Melamine polyphosphate/silicon‐modified phenolic resin flame retardant glass fiber reinforced polyamide‐6

The halogen‐free flame retardance of glass fiber reinforced polyamide‐6 (PA6) is an everlastingly challenge due to well‐known wick effect. In this research, a novel system composed of a nitrogen–phosphorous flame retardant, melamine polyphosphate combined with a macromolecular charring agent, silicon‐modified phenolic resin (SPR), was employed to flame‐retard glass fiber reinforced PA6. It exhibited obvious synergistic effect between the two components at a proper ratio range. The flame retardance of the composites can be remarkably improved due to the increased amount and improved thermal stability of the produced char. The flame resistance tests indicated that the synergism system with an optimized ratio achieved V0 (1.6 mm) rating of UL94, 25.2% of Limited Oxygen Index, and only 338.2 W/g of the heat release peak rate. The corresponding synergistic mechanisms were investigated by the characterizations including the thermal gravimetric analysis, carbonation test, and the char morphology observation. It confirmed that the introduced SPR could accelerate the carbonation of PA6 resin, which was in favor of the construction of denser and more continuous charring structure. In addition, the flame retardant materials also indicated the acceptable mechanical properties, showing the advantages in the overall performance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A phosphorus‐containing inorganic compound as an effective flame retardant for glass‐fiber‐reinforced polyamide 6

A novel inorganic compound, aluminum hypophosphite (AP), was synthesized successfully and applied as a flame retardant to glass‐fiber‐reinforced polyamide 6 (GF–PA6). The thermal stability and burning behaviors of the GF–PA6 samples containing AP (flame‐retardant GF–PA6) were investigated by thermogravimetric analysis, vertical burning testing (with a UL‐94 instrument), limiting oxygen index (LOI) testing, and cone calorimeter testing (CCT). The thermogravimetric data indicated that the addition of AP decreased the onset decomposition temperatures, the maximum mass loss rate (MLR), and the maximum‐rate decomposition temperature of GF–PA6 and increased the residue chars of the samples. Compared with the neat GF–PA6, the AP‐containing GF–PA6 samples had obviously improved flame retardancy: the LOI value increased from 22.5 to 30.1, and the UL‐94 rating went from no rating to V‐0 (1.6 mm) when the AP content increased from 0 to 25 wt % in GF–PA6. The results of CCT reveal that the heat release rate, total heat release, and MLR of the AP‐containing GF–PA6 samples were lower than those of GF–PA6. Furthermore, the higher additive amount of AP affected the mechanical properties of GF–PA6, but they remained acceptable. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Flame retarding glass fibers reinforced polyamide 6 by melamine polyphosphate/polyurethane‐encapsulated solid acid

Melamine polyphosphate and thermal‐plastic polyurethane (TPU)‐encapsulated solid acid were applied for flame retardant glass fibers reinforced polyamide 6 (GFPA6). The introduction of TPU would change the interfacial property between glass fibers (GFs) and polyamide 6 (PA6), weakening the “candlewick effects” of GFs in PA6. Serving as a synergist, solid acid containing sulfur (CAS) played the role of a strong acid source, which could promote the system to form much more condensed and closed char layers. Macromolecular charring agent, TPU, was able to accelerate the charring process. In addition, TPU encapsulating on the unstable solid acid could isolate CAS from PA6 resin, preventing the chemical interaction between them, which would cause the degradation of material. This established technology provided an effective approach to prepare halogen‐free flame retardant GFPA6 with UL94‐1.6 mm V0 rating and good mechanical performance, showing a promise in the future commercial application. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Flame retardance and mechanical properties of a polyamide 6/polyethylene/surface‐modified metal hydroxide ternary composite via a master‐batch method

Surface‐modified aluminum hydroxide and magnesium hydroxide mixtures (SAMHs) were filled with linear low‐density polyethylene (LLDPE) with a maleic anhydride grafted polyethylene (PE) compatibilizer to produce a SAMH master batch, which was then dispersed in polyamide 6 (PA6) to yield a PA6/PE/SAMH (50/20/30 by weight ratio) ternary composite. Through such a master‐batch method, an effective flame retardance UL94 V‐0 rating at a 3.2 mm thickness with a 33% limiting oxygen index was achieved. The flame‐retardance mechanism of the ternary composite was investigated by thermogravimetric analysis and scanning electron microscopy/energy dispersive X‐ray spectroscopy analysis. A cocontinuous PA6/PE polymer host and a preferential dispersion of SAMH particles in the matrix induced the formation of a compact flame‐resistant char layer and a high residue rate during burning; this resulted in the desired flame retardance of the ternary composite. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of boron‐containing materials on the flammability and thermal degradation of polyamide 6 composites containing melamine

