Abstract
The combination of synergistic agents with intumescent flame retardants (IFRs) is an excellent strategy for the development of high-performance flame retardant composites. Zirconium-based compounds are multifunctional materials with applications in various fields. In this study, zirconium-based compounds were synthesized and then combined with an IFR composed of ammonium polyphosphate (APP) and tris (2-hydroxyethyl) isocyanurate (THEIC) to prepare flame retardant high density polyethylene (HDPE) composites. α-Zirconium phosphate (α-ZrP) and two organic–inorganic hybrids (zirconium organophosphonate), Zr-ATMP and Zr-PA, were prepared using amino tri (methylene phosphonic acid) (ATMP) and phytic acid (PA), respectively, and their thermal, mechanical and flame retardant properties were characterized by thermogravimetric analysis, tensile test, limiting oxygen index (LOI) measurement and cone calorimetry test. The results showed that the LOI value of HD/IFR/Zr-ATMP composite reached a maximum of 26.2% using 25 wt% of flame retardant containing 3 wt% of Zr-ATMP. Of the three zirconium-based compounds, Zr-ATMP and α-ZrP can reduce the peak heat release rate compared with the composite containing only IFR. However, zirconium-based compounds showed no significant improvement of tensile strength.
Highlights
Polymer/nanosheet composites have gained a growing interest in material science due to their unique properties such as high thermal stability, excellent gas barrier properties, and low ammability
With zirconium-based compounds leads to only a marginal increase in T50%. This suggests that the use of the intumescent flame retardants (IFRs) based on ammonium polyphosphate (APP)/tris (2-hydroxyethyl) isocyanurate (THEIC) can delay the degradation of the polymer and improve the thermal stability at high temperature in the oxidative environment
The results suggest that the use of zirconium-based compounds as synergistic agent leads to a decrease in the R values compared with the composite containing only IFR, suggesting the formation of char with a higher graphitic degree
Summary
Polyethylene (PE) is an important commodity plastic with excellent properties such as light weight, excellent electrical insulation, high chemical stability, and ease of processing. A-ZrP shows a catalytic carbonization effect in PP composites containing classical APP/PER based IFR system.[14] To further improve the catalytic carbonization effect of a-ZrP, a macromolecular charring agent decorated with a-ZrP (ZrP-dMCA) was synthesized and combined with APP to prepare ame retardant PP composites.[15] Zirconium phosphate showed a synergistic effect with ammonium hydroxide (ATH) in EVA composites[16] and LDPE/EVA blend.[17] During the combustion, ablative reassembling of the phosphate layer may occur on the surface of the polymer matrix, which can act as a physical barrier to heat and oxygen. Zirconium organophosphonates are important inorganic–organic hybrids synthesized by combining the metal framework with organo– phosphonic linkage These materials have been widely used in catalysis, ion exchange and adsorption due to their excellent properties such as good thermal stability, large surface area, and variability of acidity. Volatile gaseous products were analyzed by thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR), and the tensile properties of the composites were investigated
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