Impacts of multi-element flame retardants on flame retardancy, thermal stability, and pyrolysis behavior of epoxy resin

Zhou

Pan

et al. 2022

Abstact In this work, an economic and environmentally friendly phosphorus‐nitrogen‐based flame‐retardant containing benzimidazole structure and hydroxyl group (DOPO‐BHM) was successfully synthesized by a simple two‐step procedure. The as‐prepared DOPO‐BHM was characterized by 1H NMR, 31P NMR, and FTIR, and incorporated into epoxy matrix as co‐curing agent to remarkably improve the flame retardancy of epoxy resin (EP). When the amount of DOPO‐BHM in EP was 6% and the phosphorus content was as low as 0.408%, the EP/DOPO‐BHM composites achieved a high limiting oxygen index (LOI) of 32.7% and V‐0 vertical firing grade. Furthermore, the cone calorimeter (CC) test results showed that the values of total heat release (THR), heat release rate (HRR), total smoke production (TSP), and smoke production rate (SPR) of EP/6% DOPO‐BHM decreased by 12.9%, 28.5%, 30.0%, and 47.8% relative to EP, respectively, indicating that the modified EP had good performance of reducing heat release and inhibiting smoke release. In addition, FTIR, Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS) were carried on to understand the flame retardancy mechanism. The characterizations indicated that the flame retardancy effect of DOPO‐BHM was in both condensed and gaseous phase, and gaseous phase played a dominant role. In addition, the mechanical test results showed that the tensile strength, bending strength, and non‐notched impact strength of EP/6% DOPO‐BHM were improved to a certain extent. In summary, DOPO‐BHM could significantly improve the flame retardant effect of EP without loss of mechanical properties and reduce emissions of phosphorus and smoke.

Section: Introductionmentioning

confidence: 99%

Synthesis of low phosphorus flame retardant containing benzimidazole and hydroxyl and its application in reducing combustion smoke for epoxy resin

Zhou

Pan

et al. 2022

“…Whilst these studies addressed the limitations of APP to a certain degree, the flame retardancy of single phosphorus remains inadequate and therefore requires further enhancement. Hence, it is necessary to investigate on multielement synergistic flame retardants 20,21 …”

Section: Introductionmentioning

confidence: 99%

POSS‐modified ammonium polyphosphate for improving flame retardant of epoxy resins

Feng

et al. 2022

An innovative phosphorus‐silicone flame retardant (KAPP‐OGPOSS) was prepared by grafting octa (propyl glycidyl ether) polyhedral oligomeric silsesquioxane (OGPOSS) on ammonium polyphosphate (APP) through silane coupling agent (KH‐550). The chemical structure, morphology, flame retardancy, and mechanism of the obtained materials were comprehensively investigated. TG results demonstrated that EP with 15 wt% KAPP‐OGPOSS produced a char residue of 42.6% at 700°C, which is three times that of pure EP. The flame retardant tests showed that the limiting oxygen index value of EP/15 wt% KAPP‐OGPOSS was 30.6% (67.7% higher than that of neat EP) and its UL‐94 grade reached to V‐0 rating. Cone calorimeter testing indicated that the incorporation of 15 wt% KAPP‐OGPOSS to EP significantly reduced heat, smoke, CO, and CO2 release by 79%, 83%, 80%, and 82.5%, respectively. The modification of APP with OGPOSS was also beneficial for the improvement of the char yield and density of char. A flame retardant mechanism was revealed according to the investigation into the char residue. This modified approach provided an innovative yet practical means of enhancing the flame retardant properties of EP.

“…Phosphorus‐containing compounds have been extensively studied as promising, halogen‐free, additive flame retardants for epoxy resins 14 . The most popular trend is to collaborative multi‐component systems to improve the flame retardant efficiency, 15,16 for example, phosphorus‐containing compounds combined with other element, such as nitrogen, silicon, sulfur, and boron, can effectively enhance their flame retardants properties and expand the scope of use 17–19 . For instance, the presence of N element can greatly strengthen the flame retardancy of phosphorus‐based flame retardants, as nitrogen‐containing compounds can act as foaming agents 17,20 .…”

Section: Introductionmentioning

confidence: 99%

Effects of flame retardants containing POC and PC structures on the flame retardant properties of epoxy resin

Zhao

et al. 2022

So far, discussions on the effects of elements on flame retardant properties have been widespread in flame retardant‐related fields, but reports on the effects of specific structures on flame retardant properties are rare. In this work, two novel phosphorus‐nitrogen flame retardants were synthesized from diphenylphosphinyl chloride and diphenyl chlorophosphite. It was proved that the POC structure of the DOAT flame retardant is beneficial to form a more stable carbon layer with high phosphorus content and reduce the total amount of smoke, while the PC structure of DPAT flame retardant is conducive to produce a large amount of phosphorus‐containing substances in the gas phase, while the phosphorus content in the residual carbon is very low. Therefore, the DOAT flame retardant mainly plays a flame retardant role in the condensed phase. The DPAT flame retardant mainly plays a flame retardant role in the gas phase. The flame retardant action mechanism of the combustion process was also investigated by using scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and Thermogravimetric analysis/infrared spectrometry (TG‐IR).