The influence of processing on the mechanical properties and emissions of a recycled polyolefin
Höftberger Thomas (1)*, Burgstaller Christoph (1)
(1) Transfercenter fuer Kunststofftechnik GmbH - Upperaustria - Austria
Recycled plastics contain volatile compounds from materials degradation as well
as from other sources, besides monomer and oligomer residues from the
polymerisation process. These volatile compounds cause smell and emissions,
which have a negative impact on materials quality. For some applications, e.g. for
automotive interior, smell and emissions are critical, thus limiting the use of
recyclates there. A degassing step in a co-rotating twin screw extruder while is a
possible way to reduce these emissions. Therefore, the aim of this work was to
investigate the influence of melt processing on the mechanical properties and the
emissions of a recycled post-consumer polyolefin mixture. Different screw
configurations, process parameters and degassing variations, also with additives
to improve degassing, are used. The influence of the process on the emissions
was tested by headspace gas chromatography (VDA 277). Also, tensile and
impact properties were recorded to see if there is an influence of the processing.
Also Oxygen induction time was evaluated to check for the degradation of the
stabilizer during the process. These results were compared with the ones for
virgin polypropylene.
The first results show that the emissions can be reduced to one third of the
untreated recyclate with the degassing process. The sum of the emissions and
mechanical properties show some dependence on different screw configurations,
process parameters and degassing methods. Further steps are to investigate the
emission testing method, especially the influence of sample preparation and test
parameters, more in detail and to validate these results.