Flame Retardant Polypropylene Composites Research Articles

Tannic acid coated ammonium polyphosphate: For flame retardant and UV resistant of polypropylene

Polypropylene (PP) has the advantages of excellent mechanical properties and easy molding, but its shortcomings such as high flammability and poor ultraviolet (UV) resistance cannot be ignored. In this paper, APP was used as the core, 1, 10-diamino-decane (DA) was used as a "bridge" to connect TA to the surface of APP, obtaining TAPP through oxidation self-polymerization. The addition of TAPP greatly improved the flame retardancy and UV resistance of PP matrix. The limiting oxygen index of the PP/22.5 %TAPP sample was increased to 31.0 %, and it was able to pass the UL-94 V-0 rating without droplet produced. Compared with PP samples, the peak heat release rate and peak smoke release rate of PP/22.5 %TAPP sample were reduced by 65.0 % and 44.7 %, respectively. In addition, the tensile strength and impact strength of PP/22.5 %TAPP samples decreased by only 2.7 % and 15.0 % after 60 h UV irradiation. The results showed that the addition of TAPP effectively improved the flame retardancy and UV aging resistance of PP. This study provides a feasible method for the preparation of anti-UV aging and flame-retardant PP composites.

Functionalized lignin nanoparticles assembled with MXene reinforced polypropylene with favorable UV-aging resistance, electromagnetic shielding effects and superior fire-safety

Deterioration in mechanical performances and aging resistance due to the introduction of flame retardants is a major obstacle for bio-based fire-safety polypropylene (PP). Herein, we reported a kind of functionalized lignin nanoparticles assembled with MXene (MX@LNP), and applied it to construct the flame-retardant PP composites (PP-MA) with superior fire safety, excellent mechanical performance, electromagnetic shielding effects and aging resistance. Specifically, the PP-MA doped with only 18 wt% flame-retardant additives (PP-MA18) achieved the UL-94 V-0 rating. In comparison to pure PP, PP-MA18 presented a greatly decreased peak of heat release rate (pHRR), total heat rate (THR), and peak smoke production rate (pSPR) by 79.7 %, 69.0 % and 75.8 %, respectively, and satisfactory decrease in total flammable and toxic volatiles evolved. The formed fine solid microstructure of carbon residuals effectively promoted the compactness of char layers. More importantly, the nano-effect and the strong interface interaction between the complexed MX@LNP and PP enhanced the tensile strength (45.78 MPa) and elongation at break (725.95 %) of PP-MA. Additionally, the significant ultraviolet absorption and electromagnetic wave dissipation performance of MXene and lignin enabled excellent aging resistance and electromagnetic shielding effects of PP-MA compared with PP. This achieved MX@LNP afforded a novel approach for developing flame retardant materials with excellent application performance.

Surface modification of zinc oxide and its application in polypropylene with excellent fire performance and ultra-violet resistance

Despite the advantages of easy moulding and excellent mechanical properties, there are still some shortcomings with polypropylene (PP) such as high flammability and poor ultra-violet (UV) resistance. In this work, modified zinc oxide (mZnO) was prepared by reacting zinc oxide nanoparticles (ZnO) with polysiloxanes, and the effect of mZnO on the effectiveness of intumescent flame-retardant and on the UV aging resistance of polypropylene were investigated. By introducing 16 wt% (intumescent flame-retardant /mZnO) and 0.3 wt% maleic anhydride-grafted PP (MAH-g-PP), the limiting oxygen index increased to 32.7 %, and passed UL-94V-0 rating. In comparison to the controls, the peak heat release rate and the peak smoke release rate were 88.5 % and 80 % lower, respectively. In addition, PP samples showed improved mechanical properties, with a 5 % increase in tensile properties compared to the pure PP sample. After 100 h of UV irradiation, the surface of the samples was relatively flat and smooth, and the carbonyl index decreased from 81.1 of neat PP to 26.7. PP composites with 100 h aging treatment still had excellent flame retardancy and mechanical properties. The results showed that mZnO was effective in improving the flame retardancy, mechanical properties and light aging tolerance of PP. This study provides a novel approach to fabricate long-life flame-retardant PP composites with low additive content.

