Flame Retardancy Of Polypropylene Composites Research Articles

Microparticle-aggregation effect of intumescent flame retardants on flame retardancy and toughening property of polypropylene

It is a widespread problem that loading intumescent flame retardant (IFR) into polypropylene (PP) always sacrificed the mechanical properties significantly. To develop PP composites with high flame retardancy and toughness, a new intumescent flame retardant (TAIC-IFR) with microparticle-aggregation structure was synthesized by a straightforward in-situ cemented method. Through its microparticle-aggregation effect, the TAIC-IFR enhanced the toughness and charring flame retardancy of PP composites, compared with the traditional intumescent flame retardant mixtures. The 3TAIC-24IFR/PP sample exhibited an increase in impact strength and elongation at the break by 71.8 % and 233.5 % respectively compared with 27IFR/PP. The cemented TAIC-IFR particles with rough surfaces and triallyl triazine triketone component enhanced the interface performance between the fillers and PP matrix. In addition, the TAIC-IFR with particulate microparticle-aggregation characteristics promoted charring reactions among different flame retardant components, thereby enhancing its char-forming flame retardant effect in PP. Specifically, 1TAIC-24IFR/PP with cemented aggregated flame retardant particles exhibited a UL 94 V-0 rating and 28.5 % of limiting oxygen index (LOI), while PP with IFR mixture performed no UL 94 rating and a lower LOI. Moreover, the residue rate of 1TAIC-24IFR/PP increased to 15.9 % from 0 % of PP in cone calorimeter test. These results were attributed to the microparticle-aggregation effect of the acid source, carbon source, and gas source in TAIC-IFR particles, which exhibited better charring effect and barrier effect. This work provides a new idea for designing construction way of flame retardants to develop polymer materials with high flame retardancy and good toughness.

Synergistic Effect of Activated Carbon, NiO and Al2O3 on Improving the Thermal Stability and Flame Retardancy of Polypropylene Composites.

It is difficult to enhance the char yields of polypropylene (PP) due to the preferential complete combustion. Successful formation of abundant char layer structure of PP upon flammability was obtained due to the synergistic effect of NiO, Al2O3 and activated carbon (AC). From characterization of scanning electron microscopy (SEM) and transmission electron microscopy (TEM), it was revealed that the microstructure of residual char contained large amount of carbon nanotubes. Compared to the modification of AC, NiO and Al2O3 alone, the combination of AC, NiO and Al2O3 dramatically promotes the charring ability of PP. In the case of AC and NiO, NiO plays a role of dehydrogenation, resulting in the degradation product, while AC mainly acts as carbonization promoter. The addition of Al2O3 results in higher dispersion and smaller particle size of NiO, leading to greater exposure of active sites of NiO and higher dehydrogenation and carbonization activity. Compared to the neat PP, the decomposition temperature of the PP modified by combined AC, NiO and Al2O3 was increased by 90 ℃. The yield of residual char of AC-5Ni-Al-PP reached as high as 44.6%. From the cone calorimeter test, the heat release rate per unit area (HRR) and total heat release per unit area (THR) of PP composite follows the order AC-5Ni-Al-PP < AC-10Ni-Al-PP < AC-Ni-PP < AC-15Ni-Al-PP < AC-1Ni-Al-PP. Compared to the neat PP, the peak of HRR declined by 73.8%, 72.7%, 71.3%, 67.6% and 62.5%, respectively.

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.

Synthesis of a triazine-based macromolecular hybrid charring agent containing zinc borate and its flame retardancy and thermal properties in polypropylene

A triazine-based macromolecular hybrid charring agent containing zinc borate (MCA-K-ZB) was synthesized and combined with ammonium polyphosphate (APP) to improve the flame retardancy of polypropylene (PP). The flame retardancy and thermal properties of PP composites were investigated using limited oxygen index, vertical burning test, and thermogravimetric analysis. The results showed APP/MCA-K-ZB can improve the flame retardancy of PP compared with APP/MCA-K/ZB. The morphology of the char residues was investigated by scanning electron microscopy (SEM). The SEM result shows that MCA-K-ZB can improve the compactness and continuity of char residue compared with MCA-K/ZB, therefore improving the flame retardancy of PP composites.

