Flame retardant and smoke inhibition properties of microencapsulated ammonium polyphosphate on polyvinyl chloride

In this study, a network compound (HP-DP) was produced by polymerization of phosphonitrilic chloride trimer (HCCP) and p-phenylenediamine (PPD), and microencapsulated ammonium polyphosphate (APP) to create flame-retardant APP@HP-DP, which was then incorporated into polyvinyl chloride (PVC) to prepare PVC composites. Adding APP@HP-DP flame retardant to PVC composites enhanced carbon yield, thermal stability and increased LOI of the composites from 23.1 ​% to 28.6 ​%. With 9.5 ​wt% APP@HP-DP, the peak heat release rate (PHRR) and peak smoke production rate (PSPR) dropped by 47.2 ​% and 23.2 ​%, respectively, compared to the original PVC composite. Mechanical property tests showed no change in tensile strength or elongation at the break for PVC composites with APP@HP-DP addition. Therefore, the addition of APP@HP-DP to PVC composites has significantly improved its flame retardancy and smoke suppression without affecting its mechanical properties, which can effectively reduce the potential danger of fire.