Preparation and flame retardant properties of organic montmorillonite synergistic intumescent flame retardant polypropylene

Ammonium polyphosphate (APP) and aluminium diethylphosphonate (ADP) were mixed according to the mass ratio of 4:1, compounded with dipentaerythritol (DPER) to construct a novel intumescent flame retardant (IFR), and organo-montmorillonite (OMMT) as a synergistic flame retardant, then melt blended to prepare intumescent flame retardant polypropylene (PP) composites. The flame retardancy, thermal stability, and mechanical properties of flame retardant polypropylene composites were examined using the limiting oxygen index (LOI), vertical combustion test, thermogravimetric analysis, and cone calorimetry test. The results showed that the LOI value of the flame retardant composite PP3 reached 31.3%, UL-94 reached V-0 level, the peak heat release rate (pHRR) and the total heat release (THR) decreased by 87.8% and 33.7%, respectively, compared with the original sample of PP, and the break elongation increased by 216.4% compared with that of the sample PP1 without the addition of OMMT. The findings demonstrated that adding OMMT to IFR in the right dosage can have a positive synergistic flame retardant impact.

Effect of hollow glass microsphere on the processing and flame retardancy of intumescent flame retardant polypropylene composites prepared by selective laser sintering

Effect of hollow glass microsphere on the processing and flame retardancy of intumescent flame retardant polypropylene composites prepared by selective laser sintering

Preparation and characterisation of a triazine structure charring agent and its application in polypropylene

ABSTRACT A triazine long chain charring agent (TCA) was synthesised using cyanuric chloride, morpholine and anhydrous piperazine. The synthesised TCA was compounded with ammonium polyphosphate (APP) to obtain an intumescent flame retardant (IFR). When the TCA content in the IFR was 35 wt% to 45 wt%, the IFR had good expansion properties. Then, different proportions of IFR were incorporated into polypropylene (PP) to prepare flame retardant PP composites, and the flame retardancy, thermal degradation behaviour and flammability behaviour for PP composites were investigated by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter test. When 20 wt% of IFR (With TCA 35 wt%) were added into the PP matrix, the composite achieved a V-0 rating for the UL-94 test and its LOI value was increased to 28.8%. Compared with neat PP, peak heat release rate (PHRR) and total heat release (THR) decreased from 827.30(KW·m−2) and 120.48(MJ·m−2) to 210.50(KW·m−2) and 75.08(MJ·m−2).

Simultaneously Enhancing the Flame Retardancy, Water Resistance, and Mechanical Properties of Flame-Retardant Polypropylene via a Linear Vinyl Polysiloxane-Coated Ammonium Polyphosphate.

It is challenging to improve the water resistance, flame retardancy, mechanical performance, and balance of halogen-free flame-retardant polypropylene (PP) composites. For this purpose, a linear vinyl polysiloxane (PD) was synthesized and then self-crosslinked under benzoyl peroxide to prepare surface-coated ammonium polyphosphate (APP@PD). Apparently, this linear vinyl polysiloxane self-crosslinking coating strategy was completely different from the commonly used sol-gel-coated APP with silane monomers. After coating, the water contact angles (WCA) of APP and APP@PD were 26.8° and 111.7°, respectively, showing high hydrophobicity. More importantly, PP/APP@PD/dipentaerythritol (DPER) showed a higher limiting oxygen index (LOI) and better UL-94 V-0 rate in comparison with PP/APP/DPER composites. After water immersion at 70 °C for 168 h, only PP/APP@PD/DPER kept the UL-94 V-0 rate and lowered the deterioration of the LOI, reflecting the better water-resistance property of APP@PD. Consistently, the cone calorimeter test results displayed a 26.2% and 16.7% reduction in peak heat release rate (PHRR) and total smoke production (TSP), respectively. Meanwhile, the time to peak smoke production rate (TPSPR) increased by 90.2%. The interfacial free energy (IFE) between APP@PD and PP was calculated to evaluate the interfacial interaction between PP and APP@PD. A reduction of 84.2% in the IFE between APP@PD and PP is responsible for the improvement in compatibility and the increase in flame retardancy, water resistance, and mechanical properties of the composites.

