Ruenpakdan P.Srikhirin T.Mougin K.Valla M.F.Duquesne S.Amornsakchai T.Mahidol University2026-02-152026-02-152025-09-01Songklanakarin Journal of Science and Technology Vol.47 No.5 (2025) , 349-35701253395https://repository.li.mahidol.ac.th/handle/123456789/115067This study introduces an improved approach to enhance polypropylene (PP) flame retardancy. High intumescent flame retardant (IFR) loadings (30 wt%) often compromise PP's mechanical properties. The research investigates the impact of different mixing sequences, including novel direct and multi-step methods, on the flame retardancy and properties of PP/IFR-silane composites. Composites, prepared via a two-roll mill and melt-spun into fibers, showed significant performance improvement with a proper multi-step mixing sequence (M-1) where ammonium polyphosphate (APP) particles were pre-treated with silane. This approach allowed reducing IFR content from 30 wt% to 25 wt% while maintaining a V0 UL94-V rating. The M-1 sequence resulted in silane strongly coating APP and enhancing thermal stability because of reduced phosphorus degradation and strong C-N and C=N bond formation, indicating enhanced chemical interactions. Rheological analysis also showed greater early-stage char expansion, improving polymer protection during combustion. The PP/mod-IFR composite fibers exhibited homogeneous additive distribution and chemical compatibility.MultidisciplinaryArticleSCOPUS2-s2.0-105029500974