Three different boron‐containing substances—zinc borate (ZnB), borophosphate (BPO₄), and a boron‐ and silicon‐containing oligomer (BSi)—were used to improve the flame retardancy of melamine in a polyamide 6 (PA‐6) matrix. The combustion and thermal degradation characteristics of PA‐6 composites were investigated with the limiting oxygen index (LOI), the UL‐94 standard, thermogravimetric analysis (TGA)/Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). A slight increase was seen in the LOI values of a sample containing BSi (1 wt %). BPO₄ at high loadings showed a V0 rating (indicating the best flame retardancy) and slightly lower LOI values in comparison with samples with only melamine. For ZnB and BSi, glassy film and char formation decreased the dripping rate and sublimation of melamine, and this led to low LOIs. According to the TGA–FTIR results, the addition of boron compounds did not change the decomposition product distribution of melamine and PA‐6. The addition of boron compounds affected the flame retardancy by physical means. The TGA data showed that boron compounds and melamine reduced the decomposition temperature of PA‐6. According to the DSC data, the inclusion of boron compounds increased the onset temperature of sublimation of melamine and also affected the flame retardancy negatively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Flame retardancy and thermal and mechanical performance of intercalated,layered double hydroxide composites of polyamide 11, aluminum phosphinate,and sulfamic acid

Sulfamic acid‐intercalated MgAl‐layered double hydroxide (SA‐LDH) was prepared and added with aluminum phosphinate (AlPi) into polyamide 11 (PA11). The results showed that AlPi/SA‐LDH made a positive contribution to both flame retardancy and thermostability, and the effect was demonstrated with the limiting oxygen index (LOI), vertical burning tests (UL‐94), cone calorimetry (CONE), and thermogravimetric analysis (TGA). The char morphologies were observed by SEM, and its chemical composition was investigated by Fourier transform infrared spectroscopy (FTIR). The decomposition mechanism was examined by TGA‐FTIR. The results showed that the LOI of PA11 was only 23.0 and cannot pass any UL‐94 rating. The addition of 20% AlPi increased the LOI to 31.5 and passed the UL‐94 V‐1 rating, and AlPi/SA‐LDH 15%/5% increased the LOI to 32.4 and also passed the UL‐94 V‐1 rating. The CONE results revealed that 20% of either AlPi or AlPi/SA‐LDH brought about a 30% decrease in the peak heat release rate (pHRR). The contribution of SA‐LDH to flame behavior was especially reflected in the postponement of pHRR. SEM showed that the char morphologies became denser after SA‐LDH incorporation. The improvement in thermal stability of the AlPi/SA‐LDH combination was documented by TGA in both N₂ and air atmospheres. The mechanical performance deterioration caused by AlPi was partly improved by SA‐LDH. The storage modulus (E′) below the T_g of AlPi/SA‐LDH 15%/5% was about 300 MPa higher than with 20% AlPi. This was attributed to a compatibility improvement. The interaction forces among PA11, AlPi, and SA‐LDH were probed by X‐ray photoelectron spectrometry. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43370.     

Flame retardancy and nondripping properties of ammonium polyphosphate/poly(butylene succinate) composites enhanced by water crosslinking

Ammonium polyphosphate (APP)/poly(butylene succinate) (PBS) composites were prepared with a unique water‐crosslinking technique to improve the flame retardancy and nondripping properties of the composites and to maintain the main structure of the composites during flame tests. The composites were treated with a coupling agent (tetraethoxysilane) and then were compounded in a twin‐screw extruder. The compound was moisture‐crosslinked. Fourier transform infrared spectra were used to monitor the water‐crosslinking reaction. The composites via the water‐crosslinking treatment exhibited improved mechanical properties because of the interfacial bonding between the APP and PBS matrix. Scanning electron microscopy of the fractured surfaces of the water‐crosslinked composites showed that the void size increased with increasing water‐crosslinking time. Composites with 15 wt % APP were classified as UL‐94 V‐2; however, the ones with only a 0.5‐h water‐crosslinking reaction were classified as UL‐94 V‐0. Thermal analyses of the water‐crosslinked composites indicated that the thermal degradation temperature of the composites increased with increasing water‐crosslinking time. Differential scanning calorimetry results revealed that the water‐crosslinking reaction could limit the crystallization rate of PBS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2935–2945, 2006     

Flame retardancy and mechanical properties of ferrum ammonium phosphate–halloysite/epoxy polymer nanocomposites