Synergistic effects of zeolitic imidazolate frameworks (ZIFs) with different transition metals on intumescent flame-retarded polypropylene composites: A comparative study

The use of intumescent flame retardants (IFRs) is considered an environmentally friendly and cost-effective strategy to suppress potential fire hazards from synthetic polymers. However, some conventional IFRs are neither efficient in developing a thermally stable char layer nor reducing the release of toxic byproducts during polymer combustion. In this work, we aim to discuss the effects of zeolitic imidazolate frameworks (ZIFs) on synergistically improving the flame retardancy behaviors in polypropylene (PP) composites, including thermal degradation (evolved gas analysis), free radical reactions in the gaseous phase (in-situ chemiluminescent image analysis), and carbonaceous structure in the condensed phase (micro-morphology and composition analysis). It is found that the transition metals in ZIFs can catalytically accelerate the crosslinking reaction at a lower initial temperature and decrease the amount of hydrocarbon volatiles in the gaseous phase. Once ignited, the embedded ZIFs can firstly bridge adjacent phosphorus chains in the polymer matrix to expand crosslinking degrees and then they are anchored in the developed N-doped phospho-carbonaceous networks after pyrolysis. As a result, more compact char residue structures are observed in the condensed phase for ZIF-reinforced composites. For example, by replacing 2 wt% of IFR with ZIF-67, the peak heat release rate, peak smoke production rate, and peak CO production rate are reduced by 69%, 80%, and 72%, respectively, when compared to the conventional composite. These results indicate an excellent solution to resolve inherent fire hazards associated with IFRs in polymers and achieve necessary efficiency for industrial applications. It also provides a new strategy for determining flammability characteristics and combustion mechanisms of polymer composites using in-situ chemiluminescence analysis.

Influence of chicken feather fibre processing technique on mechanical and fire performances of flame-retardant polypropylene composites

Influence of chicken feather fibre processing technique on mechanical and fire performances of flame-retardant polypropylene composites

From physical mixtures to block copolymer: Impose outstandingly toughening and flame retardant effect to polypropylene

To explore new flame retardant molecules with higher flame retardancy and toughening effect, a series of non-halogen block copolymer flame retardants PAPO-MP were designed and synthesized. Importantly, compared with the control sample 24(7PAPP/3MPP)/76PP in which the intumescent flame retardant was physically blended, the mechanical properties of 24(7PAPO-3MP)/76PP with the block copolymer was greatly increased. Its impact strength and elongation at break of 24(7PAPO-3MP)/76PP were 55.1 kJ/m2 and 140.6%, increased by 166% and 965% in contrast to those of 24(7PAPP/3MPP)/76PP, respectively. Because the block copolymerized structure led to the low crystalline degree, 7PAPO-3MP can change its particle shape from lamellar to water droplet morphology during thermal processing, which contributed to better compatibility and stronger interaction with PP matrix under the action of maleic anhydride grafted polypropylene, thereby dramatically enhancing the mechanical properties of PP composites. When the addition amounts of 7PAPO-3MP were 20 wt% and 24 wt% in polypropylene (PP) composite, the two flame retardant PP composites all passed UL94 V-0 rating and had the LOI values of 28.1% and 30.2%, respectively. Their peak of heat release rate values was all decreased by over 81% compared with that of neat PP. Moreover, their total heat release and average effective heat of combustion were also decreased and brought higher residue yields. Moreover, the more release of P-containing components in block copolymer also imposed more effective gas-phase quenching effect and flame inhibition effect during combustion. The research on the block copolymer in PP composites revealed a superior way to construct high-performance non-halogen polyolefin materials.

Synergistic Effect of 4A Molecular Sieve on Intumescent Ternary H-Bonded Complex in Flame-Retarding of Polypropylene

In this study, a ternary hydrogen (H)-bonded complex intumescent flame retardant (TH-IFR) of melamine (ME) · phosphoric acid (PA)…pentaerythritol (PER) was synthesized through hydrothermal reaction. The combination of the synthesized TH-IFR with 4A molecular sieve as the synergist was used for the first time to improve the flame retardancy of polypropylene (PP). The involved structure, morphology, flame retardancy, flame-retarding mechanism and mechanical properties of the prepared PP composites were systematically investigated. The results show that incorporation of 1 wt% synergist 4A shows the optimum synergistic effect, and the flame retardancy and mechanical properties of the flame-retarded (FR) PP composites are significantly improved. Incorporation of 4A could change the pyrolysis process of the entire system and promote the char-forming chemical interaction, thereby further enhancing the flame retardancy of FR PP composite. The synergistically flame-retarding mechanism of 4A is explained by the significantly improved quality and quantity of the solid-phase char layer, which is formed through generation of SiO2 and Al2O3 substances, and also participation of PP macromolecular chains in the final char layer formation during burning. Furthermore, the improved dispersion and compatibility of TH-IFR in the composite is largely beneficial to the improvement of flame retardancy and mechanical properties.

