In this study, cerium based DOPO derivative (Ce@DDP) was synthesized by hydrothermal method, and its effects on flame retardancy, thermal stability, and mechanical properties of intumescent flame retardant polypropylene (PP) are investigated. When addition of 17 wt% of intumescent flame retardants (IFR) and 1 wt% of Ce@DDP, the results indicate that the peak heat release rate (PHRR) and peak smoke production rate (PSPR) of the resulted PP composite is reduced by 62.0% and 42.3%, respectively. Meanwhile, the vertical burning rating reaches UL94 V-0, and the limiting oxygen index (LOI) is 33.8%. Furtherly, the Ce@DDP significantly improves the thermal stability and char formation ability of PP/IFR. Notably, Ce@DDP exhibits better synergistic flame retardant and mechanical strength for PP/IFR than CeO 2 . Finally, it was speculated that there was dilution effect and radical quenching effect in gas phase, and catalytic carbonization effect in condensed phase of IFR/Ce@DDP system, and the combined action of the these aspects led to high-efficiency flame retardant.DOPO derivative, flame retardancy, intumescent flame retardant, polypropylene, rare earth | INTRODUCTIONPolypropylene (PP) has excellent mechanical properties, high performance, easy processing and good chemical resistance. [1][2][3] It is widely used in automobile, wire, cable, electronic, electrical and building materials, etc. However, PP is a flammable material, it burns with flammable dripping and releases smoke and toxic gases, these disadvantages restrict its applications. Thus, the flame retardant research of PP is of great significance to expand its practical applications.Recently, intumescent flame retardants (IFR) have attracted more attention in flame retardant PP due to their advantages in terms of low toxicity, low smoke, and anti-dripping. 4 During combustion process, IFR undergoes a series of chemical reactions such as esterification, aromatic cyclization, expansion and curing to form an expanded char layer, which acts as a barrier and slows down the transfer of heat and substances. 5 Nevertheless, on the one hand, the traditional IFR has poor water resistance and is easy to migrate to the polymer surface during processing; on the other hand, the
Currently, intumescent flame retardants (IFR) are often used in the flame retardant modification of polylactic acid (PLA). Due to the high loading, it will weaken the mechanical properties of PLA. In this study, lamellar lanthanum-based DOPO derivative (La@DDP) is prepared by solution method, and it acts as a flame retardant agent was added into PLA with IFR. The results show that PLA composite passes the UL94 V-0 rating with a limiting oxygen index (LOI) of 32.0, in the addition of 4.5 wt% IFR and 1.5 wt% La@DDP. Moreover, the peak heat release rate (PHRR) and total heat release (THR) of the PLA composite reduces by 31.0% and 23.2% compared to pure PLA, respectively. IFR/La@DDP agents assign the PLA composite with excellent thermal stability and carbon-forming ability. Through the analysis of residual char, the synergistic flame retardant mechanism between IFR and La@DDP in PLA composite is discussed. Notably, the tensile strength and elongation at break of the PLA composites are only reduced by 4.03% and 9.51% compared to pure PLA. This work provides a novel lanthanum-based flame retardant agent for designing PLA composites with good fire safety and mechanical properties, and it will broaden the application range of PLA.
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