Synthesis, Characterization of sym-2,4,6-trisubstituted-s-Triazine Derivatives and Their Effects on Flame Retardancy of Polypropylene Composites

Polypropylene (PP) is flammable material, which brings latent danger to the environment and human society. Therefore, developing new environmentally friendly and effective flame-retardant is one of the most important ways to improve the flame retardancy of PP and improve safety during its lifetime. Herein, we describe the synthesis of five sym-2,4,6-trisubstituted-s-triazine derivatives, namely, N2,N4,N6-triphenyl-1,3,5-triazine-2,4,6-triamine (TAT), N2,N4,N6-tris(4-bromophenyl)-1,3,5-triazine-2,4,6-triamine (TBAT), N2,N4,N6-tris(4-chlorophenyl)-1,3,5-triazine-2,4,6-triamine (TCAT), 4,4′,4″-((1,3,5-triazine-2,4,6-triyl) tris(azanediyl)) triphenol (THAT), and N2,N4,N6-tris(4-methoxyphenyl)-1,3,5-triazine-2,4,6-triamine (TMAT), from the reaction of cyanuric chloride and p-substituted aniline employing conventional heating or microwave irradiation. The prepared compounds characterized by different techniques, such as Fourier-transform infrared (FTIR), Ultra-Violet and Visible (UV-Vis), Nuclear Magnetic Resonance spectroscopy (1H-NMR and 13C-NMR), Thermogravimetric Analysis (TGA), and differential scanning calorimetry (DSC). The effect of substituent on the aniline moiety has great impact on its thermal stability, as observed from the TGA and DSC data. Based on the TGA and DSC results, three triazine derivatives TAT, TBAT, and TMAT were used as charring agents in the presence of different proportions of ammonium polyphosphate (APP) to form an intumescent flame-retardant (IFR) system, to improve the flame retardancy of PP. The flammability property of PP was investigated by a vertical burning test (UL94). The results of UL94 revealed that the TXAT/APP (IFR) system influence the PP and could improve the flame retardancy of PP. Best results were obtained with the mass ratio of APP and TXAT 2:1. When the IFR loading was 25 wt%, it displayed great influence and passed V-0 with TMAT, and V-1 with both TAT and TBAT in the UL94 test.

Flame Retardant Polypropylene Composites with Low Densities.

Polypropylene (PP) is currently widely used in areas requiring lightweight materials because of its low density. Due to the intrinsic flammability, the application of PP is restricted in many conditions. Aluminum trihydroxide (ATH) is reported as a practical flame retardant for PP, but the addition of ATH often diminishes the lightweight advantage of PP. Therefore, in this work, glass bubbles (GB) and octacedylamine-modified zirconium phosphate (mZrP) are introduced into the PP/ATH composite in order to lower the material density and simultaneously maintain/enhance the flame retardancy. A series of PP composites have been prepared to explore the formulation which can endow the composite with balanced flame retardancy, good mechanical properties, and low density. The morphology, thermal stability, flame retardancy, and mechanical properties of the composites were characterized. The results indicated the addition of GB could reduce the density, but decreased the flame retardancy of PP composites at the same time. To overcome this defect, ATH and mZrP with synergetic effect of flame retardancy were added into the composite. The dosage of each additive was optimized for achieving a balance of flame retardancy, good mechanical properties, and density. With 47 wt % ATH, 10 wt % GB, and 3 wt % mZrP, the peak heat release rate (pHRR) and total smoke production (TSP) of the composite PP-4 were reduced by 91% and 78%, respectively. At the same time, increased impact strength was achieved compared with neat PP and the composite with ATH only. Maintaining the flame retardancy and mechanical properties, the density of composite PP-4 (1.27 g·cm−3) is lower than that with ATH only (PP-1, 1.46 g·cm−3). Through this research, we hope to provide an efficient approach to designing flame retardant polypropylene (PP) composites with low density.

