Thermal and flame retardant properties of novel intumescent flame retardant polypropylene composites

Novel intumescent flame retardant polypropylene (PP) composites were prepared based on a char forming agent (CFA) and silica-gel microencapsulated ammonium polyphosphate (Si-MCAPP). The thermal and flame retardancy of flame retardant PP composites were investigated by limiting oxygen index, UL-94 test, cone calorimetry, thermogravimetric analysis, scanning electron micrograph, and water resistance test. The results of cone calorimetry show that the flame retardant properties of PP with 30 wt% novel intumescent flame retardants (CFA/Si-MCAPP = 1:3) improve greatly. The peak heat release rate and total heat release decrease, respectively, from 1,140.0 to 156.8 kW m^?2 and from 96.0 to 29.5 MJ m^?2. The PP composite with CFA/Si-MCAPP = 1:3 has the excellent water resistance, and it can still obtain a UL-94 V-0 rating after 168 h soaking in water.     

Preparation of gel‐silica/ammonium polyphosphate core‐shell flame retardant and properties of polyurethane composites

A novel intumescent gel‐silica/ammonium polyphosphate core‐shell flame retardant (MCAPP), which contains silicon, phosphorus, and nitrogen, has been prepared by in situ polymerization. The structure of MCAPP was characterized by Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS). The properties of MCAPP were investigated by water solubility, hydrophilicity, and morphological determination. The flame retardancy and thermal stability of polyurethane (PU) composite with MCAPP were evaluated by limiting oxygen index (LOI), UL‐94 test, cone calorimetry, and thermogravimetric analysis (TGA). The results showed that MCAPP could decrease the heat release rate (HRR) and increase the thermal stability of PU materials greatly. Finally, water‐resistant properties of PU/FR composites were also studied. Copyright © 2010 John Wiley & Sons, Ltd.     

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.     

Intumescent flame retardation of polypropylene/bamboo fiber semi-biocomposites

Polypropylene/bamboo fiber (BFP) semi-biocomposites were prepared by melted blend method. Microencapsulated ammonium polyphosphate was added to the BFP semi-biocomposites to improve the flame-retardant properties of the BFP semi-biocomposites. The flame-retardant properties of the BFP semi-biocomposites have been investigated by limited oxygen index, UL-94 test and cone calorimeter test. The results of cone calorimeter show that the peak of heat release rate (pHRR) and total heat release (THR) of the flame-retardant BFP semi-biocomposites decrease substantially compared with that without MCAPP. The pHRR value of flame-retardant BFP semi-biocomposite decreases from 540.0 to 227.5 kW m^?2, and the THR value decreases from 75.3 to 49.2 MJ m^?2. The thermal degradation and gas products of the flame-retardant BFP semi-biocomposites were monitored by thermogravimetric analysis and thermogravimetric analysis-infrared spectrometry.     

Fire hazard suppression of intumescent flame retardant polypropylene based on a novel Ni‐containing char‐forming agent

Reducing the fire hazard of polypropylene (PP) is an important research direction in the fields of fire safety materials. In this article, a novel Ni‐containing char‐forming agent (TTPN) was successfully synthesized, using tris(2‐hydroxyethyl) isocyanurate (THEIC), terephthalic acid, and nickel dihydrogen phosphate. Then, TTPN was combined with the silica‐gel microencapsulated ammonium polyphosphate (OS‐MCAPP) to prepare intumescent flame retardant PP composites. From the results of the limiting oxygen index (LOI) test and cone calorimeter, the composite containing 30% IFR (OS‐MCAPP: TTPN = 3:2) shows the highest LOI value of 33.5%, and its peak heat release rate is 275.5 kWm^?2, decreased by 79.0% and 37.4% than those of pure PP and the composite containing the char‐forming agent without Ni. Meanwhile, the composite containing TTPN present the best smoke and CO₂/CO suppression. The results indicate that TTPN has an excellent ability to dramatically reduce the fire hazard of PP.     

