The Effect of Paint Removal on Oxidative Induction Time of Thermoplastic Olefins

摘要

Thermoplastic olefins (TPOs) are used in various automotive applications such as bumper fascias, instrument panels and door panels. Since scrap is unavoidable in manufacturing these components, recycling of molding scrap is crucial for manufacturing facilities to optimize resin usage. In addition to using unpainted regrind, painted TPO can also be recycled via a paint removal process for reuse in the same component. Painted exterior bumper TPO fascia scrap can therefore be sent to recycling companies for recovery for use in closed-loop recycling. The paint removal process employed in this paper involves a chemical based system with temperature and pressure variation followed by a final extrusion/re-pelletization step. Evaluation of the resulting recycled material is crucial to ensure that no negative effects are incurred by way of the paint removal process. In addition to evaluating the resulting physical properties with the paint removed recycled material, chemical property changes need to be accounted for as well. Since the paint removal process is chemically based, it can potentially affect the various stabilizer packages added to the TPO materials. The Oxidative Induction Time (OIT) test allows for a qualitative analysis of the oxidative stability of the resulting paint removed materials. OIT data for various paint removed exterior TPO bumper fascia materials was obtained using a differential scanning calorimeter (DSC). The OIT data obtained revealed depletion of the heat stability of the various TPO materials as well as the effects of varying parameters in paint removal process. As a result, the OIT test method proved to be an effective as well as accelerated method of evaluating heat stability of paint removed recycled TPO.