diameter of 10 – 20 mm so to allow it to be distributed over the product area it is scanned using a magnetic field in the same way the spot was scanned in an old style television. Scan horn Product handling system There is a range of different product handling...

Page 9 white paper Electron-beam crosslinking technology Radiation shielding and personnel safety system When the electrons strike the product or parts of the product handling system a large number of x-rays are generated so the process needs to be enclosed in suitable radiation shielding. For smaller systems (up to 1 MeV) this shielding is often made of steel and lead and is part of the machine structure. For larger systems a separate concrete bunker is constructed. To ensure safety for the operators a multiple interlock system is used so that the accelerator cannot be operated when the access...

Page 10 white paper Electron-beam crosslinking technology Process optimisation by three dimensional computer simulation Today process parameters are in general generated using empirical data and analytical formulas based on very general one-dimensional (1D) depth dose profiles. These tools are not tailored to specific accelerator facilities and radiation processes, and neither consider the full three-dimensional (3D) problem nor time-dependency. For these reasons their validity must be checked for each product new product and the models as well as the machine parameters must be adjusted empirically...

Page 11 white paper Electron-beam crosslinking technology Applications of electron-beam crosslinked cables Electron-beam crosslinked products offer a huge variety of applications in severe and harsh environment and can be tailored by electron-beam crosslinking to meet the expectations of the various markets. Requirements of the railway industry • Fluid resistance • Reduced walls • Higher current load • Extended lifetime by improved ageing • Improved fire performance Requirements of the solar industry • UV resistance • Higher current load • Extended lifetime by improved ageing • Heat resistance...

Page 12 white paper Electron-beam crosslinking technology Requirements of the automotive industry • Fluid resistance • Reduced walls • Short circuit resistance • Heat resistance • Mechanical stress resistance Requirements for coil winding • Resistance against varnish • Short circuit resistance • Heat resistance • Mechanical stress resistance Other applications of electron-beams Electron-beams are used for many other applications besides crosslinking of wire and cable products. • Polymer modification: - Production of heatshrink tubing - Floor heating pipes - Production of shrinkwrap foils for...