Effects of kaolin on the thermal stability and flame retardancy of polypropylene composite

Kaolin clay was introduced into an intumescent flame retardant (IFR) system containing ammonium polyphosphate as an acid source and pentaerythritol as a carbonization agent in order to improve the thermal stability and flame retardancy of polypropylene (PP) composite. The flame retardancy and smoke suppression was evaluated by the limiting oxygen index, vertical burning UL‐94, and cone calorimeter (CONE) tests. The limiting oxygen index value was increased from 30 to 33 at the presence of 2 phr kaolin. The peak heat release rate value decreased from 1002 kW/m² of neat PP to 318 kW/m² of PP/40 phr IFR and then to 222 kW/m² of PP/38 phr IFR/2 phr kaolin. The time of the peak heat release rate was significantly prolonged after the introduction of kaolin. The morphology of char after combustion was characterized by a scanning electron microscope, and it revealed more compact char structure that was obtained at the presence of kaolin. The mechanism of kaolin on improving the retardancy and smoke suppression of PP/IFR composite was proposed on the basis of X‐ray photoelectron spectroscopy analysis. Copyright © 2014 John Wiley & Sons, Ltd.     

Synergistic effect of DOPO immobilized silica nanoparticles in the intumescent flame retarded polypropylene composites

The synergistic effect of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) immobilized silica (SiO₂‐DOPO) nanoparticles with an intumescent flame retardant (IFR) on the flame retardancy of polypropylene (PP) was investigated by UL 94 vertical tests and limiting oxygen index (LOI) measurements. It was found that the PP/IFR composites (25 wt%) achieved the UL94 V0 grade and LOI increased to 32.1 with an incorporation of 1.0 wt% SiO₂‐DOPO nanoparticles. Based on thermogravimetric analysis, scanning electronic microscopy and rheological analysis, it is speculated that three factors are mainly contributed to the improvement of the flame retardancy. First, the thermal stability of PP/IFR composites was improved by incorporating SiO₂‐DOPO nanoparticles. Second, the presence of SiO₂‐DOPO nanoparticles could induce the formation of a continuous char skin layer during combustion. The compact char layer could effectively impede the transport of bubbles and heat. Third, rheological analysis indicated that SiO₂‐DOPO nanoparticles could increase viscosity of the PP/IFR composites, which was also benefited to increase flame retardancy. Copyright © 2013 John Wiley & Sons, Ltd.     

Synergistic fire safety improvement between oyster shell powder and ammonium polyphosphate in TPU composites

In this article, oyster shell powder (OSP) was used as fire safety agent with ammonium polyphosphate (APP) in thermoplastic polyurethane (TPU) composites. The synergistic fire safety improvement between OSP and APP was intensively investigated using limiting oxygen index (LOI), UL‐94, smoke density test (SDT), and cone calorimeter test (CCT). There is a good synergistic effect of reducing the fire hazards when OSP was used with APP in TPU. The peak heat release rate (pHRR) of the sample with 2.0‐wt% OSP and 8.0‐wt% APP decreased to 86.8 kW/m² from 175.7 kW/m² of the sample with only 10.0‐wt% APP. The SDT results showed that the luminous flux of sample OSP2/APP8 was up to 28.9% at the end of experiment with flame, which was much higher than that of pure TPU (1.5%). The thermal stability and thermal decomposition of TPU composites were characterized by thermogravimetric analysis/Fourier infrared spectrum analysis (TG‐IR). The result revealed the inert gasses (including CO₂ and water vapor) produced by the reaction between OSP and APP. A char formed on the surface of composites, hindered the flame spread, reduced the release of combustible gas, and restricted the precursor of smoke into combustion zone.     

Synergistic effect between a char forming agent (CFA) and microencapsulated ammonium polyphosphate on the thermal and flame retardant properties of polypropylene

The synergistic effect between a char forming agent (CFA) and microencapsulated ammonium polyphosphate (MAPP) on the thermal and flame retardancy of polypropylene (PP) are investigated by limiting oxygen index (LOI), UL‐94 test, cone calorimetry, thermogravimetric analysis (TGA), scanning electron micrograph (SEM), and water resistance test. The results of cone calorimetry show that heat release rate peak (PHRR), total heat release (THR), and the mass loss of PP with 30 wt% intumescent flame retardant (IFR, CFA/MAPP = 1:2) decreases remarkably compared with that of pure PP. The HRR, THR, and mass loss decrease, respectively from 1140 to 100 kW/m², from 96 to 16.8 MJ/m², and from 100 to 40%. The PP composite with CFA/MAPP = 1:2 has the best water resistance, and it can still obtain a UL‐94 V‐0 rating after 168 hr soaking in water. Copyright © 2008 John Wiley & Sons, Ltd.     

