Liquid Crystals Recycling from End-of-Life LCD Displays

For several decades, Liquid Crystal Displays (LCDs) have been widely used in televisions, laptops, mobile phones, and other devices. Nowadays, considerable quantities of LCDs arrive to their end-of-life (EOL) phase, and are gathered as WEEE (Waste Electrical and Electronic Equipment), with strong economic and environmental impact. Liquid crystals (LCs) represent an important economic value of the recycling system of EOL-LCDs. In view of their technological and economic interest, this investigation is focused particularly on recycling of LCs molecules from EOL-LCD panels. At first, EOL-LCDs were subjected to a disassembly process for the separation of various valuable components. This process consists of an ordered dismantling including separating and recycling of electronic boards, lightning tubes that can contain mercury, metals, polymers, and other valuable parts. In a second step, LCs were extracted in an ultrasonic-activated organic solvent bath. The advantages of this extraction method lies in the speed of recovery of these molecules, and the low contamination effects. Therefore only few purification processes had to be performed to obtain high quality materials in high yield. Finally, the obtained LCs mixtures were characterized essentially by spectroscopic and chromatographic techniques, in order to determine their chemical, optical, thermal and dielectric properties. A study of the influence of adding diamond nanoparticles (DNP) at 0.05, 0.1 and 0.2 wt% to recycled LCs was also performed using dielectric spectroscopy.