Identification of TPO blooming products after environmental exposure by Fourier-transform infrared (FTIR) & gas chromatography coupled to mass spectrometry (GC-MS)

A visible exudation of additives on Thermoplastic Polyolefin (TPO) compounds part surface called as blooming is always a challenge to Polypropylene (PP) compounders due the complex chemistry involved and reactions occurred under specific environmental conditions. Slip agents, light stabilizers, antioxidants, plasticizers, nucleants, pigments and fillers should keep certain stability under severe humidity, temperature and ultra violet (UV) light during an environmental aging. As expected, some of these additives should migrate to part surface to enable their functionality such as anti-scratch and light stabilizers. A faster migration leads to a blooming issue that promotes changes in gloss, tactual and appearance. An alternative to reduce the high migratory velocity of slip agents is to switch to high molecular weight as polysiloxane. The result expected with this change is to reduce blooming and enhancement of anti-scratch effect. However, this material has disadvantages regarding higher costs and more interactions with fillers. A new class of migratory slip agents based on Fatty Acid Amide was introduced in the market in 2014. This new material is migratory, vegetable-sourced, fully saturated and low blooming with high oxidative stability. Only point of concern that remains is the degradation observed due to the presence of metal oxides and contaminants in polymer base along with other additives. This paper aims to understand if blooming after high temperature and UV exposure is caused by the migration or degradation of slip agent by Fourier-Transform Infrared Spectroscopy (FTIR) and Gas Chromatography Coupled to Mass Spectrometry (GC-MS). A comparison between retention times of solvent containing extractible products from surface and backside after of a plastic plaque under severe temperature and UV exposure showed the delta and new molecules products generated by material degradation. The blooming observed from slip agent degradation forms a lower molecular weight product identified by chromatograms explaining the faster surface migration.