The influence of organo-modified sepiolite on the flame-retardant and thermal properties of intumescent flame-retardant polylactide composites

Polylactide (PLA) composites based on intumescent flame-retardant (IFR) and organo-modified sepiolite (OSEP) were prepared via direct melt compounding. The uniform dispersion of OSEP in the PLA matrix was observed by TEM, but some agglomerates still existed at the high loading. Tensile results showed that high loading of the conventional IFR led to a reduction in tensile strength of PLA composites; however, replacing a portion of the IFR with modified sepiolite in the PLA matrix improved this result. The thermal degradation temperature of the PLA/IFR/OSEP composites determined by thermogravimetric analysis was lower than that of neat PLA, as a consequence of the catalyzed carbonization induced by the addition of IFR and OSEP. The formulation with 13 mass% IFR and 2 mass% OSEP exhibited the highest LOI value of 32 vol% and also reached UL-94 V-0 rating in the vertical burning tests. Furthermore, the co-addition of IFR and OSEP gave rise to a significant reduction in peak heat release rate (PHRR) and total heat release (THR) of PLA composites during combustion, particularly in the case of PLA/IFR13/OSEP2 (82% reduction in PHRR and 69% in THR). The excellent fire resistance of PLA/IFR13/OSEP2 could be attributed to that IFR catalyzed carbonization of PLA to form the char, while OSEP resulted in further stabilization in the charred layers.     

Thermal stability and fire reaction of poly(butylene succinate) nanocomposites using natural clays and FR additives

Thermal stability and fire retardancy of poly(1,4‐butanediol succinate) (PBS) nanocomposites with sepiolite and 2 halloysites was investigated using thermogravimetric analysis. Despite detrimental influence on thermal stability, confirmed by the use of isoconversional methods, nanoclays improve PBS fire behavior, studied using pyrolysis combustion flow calorimetry and cone calorimeter. Combinations of nanoclays with ammonium polyphosphate (APP) and aluminum diethyl phosphinate at 20 wt% global loading were tested using cone calorimeter at 50 kW/m². It was noticed that the formation of protective structures of metallic phosphates with APP improves fire performance. The influence of ternary compositions combining sepiolite, APP, and lignin on fire performance was investigated. The composition having equimassic loading of each component leads to strong reductions in peak of heat release rate and Maximum of Average Heat Release Evolved (MAHRE) through the formation of a cohesive protective residue, containing new types of metallic phosphates and reinforced by sepiolite particles. This composition also allows smoke release rate to be minimized.     

Synthesis of a novel ionic liquid containing phosphorus and its application in intumescent flame retardant polypropylene system

A novel ionic liquid containing phosphorus ([PCMIM]Cl) was synthesized and characterized by FTIR, ¹H NMR, ¹³C NMR and ³¹P NMR. Moreover, a new intumescent flame retardant (IFR) system, which was composed of [PCMIM]Cl and ammonium polyphosphate (APP), was used to impart flame retardancy and dripping resistance to polypropylene (PP). The flammability and thermal behaviors of intumescent flame‐retarded PP (PP/IFR) composites were evaluated by limiting oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA) and cone calorimeter test. It was found that there was an obvious synergistic effect between [PCMIM]Cl and APP. When the weight ratio of [PCMIM]Cl and APP was 1:5 and the total amount of IFR was kept at 30 wt%, LOI value of PP/IFR composite reached 31.8, and V‐0 rating was obtained. Moreover, both the peak heat release rate and the peak mass loss rate of PP/IFR composites decreased significantly relative to PP and PP/APP composite from cone calorimeter analysis. The TGA curves suggested that [PCMIM]Cl had good ability of char formation, and when combined with APP, it could greatly promote the char formation of PP/IFR composites, hence improved the flame retardancy. Additionally, the rheological behaviors and mechanical properties of PP/IFR composites were also investigated, and it was found that [PCMIM]Cl could also serve as an efficient lubricant and compatibilizer between APP and PP, endowing the materials with satisfying processability and mechanical properties. Copyright © 2013 John Wiley & Sons, Ltd.     