Nickel‐Aluminum Hydrotalcite for Improving Flame Retardancy and Smoke Suppression of Intumescent Flame Retardant Polypropylene: Preparation, Synergy, and Mechanism Study

AbstractIntumescent flame retardants (IFR) are widely used in the field of flame retardant polypropylene (PP), but their flame retardant efficiency and smoke suppression properties need to be further improved. Herein, a Ni‐Al LDH (layered double hydroxide) is obtained successfully by coprecipitation and microwave hydrothermal technique and used as a synergist to improve the flame‐retardant and smoke‐suppression properties of triazine‐based IFR. The results showed that IFR/Ni‐Al LDH exhibited the best synergistic effect when the IFR is replaced by 5 wt% Ni‐Al LDH. 17 wt% IFR/Ni‐Al LDH enabled the PP composites to achieve UL‐94 V‐0 rating with a high LOI of 29.8%. Besides, the introduction of Ni‐Al LDH effectively decreased the heat and smoke release of the PP/IFR composites due to its catalytic charring effect. This is mainly attributed that the introduction of metal ions in Ni‐Al LDH effectively improved the strength and crosslinking degree of char layer and promoted the formation of a cohesive and dense char layer. The formed high‐quality char layer effectively exerted the barrier effect in condensed phase. Therefore, the PP/IFR/Ni‐Al LDH composites exhibited excellent flame‐retardant and smoke‐suppression performance. This investigation provided a facile way to prepare environment‐friendly and high‐performance flame retardant PP composites with wide application prospects.

Synergistic Effects of DOPO-Based Derivative and Organo-Montmorillonite on Flame Retardancy, Thermal Stability and Mechanical Properties of Polypropylene.

Polypropylene (PP), as a general thermoplastic polymer, is broadly used in different fields. However, the high flammability, melt dripping and poor mechanical properties of PP are a constraint to the expansion of its applications. In this paper, PP composites containing a combination of a phenethyl-bridged DOPO derivative (PN-DOPO) and organic montmorillonite (OMMT) were prepared via melt blending. The synergistic effects of PN-DOPO and OMMT on the flame retardancy, thermal stability and mechanical properties of PP composites were investigated systematically. The results showed that 20 wt% addition of PN-DOPO with OMMT improved the flame retardancy of PP composites. In particular, the introduction of 17 wt% PN-DOPO and 3 wt% OMMT increased the LOI values of the PP matrix from 17.2% to 23.6%, and the sample reached the V-0 level and reduced the heat release rate and total heat release. TGA indicated that OMMT could improve the thermal stability of the PP/PN-DOPO blends and promote the char residues of PP systems. Rheological behaviour showed a higher storage modulus, loss modulus and complex viscosity of PP/PN-DOPO/OMMT composites, suggesting a more effective network structure. In addition, the tensile strength, flexural properties and impact strength of the PP/PN-DOPO/OMMT composites actually increased for a good dispersion effect. Combined with the char layer analysis, the introduction of OMMT promoted more continuous and compact structural layers containing an aluminium–silicon barrier and phosphorus-containing carbonaceous char in the condensed phase. OMMT can improve the flame retardancy, thermal stability and mechanical properties of PP, and, thus, PN-DOPO/OMMT blends can serve as an efficient synergistic system for flame-retarded PP composites.

The synergistic effect between bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate and polysiloxane on the photo-aging resistance and flame retardancy of polypropylene

The introduction of flame retardants often decreases the ultraviolet (UV) resistance ability of the photo stabilizer . In this work, the antagonistic effect between APP and a light stabilizer HLAS770 was investigated, and the microencapsulated APP (Si-APP) was prepared by coating ammonium polyphosphate (APP) with polysiloxane . Si-APP was introduced into polypropylene (PP) in association with a light stabilizer bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate (HALS770) to synchronously improve both the photo-aging resistance and flame retardancy . The characterization of surface topography , carbonyl index, and mechanical properties demonstrated that the antagonistic effect between APP and HALS770 was eliminated by the presence of polysiloxane. The limiting oxygen index and cone calorimeter test results revealed that the heat and smoke release of aged PP composites containing Si-APP and HALS770 was decreased by 28% and 35% respectively, compared with that of the aged control PP sample, which is crucial to the practical application of PP. It was proved that polysiloxane and HALS770 synergistically improved the photo-aging resistance and flame retardancy of PP. It is suggested that this work provides a new strategy for fabricating long-life flame retardant polypropylene composites. • Si-APP was prepared by microencapsulating APP with a polysiloxane. • Si-APP eliminated the antagonistic effect between APP and HLAS770. • Si-APP showed synergy effect with HLAS770 on delaying photoaging of PP. • HALS770 and Si-APP synergistically improved the flame retardancy of PP.

