Epoxy resins (EPs) have superior physical and chemical features and are used in a wide range of applications in everyday life and engineering. However, its poor flame-retardant performance has hindered its wide application. Over the past decades of extensive research, metal ions have received increasing attention for their highly effective smoke suppression properties. In this work, we used an "aldol-ammonia condensation" reaction to structure the Schiff base structure, together with grafting using the reactive group on 9,10-dihydro-9-oxa-10-phospha-10-oxide (DOPO). Then, Cu 2+ was used to replace Na + to obtain DCSA-Cu flame retardant with smoke suppression properties. Attractively, DOPO and Cu 2+ can collaborate, thus effectively improving EP fire safety. At the same time, the addition of a double-bond initiator at low temperatures allows small molecules to form in situ macromolecular chains through the EP network, enhancing the tightness of the EP matrix. With the addition of 5 wt % flame retardant, the EP shows well-defined fire resistance, and the limiting oxygen index (LOI) reaches 36% with a significant reduction in the values of peak heat release (29.72%). In addition, the glass-transition temperature (T g ) of the samples with in situ formations of macromolecular chains was improved, and the physical properties of EP materials are also retained.
Epoxy resins (EP) have great chemical and physical properties, but their poor flame retardant properties have prevented their widespread use. To improve the flame retardancy properties of EP, an active P/N/Si flame retardant (KDC) containing a double bond was successfully synthesized in this work by using a typical aldehyde amine condensation reaction. This flame retardant not only can form a large molecule flame retardant in situ by double bond reaction and increase the tightness with EP matrix, but also has the advantage of P/N/Si three elements synergistic flame retardant, and at the same time play the flame retardant performance of each element, can achieve excellent flame retardant performance and low smoke and toxicity with low addition amount. Subsequently, the performance of the flame retardants was tested. When 7 wt% of KDC was added, the pHRR and TSR of the EP composites were reduced by 51.7% and 29.8%, respectively. More importantly, the addition of KDC inhibited the release of toxic fuels and smoke from EP, where the TSP values of EP/3-KDC were 18.14% below those of neat EP and increased the residual amount of charcoal, while the inhibition of CO and CO 2 release was particularly pronounced with the presence of KDC.
Epoxy resins (EP) have been commonly used, but their poor flame retardant properties have prevented their widespread use. In order to improve the flame retardant properties of EP, an organic-inorganic composite flame retardant (HKDC) containing multi-element P/N/Si was successfully synthesized in this work using a typical aldehyde amine condensation reaction. This flame retardant utilizes the synergistic effect of multiple elements to simultaneously perform the flame retardant function of each element, and it can achieve excellent flame retardant effect by using low addition amount in EP. At the same time, this flame retardant can not only reduce the migration of molecules through the structure of inorganic substances, but also the C = C reaction in EP can form large molecules and increase the compactness with the EP matrix. The flame retardants were then quantified by measuring their flame retardant properties, combustion behavior and thermal stability. When the flame retardant HKDC is added, the flame retardant performance of EP is improved and the vertical combustion test achieves a V-0 rating. Most importantly, the addition of flame retardant HKDC effectively suppressed the toxic gas and smoke emissions of EP, with TSP values much lower than those of pure EP, and CO and CO2 emissions were suppressed.
To gain insight into more about how flame retardants containing phosphorus, sulfur, and nitrogen affect epoxy resin (EPs), a multicomponent flame retardant (Sp-ACDH) containing P/N/S was synthesized from sodium p-aminobenzene sulfonate (Sp-A), cinnamaldehyde and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and applied to epoxy resin. Sp-ACDH enables the epoxy resin to achieve the desired flame retardancy. For example, with the addition of 10 wt% Sp-ACDH, the epoxy composite passed the UL-94 V-0 rating and achieved an LOI of 32.7%. Additionally, Sp-ACDH effectively slowed down EP’s ability to release heat, with EP-15 Sp-ACDH exhibiting a peak heat release rate (PHRR) that was 680 kW/m2 rather than pure EP’s 1204.4 kW/m2. Eventually, the samples were characterized using Scanning electron microscopy (SEM), Raman spectroscopy, and Thermogravimetric analysis-fourier transform infrared spectroscopy (TG-FTIR) spectra, and the samples were analyzed, it revealed that Sp-ACDH’s flame-retardant properties were active in both the gas and condensed phases.
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