Intumescent Flame Retardant Polypropylene Research Articles

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

The preparation of ZIF-67 and its synergistic effect on fire performance of intumescent flame retardant polypropylene

The preparation of ZIF-67 and its synergistic effect on fire performance of intumescent flame retardant polypropylene

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.

Synergistic flame retardant effect of cerium‐based DOPO derivative and intumescent flame retardants in polypropylene

AbstractIn this study, cerium based DOPO derivative (Ce@DDP) was synthesized by hydrothermal method, and its effects on flame retardancy, thermal stability, and mechanical properties of intumescent flame retardant polypropylene (PP) are investigated. When addition of 17 wt% of intumescent flame retardants (IFR) and 1 wt% of Ce@DDP, the results indicate that the peak heat release rate (PHRR) and peak smoke production rate (PSPR) of the resulted PP composite is reduced by 62.0% and 42.3%, respectively. Meanwhile, the vertical burning rating reaches UL94 V‐0, and the limiting oxygen index (LOI) is 33.8%. Furtherly, the Ce@DDP significantly improves the thermal stability and char formation ability of PP/IFR. Notably, Ce@DDP exhibits better synergistic flame retardant and mechanical strength for PP/IFR than CeO2. Finally, it was speculated that there was dilution effect and radical quenching effect in gas phase, and catalytic carbonization effect in condensed phase of IFR/Ce@DDP system, and the combined action of the these aspects led to high‐efficiency flame retardant.

A novel highly efficient intumescent flame-retardant polypropylene: Thermal degradation, flame retardance and mechanism

A novel highly efficient intumescent flame-retardant polypropylene: Thermal degradation, flame retardance and mechanism

Micro-Nanometer Particle Composition and Functional Design of Surface Nano-Structured Ammonium Polyphosphate and Its Application in Intumescent Flame-Retardant Polypropylene.

A novel composite and functional micro-nanometer particle is designed by the hydrolysis of aluminium isopropoxide on the surface of ammonium polyphosphate (APP) to prepare surface nanostructured ammonium polyphosphate (NSAPP). NSAPP is characterised by XPS, XRF, SEM, water solubility tests, and TGA. Results indicate that nanosized aluminium hydroxide is deposited on the surface of NSAPP, which enhanced its water resistance and thermostability. Then, APP and NSAPP coupled with dipentaerythritol (DPER) is used for the flame retardant of polypropylene (PP). The limiting oxygen index (LOI) value of the PP/DPER/NSAPP composite is higher than that of PP/DPER/APP. Besides, the UL 94 vertical burning test of PP/DPER/NSAPP composites can reach the V-0 rating easily. According to the study of the combustion behaviour of FR-PP composites, NSAPP contributes to form a dense and multi-layered char in the combustion process. Thus, such an intumescent char with a ceramic-like, continuous, and dense structure over the PP matrix protects the underlying matrix and enhances the thermal stability of the condensed phase, thereby improving the flame retardant performance of FR-PP.

Synergistic Flame-Retardant Effect of Aluminum Diethyl Phosphinate in PP/IFR System and the Flame-Retardant Mechanism

Abstract Synergistic flame-retardant effect of aluminum diethyl phosphinate (AlPi) in intumescent flame retardant polypropylene (PP/IFR) system and the flame-retardant mechanism were investigated. The flame retardancy of PP/IFR/AlPi (the mass ratio of IFR to AlPi is 2 : 1) was the best, which was proved by the results of the limiting oxygen index (LOI) test, UL-94 test, and cone calorimeter test ( CCT) test. Here, the LOI value of the sample was as high as 34% and passed the V–0 rating in UL–94 test. The peak heat release rate (PHRR) decreased by 92.57%, the total heat release (THR) reduced by 90.52%. Thermogravimetric (TGA) data showed that the introduction of AlPi improved thermal stability and changed the thermal degradation behavior of PP/IFR composites. Interestingly, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS) and laser Raman spectroscopy (LRS) proved that PP/IFR/AlPi had formed more residual carbon, but the flame retardancy was worse than PP/IFR/AlPi. This is because when the mass ratio of IFR to AlPi is 2 : 1, the synergy between IFR and AlPi was significant, gas-phase flame retardant and condensed-phase flame retardant reached a balance and obtained the best flame retardant effect.

