RESUMO
Intumescent flame retardants (IFRs) are mainly composed of ammonium polyphosphate (APP), melamine (ME), and some macromolecular char-forming agents. The traditional IFR still has some defects in practical application, such as poor compatibility with the matrix and low flame-retardant efficiency. In order to explore the best balance between flame retardancy and mechanical properties of flame-retardant polyformaldehyde (POM) composite, a biobased calcium magnesium bi-ionic melamine phytate (DPM) synergist was prepared based on renewable biomass polyphosphate phytic acid (PA), and its synergistic system with IFRs was applied to an intumescent flame-retardant POM system. POM/IFR systems can only pass the V-1 grade of the vertical combustion test (UL-94) if they have a limited oxygen index (LOI) of only 48.5%. When part of an IFR was replaced by DPM, the flame retardancy of the composite was significantly improved, and the POM/IFR/4 wt%DPM system reached the V-0 grade of UL-94, and the LOI reached 59.1%. Compared with pure POM, the PkHRR and THR of the POM/IFR/4 wt%DPM system decreased by 61.5% and 51.2%, respectively. Compared with the POM/IFR system, the PkHRR and THR of the POM/IFR/4 wt%DPM system were decreased by 20.8% and 27.5%, respectively, and carbon residue was increased by 37.2%. The mechanical properties of the composite also showed a continuous upward trend with the increase in DPM introduction. It is shown that the introduction of DPM not only greatly reduces the heat release rate and heat release amount of the intumescent flame-retardant POM system, reducing the fire hazard, but it also effectively improves the compatibility between the filler and the matrix and improves the mechanical properties of the composite. It provides a new approach for developing a new single-component multifunctional flame retardant or synergist for intumescent flame-retardant POM systems.
RESUMO
Ammonium polyphosphate (APP) was successfully modified by a titanate coupling agent which was compounded with benzoxazine (BOZ) and melamine (ME) to become a new type of intumescent flame retardant (Ti-IFR). Ti-IFR and CaCO3 as synergists were utilized to modify polyoxymethylene (POM), and the flame-retardant properties and mechanism of the composites were analyzed by vertical combustion (UL-94), limiting oxygen index (LOI), TG-IR, and cone calorimeter (Cone), etc. The results show that Ti-IFR can enhance the gas phase flame retardant effect, while CaCO3 further strengthens the barrier effect in the condensed phase. When they were used together, they can exert their performance, respectively, at the same time showing excellent synergistic effect. The FR-POM composite with 29% Ti-IFR and 1% CaCO3 can pass the UL-94 V0 level. The LOI reaches 58.2%, the average heat release (Av HRR) is reduced by 81.1% and the total heat release (THR) is decreased by 35.3%.