Flame retardancy and smoke suppression of molybdenum trioxide doped magnesium hydrate in flexible polyvinyl chloride

In this paper, an effective flame retardant consisting of hierarchical magnesium hydrate (MH) nanosheets doped with molybdenum trioxide nanoparticles (MO@MH) was successfully synthesized via a hydrothermal process. Then, MO@MH, MH, and MH/MO were respectively incorporated into flexible polyvinyl chloride (fPVC) to prepare a series of composites via melt blending. The results of limiting oxygen index (LOI), UL‐94, and cone calorimetry test showed that MO@MH exhibited better flame retardancy and smoke suppression than MH and MH/MO due to the synergistic effect of MO and MH, and the hierarchical structure of MO@MH. With the addition of 20 phr MO@MH, LOI value of fPVC was increased from 23.9% to 33.8% , and UL‐94 reached V0 rating. The peak heat release rate, total heat release, peak smoke production rate, and total smoke production were decreased to 143.0 kW/m², 44.9 MJ/m², 0.0093 m²/s and 29.4 m², respectively. The thermogravimetric analysis results suggested that MO@MH greatly promoted the dehydrochlorination of fPVC at lower temperature, so that more compact and continuous char residues were formed. The Fourier transform infrared spectroscopy results indicated that MO@MH can prevent chain scission and oxidation of fPVC carbonaceous backbone, and as a result less smoke was released.     

Effect of Organo‐Modified Nanosepiolite on Fire Behaviors and Mechanical Performance of Polypropylene Composites

The objective of the study was to investigate the effect of the organo‐modified nanosepiolite (ONSep) on improving the fire safety of polypropylene (PP). The composites based on PP, flame retardant master batch (MB‐FR, 25 wt% PP+50 wt% decabromodiphenyl ether (DBDPE)+25% antimony trioxide (ATO)) and ONSep were prepared via melt blending. The results of the limiting oxygen index (LOI) and vertical burning rating (UL‐94) test indicated that PP/40 wt% MB composites had no rating with seriously dripping phenomenon, while the LOI value was only 22.5. However, as 4 wt% ONSep was added in PP/40 wt% MB composites, the composites achieved UL94 V‐0 rating and the LOI value was 24.3. In comparison, PP/50 wt% MB composites could not reach the V‐0 rating either. The TGA results revealed that the addition of ONSep enhanced the thermal stability of the PP/MB‐FR composites. The cone calorimeter results indicated that the heat release rate, average mass loss rate, smoke production rate and smoke temperature of the PP/40 wt% MB‐FR/4 wt% ONSep composites decreased in comparison with those of PP/40 wt% MB‐FR composites. Simultaneously, the Young modulus and impact strength were also much better improved with the increase of ONSep loading. Therefore, the synergistic flame retardancy of ONSep in PP/MB‐FR matrix significantly containing a halogen based flame retardant (DBDPE) significantly improved the fire safety and mechanical properties of the composites, and allowed to decrease the total amount of brominated fire retardants.     

Preparation of a novel phosphorus‐containing organosilicon and its effect on the flame retardant and smoke suppression of polyethylene terephthalate

A novel phosphorus‐containing silicone flame retardant (PDPSI) was prepared by Mannish reaction, and a series of PDPSI/PET composites were prepared by melt blending method. The nuclear magnetic resonance (¹H NMR), Fourier transformation infrared (FTIR), and the thermogravimetric analyzer (TGA) results indicated that PDPSI showed network structure and owned good thermal stability, with the char residue of 62.2% at 800°C. The flame retardancy of PDPSI/PET composites was characterized by limiting oxygen index (LOI), vertical burning tests (UL‐94), and cone calorimeter (CCT). The results revealed that the addition amount of PDPSI was 5%, the LOI value of PDPSI/PET composites increased to 27.3%, and UL‐94 test passed V‐0 rating. When the PDPSI loading was 3%, PET composites showed excellent flame retardancy and smoke suppression, with a decrease in the peak heat release rate (PHRR) by 71.19% and the total smoke release (TSP) reduced from 14.4 to 11.1m². The scanning electron microscopy (SEM) and FTIR results of char residue demonstrated that the flame‐retardant mechanism of PDPSI was solid phase flame retardant. PDPSI catalyzed the aromatization reaction of PET to promote the formation of a dense and continuous carbon layer, finally improving the flame retardancy and smoke suppression properties of PET.     

