POS9-1487
Composition-Dependent Thermo-Mechanical Degradation and Quantitative Degradation Indices of PP/HDPE Blends under Repeated Extrusion
Topic
S9. Polymer Technology for Sustainability
When and Where
Oct 1, 2026
08:30 - 09:30
Room 301 (Grand Ballroom)
Session Chairs
Jinkee HONG
Ki Su KIM
Presenter(s)
Sungwoong Choi (KITECH)
Co-Author(s)
Abstract
Polyolefins (PP and HDPE), the largest fraction of post-consumer plastic waste, have similar densities and molecular structures, making complete separation during sorting uneconomical; as a result, most post-consumer recycled (PCR) feedstocks are traded as PP/HDPE mixtures. As collection and reprocessing are repeated, thermo-mechanical degradation accumulates in these mixed recyclates, lowering mechanical properties and widening their variability, which has limited their adoption in high-value applications such as automotive, construction, and packaging. Reliable use and quality grading of recyclates require quantitative reference data on the rate and mechanism by which degradation proceeds as a function of composition, yet systematic studies spanning the full composition range remain scarce. In this study, virgin PP and HDPE were blended at various compositions and repeatedly extruded under fixed processing conditions to simulate the thermo-mechanical history accumulated during recycling. As the number of recycling cycles increased, changes in the chemical structure, thermal characteristics, rheological behavior, and mechanical properties of the samples were analyzed, in order to quantitatively evaluate composition-dependent degradation behavior. The resulting composition- and cycle-dependent property data are expected to serve as a quality-control basis for diagnosing the degradation state of incoming recyclates and assessing their remaining processing margin, thereby supporting high-value upcycling of mixed polyolefin recyclates and the growth of circular-economy materials industries
