Phosphotungstic Acid Intercalated MgAlLa Ternary Layered Double Hydroxides as High-Efficiency Additives for Epoxy Resin: Synergistic Enhancement of Flame Retardancy and Smoke Suppression

Abstract

The inherent flammability and toxic smoke emission of epoxy resins (EPs) pose significant challenges to their advanced engineering applications. To address this limitation, we developed a novel flame-retardant additive through the organic modification of layered double hydroxides (LDHs) using a ternary MgAlLa hydrotalcite structure intercalated with phosphotungstic acid (PWA). This innovative design established a synergistic mechanism by combining the catalytic carbonization effect of lanthanum with the radical scavenging capability of PWA. The optimized MgAlLa-PWA/EP composite demonstrated remarkable flame retardancy and smoke suppression improvements, exhibiting 77.9% and 62.4% reductions in the peak heat release rate (pHRR) and total heat release (THR), respectively, compared to pure EP. Particularly noteworthy was the 72.6% decrease in total smoke release (TSR), accompanied by a significant elevation of the limiting oxygen index (LOI) value to 26.8% and achievement of UL-94 V-0 rating. Microstructural analysis revealed that the modified composite formed a continuous and uniform layer with increased density during combustion, effectively inhibiting oxygen exchange, smoke diffusion, and heat transfer. This study provides a novel strategy for designing multi-element synergistic LDHs additive for high-efficiency flame retardancy and smoke suppression of EP.

1. Introduction

Polymeric materials are widely used in various industrial and consumer applications due to their excellent mechanical properties, flexibility, and cost-effectiveness [1]. However, their inherent flammability poses significant safety risks, particularly in construction, transportation, and electronic devices [2]. The increasing number of fire-related incidents has spurred extensive research into flame-retardant materials that can mitigate fire hazards and reduce smoke emissions. Traditional flame retardants include halogenated compounds, phosphorus-based additives, and inorganic fillers, each with unique advantages and limitations [3,4]. Halogenated flame retardants, for instance, demonstrate high efficiency in reducing flammability, but raise environmental and health concerns due to toxic gas emissions during combustion [5]. In contrast, phosphorus-based retardants exhibit lower toxicity but may compromise material properties, and inorganic fillers such as aluminum hydroxide and magnesium hydroxide often require high loading levels to achieve a desirable performance [6,7]. Among emerging flame-retardant materials, layered double hydroxides (LDHs) have attracted increasing attention due to their environmentally friendly nature and multifunctional properties [8,9]. As a class of anionic clays, LDHs have demonstrated potential as effective additives for improving the flame retardancy and smoke suppression performance of epoxy resin (EP) materials.

LDHs possess a unique layered structure, consisting of positively charged brucite-like layers and intercalated anions that balance the charge. The general chemical formula of LDHs could be defined as ${\left[{\mathrm{M}}_{1-\mathrm{x}}^{2+}{\mathrm{M}}_{\mathrm{x}}^{3+}{\left(\mathrm{OH}\right)}_2\right]}^{\mathrm{x}+}{\mathrm{A}}_{\mathrm{x}/\mathrm{n}}^{\mathrm{n}-} \mathrm{m}{\mathrm{H}}_2\mathrm{O}$, where M(II) and M(III) are divalent and trivalent metal cations, respectively, x is in the range of 0.2–0.33, and A⁻ represents the interlayer anions. The tunability of metal cations and interlayer anions allow LDHs to exhibit tailored properties, making them highly versatile for various applications, including catalysis [10], drug delivery [11], and fire retardancy [12]. Previous studies have demonstrated that LDHs act as effective flame retardants in polymeric materials by releasing water molecules and forming a protective barrier during thermal decomposition, thereby inhibiting heat transfer and reducing combustible gas emissions [13]. Furthermore, the char-forming ability of LDHs contributes to smoke suppression, an essential factor in fire safety. Several studies have explored the incorporation of LDHs into EP systems, highlighting improvements in the limiting oxygen index (LOI), reduced peak heat release rate (pHRR), and decreased total smoke production (TSP) [14,15]. These findings underscore the significance of LDHs as a promising alternative to conventional flame retardants, addressing both environmental concerns and fire safety requirements.