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.

Effect of modified layered double hydroxide on the flammability of intumescent flame retardant PP nanocomposites

AbstractThe dodecyl sulfate intercalated CaMgAl‐hydrotalcites (layered double hydroxides [LDHs]) were successfully prepared by co‐precipitation method, and characterized by X‐ray diffraction analysis, infrared spectroscopy (Fourier transform infrared spectra [FT‐IR]), thermogravimetry (TG‐DTA), scanning electron microscope, and Brunner−Emmet−Teller (BET). The prepared LDHs were added to the intumescent flame retardant (IFR) polypropylene (PP) nanocomposites, and the limiting oxygen index method (LOI), vertical combustion method (UL‐94), cone calorimetry (CCT), and other test methods were used to study its thermal stability and combustion performance. The results showed that when the flame retardant was composed of 23 wt% IFR and 2 wt% O‐SDS‐LDHs, the LOI value of the material was increased to 31.5%, reaching the V‐0 level, and the flame retardant performance was significantly improved. The results also showed that there was a significant synergistic effect between IFR and O‐SDS‐LDHs, which could improve the thermal stability and graphitization degree of PP nanocomposites. In addition, the peak heat release rate, total heat release, and total smoke production of the PP/IFR/O‐SDS‐LDHs system were 177 kW/m2, 101 MJ/m2, and 15.4 m2, respectively, which were 82.2%, 51.0%, and 23.0% lower than those of pure PP, respectively. These improvements could be attributed to the presence of dense and continuous char layer formed by the synergistic effect.

Synergistic effect of fly ash on hydroxymethylated lignin‐containing flame retardant polypropylene: Flame retardancy and thermal stability

In this study, fly ash (FA) was used as a synergist to enhance the fire resistance of intumescent flame retardant polypropylene containing hydroxymethylated lignin. Effects of fly ash on flame retardancy and thermal stability properties of polypropylene (PP) composites were investigated using a limiting oxygen index (LOI) meter, UL‐94 vertical combustion tester, cone calorimeter, and thermogravimetric analyzer. The results showed that during combustion, incorporation of FA can effectively solve the dripping problem of the PP composites. Addition of 0.5% loading amount fly ash into the PP composite (0.5FA/IFR/PP) enhanced the flame retardancy significantly. Additionally, its LOI value increased from 28% to 33%, and UL‐94 vertical burning passed V‐0 grade from V‐2 rate. Notably, owing to addition of the fly ash, the peak of heat release rate of the pure PP decreased by 58.0%. Moreover, the release of CO2 and CO was largely suppressed, and higher char residue was obtained for 0.5FA/IFR/PP. Fire safety of the PP composites was significantly improved. From the analysis of charring residues, a possible flame retardant mechanism was proposed. That is, incorporation of fly ash increased the formation of a denser and intact char layer, which is important in inhibiting heat and flammable gases generated during combustion of underlined matrix.

Enhancement of the intumescent flame retardant efficiency in polypropylene by synergistic charring effect of a hypophosphite/cyclotetrasiloxane bi-group compound

The influence of a hypophosphite/cyclotetrasiloxane bi-group compound (MVC-AlPi) on the efficiency of intumescent flame retardant polypropylene (PP/IFR) consisting of ammonium polyphosphate (APP) and hyperbranched triazine-based charring agent (HTCFA) was investigated through evaluating the fire behavior and thermal stability by limiting oxygen index (LOI), the vertical burning tests (UL94), cone calorimeter and thermogravimetric analysis (TGA). The scanning electron microscopy (SEM), fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the final residues. The thermal decomposition and char-forming behavior between MVC-AlPi and each IFR formulation was studied by TGA and thermogravimetry-fourier transform infrared spectroscopy (TG-IR) test. Results revealed that a little amount substitution of IFR by MVC-AlPi imparted overall improvement in flame retardancy with reduced heat/smoke release and UL 94 V-0 rating for composites with a total loading of only 18 wt% instead of 25 wt%. The thermal decomposition behavior analysis exhibited a synergistic char-forming effect after the combination of MVC-AlPi, improving high-temperature thermal stability and yield of residual char with phosphorus- and silicon-containing crosslinked structures due to the interactions between MVC-AlPi and IFR, especially APP. The introduction of silicon into the cross-linked structures generated a fishnet-like protective device covering on the char surface inhibiting bursting the foamed carbonaceous structures and buttressed cell walls not to be fractured, leading to the formation of an integrated and thick intumescent char layer, plus the factor of the early and gentle release of non-flammable gases. This lifted flame retardant efficiency mainly contributed to the condense-phase mechanism with not ignored flame inhibition of phosphorus-containing free radicals generated from MVC-AlPi pyrolysis in gas phase. This work provided a potential way to enhance the flame retardant efficiency of IFR system.

