Focke, Walter WilhelmMhike, WashingtonAsante, Joseph Kwaku OforiVan der Westhuizen, IsbeSnyman, Eduard JacobusAtanasova, Maria Todorova2026-02-112026-02-112025-11Focke, W.W., Mhike, W., Asante, J.K.O. et al. 2025, 'Fire performance of highdensity polyethylene sheets protected by a coating of plasticized polyvinyl chloride/modified-vermiculite', Journal of Fire Sciences, vol. 43, no. 5-6, pp. 291-307. DOI: 10.1177/07349041251345362.0734-9041 (print)1530-8049 (online)10.1177/07349041251345362http://hdl.handle.net/2263/108085Treatment of Palabora vermiculite with ammonium chloride or ammonium nitrate solutions caused the collapse of its structure, resulting in a reduction of the exfoliation onset temperature by more than 200°C. It is speculated that ammonium ions enter the hydrobiotite galleries as guest ions partially replacing the hydration water associated with the magnesium ions. The effectiveness of various modified vermiculite flakes as flame-retardant fillers was evaluated in laminates of high-density polyethylene and plasticized polyvinyl chloride/vermiculite-modified composites. The laminates comprised a high-density polyethylene sheet coated with polyvinyl chloride plasticized with 100 phr of a phosphate ester and filled with 40 phr vermiculite. Cone calorimetry results, measured at a radiant flux of 35 kW m−2, revealed that copper-ion modified vermiculite was the most effective flame-retardant additive. Laminates coated with polyvinyl chloride containing copper-ion-modified vermiculite exhibited a significantly reduced peak heat release rate of 64kW/m2, compared to 677kW/m2 for uncoated high-density polyethylene, demonstrating the potential of polyvinyl chloride–based flame-retardant coatings incorporating copper-ion-modified vermiculite for polyethylene.en© 2025 The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CC BY-NC-ND).VermiculiteIntercalationPolyvinyl chlorideExfoliationFire retardantThermomechanical analysisArticle