It is of great interest and remains a challenge to simultaneously improve the compatibility and flame-retardant performance of lignin/epoxy resin (EP) composites. In this work, a polysiloxane-enwrapped phosphorus-containing lignin-based flame retardant (PHMS-lig-P) was prepared through reactions of lignin, PHMS and TCP to address this issue, with results showing significantly improved flame-retardant performance and comprehensive performance. The influence of PHMS-lig-P on the flame retardancy of EP was investigated by vertical burning test (UL-94V), limiting oxygen index (LOI), smoke density test and cone calorimeter (CC) test. The PHMS-lig-P/EP achieved a V-1 rating, and its LOI value increased to 25. 3%. The maximum smoke density (Ds, max) decreased by 83. 2%. Furthermore, pHRR, avHRR, and MLR of PHMS-lig-P/EP decreased by 37. 5%, 22. 6%, and 25. 1%, respectively. In addition, the evolved gases and char residues were studied using thermogravimetric analysis coupled with Fourier transform infrared spectrometry (TG-FTIR) and scanning electron microscopy (SEM). The results certified the flame-retardant mechanism of PHMS-lig-P was attributed to the synergistic effect of lignin, phosphonate, and polysiloxane, producing a compact and cohesive char layer that acted as a physical barrier, limiting the transfer of heat and oxygen and preventing the spread of pyrolysis volatiles and flammable gases. Moreover, the flame-retarded epoxy resin possessed good dispersion uniformity in mechanical properties and insulation performance, showing good applicability.

In this work, melamine cyanurate (MCA) and boehmite (BM) were used to improve the flame retardancy of polyamide 6 (PA6), and a series of BM/MCA/PA6 composites were prepared. The effects of MCA and BM on flame retardancy, combustion and thermal degradation behavior of 15-MCA/PA6 and BM/MCA/PA6 composites were investigated by methods of limited oxygen index (LOI) measurement, vertical burning test, cone calorimeter test and thermogravimetric analysis (TGA). The results showed that MCA can effectively flame retardant PA6. When 15 wt% MCA was added to PA6, composite sample (15-MCA/PA6) possessed LOI value of 30. 4% and V0 rating (3. 2 mm) in UL-94 test. By replacing part of MCA with BM, with an increase of BM amount, the flame retardancy of BM/MCA/PA6 composite was better at first, but then got worse, and mechanical properties were increased. The flame retardancy, thermal stability and combustion behavior data of 4-BM/11-MCA/PA6 composite were better than 15-MCA/PA6 composite, indicated that appropriate amounts of MCA and BM in PA6 had synergistic flame-retardant effects. The time to ignition (TTI), the peak of heat release rate (PHRR), total heat rate (THR), total smoke release /total mass loss (TSR/TML) and fire performance index (FPI) of 4-BM/11-MCA/PA6 composite were 53 s, 322. 5 KW. m−, 2, 79. 8 MJ. m−, 2, 98. 3 g−, 1 and 0. 16 s. m2. kw−, 1, respectively. The LOI value of 4-BM/11-MCA/PA6 composite was 33. 8% with V0 rating (2. 0 mm) in UL-94 test.

In the present work, the hexabromocyclododecane and the antimony trioxide were introduced into the bisphenol A epoxy resin to improve its flame retardancy. The effects of hexabromocyclododecane and antimony trioxide on flame retardancy of bisphenol A epoxy resin were estimated according to ASTM D2512-95 (2008). The specimen cured by T-31, with the addition of hexabromocyclododecane, did not show any flash and explosion during the 20 times of mechanical impact, whereas slightly empyreumatic scent was detected. The explosion was observed for the other specimens. The resin particles on the surface of the specimen after the mechanical impact were more than that before the mechanical impact, which was attributed presumably to the mechanical impact at the low temperature resulted in the crushing of the resin materials. It also indicated that bisphenol A epoxy resin cured by 593 with antimony trioxide at the low temperature had low flexibility. The XPS analysis confirmed that the surface of the specimen observed explosion was readily reacted with liquid oxygen. The O/C ratios of the specimen cured by T-31, with the addition of hexabromocyclododecane, before and after the mechanical impact were statistically approximate to 0.223 and 0.238, respectively, which revealed that the specimen was compatible with liquid oxygen.

The current study is directed towards the evaluation of thermal stability and flame retardancy of the epoxy resin hexaglycidyl cyclotriphosphazene (HGCP) cured with 4, 4′,-methylene dianiline (MDA) and its polymer composite reinforced with bisphenol-A diglycidyl ether (DGEBA) by means of experimental, computational, and statistical approaches. The thermal properties of the polymer materials DGEBA-MDA (M1), HGCP-MDA (M2), and their mixture DGEBA-20%HGCP-MDA (M3) were evaluated using differential scanning calorimetry (DSC) and thermogravimetry–, infrared spectroscopy (TG-FTIR) coupled analysis. The morphology was studied by scanning electron microscopy–, energy dispersive X-ray analysis (SEM–, EDX). The vertical flammability test was done used for the evaluation of the flame retardancy. The temperatures of exothermic peak (To) of the polymer materials M1, M2 and M3 were 95 °, C, 77 °, C and 93 °, C, respectively. The results revealed that the addition of 20% of HGCP enhances the thermal stability compared to DGEBA and provides a DGEBA UL-94 V0 rating. SEM–, EDX analysis showed that HGCP promotes the foaming and expansion of the coal as well as improved the gullies on the coal surface. Heteroskedasticity and autocorrelation consistent (HAC) covariance were performed to combine the results of the thermal degradation of the examined epoxy resins as a function of EHOMO and ELUMO, which were obtained from the optimized structure of the epoxy resins using the density functional theory. Consequently, the HAC model was validated by comparing the predicted theoretical results with experimental thermal degradation of the serial of compounds studied.