Synthesis of a bio‐based triazine derivative and its effects on flame retardancy of polypropylene composites

ABSTRACTA triazine derivative CC–Cy was synthesized using cytosine (Cy) and cyanuric chloride (CC). The CC–Cy was used as a charring agent and combined with ammonium polyphosphate (APP) to form an intumescent flame‐retardant (IFR) system. The IFR system was applied to improve the flame retardancy of polypropylene (PP). Moreover, bisphenol‐A bis(diphenyl phosphate) (BDP) was introduced in the IFR system to regulate the suitability between the IFR and PP. The results showed the PP containing 20 wt % APP and 5 wt % CC–Cy achieves the UL‐94 V‐2 rating. While the PP with 18 wt % APP/CC‐Cy (4:1) and 3 wt % BDP obtains the UL‐94 V‐0 rating indicating the improved flame‐retardant efficiency. Thermal degradation behaviors and char morphology both showed that the reactions between APP and CC–Cy promote the formation of char residues, and BDP works in gas phase to enhance the flame retardancy of PP composites. Thus, a synergistic IFR system based on APP, CC–Cy, and BDP is formed, which can protect PP from fire effectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 47367.

Regulating Effect of Exfoliated Clay on Intumescent Char Structure and Flame Retardancy of Polypropylene Composites

An exfoliated montmorillonite (E-MMT) was prepared by introducing Ni2+ and melamine formaldehyde into layers of MMT. The E-MMT was applied to regulate the flame retardant properties of polypropylene (PP)/intumescent flame retardant (IFR) composites. The IFR used consists of ammonium polyphosphate (APP) and a charring agent, 1,3,5-triazine-2,4,6-trimorpholinyl (TTM). The results revealed that the E-MMT has good synergistic effect on flame retardancy of PP/IFR composites. The PP composites with 16 wt % IFR and 3 wt % E-MMT can pass the UL94 V-0 test. Moreover, the E-MMT not only improves the char residues of IFR and PP/IFR blend but also changes the micromorphology of char, turning the compact surface char produced by PP/IFR into microporous char. This microporous char is so good for isolating heat and mass between PP and the outside that a better flame retardant property is obtained.

Mechanical performance and flame retardancy of polypropylene composites containing zeolite and multiwalled carbon nanotubes

ABSTRACTIntumescent‐flame‐retarded polypropylene (PP‐IFR) composites were prepared by the incorporation of methyl hydrogen siloxane treated ammonium polyphosphate and dipentaerythritol in a twin‐screw extruder. The effects of zeolite (Z), multiwalled carbon nanotubes (CNTs), and maleic anhydride grafted polypropylene on the flame retardancy, mechanical properties, and thermal stability of PP‐IFR were investigated. The addition of Z and CNT promoted the flame retardancy of PP‐IFR, and the highest limited oxygen index was 35.6%, obtained on PP‐M‐IFR‐2–Z, for which the heat‐release rate, total heat release, and smoke production rate based on cone calorimetry analyses decreased by 45.0, 51.0, and 66.3%, respectively, in comparison with those values of the PP‐IFR composites. Additionally, scanning electron microscopy analyses showed that there was a good interface interaction between the polypropylene matrix and additives. The flexural, tensile, and impact strengths of the PP‐IFR composites were improved significantly with the incorporation of CNT. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42875.

Synthesis of a New Silicon-Phosphorus Hybrid Flame Retardant from Waste Silicon Oil and its Application in Polypropylene System

A new silicon-phosphorus hybrid (SPH) flame retardant was synthesized by condensation reaction of 1-oxo-4-hydroxymenthyl-2,6,7-trioxa-1-phosphabicy[2,2,2] octane (PEPA) with waste silicon oil which is mainly consisted of the compounds of CxHySizCln. The effect of Si/P hybrid on the flame retardancy of polypropylene composites (PP/Si-P) was studied by limiting oxygen index (LOI) test and thermogravimetric analysis (TGA). The flame retarding performance of PP/SPH/MP/PER at the same loading amount is slightly higher relative to MP/PER. This, in plus to the low cost and the value in environmental protecting, makes SPH possess the application potential in flame retardants.

