Nanoscale chemical imaging of rubber/PE/PP recycled blends using tapping-mode AFM-IR

Abstract

Polyolefins such as polypropylene (PP) or polyethylene (PE) are among the most produced plastics in the world, and their efficient recycling is thus of great interest. One option to reduce the costs of the recycling process could be to reduce the amount of sorting to include polymers such as PE and PP in the same final recyclate. It is known, that the nanoscale structure and chemical composition of a polymer has an influence on its bulk properties. Typically used methods to investigate this include SEM, TEM, and AFM, however, these methods either require tedious sample preparation and/or provide no specific chemical information at the nanoscale. In this work, we use for tapping mode AFM-IR for the nanoscale analysis of recycled polymer blends. AFM-IR is a combines the chemical information provided by IR spectroscopy with the nanoscale resolution achieved by AFM. We analyse a commercially available PE/PP/rubber blend derived entirely from post-consumer waste. In addition to the detection of polyamide and other polymeric particles in the micro and nano scale size, the distribution of the rubber at the interface of the PE and PP phases was also imaged. This latter result could be obtained with the help of a gaussian mixture model applied to the IR images obtained and is in agreement with both AFM-IR full spectra obtained in the same area, as well as with reference TEM measurements. Thus, we believe AFM-IR could be valuable addition to routine nanoscale polymer measurements.