Flame retardancy and thermal degradation of intumescent flame retardant polypropylene material

The flame retardancy and thermal degradation properties of polypropylene (PP) containing intumescent flame retardant additives, i.e. melamine pyrophosphate (MPyP) and charring‐foaming agent (CFA) were characterized by limiting oxygen index (LOI), UL 94, cone calorimeter, microscale combustion calorimetry, and thermogravimetric analysis (TGA). It has been found that the PP material containing only MPyP does not show good flame retardancy even at 30% additive level. Compared with the PP/MPyP binary system, the LOI values of the PP/MPyP/CFA ternary materials at the same additive loading are all increased, and UL 94 rating is raised to V‐0 from no rating (PP/MPyP). The cone calorimeter results show that the heat release rate and mass loss rate of some ternary materials decrease in comparison with the binary material. The microscale combustion calorimetry results indicate that the sample containing 22.5 wt% MPyP and 7.5 wt% CFA has the lowest heat release rate among all samples. The TGA results show that the thermal stability of the materials increases with the addition of MPyP, while decreases with the addition of CFA. Copyright © 2009 John Wiley & Sons, Ltd.     

Construction of crosslinking network structures by adding ZnO and ADR in intumescent flame retardant PLA composites

Different proportion of nano zinc oxide (nano ZnO) and chain extender (ADR) were combined with the intumescent flame retardant and then added into the PLA matrix. The thermal stability, flame retardant performance, and mechanical properties were studied. The gel content results showed that crosslinking structures were obtained after the addition of nano ZnO and ADR, which were generated by the catalytic chain scission effect of nano ZnO and chain extension effect of ADR. With addition of 1% nano ZnO and 1.6% ADR, the gel content of flame retardant PLA composite reached the highest value (14.2%). Meanwhile, the corresponding flame retardant PLA composite with 1% nano ZnO and 1.6% ADR, named FRPLA/ZnO/ADR-1, exhibited an overall improved properties including the flame retardant properties and mechanical performance, which passed the UL94 V-0 level with a limiting oxygen index value of 40.1%. Compared to FRPLA (flame retardant PLA without ZnO and ADR), the peak heat release rate and the total smoke production of FRPLA/ZnO/ADR-1were reduced by 60% and 67% respectively, and the final mass improved from 12% to 38%. In addition, the tensile strength and elongation at break of FRPLA/ZnO/ADR-1 increased by 25%, 14% compared with that of FRPLA. The impact strength was 15.1 kJ/m², which is similar to the pure PLA (15.6 kJ/m²). It indicated that the addition of nano ZnO and ADR could balance the flame retardant performance and the mechanical properties of the flame retardant PLA.     

Aluminum phosphate modified brucite and its flame retardant and smoke suppression performance on ethylene‐vinyl acetate resin

A novel halogen‐free flame retardant (FR) consisting of brucite, aluminum phosphate (AlP), and silane coupling agent (B/AlP/A) was prepared via co‐precipitation assembly technique. The morphology, chemical compositions, size distribution, and thermal stability of B/AlP/A were investigated. When used in ethylene‐vinyl acetate (EVA) resin, the B/AlP/A could significantly enhance the flame retardant and smoke suppression performance of the EVA composites, which is mainly attributed to the AIP. With 50 wt% FR loading, the peak heat release rate (PHRR) of EVA‐B/AlP/A (299.2 kW · m^?2) is much lower than that of EVA‐B/A (387.4 kW · m^?2). Moreover, B/AlP/A shows an excellent smoke suppression performance. For example, the smoke production rate is 0.017 m² · g^?1 that has been decreased by 72.1%, compared with B/A. The improvement arises from the amorphous AlP layer on brucite, which helps to create a firm and porous protective char layers on the burning EVA composites. Meanwhile, better mechanical property could be simultaneously obtained with the large FR amount. The fluffy surface of B/AlP/A has good compatibility with EVA and tangle more polymer chains, enhancing the mechanical properties. In a word, this simple and convenient method could pave the way for developing a more efficient and cost‐effective brucite‐based FR.     