To enhance the performance of LDHs as flame retardants in epoxy resins, various modification strategies have been investigated. Surface modification and interlayer anion exchange are commonly employed techniques to improve the dispersion, compatibility, and thermal stability of LDH-based additives. Organic functionalization, such as grafting with silane coupling agents or incorporating phosphorus-based anions, has been shown to enhance LDH compatibility with polymer matrices while simultaneously improving char formation and flame-retardant efficiency. Li et al. developed a catalytic approach by covalently inducing an interfacial supramolecular assembly of a Salen-Fe complex on organic LDH-DBS, achieving a remarkably low LDH-DBS loading of 2 wt%, which conferred a UL-94 V-0 rating to the epoxy resin [16]. Zhu et al. synthesized LDH via the intercalation of gluconate anion and surface assembly of ultrafine copper hydroxide, leading to significant improvements in both the mechanical properties and fire safety of epoxy resins [15]. Additionally, hybridization with other flame-retardant materials, including h-BN compounds and graphene derivatives, has been explored to achieve synergistic effects, leading to superior fire resistance and mechanical performance. Yang et al. modified h-BN-based coral-like CuAl-LDH nanosheets using triphosphate, yielding an environmentally friendly flame retardant capable of improving the fire safety of epoxy resins [2]. Wang et al. employed an assembly strategy utilizing a thin MXene veil to construct a sandwiched ternary nanostructure (MX-Fe@LDH), resulting in fire-safe epoxy composites with reduced toxicity [14]. These advancements suggest that modifying LDHs provides an effective strategy for optimizing their flame-retardant performance in polymeric materials. Tailored modifications of LDHs offer promising routes for developing high-performance flame-retardant systems, reinforcing their potential application in fire-safe epoxy composites.

Phosphotungstic acid (PWA) is a kind of typical polyoxometalates with remarkable features such as redox characteristics, great chemical stability, non-toxicity, and low cost. Therefore, it has attracted attention in a variety of applications [17,18,19,20]. PWA can synergistically promote the char formation and improve the fire resistance of polymer composite [18,21]. Lanthanum (La) is an environment-friendly rare earth element which has a strong affinity for oxygen, flexible coordination, great polyvalence [22], and an empty 5d orbital, which acts as an efficient promoter in various chemical reactions, enhancing catalytic activity in oxidative processes [23]. Despite a range of existing research on PWA or La-modified flame-retardant additives for the polymer matrix, a few aspects still need further exploration: the design and synthesis of multi-functional LDHs involving PWA and La as well as the synergistic effort of PWA and La in enhancing the flame-retardant performance.

In this study, we developed a novel flame retardant through the organic modification of LDHs utilizing a ternary MgAlLa hydrotalcite structure intercalated with PWA (shown in Figure 1). Characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), confirmed the successful incorporation of La and PWA into the LDH structure. The optimized MgAlLa-PWA/EP composite exhibited significant enhancements in flame retardancy and smoke suppression. In the Cone Calorimeter Test (CCT), MgAlLa-PWA/EP composite demonstrated reductions of 77.9% and 62.4% in pHRR and total heat release (THR), respectively, compared to pure EP. In the LOI test, the LOI value of MgAlLa-PWA/EP composite reached 26.8%. Furthermore, in the UL-94 test, the MgAlLa-PWA/EP composite achieved a V-0 rating. Microstructural analysis revealed that the modified composite formed a continuous and uniform layer with increased density during combustion, effectively inhibiting oxygen exchange, smoke diffusion, and heat transfer. The synergistic effect of PWA and La contributes to the formation of a stable intumescent char layer, which effectively isolates the underlying material from heat and oxygen, thereby reducing the flammability of the polymer matrix. This study presents a novel strategy for designing multi-element synergistic LDH additives to achieve high-efficiency flame retardancy and smoke suppression in epoxy composites.

2. Materials and Methods

2.1. Materials

Anhydrous sodium carbonate (Na₂CO₃, AR) was purchased from Tianjin Damao Chemical Reagent Co., Ltd., Tianjin, China. Magnesium nitrate hexahydrate (Mg(NO₃)₂·6H₂O, AR), Aluminum nitrate hexahydrate (Al(NO₃)₃·9H₂O, AR), lanthanum nitrate hexahydrate (La(NO₃)₃·6H₂O, AR), sodium hydroxide (NaOH, AR), PWA (AR) and epoxy resin (EP, E51), triethylene tetramine (TETA, 70%) were purchased from Shanghai Maclin Biochemical Technology Co., Ltd., Shanghai, China.