Synthesis of New S-Triazine Bishydrazino and Bishydrazido-Based Polymers and Their Application in Flame-Retardant Polypropylene Composites.

In this study six new s-triazine bishydrazino and bishydrazido-based polymers were synthesized via condensation of bishydrazino s-triazine derivatives with terephthaldehyde or via nucleophilic substitution of dichloro-s-triazine derivatives with terephthalic acid hydrazide. The synthesized polymers were characterized by different techniques. The new polymers displayed good thermal behavior with great values in terms of limited oxygen indexed (LOI) 27.50%, 30.12% for polymers 5b,c (bishydrazino-s-triazine based polymers) and 27.23%, 29.86%, 30.85% for polymers 7a–c (bishydrazido-s-triazine based polymers) at 800 °C. Based on the LOI values, these polymers could be classified as flame retardant and self-extinguishing materials. The thermal results also revealed that the type of substituent groups on the triazine core has a considerable impact on their thermal behavior. Accordingly, the prepared polymers were mixed with ammonium polyphosphate (APP) in different proportions to form an intumescent flame-retardant (IFRs) system and were introduced into polypropylene (PP) to improve the flame-retardancy of the composites. The best results were obtained with a mass ratio of APP: 5a–c or 7a–c of 2:1, according to the vertical burning study (UL-94). In addition, the presence of 25% “weight ratio” of IFR in the composite showed great impact and passed UL-94 V-0 and V-1 tests.

The effect of boric acid on flame retardancy of intumescent flame retardant polypropylene composites including nanoclay

In this study, different amounts of boric acid (BA, 1.25, 2.5, 3.75 and 5.0 wt%) were used to enhance the effectiveness of an intumescent flame retardant (IFR) system composed of ammonium polyphosphate (APP) and pentaerythritol (PER) in polypropylene (PP) including 2 wt% montmorillonite nanoclay (MMT). Meanwhile, metaboric acid and boron oxide which were generated by the decomposition of BA appeared in the melt compounding and the burning processes, respectively. Extensive experimental studies were performed to investigate the effects of BA/boron oxide and MMT combinations on the properties of PP/IFR. The fire resistances of the composites were studied by UL 94, limiting oxygen index (LOI) and cone calorimetry tests. The thermal properties were determined by using thermogravimetric analysis, differential scanning calorimetry and thermal conductivity measurements. In addition, the mechanical properties of the composites were examined. The experimental results revealed that although the additions of 1.25 and 2.5 wt% BA with 2 wt% MMT significantly enhanced thermal and flame resistances of PP composites, 3.75 and 5.0 wt% BA additions generated antagonistic effects and deteriorated the fire resistance of the composites. The sample including 2.5 wt% BA addition achieved the best flame retardancy. The LOI value was increased from 18 to 31% with UL 94 V-0 rating. In addition, the peak heat release rate was reduced from 668.6 to 150.0 kW/m2 and the total heat release value was decreased from 247.9 to 98.4 MJ/m2. In the meantime, the thermal conductivity was increased from 0.22 up to 0.28 W/mK. Furthermore, CO, CO2 and the smoke productions were significantly decreased with respect to PP. NO generation was decreased with BA replacements. At the same time, although there was a slight decrease in the tensile strength, the flexural strength significantly increased with BA and MMT additions.

Flame retardant polypropylene reinforced with natural additives

Flame retardant polypropylene composites were modified with fibers and hybrid combination of natural additives (coconut, wood flour, and walnut shell fibers) with high-strength basalt fiber. The composites were subjected to strength tests and flammability analysis to assess the impact of the fibers on flame retardant material, with the fiber content of 5–20 wt%. Mechanical tests showed the positive effect of fibers on strengthening of polypropylene. The introduction of basalt fibers by 5 and 10 wt% increases the strength by 20 and 40 %, and stiffness by 60 and 160 %, respectively. Natural additives as hybrid reinforcement caused approximately 10 % increase in strength and more than twofold increase in stiffness of the composite materials. Burning behavior assessment showed that the use of natural fibers slows down the process of peak heat release by approximately 20 %. The paper also indicates the positive effect of water and accelerated thermal aging on the mechanical properties of the tested composites. The presented research results point the potential of composites with natural additives as construction materials.