Synergistic effects between iron–graphene and melamine salt of pentaerythritol phosphate on flame retardant thermoplastic polyurethane

A comparison of melamine salt of pentaerythritol phosphate (MPP), and a synergistic agents, iron–graphene (IG) was performed in thermoplastic polyurethane (TPU) by masterbatch‐melt blending on thermal and flame retardant properties. The flame retardant properties of TPU composites were characterized by limiting oxygen index (LOI), UL 94 and cone calorimeter test (CCT). The CCT results revealed that IG can significantly enhance flame retardant properties of MPP in TPU. The peak heat release rate of neat TPU and flame retardant TPU/MPP composites decreased from 2192.6 and 226.7 to 187.2 kW/m² compared with that of TPU containing 0.25 wt% IG. The thermal stability and thermal decomposition of TPU composites were characterized by thermogravimetric analysis (TGA) and thermogravimetric/Fourier infrared spectrum analysis (TG‐IR). The results indicated IG and MPP can improve the thermal stability of TPU. The formation of thermal conductive network by IG can promote the decomposition of MPP into nonflammable melt, which can play the role of heat barrier and restrict the diffusion of fuels into combustion zone and access of oxygen to the unburned fuels. Copyright © 2016 John Wiley & Sons, Ltd.     

Synergistic effects of aluminum hypophosphite on intumescent flame retardant polypropylene system

The effects of aluminum hypophosphite(AHP) as a synergistic agent on the flame retardancy and thermal degradation behavior of intumescent flame retardant polypropylene composites(PP/IFR) containing ammonium polyphosphate(APP) and triazine charring-foaming agent(CFA) were investigated by limiting oxygen index(LOI), UL-94 measurement, thermogravimetric analysis(TGA), cone calorimeter test(CONE), scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). It was found that the combination of IFR with AHP exhibited an evident synergistic effect and enhanced the flame retardant efficiency for PP matrix. The specimens with the thickness of 0.8 mm can pass UL-94 V-0 rating and the LOI value reaches 33.5% based on the total loading of flame retardant of 24 wt%, and the optimum mass fraction of AHP/IFR is 1:6. The TGA data revealed that AHP could change the degradation behavior of IFR and PP/IFR system, enhance the thermal stability of the IFR and PP/IFR systems at high temperatures and promote the char residue formation. The CONE results revealed that IFR/AHP blends can efficiently reduce the combustion parameters of PP, such as heat release rate(HRR), total heat release(THR), smoke production rate(SPR) and so on. The morphological structures of char residue demonstrated that AHP is of benefit to the formation of a more compact and homogeneous char layer on the materials surface during burning. The analysis of XPS indicates that AHP may promote the formation of sufficient char on the materials surface and improve the flame retardant properties.     

Effect of aluminum diethylphosphinate on flame retardant and thermal properties of rigid polyurethane foam composites

Rigid polyurethane foam/aluminum diethylphosphinate (RUPF/ADP) composites were prepared by one-step water-blown method. Furthermore, scanning electron microscope (SEM), thermal conductivity meter, thermogravimetric analysis (TGA), limiting oxygen index, Underwriters Laboratories vertical burning test (UL-94) and microsacle combustion calorimetry were applied to investigate thermal conductivity, thermal stability, flame retardancy and combustion behavior of RPUF/ADP composites. Thermogravimetric analysis–Fourier transform infrared spectroscopy (TG–FTIR) was introduced to investigate gaseous products in degradation process of RPUF/ADP composites, while SEM and X-ray photoelectron spectroscopy were used to research char residue of the composites. It was confirmed that RPUF/ADP composites presented well cell structure with density of 53.1–59.0 kg m^?3 and thermal conductivity of 0.0425–0.0468 W m^?1 K^?1, indicating excellent insulation performance of the composites. Flame retardant test showed that ADP significantly enhanced flame retardancy of RPUF/ADP composites, RPUF/ADP30 passed UL-94 V-1 rating with LOI of 23.0 vol%. MCC test showed that ADP could significantly decrease peak of heat release rate (PHPR) of RPUF/ADP composites. PHPR value of RPUF/ADP20 was decreased to 158 W g^?1, which was 21.8% reduced compared with that of pure RPUF. TG–FTIR test revealed that the addition of ADP promoted the release of CO₂, hydrocarbons and isocyanate compound in first-step degradation of RPUF matrix while inhibited the release of CO in second step degradation. Char residue analysis showed that the addition of ADP promoted polyurethane molecular chain to form aromatic and aromatic heterocyclic structure, enhancing strength and compactness of the char. This work associated a gas–solid flame retardancy mechanism with the incorporation of ADP, which presented an effective strategy for preparation of flame retardant RPUF composites.