2.2. Preparation of MgAlLa-PWA

The molar ratio of M²⁺ to M³⁺ is 3:1, with a La³⁺/Al³⁺ molar ratio of 0.02. Accurate amounts of Mg(NO₃)₂·6H₂O, Al(NO₃)₃·9H₂O, and La(NO₃)₃·6H₂O were weighed and dissolved in 70 mL of CO₂-free deionized water to prepare solution A. Simultaneously, NaOH was weighed and dissolved in 70 mL of CO₂-free deionized water to prepare solution B. Under a nitrogen atmosphere, solutions A and B were simultaneously added at a controlled rate to a four-necked flask containing 20 mL of phosphotungstic acid (PWA) solution, with vigorous stirring to maintain pH = 9. After the addition, the mixture was crystallized at 80 °C for 12 h, followed by washing and drying, to obtain MgAlLa-PWA. Methods for making MgAlLa-CO₃ and MgAl-CO₃ are accessible in the Supplementary Materials.

2.3. Preparation of LDHs/EP Composite Materials

A specified amount of EP was weighed and mixed with an appropriate quantity of MgAlLa-PWA. The mixture was stirred at room temperature. The calculated amount of TETA was added, and the mixture was stirred for 10 min followed by ultrasonic treatment. The mixture was then poured into a mold and cured at 80 °C for 24 h to obtain MgAlLa-PWA/EP. Similarly, MgAl-CO₃/EP and MgAlLa-CO₃/EP composites can be synthesized following the same procedure. Detailed information is provided in the Supplementary Materials.

3. Results and Discussion

3.1. Characterization of LDHs

3.1.1. XRD Analysis

The powder XRD patterns of MgAl-CO₃, MgAlLa-CO₃, and MgAlLa-PWA are provided in Figure 2a, and the crystal parameters are summarized in

Table 1. Crystal parameters of MgAl-CO₃, MgAlLa-CO₃, and MgAlLa-PWA.

Sample	Crystalline Lattice	2θ (°)	d (nm)	c (nm)
MgAl-CO3	(003)	11.37	0.778	2.335
MgAlLa-CO3	(003)	11.24	0.787	2.362
MgAlLa-PWA	(003)	8.20	1.078	3.234

The radiation source is Cu-Kα.

. All samples exhibit characteristic diffraction peaks at (003), (006), and (009), confirming the typical layered structure of LDHs [24]. Among these, the diffraction peaks of MgAl-CO₃ are the sharpest and narrowest with the highest intensity, indicating a well-ordered crystalline structure with good interlayer regularity. The (003) diffraction angle of MgAlLa-CO₃ slightly shifts from 11.37° to 11.24° compared to MgAl-CO₃. According to the Bragg equation, the basal spacings of MgAl-CO₃ and MgAlLa-CO₃ are 0.778 nm and 0.787 nm, respectively, both approximating 0.78 nm. These values indicate that both samples corresponding to a Mg/Al molar ratio of 3/1, consistent with the previously reported literature [25]. Furthermore, the observed increase in basal spacing can be attributed to the larger ionic radius of La(III) compared to Al(III) [26]. In contrast, MgAlLa-PWA exhibits significantly broadened and less intense diffraction peaks, indicating the reduced crystallinity and interlayer regularity after modification. Notably, the (003) diffraction peak of MgAlLa-PWA shifts to 8.20°, and the corresponding basal spacing exhibits marked increase to 1.078 nm, leading to a significant increase in parameter c [27]. This value of basal spacing is aligned to the corresponding reported literature [18] and demonstrates the successful intercalation of PWA into the interlayer space, as confirmed by XRD results.

3.1.2. FT-IR Analysis

The FT-IR curves of MgAl-CO₃, MgAlLa-CO₃, and MgAlLa-PWA are presented in Figure 2b. A broad absorption band around 3450 cm⁻¹ corresponds to the overlapping stretching vibrations of hydroxyl groups and interlayer water [28]. Meanwhile, the observation of absorption peak at 1650 cm⁻¹ is attributed to the O-H bending vibration [29]. For MgAl-CO₃ and MgAlLa-CO₃, the absorption peaks at approximately 1375 cm⁻¹ corresponds to the stretching vibration of carbonate anions [30]. Additionally, the lattice vibrations of M-O groups are evident in the 400–800 cm⁻¹ region presenting in all samples, demonstrating the LDH structure [31]. As a comparison, the disappearance of the 1375 cm⁻¹ peak in MgAlLa-PWA implies an absence of carbonate. The observation of peaks at 1080 cm⁻¹ corresponding to P-O bond stretching vibration jointly reveals that the interlayer ions have been substituted by PWA anions [32]. The FT-IR results manifest that PWA is successfully incorporated into the LDH interlayer, consistent with the findings from the XRD analysis.