Silicone filled halloysite nanotubes for polypropylene composites: Flame retardancy, smoke suppression and mechanical property

The halloysite nanotubes (HNTs-Si) was filled with poly-siloxane and introduced into polypropylene (PP) composite containing intumescent flame retardants (IFR) in order to simultaneously improve the fire performance and mechanical properties. The fire behavior investigation indicated that the peak heat release rate and the peak smoke release rate of PP/IFR sample containing HNTs-Si were reduced by 31% and 26% respectively compared with that of the PP/IFR sample containing HNTs. The elongation at break was greatly increased by the presence of HNTs-Si. The charring mechanism analysis suggested that HNTs-Si was capable of keeping the original tube structure and twisting with degraded PP chains to form “fiber-like” compact char layers in the high temperature range. Consequently, the combination of HNTs-Si and IFR exhibited excellent heat and smoke suppression during the combustion of PP composite. This work has proved that HNTs-Si is an effective synergist in producing flame retardant PP composites with comprehensive properties.

Highly efficient replacement of traditional intumescent flame retardants in polypropylene by manganese ions doped melamine phytate nanosheets

The intumescent flame retardant (IFR) with ammonium polyphosphate (APP) as the main component has many defects in practical applications, more than that, APP can be traced to non-renewable phosphate rock resources. For the foregoing reasons, the melamine phytate supramolecular nanosheet flame retardant incorporating manganese ion (PAMA-Mn) was successfully prepared with a facile and environmental friendly hydrothermal procedure based on renewable bio-based material phytic acid (PA). The flame retardant polypropylene composite (PPI) with 13.5 wt% APP and 4.5 wt% pentaerythritol (PER) failed to the UL-94 test, and its limiting oxygen index (LOI) value was only 26.5%. After 33 wt% of APP was replaced by PAMA-Mn, the PPMn33 incorporating only 18 wt% flame retardant additives passed the UL-94 V-0 rating, and its LOI value was increased to 31.9%. Compared with PP, pHRR and pSPR values of PPMn33 were reduced by 56% and 23%, respectively. The fire retardant mechanism of PPMn33 was thoroughly discussed via a variety of characterization methods. It was found that the peak of the Gram-Schmidt curve of PPMn33 was drastically reduced by 49% relative to that of PPI, indicating a remarkably decrease of combustible volatile products owing to the incorporation of PAMA-Mn, thereby rapidly reducing the fire hazard risk.

Intumescent flame retardant behavior of charring agents with different aggregation of piperazine/triazine groups in polypropylene

To explore the structure mode of charring agent with higher flame retardant efficiency, two charring agents (PT-Cluster and PT) with different aggregation structure of piperazine/triazine groups were synthesized and characterized, and then were applied to preparing intumescent flame retardant polypropylene (PP) composites with ammonium polyphosphate (APP). Both PT-Cluster/APP/PP and PT/APP/PP composites performed excellent intumescent flame retardant effects. The values of LOI reached over 32% while the mass ratio of charring agent was only 3 wt% in the case of 25 wt% IFR loading. The pk-HRR values of 5%PT-Cluster/20%APP/75%PP and 5%PT/20%APP/75%PP were 242 kW/m2 and 330 kW/m2, respectively, which were all decreased by over 73% compared with neat PP. Besides, the total heat release (THR) and average effective heat of combustion (av-EHC) of charring agent/APP/PP were also decreased. More importantly, the aggregated piperazine/triazine groups in PT-Cluster further raised the flame retardant efficiency of charring agent/APP system. PT-Cluster/APP system brought higher residue yields and lower THR, av-EHC and total smoke release than PT/APP in cone calorimeter test, implying that PT-Cluster/APP exhibited better charring and barrier effect, and more effective quenching effect than PT/APP during combustion. The enhanced flame retardant effect was resulted by the aggregated piperazine/triazine groups in PT-Cluster. By means of the macromolecular structure of PT-Cluster, more residues were remained in condensed phase and more phosphorus-containing components were released to gas phase. Accordingly, PT-Cluster/APP performed better condensed-phase and gas-phase effects than PT/APP.