PETpla.net Insider 04 / 2018

BOTTLE MAKING 30 PET planet Insid er Vol. 19 No. 04/18 www.petpla.net www.npeguestpass.org/588580 Visit us at Booth S15089 Free Ticket at: Infrared lamps The lamps them- selves consist of tungsten filaments sealed in quartz tubes. Quartz is transpar- ent to infrared radiation and can withstand the high temperatures that the lamp generates. The filament temperature determines the wavelength emitted (Table 4.1). The tubes are filled with halogen and an inert gas to avoid oxidation and black- ening of the tube as well as lowering the operating temperature to about 800°C (1472°F). Lamp emission peaks at 1200nm, which is the optimum for PET pro- cessing (Chapter 6) (Fig. 4.4). Figure 4.4 Typical infrared lamp. Photo courtesy of Philips. Pinch sections of the lamp, where the tungsten filament connects to the elec- trical supply, must be kept below 350°C (662°F), otherwise the molybdenum film at the contacts starts to oxidise and the pinch may actually crack, causing the lamp to leak. Most ovens have blowers at the back of the lamps accomplish- ing this task and also monitor the tem- perature with spe- cial thermocouples. Operating Percentage Respective Voltage (V) Temperature (K) Temperature (°C) Temperature (°F) 40 88 1800 1527 2780 70 154 2000 1726 3140 100 220 2600 2327 4220 Table 4.1 Relationship between operating percentage, used Voltages, and temperature output of a typical infrared lamp