3.1.3. SEM-EDS Analysis

The morphology and elemental composition of MgAl-CO₃, MgAlLa-CO₃, and MgAlLa-PWA were analyzed using SEM-EDS. In Figure 2c–e, the distinct platelet morphology observed in MgAl-CO₃ and MgAlLa-CO₃ conclusively reveals their LDH structure [33]. Elemental mapping of MgAlLa-PWA confirms the uniform distribution of Mg, Al, La, P, W, and O elements (Figure 2f), indicating the successful incorporation of La(III) into LDH backbone and the intercalation of PWA between LDH layers. The EDS mapping and spectrum of MgAlLa-PWA are shown in Figures S1 and S2, and the EDS analysis of MgAlLa-PWA is summarized in Table S1, which lists the atomic concentrations of all elements. The molar ratio of Mg/Al approximates to 3/1, while the actual molar ratio of Al/La is 33:1. Additionally, the addition of La(III) and PWA into MgAlLa-PWA retains the characteristic lamellar structure of the LDHs, only leading to the decreased grain size of MgAlLa-PWA. This phenomenon suggests the successful incorporation of La(III) and PWA into the LDHs without compromising the LDH structure.

3.1.4. XPS

Figure S3 displays the XPS survey spectra of three LDH samples. As predicted, the Mg 1s peak at 1304.8 eV and the Al 2p peak at 74.08 eV are common to all three samples, corresponding to the LDH host layer [34]. As illustrated in Figure 2g, MgAlLa-CO₃ exhibits a distinct La-O signal at 855.4 eV and 851.2 eV, corresponding to La 3d_3/2, as well as 838.4 eV and 834.5 eV, corresponding to La 3d_5/2 [35]. This indicates the successful incorporation of La(III) into the LDH host layer. For MgAlLa-PWA, a notable peak appearing at 133.28 eV assigned to P 2p is depicted in Figure 2h. As displayed in Figure 2i, the peaks at 37.4 eV (W 4f_5/2) and 35.3 eV (W 4f_7/2) in the MgAlLa-PWA spectrum collectively demonstrate the presence of PWA [36].

3.1.5. TGA of LDHs

The thermogravimetric analysis (TGA) of MgAl-CO₃, MgAlLa-CO₃, and MgAlLa-PWA are shown in Figure 3a–c. All three samples display two distinct weight-loss stages. The first stage, between 50 °C and 250 °C, corresponds to the loss of interlayer water. A continuous reduction in first-stage mass loss has been observed in LDH samples upon the sequential incorporation of La(III) and PWA. The strong polarization effect of La(III) may weaken the hydrogen bonding interactions between the host layers and interlayer water, resulting in a decrease in interlayer water content. Meanwhile, the substitution of PWA causes the interlayer water in LDHs to no longer be as crucial for maintaining the layered structure as in carbonate-type LDHs [37]. The second stage, between 250 °C and 600 °C, is attributed to the dehydroxylation of the LDH layers and the decomposition of interlayer carbonate ions. Notably, MgAlLa-CO₃ exhibited a 1.65% higher residual mass at 800 °C compared to MgAl-CO₃, suggesting that the incorporation of La(III) enhances the thermal stability of LDHs samples. Among three samples, MgAlLa-PWA exhibits the highest residual weight of 79.9% at 800 °C, significantly exceeding that of MgAl-CO₃. This improvement is attributed to the synergistic effect of La(III) and PWA. The thermally generated La₂O₃ and WO₃ phases form a nanoceramic matrix that impede heat conduction pathways [38]. Concurrently, PWA promotes interlayer dehydration of LDHs through acid–base interactions. This dual mechanism results in the formation of a dense oxide framework, which enables MgAlLa-PWA to achieve a minimal second-stage mass loss of 7%.

3.2. Flame Retardancy of Composite EP

3.2.1. TGA of Composite EP

The thermal stability of MgAl-CO₃/EP, MgAlLa-CO₃/EP, and MgAlLa-PWA/EP was assessed using thermogravimetric analysis (TGA). The results are presented in Figure 4a, Figure S4, and

Table 2. TGA results of pure EP and EP composites under nitrogen atmosphere.

