Polydispersity Analysis of Visbroken Polypropylene: Comparative Insights From Triple Detection Size Exclusion Chromatography and Rheological Crossover Modulus

ABSTRACT Visbreaking is a widely employed strategy to fine‐tune the molecular weight distribution (MWD) of polypropylene (PP), yet direct comparisons of polydispersity index (PDI) across analytical techniques remain limited. In this study, polypropylene homopolymer (H‐PP) powder was visbroken using varying concentrations of an organic peroxide (0 to 800 ppm), aiming to achieve high melt flow rate (MFR) grades while optimizing peroxide consumption. Molecular weight averages and polydispersity index were evaluated using triple detection size exclusion chromatography (SEC) equipped with infrared (IR5), online viscometer, and multi‐angle light scattering (MALS) detectors. Rheological crossover modulus measurements were used to estimate PDI independently. The SEC studies confirmed systematic chain scission with increasing peroxide concentration, reflected in declining M n and M w values. Notably, PDI trends from MALS closely aligned with rheological estimates across all peroxide levels, while IR5 and viscometer‐based values showed significant deviations. These findings demonstrate that MALS is a reliable SEC detector for detecting molecular weight distribution changes relevant to melt relaxation and processability. The study provides a framework linking chromatographic characterization with rheological behavior in polypropylene, offering a practical analytical pathway for industrial polyolefin evaluation.