The 39th International Conference of the Polymer Processing Society (PPS-39) was hosted by Uni versidad de los Andes and ICIPC and attended by nearly 435 participants from 41 countries. Besides traditional symposia about polymer processing, the PPS-39 program included four special symposia on Biopolymers, Biocomposites, and Bioprocessings; Circular Economy of Polymers; Degradation; and Biodegradation and Composting, and Polymers in the United Nations Sustainable Development Goals, for a total of 20 symposia. These proceedings contain papers from prominent professors, scientists, students, and engineers active in the field of polymer processing. These proceedings will be of interest to Researchers from academia and industry, students, and postdoctoral fellows