Development of an advanced extrusion process for the reduction of volatile and semi-volatile organic compounds of recycled HDPE from fuel tanks

a Proplast, Via Roberto di Ferro 86, 15122 Alessandria (AL), Italy
b Disit, Università del Piemonte Orientale, Via T. Michel 11, 15121 Alessandria (AL), Italy
c F.lli Maris S.p.A., Corso Moncenisio 22, 10090 Rosta (TO), Italy
d DISSTE, Università del Piemonte Orientale, Piazzale S. Eusebio 5, 13100 Vercelli (VC), Italy

Plastic fuel tanks of vehicles are typically made by high density polyethylene (HDPE). The easiness of the
dismantling procedure from end-of-life vehicles and the intrinsic recyclability of HDPE allows them to be
accounted in principle in the “white list” of recyclable components. However, the strong contamination and odor
produced by the volatile (VOCs) and semi-volatile (SVOCs) organic compounds which have been absorbed
during the service life, drastically hinders the use of this end-of-life material. This aspect reduces its actual
recyclability, especially in higher-value applications. In this paper, we report a study on an innovative extrusion
process specifically designed for the stripping out of these organic contaminants. We also report an in-depth
analytic approach to identify their nature and fraction, as a way for ranking the effect of the different processing
conditions, which have been tested. The developed extrusion process uses a co-rotating twin-screw
extruder with degassing points and the injection of water as medium for desorbing the organic contaminants. The
analytic approach is based on headspace (HS) sampling associated to gas chromatography coupled to a mass
spectrometric detection (GC–MS). The multivariate approach of the Principal Components Analysis (PCA) was
applied on the entire dataset collected in the experiments, comprising the HS GC–MS data, the different process
parameters, and the mechanical and thermal data. As a result, the effect of the processing conditions and all the
organic contaminants present in the material were identified.
The developed extrusion process allows one to obtain a material with higher opportunity to be used in applications
which require enhanced performance, therefore, to be considered effectively recyclable, further
reducing the environmental impact of the end-of-life vehicles.

https://doi.org/10.1016/j.resconrec.2022.106691