Enhanced Flame Retardancy and Mechanical Properties of Intumescent Flame-Retardant Polypropylene with Triazine Derivative-Modified Nano-SiO2

Nano-silica was modified with triazine derivative and characterized using FTIR and TGA techniques. Then the hybrid nano-silica was blended with polypropylene and intumescent flame retardant to prepare a novel intumescent flame-retardant polypropylene. Nitrogen and phosphorus elemental mapping micrographs and SEM micrographs elucidated that the hybrid nano-silica could facilitate intumescent flame retardant to disperse more uniformly in polypropylene. TGA results showed that hybrid nano-silica could improve the thermal stability of polypropylene. With 18% intumescent flame retardant and 2% hybrid nano-silica, the novel intumescent flame-retardant polypropylene got a limiting oxygen index of 29.7% and passed the vertical burning (UL-94) V-0 rating. Cone calorimeter test showed that the peak heat release rate and total heat release clearly decreased.

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.

Effect of hollow glass microsphere on the flame retardancy and combustion behavior of intumescent flame retardant polypropylene composites

Nowadays, increasing the fire safety of polypropylene (PP) is an important research direction. In this article, the investigation mainly focuses on the effect of hollow glass microsphere (HGM) on improving the fire safety of PP/intumescent flame retardants (IFR) composites. The flame retardancy, smoke suppression and thermal stability of PP/IFR/HGM system were studied by limiting oxygen index (LOI), vertical burning (UL-94), cone calorimeter tests (CCT) and thermogravimetric analysis. All the results demonstrated that the incorporation of HGM into PP/IFR system can clearly improve the fire safety of PP/IFR materials. The result of the LOI can be as high as 36.5% with only 1 wt% HGM and 24 wt% IFR addition. Scanning electron microscope–energy-dispersive spectrometer (SEM–EDS) and CCT results illustrated that during the combustion, HGM would migrate onto the surface of the sample to form a compact char layer and prevent further combustion of the material. Furthermore, the CCT results indicated that HGM can slow down the peak heat release rate (from 94.9 to 61.6 kW/m2) and make the total smoke release (TSR) decrease from 1210 m2/m2 (PP/IFR) to 544 m2/m2 (PP/IFR/HGM), reduced by 55.0%. In addition, HGM can improve the thermal stability of PP/IFR systems.

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.

Comparison of Pentaerythrotol and Its Derivatives as Intumescent Flame Retardants for Polypropylene

Hydroquinol bis[di(2,6,7-trioxa-phosphabicyclo[2.2.2]-octane-1-oxo-4-hydroxylmethyl)]phosphate (PBPP), which contains caged phosphates and benzene groups, was synthesized. The caged phosphate structure of PBPP was characterized by Fourier transform infrared spectroscopy (FT-IR), hydrogen nuclear magnetic resonance (1H-NMR), and phosphorus nuclear magnetic resonance (31P-NMR). The experimental results showed that PBPP had better performance than 1-oxo-4-hydroxymethy1-2,6,7-trioxa-1-phosphabicyclo[2.2.2]-octane (PEPA) and pentaerythritol (PER) in water resistance, compatibility with polypropylene (PP), thermal stability, and flame retardancy of intumescent flame retardant PP (IFR-PP) systems. It was attributed to the symmetrical structure and stereohindrance effect of PBPP. The IFR-PP systems reached UL94 V-0 flammability rating when the minimal addition of IFR with PBPP, PEPA, or PER was 25%, 23%, and 28%, respectively. The flame retardant mechanisms of IFR containing PBPP, PEPA, and PER were investigated by FT-IR and scanning electron microscopy (SEM). PBPP formed a perfect charring layer, with the high carbon content of PBPP helping it form the charring layer more quickly.

