Poster: processing virgin and recycled polyolefins using TREF and GPC

By Laura Santonja, Esther López, Tonica González, Alberto Ortín. Polymer Char, Valencia, Spain.

Solving industrial challenges in processing virgin and recycled polyolefins using TREF and GPC separation techniques.

Abstract:

The variety of polymeric materials available on the market, from virgin to recycled (post-consumer or post-industrial), highlights the need for more advanced quality control methods. Conventional average properties such as melt flow index or density are not always sufficient to detect small compositional differences, which can significantly affect final applications. Such variations are often ignored during processing, but products manufactured under identical conditions may show considerable differences depending on the source material. This challenge is particularly critical for recycled plastics, where batch-to-batch variability makes it difficult to ensure consistency. In this context, identifying microstructural parameters that allow differentiation between materials provides added value by enabling their allocation to the most suitable applications and reducing performance risks.

This work presents case studies illustrating these issues. In one case, virgin HDPE from the same supplier and grade, intended for identical applications, exhibited significant differences in tensile impact performance after processing, with the presence of long-chain branching (LCB) identified as the main factor. In another case, three well-blended batches of post-consumer rPP from the same source and for the same purpose were analyzed, where differences of up to 45% in melt flow index were detected between the highest and lowest values, causing processing issues such as incomplete filling of large parts. To better understand these discrepancies, gel permeation chromatography (GPC) and temperature rising elution fractionation (TREF) were applied, revealing microstructural variations that explained the differences in performance.