Synergistic flame retardant linear low-density polyethylene based on piperazine pyrophosphate and melamine cyanurate

Linear low-density polyethylene (LLDPE) combined with the piperazine pyrophosphate (PAPP) and melamine cyanurate (MCA) was adopted to prepare the flame retardant LLDPE composite by melt blending. The research results showed that the PAPP/MCA mixture with a mass ratio of 4:1 presented the optimal flame retardant effect. With the 25 wt% addition amount, the LLDPE composite passed the UL-94 V-0 level (1.6 mm), and the limiting oxygen index (LOI) reached 29.4%. The peak of heat release rate (PHRR) decreased by 78.9% from 877.5 to 185.0 kW/m(2), which is attributed to the good synergistic effect between PAPP and MCA, forming the stable and compact char layer. Besides, the thermal behaviors were characterized through thermogravimetric (TG) analysis, and the synergistic mechanism was investigated by scanning electron microscopy (SEM), TG analysis-infrared spectrometry (TG-IR), and x-ray photoelectron spectroscopy (XPS). The results indicate that the good synergistic flame retardant effect can enhance the flame retardancy of LLDPE materials, and with the addition of MCA and PAPP, a flame retardant LLDPE composite with good thermal stability and mechanical properties can be prepared with no molten droplets on combustion, which provides a feasible solution for the application of high-performance halogen-free flame retardant LLDPE materials.

Automated summary

LLDPE was combined with PAPP and MCA to prepare a flame retardant LLDPE composite. The optimal flame retardant effect was achieved with a PAPP/MCA mass ratio of 4:1. The LLDPE composite, with 25 wt% addition amount, passed the UL-94 V-0 level and had a limiting oxygen index of 29.4%. The decrease in peak heat release rate by 78.9% was attributed to the synergistic effect between PAPP and MCA, resulting in the formation of a stable and compact char layer. Thermal behaviors were characterized through TG analysis and the synergistic mechanism was investigated using SEM, TG-IR, and XPS.