Regulation of Thermal Degradation and Char Evolution of Polypropylene by Core–Shell MF@β-CD and Amino-Modified Attapulgite

In this work, a core–shell flame retardant (MF@β-CD) was prepared by coating β-cyclodextrin (β-CD) with melamine-formaldehyde (MF) resin through in situ polymerization. Amino-functionalized attapulgite (ATP-NH 2 ) was also prepared via silane modification. MF@β-CD and ATP-NH 2 were incorporated with piperazine pyrophosphate (PAPP) to fabricate flame-retardant PP composites through melt blending. The incorporation of MF@β-CD and ATP-NH 2 improved the fire performance and thermal stability of PP composites. The PP composite containing the MF@β-CD/ATP-NH 2 system exhibited a limiting oxygen index (LOI) of 33.8% and achieved a UL-94 V-0 rating. Compared with neat PP, the peak heat release rate and total smoke production decreased by 91.9% and 87.7%, respectively. Thermal analysis and char characterization suggested that the MF@β-CD/ATP-NH 2 system promoted the formation of a more continuous and stable char layer during combustion. The MF shell contributed to improved interfacial compatibility between β-CD and the PP matrix, while ATP-NH 2 helped maintain the integrity of the char structure. This work provides a feasible approach for improving the fire safety and condensed-phase stability of PP using bio-based flame-retardant components. Graphical Core–shell structured MF@β-CD was prepared via in situ polymerization and combined with amino-modified attapulgite (ATP-NH 2 ) and piperazine pyrophosphate (PAPP) to synergistically modify polypropylene (PP). The optimized composite achieved a limiting oxygen index (LOI) of 33.8% and a UL-94 V-0 rating. The incorporation of ATP-NH 2 resulted in a distinct lamellar stacking structure on the char residue surface, with the layered silicate sheets of ATP-NH 2 uniformly embedded in the organic char matrix. This enhanced the structural stability and thermal shock resistance of the char layer, preventing its cracking and peeling during high-temperature combustion.