Synergistic effect of boron containing substances on flame retardancy and thermal stability of clay containing intumescent polypropylene nanoclay composites

AbstractThe functions of nanoclay and three different boron containing substances, zinc borate (ZnB), borophosphate (BPO4), and boron silicon containing preceramic oligomer (BSi), were studied to improve the flame retardancy of polypropylene (PP)‐nanoclay‐intumescent system composed of ammonium polyphosphate (APP) and pentaerythritol (PER). The flame retardancy of PP composites was investigated using limiting oxygen index (LOI), UL‐94 standard, thermogravimetric analysis (TGA), and cone calorimeter.According to the results obtained, the addition of 20 wt% intumescent flame retardant (IFR) improved the flame retardancy by increasing the char formation. Addition of clay slightly increases the LOI value and reduces the maximum heat release rate (HRR). Addition of clay also increases the barrier effect due to intumescent char, especially in thin samples. Boron compounds show their highest synergistic effect at about 3 wt% loading. According to UL‐94 test and LOI test, 3 wt% ZnB containing composite shows the highest rating (V0) and BPO4 containing sample shows the highest LOI value (26.5). Copyright © 2010 John Wiley &amp; Sons, Ltd.

Synergistic effect of boron containing substances on flame retardancy and thermal stability of intumescent polypropylene composites

The synergistic effect of four different boron containing substances, zinc borate (ZnB), borophosphate (BPO 4), boron silicon containing preceramic oligomer (BSi) and lanthanum borate (LaB), were studied to improve the flame retardancy of a polypropylene (PP) intumescent system composed of ammonium polyphosphate (APP) and pentaerythritol (PER). The flame retardancy of PP composites was investigated by limiting oxygen index (LOI), UL-94 standard, thermogravimetric analysis (TGA) and cone calorimeter tests. The addition of 20 wt% intumescent flame retardant (IFR) improves the flame retardancy by increasing the char formation. According to LOI and UL-94 test, boron compounds show their highest synergistic effect at 1 wt% loading. BPO 4 containing composite shows the highest LOI (30), lowest maximum heat release rate (HRR) and lowest total heat release rate (THR) value. Although the char yield increases as the amount of boron compounds increases, the flame retarding effect decreases. Cone calorimeter and TGA data indicate that the boron compounds are likely to show their synergistic effect by reinforcing the integrity of char which improves its barrier effect rather than increasing the char yield.

Influence of surface modification of fillers and polymer on flammability and tensile behaviour of polypropylene-composites

An intumescent system consisting of ammonium polyphosphate (APP) as an acid source and blowing agent, pentaerythritol (PER) as a carbonific agent and natural zeolite (clinoptilolite, Gördes II) as a synergistic agent was used in this study to enhance flame retardancy of polypropylene (FR-PP). Zeolite was incorporated into flame retardant formulation at four different concentrations (1, 2, 5, and 10 wt%) to investigate synergism with the flame retardant materials. Filler content was fixed at 30 wt% of total amounts of flame retardant PP composites. Zeolite and APP were treated with two different coupling agents namely, 3-(trimethoxysilyl)-1-propanethiol and (3-aminopropyl)-triethoxysilane for investigation of the influence of surface treatments on mechanical properties and flame retardant performance of composites. Maleic anhydride grafted polypropylene (MAPP) was used for making polypropylene hydrophilic. Flammability of FR-PP composites was measured by the determination of limiting oxygen index (LOI). The LOI values reached to a maximum value of 41% for mercapto silane treated APP:PER (2:1) PP composite containing 5 wt% zeolite. The tensile strength of composites was increased by the addition of MAPP and elongation at break of composites was increased with silane treatments.