The new polyamides and polyurethanes have prepared by reaction of N-tetrachlorophthalimido succinic acid or its diol derivatives with different diisocyanates. The synthetic procedures for preparation of monomers, model compounds and polymers have been described and their chemical structures are characterized by FTIR and 1H NMR spectroscopic techniques. The physical properties of polymers including inherent viscosity, solubility properties, thermal behaviour, thermal stability and flame resistance have studied as well. The result showed that, the incorporation of the pendent N-tetrachlorophthalimide group into polyamides and polyurethanes backbone increases the thermal stability as well as flame resistance compared to the unmodified analogues compound.

A hybrid flame retardant, of excellent stability in aqueous media, was designed to develop flame-retarded polyethyleneimine (PEI) foam. In this case, iron phosphonate (FeP) with carboxyl group and hydroxyl group was first designed and synthesized. The carboxyl group could be hydrogen bonded with the water-soluble ammonium polyphosphate (APP) in aqueous media, and then dispersed as nano-sized particles. Subsequently, the well-dispersed nano-hybrid of FeP and APP (FeP/APP) was blended with hydrophilic PEI to prepare a kind of composite foam through a freeze-drying process. For FeP/APP, the transition metal iron showed excellent catalytic carbonization performances. Meanwhile, APP could also catalyze the degradation of polymers to form a protective char layer. The thermogravimetric analysis coupled with Fourier transform infrared analysis (TG-FTIR) test disclosed that the improvement of flame retardancy for PEI-based foams was ascribed to the synergistic effect of FeP and APP in the condensed phase. The composite foam containing 30 wt% FeP/APP could self-extinguish and reach V-1 rating in UL-94 test. When the loading level of 45% FeP/APP reached 45%, the composite foam could elevate up to V-0 rating, and the peak of heat release rate and total heat release were reduced by 71. 8% and 74. 2%, respectively, compared to a neat PEI foam. It is worth noting that our work presents a promising way for preparation of stable aqueous flame retardant, and is expected to enhance the fire safety of aqueous foams, coatings, cotton textiles, and other flammable materials.

Poly(lactic acid) (PLA) can be functionalized with maleic anhydride (MA) to obtain MA-grafted PLA (PLA-g-MA), which in turn, can be functionalized with ammonium polyphosphate (APP) to obtain PLA-g-APP. This functionalization should facilitate the obtaining of compounds with flame-retardant properties through intumescence and also could function as a compatibilizer for the addition of bio-fillers. To achieve this, the PLA was first functionalized with MA using dicumyl peroxide (DCP) as free radical former, at varying peroxide and maleic anhydride concentrations. FTIR and NMR confirmed the functionalization. In addition, it was found that at certain DCP and MA concentrations, the attained grafting values were close to 1% MA into PLA. Thereafter, APP was grafted onto PLA-g-MA, in order to obtain PLA-g-MA/APP. XPS analyzes showed the effective functionalization of PLA with MA and subsequently, the grafting of APP. The SEM images showed that the “, new”,material (PLA-g-APP) does not show a brittle fracture as that of pure PLA, although a tough fracture and an interfacial adhesion between PLA and APP is improved revealing its compatibilization effect. This compatibilization allowed an improvement in tensile strength, impact resistance and a slight increase in HDT of the PLA. Finally, it was observed that the use of PLA-g-APP in a pure PLA matrix has a positive effect on its mechanical properties. The flame retardancy was tested by cone calorimeter which showed that pHRR and THR are reduced at 30% and 35%, respectively. In addition, the better flame retardancy was obtained when using PLA-g-APP with 15% (by weight) of grafted APP. This functionalized PLA (PLA-g-APP) is a new and good option to prepare bio-fire retardant composites with enhanced flame-retardant properties, in sustainable and environmentally friendly applications.

The range of application for silicone rubber (SR) is limited due to its poor flame retardant and antistatic properties. For the purpose of improving SR properties, in this study, a core–, shell structured carbon nanotubes (CNTs)/cobalt copper hydroxide (CuCo-DH) hybrid was successfully prepared by a hydrothermal method, with cobalt copper hydroxide (CuCo-DH) as its core and carbon nanotubes (CNTs) as its shell. CNTs/CuCo-DH hybrid was added to SR to prepare an SR composite material, and the effect of the hybrid on flame retardancy and antistatic properties of the SR material was investigated. The cone calorimeter test (CCT) results showed that the total heat release (THR) of the SR composite with the addition of 3 phr of CNTs/CuCo-DH decreased by 25. 2%, its peak heat release rate (pHRR) decreased by 31. 2%, and its total smoke production (TSP) decreased by 28. 1%. In addition, with 3 phr of CNTs/CuCo-DH hybrid added, the volume resistivity of the SR composite decreased from 1. 96 , × , 1014 to 3. 52 , × , 1010 Ω, •, cm, which met the requirements of antistatic materials. Therefore, the prepared new SR/CNTs/CuCo-DH composite would help to expand the range of applications of SR materials. In addition, the residual char of the composite was analyzed by SEM, FTIR and XRD, and the fire retardant mechanism was studied in detail.