     

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.     

协效剂对膨胀阻燃聚丙烯基木塑复合材料的阻燃增效研究

赋予木塑复合材料(WPC)的阻燃性能成为近年来该领域国内外的研究热点之一。本文通过两轮正交试验,研究8种常见的协效剂对膨胀型阻燃剂(IFRs,m(聚磷酸铵,APP)∶m(季戊四醇,PER)=2∶1)的阻燃增效作用,筛选出具有显著协效作用的协效剂组MgO/EG(可膨胀石墨)/SiO_2,其组成为m(MgO)∶m(EG)∶m(SiO_2)=1∶5∶5,其与IFRs的最佳配比为m(IFRs)∶m(MgO/EG/SiO_2)=1∶0.18,得到性能良好的阻燃型聚丙烯基木塑复合材料。通过热重分析(TGA)和锥形量热分析(CONE)评价IFRs及协效剂组对聚丙烯(PP)基木塑复合材料(WPC)热稳定性能和阻燃性能的影响。结果表明,IFRs及MgO/EG/SiO_2的加入可以有效提高WPC的热稳定性,WPC/IFRs/MgO/EG/SiO_2600℃的残炭率达到22.42%。WPC/IFRs的热释放速率峰(PHRR)、总热释放量(THR)和总烟释放量(TSP)相比于WPC分别降低了21.9%、8.7%和22%。MgO/EG/SiO_2的加入可以进一步提高IFRs的阻燃效率,WPC/IFRs/MgO/EG/SiO_2的PHRR和THR相比于WPC分别降低了33.0%和13.8%。     

Modified montmorillonite combined with intumescent flame retardants on the flame retardancy and thermal stability properties of unsaturated polyester resins

Modified montmorillonite‐containing phytic acid (PA‐MMT) has been prepared by acid treatment and then introduced into unsaturated polyester resin (UPR) with an intumescent flame retardant (IFRs). The flame retardancy and thermal degradation of UPR/IFRs/PA‐MMT were evaluated by a limiting oxygen index (LOI) test, a vertical burning test (UL‐94), a thermogravimetric analysis (TGA), and a cone calorimeter test (CCT). Besides, the mechanical properties were studied by a universal testing machine. The LOI value of UPR/IFRs/PA‐MMT composites was increased to 29.2%. The CCT results indicated that the incorporation of PA‐MMT and IFRs significantly improved the combustion behavior of UPR. The results of the mechanical properties indicated that 1.5 wt% loading of PA‐MMT in UPR/IFRs showed the highest improvement in flexural strength and tensile strength. The flame‐retardant mechanism of PA‐MMT/IFRs was examined and discussed based on the results of combustion behavior and char analysis.     

Cone calorimeter analysis of flame retardant poly (methyl methacrylate)-silica nanocomposites