Morphology Influence of Nanoporous Nickel Phosphate on Intumescent Flame Retardant Polypropylene Composites

Abstract The morphology of nanoporous nickel phosphate (NP) has a close relationship with its properties, so in this work NP with needle-like and mushroom-like shape was synthesized. Then NP with needle-like and mushroom-like shape was applied in intumescent flame retardant polypropylene (PP) composites. With the addition of suitable content of NP, both mushroom-like and needle-like NP can improve the combustion and thermal properties of intumescent flame retardant PP composites. Needle-like NP shows a better thermal ant flame retardant synergist effect with intumescent flame retardants compared to mushroom-like NP. However, mushroom-like NP shows a better effect on smoke suppression. With the addition of suitable content of needle-like NP, the peak heat release rate of flame retardant PP composite decreases by 68.2 % comparing with that of the pure PP, and decreases by 23.8 % comparing with that of flame retardant PP composite without NP. The maximum weight loss temperature of PP composites can be increased from 408 °C to 485 °C with the addition of needle-like NP. Furthermore, the pyrolysis products of flame retardant PP composite with needle-like NP were investigated. From the research, it provides a further understanding of the influence on synergic effects in intumescent flame retardant systems.

Synthesis and characterization of a novel organic-inorganic hybrid char-forming agent and its flame-retardant application in polypropylene composites

A novel organic-inorganic hybrid char-forming agent (SCTCFA-ZnO) was synthesized and characterized by Fourier transform infrared spectrometry (FTIR) and solid state nuclear magnetic resonance (SSNMR). SCTCFA-ZnO was combined with ammonium polyphosphate (APP) to prepare intumescent flame retardant polypropylene (PP) composites. The flame retardancy and thermal degradation behaviour of composites were investigated by the means of limited oxygen index (LOI), vertical burning test (UL-94), cone calorimeter test (CONE) and thermogravimetric analysis (TGA). The flame retardant pattern and mechanism of PP composites were studied by thermogravimetric analysis/infrared spectrometry (TG-IR), scanning electron microscopy (SEM), laser Raman spectroscopy analysis (LRS), FTIR and X-ray photoelectron spectroscopy (XPS). The results indicated APP/SCTCFA-ZnO system with the mass ratio of 2:1 showed the best flame retardant properties and smoke suppression performance in PP composites. TGA results showed that APP/SCTCFA-ZnO could clearly improve the thermal stability of composites and promote the char residue formation. The residue analysis results further revealed higher graphitic cross-linking structures containing more P, O, N and Si in PP/APP/SCTCFA-ZnO consequently resulted in more obvious reduction of the combustion and smoke production than PP/APP/SCTCFA/ZnO.

Studies on intumescent flame retardant polypropylene composites based on biodegradable wheat straw

SummaryWheat straw (WS) has numerous advantages compared with traditional bioadditives such as starch and lignin. So in this work, based on WS and silica microencapsulated ammonium polyphosphate, flame retardant polypropylene/wheat straw (WSP) composites were prepared by melted blend method. Flame retardant and thermal properties of WSP composites have been investigated. The results of cone calorimeter show that peaks of heat release rate and total heat release of the flame retardant WSP composite decrease substantially compared with those of pure polypropylene. The peak of heat release rate value of the flame retardant WSP composite decreases from 1290.5 to 247.9 kW/m2, and the total heat release value decreases from 119.4 to 46.3 MJ/m2. Meanwhile, thermal degradation and gas products of the flame retardant WSP composite were monitored by thermogravimetric analysis and thermogravimetric analysis‐infrared spectrometry. The result of thermal analysis shows that the flame retardant WSP composite has a high thermal stability and has a 30.0 wt% residual char at 600°C. From this work, we hope to provide a method to prepare flame retardant polymer composites with a biodegradable natural material‐WS.