Effect of anion of polyoxometalate based organic–inorganic hybrid material on intumescent flame retardant polypropylene

In this work, 12‐tungestocobaltic acid based organic–inorganic hybrid material, [Bmim]₆CoW₁₂O₄₀ (CoW) was synthesized and applied as a synergist in polypropylene (PP)/intumescent flame retardant (IFR) composites. The flame retardant properties were investigated by the limiting oxygen index (LOI), UL‐94 vertical burning test, thermal gravimetric analyzer (TGA), cone calorimeter and scanning electron microscopy (SEM) etc. The results showed that the PP composites with 16 wt% IFR and 1 wt% CoW achieves the UL‐94 V‐0 rating and gets a LOI value 28.0. However, only add no less than 25 wt% single IFR, can the PP composites obtain the UL‐94 V‐0 rating, which suggests that CoW has good synergistic effects on flame retardancy of PP/IFR composites. In addition, the SEM and cone calorimeter tests indicated the CoW improves the quality of char layer. The rate of char formation has been enhanced also because of the existence of CoW. It is the combination of a better char quality and a high rate of char formation promoted by CoW that results in the excellent flame retardancy of PP/IFR composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of water content on failure of phenolic composites in fire

This paper evaluates the structural performance of flame resistant phenolic matrix composites exposed to fire. Experimental fire tests were performed on a glass-phenolic composite under combined static loading and one-sided radiant heating. The reduction to the tension and compression failure strengths of the phenolic composite was measured in these tests for heat flux conditions ranging from 10 kW/m² (∼225 °C) to 75 kW/m² (∼700 °C). It was discovered that the failure strengths of the phenolic composite decreased rapidly in the event of fire, particularly under compressive loading when failure occurred more rapidly than under tensile loading. The phenolic composite, despite having high flame resistance, loses strength more rapidly and fails sooner than a more flammable vinyl ester composite. The study shows that greater flammability resistance does not necessarily result in better structural performance in fire. The poor structural performance of the phenolic composite was due to explosive delamination damage and cracking caused by vaporisation of water in the matrix phase. It is shown that removing water from phenolic composites by natural or artificial ageing reduces the incidence of delamination cracking and thereby improves the materials' structural performance in fire. It is concluded that phenolic composites do not provide good structural performance in fire, even though they have low flame and smoke properties. However, reducing the water content in the matrix phase below about 10% can greatly improve the structural performance of phenolic composites during fire.     

Flammability and Thermal Oxidative Degradation Kinetics of Magnesium Hydroxide and Expandable Graphite Flame Retarded Polypropylene Composites

The flammability and the thermal oxidative degradation kinetics of expandable graphite (EG) with magnesium hydroxide (MH) in flame‐retardant polypropylene (PP) composites were studied by limiting oxygen index (LOI), UL‐94 test, and thermogravimetric analysis (TGA). The results show that EG is a good synergist for improving the flame retardancy of PP/MH composite and the effect is enhanced with decreasing EG particle size. The Kissinger method and Flynn‐Wall‐Ozawa method were used to determine the apparent activation energy (E) for degradation of PP and flame retarded PP composites. The data obtained from the TGA curve indicate that EG markedly increases the thermal degradation temperature of PP/MH composites and improves the thermal stability of the composites. The kinetic results show that the values of E for degradation of flame retarded PP composites is much higher than that of neat PP, especially PP/MH composites with suitable amount of EG, which indicates that the flame retardants used in this work have a great effect on the mechanisms of pyrolysis and combustion of PP.     

Synthesis of MoO3 with different morphologies and their effects on flame retardancy and smoke suppression of polyurethane elastomer

Molybdenum trioxide (MoO₃) microrods, nanofibers, and nanoplates were synthesized via the hydrothermal method and high‐temperature calcination method, respectively. Then the MoO₃ was added into polyurethane elastomer, respectively. The flame retardancy and smoke suppression of the composites added with different MoO₃ were studied by thermal gravimetric analysis, cone calorimeter, and smoke density. The results show that the three kinds of MoO₃ with different morphologies could promote the formation of char and possess flame retardancy and smoke suppression, and MoO₃ nanofibers exhibit a higher degree of flame retardancy, and 1 wt% addition could make the peak heat release rate of polyurethane elastomer composites reduce from 881.6 kW m^?2 for a pure sample to 343.4 kW m^?2, a decrease by 61.0%. As for smoke suppression, MoO₃ nanoplates possess the best smoke suppression; 5 wt% could decrease a pure sample's smoke density by 41.3% from 361 to 212. Moreover, the char residue of composites after combustion was analyzed by Raman spectra and X‐ray photoelectron spectroscopy, and the flame retardancy and smoke suppression mechanisms of MoO₃ were discussed.     

