Small core of piperazine/silane aggregation initiate efficient charring flame retardant effect in polypropylene composites

• Published in: Polymer degradation and stability Vol. 208; p. 110265
• Main Authors: Tang, Wei, Qian, Lijun, Prolongo, Silvia González, Wang, De-Yi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-02-2023
• Subjects: Aggregation charring effect; Flame retardant; Macromolecule charring agent; Polypropylene; Flame retardant; Aggregation charring effect; Macromolecule charring agent; Polypropylene
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/j.polymdegradstab.2023.110265

•Novel N/Si-macromolecules with varied aggregated core were synthesized.•Small core skeleton initiate charring flame retardancy with APP.•The aggregated structure of charring groups achieved an aggregation-charring effect.•Aggregation-charring effect strengthened flame retardancy of IFR in PP.
In this work, small amounts of piperazine/phenyl-silicon charring skeleton NSi-n (n=1, 2, 3) with varied aggregation degrees were respectively inserted into a hydrogen-bonded macromolecule fabricated with melamine and cyanuric acid, to prepare a series of nitrogen/silicon-based macromolecules MNSi-n (n=1, 2, 3), which achieved the efficient charring flame retardant effect of MNSi-n/ammonium polyphosphate (APP) in polypropylene (PP). Due to the formation of compact barrier char layers with rich phosphorus and silicon contents, (MNSi-n/APP)/PP performed higher limited oxygen index, glow-wire flammable index and UL 94 V-0 level, and also exhibited lower heat release rate. Comparatively, the melamine cyanurate macromolecule without NSi-n skeleton with APP only formed ineffective char layers and weaker flame retardancy. More importantly, the higher aggregation degree of piperazine and phenyl-silicon groups in MNSi-n apparently led to higher intumescent flame retardant efficiency. The high aggregation degree of NSi-n structure strengthened the full interaction between macromolecules MNSi-n and APP, thus forming compact char layers and increasing flame retardancy. It disclosed an effective way to enhance charring flame retardancy by small changes in molecular structure.
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