Composites	T5% (°C)	T50% (°C)	Tmax (°C)	Char Residues at 800 °C (%)
EP	334.8	381.0	370.0	12.6
MgAl-CO3/EP	314.6	370.2	358.6	17.5
MgAlLa-CO3/EP	311.6	361.6	355.9	20.9
MgAlLa-PWA/EP	308.7	357.9	341.2	26.2

. All the samples, including pure epoxy resin (EP), exhibit a single-step thermal decomposition process. For pure EP, thermal decomposition begins at 335 °C, followed by significant weight loss between 335 °C and 550 °C, resulting in a residue mass of 12.6% at 800 °C. In comparison, the onset decomposition temperature (T_5%) of the composite EP occurs earlier, primarily due to the evaporation of surface-adsorbed water and interlayer water in the LDHs.

Compared to pure EP, the char residues of MgAl-CO₃/EP, MgAlLa-CO₃/EP, and MgAlLa-PWA/EP increase to 17.5%, 20.9%, and 26.2%, respectively. This enhancement originates from the earlier thermal degradation process, which involves the formation of a protective char layer and subsequent shielding of the underlying polymeric substrate from flame propagation. Notably, the char residues of MgAlLa-PWA/EP demonstrate a particularly significant increase, with char residues exceeding that of MgAl-CO₃/EP by approximately 25.4%. This enhancement is attributed to the synergistic interactions among La(III), PWA, and LDHs. Both La(III) and degradation products of phosphotungstic acid (PWA) exhibit functionalities in catalyzing carbonization, while the endothermic decomposition of LDHs absorbs substantial heat, with their resultant metal oxide layers synergistically providing thermal insulation against flame [18,39].

3.2.2. Burning Behaviors (LOI and UL-94 Tests)

Table 3. LOI and UL-94 results of pure EP and its composites.

Samples	Combustion Performance
	LOI (%)	UL-94
EP	22.4	NR
MgAl-CO3/EP	24.4	V-2
MgAlLa-CO3/EP	24.6	V-2
MgAlLa-PWA/EP	26.8	V-0

presents the LOI and UL-94 test results for the composites and evaluates the influence of MgAl-CO₃, MgAlLa-CO₃, and MgAlLa-PWA on the flame retardancy of EP. The LOI value of pure EP is 22.4%. The incorporation of LDH samples noticeably increases the LOI value of composite EP. Among these, MgAlLa-PWA/EP achieves the highest LOI value of 26.8%, outperforming that of other EP samples. This is due to the enhanced flame-retardant effect of La(III) and PWA on the composite EP. The UL-94 test reveals that pure EP failed to attain any rating (NR), indicating its limited suitability for applications requiring flame retardancy. In contrast, composite EP all present controlled combustion, effectively inhibiting flame propagation and eliminating dripping behavior, and achieve a UL-94 rating of V-2 or higher. Notably, the MgAlLa-PWA/EP attains the highest UL-94 rating of V-0 among all composite EP samples, which is attributed to the synergistic effect between La(III) and PWA. This synergy promotes char formation in the EP and enhances the thermal barrier effect of the generated metal oxide layer.

