Nanoscale chemical characterization of a post-consumer recycled polyolefin blend using tapping mode AFM-IR

• Published in: Analyst (London) Vol. 147; no. 16; pp. 3741 - 3747
• Main Authors: dos Santos, A. Catarina, Tranchida, Davide, Lendl, Bernhard, Ramer, Georg
• Format: Journal Article
• Language: English
• Published: London Royal Society of Chemistry 08.08.2022
• Subjects: Atomic force microscopy; Electron microscopy; Heavy metals; Infrared spectroscopy; Mechanical properties; Microscopes; Microscopy; Polyethylenes; Polymer blends; Polymers; Polyolefins
• ISSN: 0003-2654; 1364-5528
• DOI: 10.1039/d2an00823h

The routine analysis of polymer blends at the nanoscale is usually carried out using electron microscopy techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which often require several sample preparation steps including staining with heavy metals and/or etching. Atomic force microscopy (AFM) is also commonly used, but provides no direct chemical information about the samples analyzed. AFM-IR, a recent technique which combines the AFM's nanoscale resolution with the chemical information provided by IR spectroscopy, is a valuable complement to the already established techniques. Resonance enhanced AFM-IR (contact mode) is the most commonly used measurement mode, due to its signal enhancement and relative ease of use. However, it has severe drawbacks when used in highly heterogenous samples with changing mechanical properties, such as polymer recyclates. In this work, we use the recently developed tapping mode AFM-IR to chemically image the distribution of rubber in a real-world commercially available polyethylene/polypropylene (PE/PP) recycled blend derived from municipal and household waste. Furthermore, the outstanding IR resolution of AFM-IR allowed for the detection of small PP droplets inside the PE phase. The presence of micro and nanoscale particles of other polymers in the blend was also established, and the polymers identified. Tapping mode AFM-IR reveals the presence of contaminants, PP inclusions within the PE phase, and EPR rubber at the interphase between PP and PE in a real-world polyolefin recyclate.