A vanillin derivative P/N/S‐containing high‐efficiency flame retardant for epoxy resin

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Epoxy resin (EP) has excellent comprehensive properties, but its inherent flammability limits its further application in high‐end industries. The present study focuses on the preparation of an efficient phosphorus/silicon‐containing flame retardant for improving the flame retardancy and smoke suppression of EP. The intermediate product ED was first obtained by the addition reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) with eugenol, and then the target flame retardant DPSi‐ED was synthesized by the Williamson etherification reaction between ED and dichlorodiphenylsilane. The flame retardant was further incorporated into EP/4,4′‐diaminodiphenylmethane (DDM) system to prepare the modified epoxy thermosets. The flame‐retardant performance and mechanism were investigated by limiting oxygen index (LOI) test, vertical combustion test, cone calorimetry, thermogravimetric analysis‐infrared spectroscopy (TG‐IR), and so forth. At the same phosphorus content (0.5 wt%), EP/DPSi‐ED thermosets exhibited superior flame‐retardant properties to EP/ED thermosets. Moreover, EP/DPSi‐ED7 achieved a LOI of 35.3% and V‐0 rating in UL‐94 testing, and compared to EP/ED7, its peak heat release rate (pHRR) and total smoke production (TSP) were reduced by 31.5% and 10.9%, respectively. The phosphorus and silicon elements synergistically contributed to the formation of a stable char layer, which acted as a physical barrier to effectively enhance the flame‐retardant properties of the thermosets. Meanwhile, the incorporation of DPSi‐ED containing flexible SiO bonds and rigid DOPO groups to some extent also improved the mechanical properties of the cured EP. Hence, this study provides an effective strategy for the preparation of bio‐based phosphorus/silica‐containing high‐efficiency and smoke‐suppressing flame retardants.

Section: Introductionmentioning

confidence: 99%

A phosphorus/silicon‐containing flame retardant based on eugenol for improving flame retardancy and smoke suppression of epoxy resin

Quan

Lin

et al. 2023

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Construction of a hybrid flame retardant based on mesoporous silica for enhancing fire safety, smoke suppression, and mechanical properties of epoxy resins

Yue,

Shi,

Zheng

et al. 2024

In order to improve the fire safety of epoxy resins (EPs), the SBA‐15 based hybrid flame retardant (SNAZD) was synthesized via an organic–inorganic hybridization strategy of mesoporous silica SBA‐15. Relying on electrostatic interaction, the zinc amino‐tris‐(methylenephosphonate) (Zn‐ATMP) was successfully introduced into the pore channels of SBA‐15. Then, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) was successfully loaded into the pores of SBA‐15 under vacuum. The results show that the EP composites with the 5%SNAZD sample (sample EP‐5%SNAZD) showed a LOI value of 30.9% and achieved the vertical burning V‐0 rating. In comparison to EP, the peak heat release rate, peak smoke production rate, and production rate of CO of EP‐3%SNAZD were reduced by 32.2%, 31.9%, and 20.0%, respectively. This is due to the presence of Si, P, N, and Zn elements in the SNAZD, which promoted the generation of a high yield of dense char residue and inhibited the release of toxic gasses. And the impact strength and flexural strength of EP‐1%SNAZD were increased by 19.5% and 15.6%, respectively, and the E' of EP‐5%SNAZD increased by 49.1% when compared with the neat EP. This work provides a general strategy for the design of mesoporous hybrid flame retardant and creates additional opportunities for applications of EP.

Biobased Reactive Flame Retardant With the Phenylethylamine Structure for Enhancing Flame Retardancy and Mechanical Properties of Epoxy Resins

Ren,

Chen,

Hou

et al. 2024

A bio‐based reactive flame retardant (PVD) was synthesized using vanillin, phenethylamine, and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO). This study aimed to enhance epoxy resin's fire resistance and evaluate the strength of EP/PVD composites for eco‐friendly specialized applications. The chemical structure of PVD was confirmed using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. The effect of PVD on the curing kinetics of EP was studied using non‐isothermal differential scanning calorimetry (DSC). During combustion, PVD releases ∙PO2 and ∙PO radicals, which capture the active ∙H and ∙OH radicals generated during the combustion of EP. This results in a significant quenching effect, thereby achieving flame retardancy. EP with 7.5 wt% PVD and 0.49 wt% phosphorus (EP/PVD‐7.5) exhibited a V‐0 rating in UL‐94 vertical burning tests and a limiting oxygen index (LOI) of 32.4%. Additionally, compared to pure EP, EP/PVD‐7.5 showed a 41.7% reduction in the peak heat‐release rate during cone calorimetry tests. The dual‐phase flame‐retardant effect of PVD was confirmed by the analysis of the residual char and its pyrolysis behavior. Furthermore, EP/PVD exhibits superior mechanical properties and transparency compared to pure EP, indicating that PVD holds promise as a flame retardant for EP.