3.2.3. Cone Calorimeter Test

CCT was employed to further investigate the combustion behavior of MgAl-CO₃/EP, MgAlLa-CO₃/EP, and MgAlLa-PWA/EP. In Figure 4b, upon ignition, pure EP exhibits rapid combustion, with a pHRR of 1307 kW/m² and a THR of 133 MJ/m². The presence of MgAl-CO₃ slightly decreases the pHRR and THR of composite EP due to heat absorption during the decomposition process of LDHs. The incorporation of La(III) and PWA individually enhances the thermal stability of composite EP. This effect enables MgAlLa-PWA/EP, achieving a 78% reduction in pHRR value. The gradient of THR curve serves as an indicator of flame propagation [40]. The THR curve of pure EP depicted in Figure 4c exhibits the steepest slope, suggesting the highest flame propagation rate among the tested samples. The introduction of MgAl-CO₃ barely reduces the ascent of the gradient. However, MgAlLa-PWA/EP displays the minimum gradient of THR curve. Notably, after 200 s, the THR curve of MgAlLa-PWA/EP shows hardly any indication of ascent, indicating that the fire spread can be controlled within 200 s following ignition. For MgAlLa-CO₃/EP and MgAlLa-PWA/EP, the change in HRR curves and the decrease in THR curves reveal that the carbonization process involves the participation of EP chains [41]. The presence of La(III) and PWA facilitate the char formation of MgAlLa-CO₃ and MgAlLa-PWA, which are typical char-forming materials. This char layer suppresses the release of volatile compounds into the combustion zone, thereby significantly reducing heat release. In Figure 4d, the TSP of MgAl-CO₃/EP exhibit noticeably decreases compared to pure EP. The addition of La(III) and PWA further reduces the TSP of composite EP, resulting in a 72% reduction for MgAlLa-PWA/EP in contrast with pure EP. Similarly, MgAlLa-PWA/EP exhibits a 75% reduction in CO emissions and an 84% decrease in CO₂ generation relative to pure EP, as illustrated in Figure 4e,f, which are crucial for both fire escape and rescue operations. Although MgAl-CO₃ and MgAlLa-CO₃ release CO₂ during thermal decomposition, the TSP, COP, and CO₂P values all exhibit marked decrease for their composites. This phenomenon is attributable to the endothermic decomposition of LDHs, which absorbs significant thermal energy while releasing large quantities of CO₂ gas and the formation of a thermally insulating metal oxide layer that retards heat transfer to the underlying EP. The CCT results of pure EP and its composites are summarized in

Table 4. CCT results of pure EP and its composites.

Samples	TTI (s)	pHRR (kW/m2)	THR (MJ/m2)	TSR (m2)	COP (g/s)	CO2P (g/s)	Char Residue (%)
EP	64	1307.41	133.15	22.02	0.040	0.805	1.5
MgAl-CO3/EP	73	957.87	129.12	18.73	0.024	0.607	11.7
MgAlLa-CO3/EP	59	478.96	110.06	15.00	0.015	0.261	19.5
MgAlLa-PWA/EP	38	289.13	50.13	6.13	0.010	0.132	48.2

.

3.2.4. Charring Effect

Figure 5 compares the char residues of EP and its composites after CCT. Pure EP (Figure 5(a₁–a₃) exhibits rapid combustion with minimal residue (1.5%), whereas LDH-containing EP form dense char layers (Figure 5(b₃–d₃)). This improvement indicates that LDH samples exert beneficial effects on enhancing the mass of the char residue [42]. Notably, the char residue of MgAl-CO₃/EP presents a whitish coloration compared to pure EP. Combined with SEM observations, MgAl-CO₃/EP reveals a more compact morphology compared to pure EP, suggesting that the flame-retardant effect originates from the metal oxide layer formed by LDH decomposition during combustion. However, the char residue of MgAlLa-CO₃/EP and MgAlLa-PWA/EP show a darkened coloration, due to the catalytic char-forming component (La(III) and PWA) in composites. In contrast, the SEM images of composite EP exhibit progressively denser morphology, indicating a stepwise enhancement in char-forming ability.

4. Conclusions

This study investigated the structural and flame-retardant properties of La- and PWA-modified Mg-Al LDHs in EP composites. Structural characterization confirmed the successful synthesis and modification of LDHs. XRD analysis revealed that MgAlLa-PWA showed reduced crystallinity due to PWA intercalation, and FT-IR analysis further confirmed the carbonate replacement by PWA with new peaks corresponding to P-O and W-O-W bonds. SEM-EDS results showed uniform element distribution, suggesting the successful incorporation of La and PWA without compromising LDH structure. TGA demonstrated improved thermal stability, with MgAlLa-PWA retaining the highest residual weight due to the formation of a thermally stable nanoceramic matrix. In flame-retardant evaluations, MgAlLa-PWA/EP outperformed other composites. TGA showed a 26.2% char residue (vs. 12.6% for pure EP), driven by La-PWA synergy in catalyzing carbonization and forming thermal barriers. LOI values increased from 22.4% (pure EP) to 26.8% (MgAlLa-PWA/EP), achieving a UL-94 V-0 rating. Cone calorimetry demonstrated a 78% reduction in peak heat release rate and 72% lower total smoke production for MgAlLa-PWA/EP, alongside significant reductions in CO/CO₂ emissions. Char residue analysis revealed dense, thermally insulating layers formed via La-PWA interactions, suppressing heat transfer and volatile release. The modified LDHs offer a promising strategy for developing high-performance, fire-safe epoxy composites, balancing structural integrity with exceptional thermal and flame-resistant properties.