A new approach on improving the fire resistance of polyamide 11 by incorporating sulfur‐based flame retardant

In this work, a novel sulfur‐based flame retardant (SA‐M) was synthesized by the self‐assembly of melamine and sulfamic acid. The chemical structure of SA‐M was fully characterized. SA‐M, in company with Al₂O₃, was then introduced into polyamide 11 (PA 11) by melt compounding in order to improve the fire resistance of the polymer substrate. The observation by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) indicated the well dispersion of SA‐M in PA 11 matrix. The fire performance of PA 11 composites was evaluated by limiting oxygen index (LOI), vertical burning (UL‐94), and cone calorimeter tests, respectively. The results showed that the presence of 17.5% SA‐M and 2.5% Al₂O₃ increased the LOI value from 22.4% to 30.9%, upgraded the UL‐94 rating from no rating to V‐0, significantly eliminated the melt dripping, and decreased the peak heat release rate from 1024 to 603 kW/m². The thermal behaviors were investigated by thermogravimeric analysis (TGA) and TGA‐Fourier transform infrared spectroscopy (FTIR). It was suggested that SA‐M took effects mainly in gas phase by diluting the combustible fuel, leading to the improvement of the fire resistance of PA 11.     

Synergetic effect of thermal conductivity and flame retardancy of cyanate ester composites containing DOPO and BN with great dielectric properties

DOPO and boron nitride (BN) fillers with different particle sizes and several loadings were employed to improve the properties of cyanate ester (CE) resin. The effects of BN content and particle size on the thermal conductivity of the BN‐DOPO/CE ternary composites were discussed. The influence of enhancing the thermal conductivity of the ternary composites on their flame retardancy was studied. The consequences showed that increasing the thermal conductivity of BN‐DOPO/CE composites had an active impact on their flame retardancy. Approving flame retardancy of the ternary composites was certified by the high limiting oxygen index (LOI), UL‐94 rating of V‐0, and low heat release rate (HRR) and total heat release (THR). For instance, in contrast with pure CE matrix, peak of HRR (pk‐HRR), average of HRR (av‐HRR), THR, and average of effective heat of combustion (av‐EHC) of CEP/BN_{0.5 μm}/10 composite were decreased by 51.7%, 33.8%, 18.7%, and 18.9%, respectively. Thermal gravimetry analysis (TGA) showed that the addition of BN fillers improves the thermal stability of the composites. Moreover, the ternary composites possess good dielectric properties. Their dielectric constants (ε) are less than 3, and dielectric loss tangent (tgδ) values are lower than neat CE resin.     

Joint‐aggregation intumescent flame‐retardant effect of ammonium polyphosphate and charring agent in polypropylene

In order to explore the structure mode of intumescent flame retardants (IFRs) with higher efficiency, IFR particles with joint‐aggregation structure (@IFR) were obtained through the treatment of ammonium polyphosphate (APP) and a charring agent (PT‐Cluster) in their aqueous solution. Then, the joint‐aggregation IFR effect was researched using its application in polypropylene. In case of 20 wt% IFR loading, the limiting oxygen index (LOI) value of @IFR/PP was 1.1% higher than that of 15APP/5PT‐Cluster/PP mixture, and a 1.6 mm‐thick @IFR/PP composite passed the UL 94 V‐2 rating test, while 15APP/5PT‐Cluster/PP demonstrated no flame‐retardant rating in UL 94 vertical burning tests. In a cone calorimeter test, @IFR also had a better inhibition effect on heat release. The average heat release rate (av‐HRR) value during 0 to 120 seconds of @IFR/PP was only 41 kW m^?2, which was 33.9% lower than that of the 15APP/5PT‐Cluster/PP. Furthermore, the peak heat release rate (pk‐HRR) of @IFR/PP was 20.5% lower than that of 15APP/5PT‐Cluster/PP, and the time to pk‐HRR of @IFR/PP was 710 seconds, while that of 15APP/5PT‐Cluster/PP was 580 seconds. The better inhibition effect on HRR and the delay of time to pk‐HRR were caused by the joint‐aggregated structure of @IFR, which can rapidly react to form stable and efficient char layers. This kind of join‐aggregation IFR effect has great significance in suppressing the spread of fire in reality. In addition, @IFR also increased the mechanical properties of PP composites slightly compared with the APP/PT‐Cluster mixture.     

