Phenolic prepreg waste as functional filler with antioxidant effect in polypropylene and polyamide-6

Milled phenol-formaldehyde glass-fibre scrap (prepreg) was mixed with polypropylene (PP) and polyamide-6 (PA6). The oxidation induction time (OIT) of PP/prepreg composite measured by both chemiluminescence (CL) and Differential Scanning Calorimetry (DSC) was significantly longer than the oxidation induction time of unstabilised base PP. In addition, mechanical testing showed that the prepreg filler stabilised both PP and PA6 towards oxidation during long-term accelerated ageing. Headspace-gas chromatography/mass spectrometry (HS-GC/MS) showed that PP/prepreg composites emit somewhat larger amounts of volatile compounds compared to the reference PP/glass fibre composites, while the amount of volatile components emitted from PA6/prepreg composites was similar to the reference PA6/glass fibre composites. The new prepreg composites could have potential in thermally demanding applications especially if a secondary phosphite stabiliser is added to further increase the oxidative stability through synergy effects.