Nanocomposite is a promising method to reduce fire hazards of polymers. Specifically due to increased interfacial area between polymer and nanofillers, polymer nanocomposites have an advantage in reducing fire hazards efficiently even when the flame retardant additives are at a concentration of 5 mass% or less. In theory, crosslinking between the polymer chains can create a carbon-dense structure to enhance char formation, which can further promote the flame retardancy. However, little research has been done to explore the flammability of crosslinking polymer nanocomposites with a low concentration of nanosilica particles. In this study, crosslinked and non-crosslinked poly (methyl methacrylate) (PMMA) nanocomposites of a low concentration of nanosilica particles have been prepared via an in situ method. Their fire properties were tested by using the cone calorimeter at the heat flux of 50 kW m^?2. Although silica-containing flame retardants tend to negatively affect the ignitability and soot production especially at a high concentration, through the condensed phase mechanism, the samples of high loading rate of nanosilica particles show better fire retardancy performance in the aspect of flammability, including decreased heat release rate, mass loss rate, and total heat release. Additionally, crosslinking indeed attributes to the less intensive combustion of crosslinked PMMA samples, especially at a low concentration of nanosilica. The combination of nanosilica particles with the modification of the internal structure of the polymer nanocomposites might be a good strategy to improve fire retardancy.     

Layer-by-layer assembly of silica-based flame retardant thin film on PET fabric

A novel method to improve flame retardant properties of textile fabric using multilayered thin films was evaluated. In this work, PET fabrics were coated with silica nanoparticles using layer-by-layer assembly. Five bilayers of positively and negatively charged colloidal silica (<10 nm average thickness) increased time to ignition and decreased heat release rate peak of PET fabric by 45% and 20%, respectively. In vertical burn test, this same nanocoating dramatically reduced burn time and eliminated melt dripping. This study demonstrates the ability to impart flame retardant behavior using a water-based, environmentally-friendly protective coating.     

Effect of a novel charring-foaming agent on flame retardancy and thermal degradation of intumescent flame retardant polypropylene

A new triazine polymer was synthesized by using cyanuric chloride, ethanolamine and ethylenediamine as raw materials. It is used both as a charring agent and as a foaming agent in intumescent flame retardants, designated as charring-foaming agent (CFA). Effect of CFA on flame retardancy, thermal degradation and mechanical properties of intumescent flame retardant polypropylene (PP) system (IFR-PP system) has been investigated. The results demonstrated that the intumescent flame retardant (IFR) consisting of CFA, APP and Zeolite 4A is very effective in flame retardancy of PP. It was found that when the weight ratio of CFA to APP is 1:2, that is, the components of the IFR are 64 wt% APP, 32 wt% CFA and 4 wt% Zeolite 4A, the IFR presents the most effective flame retardancy in PP systems. LOI value of IFR-PP reaches 37.0, when the IFR loading is 25 wt% in PP. It was also found that when the IFR loading is only 18 wt% in PP, the flame retardancy of IFR-PP can still pass V-0 rating, and its LOI value reaches 30.2. TGA data obtained in pure nitrogen demonstrated that CFA has a good ability of char formation itself, and CFA shows a high initial temperature of the thermal degradation. The char residue of CFA can reach 35.7 wt% at 700 °C. APP could effectively promote the char formation of the APP-CFA system. The char residue reaches 39.7 wt% at 700 °C, while it is 19.5% based on calculation. The IFR can change the thermal degradation behaviour of PP, enhance T_max of the decomposition peak of PP, and promote PP to form char, based upon the results of the calculation and the experiment. This is attributed to the fact that endothermic reactions took place in IFR charring process and the char layer formed by IFR prevented heat from transferring into inside of IFR-PP system. TGA results further explained the effective flame retardancy of the IFR containing CFA.     

Synthesis of a novel synergistic flame retardant based on cyclopolysiloxane and its flame retardant coating on cotton fabric

A synergistic flame retardant (silicon, phosphorus and nitrogen) based on cyclic polysiloxane, ammonium salt of tetramethylcyclosiloxyl-piperazin-phosphinic acid (APCTSi) was successfully prepared and firmly bonded to cotton fabric through a chemical grafting method. The chemical structure of APCTSi was characterized by Fourier transform infrared (FTIR) spectroscopy, ¹H and ³¹P nuclear magnetic resonance (¹H NMR and ³¹P NMR). The scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX) proved that APCTSi successfully adhered to the surface of cotton fabric and the elements on the surface of cotton fabric were evenly distributed. The flame retardant properties were characterized by limiting oxygen index (LOI), vertical burning test, thermogravimetric (TG) analysis and TG-FTIR. The limiting oxygen index (LOI) can reach 30.9% with a char length of 8.7 cm for the weight gain of APCTSi was 16.2%. The combustion behavior was characterized by cone calorimetry test. The peak heat release rate (pHRR) and total heat release (THR) values of treated cotton fabric decreased by 30% and 48% respectively compared to that of pure cotton fabric. All the results proved that the cotton fabric treated by APCTSi had the flame retardant effect of condensed phase (forming stable char layer) and gas phase (releasing nonflammable gases).

