Role of Organo-Modifier and Metal Impurities of Commercial Nanoclays in the Photo- and Thermo-Oxidation of Polyamide 11 Nanocomposites

• Main Authors: Martina Ussia, Giusy Curcuruto, Daniela Zampino, Nadka Tzankova Dintcheva, Giovanni Filippone, Raniero Mendichi, Sabrina Carola Carroccio
• Format: Article
• Language: English
• Published: MDPI AG 2020-05-01
• Series: Polymers
• Subjects: PA11; montmorillonite; Cloisite® 30B; nanocomposites; photo-oxidation; thermo-oxidation
• Online Access: https://www.mdpi.com/2073-4360/12/5/1034

The photo-oxidative degradation processes of bio-based PA11 nanocomposites containing montmorillonite (MMT) and the organo-modified Cloisite^®30B were investigated to discriminate the influence of organo-modified components on the polymer durability. Indeed, despite the extensive studies reported, there are still ambiguous points to be clarified from the chemical point of view. To this aim, UV-aged materials were analyzed by Size Exclusion Chromatography (SEC), Inductively Coupled Plasma–Mass Spectrometry (ICP-MS) and Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS). This enabled determining changes in both chemical structure and Molar Masses (MMs) induced by light, heat and oxygen exposure. The addition of organo-modified nanoclays strongly affected the PA11 light durability, triggering the macromolecular chains scission due to the typical αH, Norrish I and II mechanisms. However, the main contribution in boosting the photo-oxidative degradation is induced by iron impurities contained into the clays. Conversely, thermo-oxidation process performed at 215 °C was unambiguously affected by the presence of the organo-modifiers, whose presence determined an enhancement of crosslinking reactions.