High Performance Recycling of Polymers by Means of Their Fluorescence Lifetimes*

Abstract

Technical polymers could be identified by means of their remarkably strong auto fluorescence. The time constants of this fluorescence proved to be characteristic for the individual polymers and can be economically determined by integrating procedures. The thus obtained unequivocal identification is presented for their sorting for recycling. Furthermore, polymeric materials were doped with fluorescent dyes allowing a fine-classification of special batches.

Improved High Performance Recycling of Polymers by Means of Bi-Exponential Analysis of Their Fluorescence Lifetimes

“…The majority of the fluorescence emission extends in the visible at short wavelengths. The fluorescence decay can be mainly described with a first-order exponential function and the lifetime τ can be precisely determined and is characteristic for the polymeric material [13]. The special advantage of first order is the independence of the time constant as well from the initial intensity as the starting time of the measurement.…”

“…The doping of polymers with fluorescent markers [10] and their re-identification by the spectral resolution of their fluorescence in combination with a binary coding is described in preceding papers [11] [12], however, a secure pre-treatment of the polymers is a prerequisite for such methods. The use of the remarkably strong autofluorescence of polymers [13] is an attractive alternative because no pre-treatment is necessary and even the workup of deposited material will become possible.…”

Classification of plastic materials by imaging laser-induced ablation plumes

“…However, this technique is quite sensitive to the color (dependent to the additives) of the plastics as well as their surface contamination [7]. More recent developments explored the auto fluorescent property of some polymers or fluorescence emission from doping fluorophores [2,8,9]. The lifetime of the excited fluorescence is thus used as the indicator of the polymeric material [10,11].…”

“…Classification with the electrostatic property of polymeric materials has been described [1]. Optical methods are generally considered as the basis of more stable and efficient separation technologies [2]. More specifically, near-infrared (NIR) spectroscopy determines the molecular structure of a polymer by detecting the reflected or transmitted radiation [3][4][5][6].…”

Sauber recycliert

“…So klingt die Eigenfluoreszenz von Luran nach einer pulsförmigen Anregung mit einer e‐Funktion erster Ordnung ab (Abbildung 2). Abbildung 3 zeigt, wie stark sich individuelle Zeitkonstanten τ des Fluoreszenzabklingens verschiedener Polymere unterschieden 3. Der Exponentialverlauf ist für eine Detektion besonders interessant, denn unabhängig von der Anfangsintensität oder vom Beginn der Messung ergibt sich immer dieselbe Zeitkonstante (ähnlich beim radioaktiven Zerfall); dies vereinfacht den Messvorgang und erhöht die Messsicherheit.…”