2024 AIChE Annual Meeting

Investigating the Effect of Plastic Additives on Polymer-Nanoparticle Interactions

Polymer upcycling is a more economically favorable method to tackle global plastic pollution compared to recycling, as it chemically alters plastics to create higher-value products. Many upcycling strategies involve polymeric reactions, driven forward by heterogeneous catalysis. These catalysts often use porous support materials, which are usually dense packings of inorganic oxide nanoparticles, to maximize catalytic surface area and improve reaction yield. However, the presence of various additives in plastics can lead to unexpected issues in such reactions. Additives, such as antioxidants, plasticizers, stabilizers and more, are added to plastics to enhance performance and prevent degradation, but some might bind strongly to the catalytic sites and render them inactive. Thus, it is important to study and quantify the effect of these additives on polymer-nanoparticle interactions to identify suitable support materials for these catalysts.

One method is to measure the polymer-nanoparticle contact angle. Silica nanoparticles, a common catalyst support material, are evenly coated on hydrogenated polycyclooctene (hPCOE) films, which is a model polymer for high density polyethylene (HDPE). The sample is then heated above the polymer’s melting point for a sufficiently long time to let the nanoparticles partially sink into the polymer film and equilibrate at the interface. The remaining height of a nanoparticle above the polymer interface is measured using atomic force microscopy (AFM), which is used to calculate the contact angle of the polymer on the nanoparticle. Various plastic additives are either incorporated into the hPCOE films or the silica nanoparticle suspension, and the contact angles are measured. We observe significant differences in polymer-nanoparticle interactions based on the presence of additives with different molecular structures. These findings provide insight on the effect of additives on polymer-nanoparticle interactions, helping us identify suitable support materials or surface modification techniques for polymer upcycling catalysts.