Flame‐retardant behavior of bi‐group molecule derived from phosphaphenanthrene and triazine groups on polylactic acid

The flame‐retardant polylactic acid (PLA) has been prepared via mixing the flame retardant TGIC‐DOPO derived from phosphaphenanthrene and triazine groups into matrix. The flame retardancy of TGIC‐DOPO/PLA composites was characterized using the limiting oxygen index (LOI), vertical burning test (UL94), and cone calorimeter test. Results reveal that the 10%TGIC‐DOPO/PLA composite obtained 26.1% of LOI and passed UL94 V‐0 rating. The flame‐retardant mechanism of PLA composites was characterized via thermogravimetric analysis (TGA), pyrolysis gas chromatography/mass spectroscopy, and TGA‐Fourier transform infrared. It discloses that TGIC‐DOPO promoted PLA decomposing and dripping early, and it also released the fragments with quenching and dilution effects. These actions of TGIC‐DOPO contribute to reducing the burning intensity and extinguishing the fire on droplets, thus imposing better flame retardancy to PLA. When TGIC‐DOPO was partly replaced by melamine cyanuric with dilution effect and hexa‐phenoxy‐cyclotriphosphazene with quenching effect in composites respectively, the results confirm that TGIC‐DOPO utilize well‐combination in dilution effect and quenching effect to flame retard PLA. Copyright © 2015 John Wiley & Sons, Ltd.     

An efficient and convenient strategy toward fire safety and water resistance of polypropylene composites through design and synthesis of a novel mono‐component intumescent flame retardant

A novel mono‐component flame‐retardant additive poly (dimethylol melamine piperazine pyrophosphate) defined as PDMPP was synthesized from formaldehyde, melamine, and piperazine pyrophosphate. Its chemical structure was well characterized by Fourier transform infrared spectroscopy, ¹³C and ³¹P solid‐state nuclear magnetic resonance, and elemental analysis tests. PDMPP was incorporated into polypropylene (PP) matrix, and the fire‐retardant performance, thermal properties, and water resistance of PP composites were investigated in detail. PP/23 wt% PDMPP composites before and after water resistance tests both achieved UL‐94V‐0 grade during vertical burning tests, and the limiting oxygen index was slightly declined from 26.7% to 26.3%. Small amount of PDMPP was extracted by hot water, and the weight loss percentage was 0.67% during water resistance tests. The piperazine and triazine rings in PDMPP contributed to a much better char‐forming capability, and then a greatly expanded and coherent char residue was generated during combustion and exhibited excellent isolation effect. The heat release rate, carbon monoxide production, and smoke production rate of the flame‐retarded PP composites before and after water resistance tests were effectively suppressed to a low level. Consequently, the introduction of PDMPP apparently improved the fire safety of PP composites as well as excellent water‐resistant performance.     

Effect of polyphenylsilsesquioxane on the ablative and flame-retardation properties of ethylene propylene diene monomer (EPDM) composite

Polyphenylsilsesquioxane (PPSQ) microspheres with ladder structure synthesized in the laboratory have been incorporated into ethylene propylene diene monomer (EPDM) composite in order to study the effect of PPSQ on the ablative and flame-retardation properties of EPDM composites. The results showed that PPSQ microspheres serve as an effective ablative additive and flame retardant for EPDM composites. Thus, PPSQ greatly improved the ablative properties of EPDM composites, with a 4.8 wt% loading leading to a remarkable reduction in the linear ablation rate of EPDM by about 50%. Moreover, this loading of PPSQ improved the flame retardancy and smoke suppression, and significantly reduced the PHRR of EPDM composite from 504 kW/m² to 278 kW/m². Moderate tensile strength could be obtained and the breaking elongation was improved for the EPDM/PPSQ composites. TGA results showed that PPSQ had little influence on the thermal decomposition of EPDM. SEM, CONE, and TG-FTIR tests showed that the char structure of EPDM composites was the primary factor through which PPSQ affected the ablative and flame-retardation properties of EPDM. The chars formed during the ablation of EPDM composites containing PPSQ had better structural stability and thermal stability, owing to the fact that they were denser, remained intact, and had an ordered arrangement of holes.