Graphic abstract

     

Fire behavior of flame retarded unsaturated polyester resin with high nitrogen content additives

The novel flame retarded unsaturated polyester resins have been developed and prepared by introduction of high nitrogen content additives into the polymer matrix in order to verify their effectiveness in the formation of swollen carbonaceous char inhibiting the burning process of the polymer. The intumescent flame retardants (IFRs) based on mixture or metal complex were developed and characterized by particle size distribution, Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), powder X-ray diffraction (XRD), elemental analysis (CHN) and thermogravimetric analysis (TGA). The evaluation of the efficiency of IFRs addition on the flammability and smoke emission of the unsaturated polyester resins (UP) was carried out using the fire hazard (UL-94), limiting oxygen index (LOI) and cone calorimeter (CC) tests, as well as smoke density chamber tests. The volatile compounds evolved during the burning of materials were determined using a steady state tube furnace and a gas chromatograph with mass spectrometer. Furthermore, the prepared materials were subjected to differential scanning calorimetry (DSC), thermogravimetric analysis and water resistance tests. The mechanical properties of the materials were investigated using Shore D hardness and dynamic mechanical thermal analysis (DMA). The structural evaluation of the manufactured materials and samples after the cone calorimetry tests was carried out using scanning electron microscopy (SEM). It was found that the incorporation of new intumescent flame retardants led to the formation of carbonaceous char layers’ inhibiting the decomposition process and limiting the smoke emission. The most promising results were obtained for the resin containing complex designated as ZN3AT, for which the highest reduction in maximum values of heat release rate (419 kW/m²) compared to unmodified polymer (792 kW/m²) were recorded. Apart from that, the prepared intumescent flame retardants affect the cross-linking process as well as the thermal and mechanical properties of the UP.     

Flame retardant properties and mechanism of an efficient intumescent flame retardant PLA composites

The charring agent (CNCA‐DA) containing triazine and benzene rings was combined with ammonium polyphosphate (APP) to form intumescent flame retardant (IFR), and it was occupied to modify polylactide (PLA). The flame retardant properties and mechanism of flame retardant PLA composites were investigated by the limited oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis, microscale combustion calorimetry, scanning electron microscopy, laser Raman spectroscopy analysis and X‐ray photoelectron spectroscopy. The analysis from LOI and UL‐94 presented that the IFR was very effective in flame retardancy of PLA. When the weight ratio of APP to CNCA‐DA was 3:1, and the IFR loading was 30%, the IFR showed the best effect, and the LOI value reached 45.6%. It was found that when 20 wt% IFR was loaded, the flame retardancy of PLA/IFR still passed UL‐94 V‐0 rating, and its LOI value reached 32.8%. The microscale combustion calorimetry results showed that PLA/IFR had lower heat release rate, total heat release, and heat release capacity than other composites, and there was an obvious synergistic effect between APP and CNCA‐DA for PLA. IFR containing APP/CNCA‐DA had good thermal stability and char‐forming ability with the char residue 29.3% at 800°C under N₂ atmosphere. Scanning electron microscopy observation further indicated that IFR could promote forming continuous and compact intumescent char layer. The laser Raman spectroscopy analysis and X‐ray photoelectron spectroscopy analysis results indicated that an appropriate graphitization degree of the residue char was formed, and more O and N were remained to form more cross‐linking structure. Copyright © 2016 John Wiley & Sons, Ltd.