Effect of Microencapsulated Magnesium Hydroxide@Fly Ash on the Properties of Synergistic Flame‐Retardant <scp>PVC</scp> Materials

ABSTRACT Magnesium hydroxide (Mg(OH) 2 , MH) exhibits excellent flame‐retardant properties, but its poor interface compatibility with the resin matrices limits its application. In this study, β‐cyclodextrin (CD) was employed to coat MH, successfully preparing a microencapsulated CD‐MH flame retardant. Various mass ratios of CD‐MH m @FA n /PVC composites were further prepared. The maximum specific optical density (pkmax) of CD‐MH 0.2 @FA 0.1 /PVC composites decreased to 7.80%, the total smoke release (THR) reduced by 26%, and residual char increased to 28.76%. The LOI increased to 27.3%, reaching the HB grade. These results demonstrate that the synergistic effect of CD‐MH and FA promotes the formation of a continuous dense carbon layer in the PVC composite during combustion, significantly reducing heat and gas exchange, thereby enhancing flame retardancy. This study provides a reference for the collaborative design of flame retardants and their application in matrix resins with high flame‐retardant properties.