To recycle the nitrogen (N) and phosphorus (P) from wastewater, ferrum ammonium phosphate (FAP)–halloysite nanotubes (HNTs) were synthesized with simulated wastewater containing N, P, and Fe pollutants as raw materials. The adsorption–chemical precipitation in situ method was used to synthesize the target products, and the optimal conditions for the synthesis of the FAP–HNTs were obtained. Fourier transform Infrared (FTIR) spectroscopy, energy‐dispersive spectroscopy (EDS), scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis were conducted to characterize the samples. The FAP particle size was 20–30 nm in the FAP–HNTs. The FTIR spectra demonstrated that a small amount of water in the FAP–HNTs promoted the curing reaction. The FAP–HNTs and Exolit OP 1230 (OP) were introduced into epoxy (EP) to prepare the polymer nanocomposites. The heat release rate (HRR) and flammability of the EP composites were tested by microscale combustion calorimetry and UL‐94 instruments. The mechanical properties of the EP composites also were tested by a tension testing system. The results indicate that the flame retardancy and mechanical properties of the EP composites were improved by FAP–HNT. The addition of FAP–HNT and OP gave rise to an evident reduction of HRR and a prolonged burning time for the EP. EP/FAP–HNT/OP (20) (where 20 is the loading weight percentage) passed the UL 94 V‐0 rating. The analysis of the char revealed the synergy of the FAP–HNTs and OP in reducing the flammability of the polymers. We concluded that these polymers show potential for applications in wastewater treatment and N/P recycling. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41681.     

The flame retardancy and mechanical properties of jute/polypropylene composites enhanced by ammonium polyphosphate/polypropylene powder

Surface flame retarded jute/polypropylene composites (J/P/A) were prepared via a modified strategy: the mixture of PP and APP powder was spread over the surface of jute/PP nonwoven felts, and then transformed into the flame retarded layer by the hot pressing process. The flame retardancy and thermal properties of composites were analyzed by limit oxygen index (LOI), horizontal burning rate (HBR), thermogravimetric analyses (TGA), and differential scanning calorimetry (DSC). We demonstrated that the flame retardancy and mechanical properties of composites was significantly improved compared with those obtained by presoaking the nonwoven fiber felts in flame retardant (FR) solvent before hot pressing. The mechanism of thermal degradation of jute fiber and flame‐retardant mechanism of composites were analyzed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and scanning electron microscope (SEM). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43889.     

Effect of graphite on the flame retardancy and thermal conductivity of P‐N flame retarding PA6

In this article, a novel flame‐retardant polyamide 6 (PA6) was prepared by introducing a halogen‐free flame‐retardant (OP1314). Graphite was added as a flame‐retardant synergistic agent, and the flame retardancy was enhanced, especially the melt‐dripping was forbidden and for the formula of PA6/12 wt % OP1314/5 wt % graphite, UL94 V‐0 grade was reached. Meanwhile, the graphite is also an excellent thermal conductive filler and with the addition of 5 wt % graphite in the flame‐retardant PA6 mixtures, the thermal conductivity (λ) rose to 1.2 W/mK which was nearly three times higher than the flame‐retardant PA6. Due to the good flame retardancy and improved thermal conductivity, the material could be suitable for applications in electronic and electrical devices. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46559.     

Influence of aging conditions on the mechanical properties and flame retardancy of HIPS composites

In this study, we evaluate the changes in physical properties and flame retardancy of HIPS composites after natural aging tests in Turpan (high sunlight radiation dose and dry) and Qionghai (high temperature and rainy) in China for 21 months. The HIPS composite aged in Turpan revealed a higher chromatic aberration than that in Qionghai due to the higher sunlight radiation dose. After aging tests for 21 months, the mechanical properties and the peak heat release of the HIPS composite aged in Qionghai decreased by more than 50% and increased by 39.7%, respectively, results that were worse than for the HIPS composite in aged Turpan. This was related to the combined effects of light, temperature, rain, and moisture in Qionghai leading to more severe degradation of HIPS composites, which results in breaking of the polymer chains and migration and erosion of the flame retardant. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46339.     

Flame retardancy and water resistance of novel intumescent flame‐retardant oil‐filled styrene–ethylene–butadiene–styrene block copolymer/polypropylene composites

A novel halogen‐free flame‐retardant composite consisting of an intumescent flame retardant (IFR), oil‐filled styrene–ethylene–butadiene–styrene block copolymer (O‐SEBS), and polypropylene (PP) was studied. On the basis of UL‐94 ratings and limiting oxygen index (LOI) data, the IFRs consisted of a charring–foaming agent, ammonium polyphosphate, and SiO₂ showed very effective flame retardancy and good water resistance in the IFR O‐SEBS/PP composite. When the loading of IFR was only 28 wt %, the IFR–O‐SEBS/PP composite could still attain a UL‐94 V‐0 (1.6 mm) rating, and its LOI value remained at 29.8% after a water treatment at 70°C for 168 h. Thermogravimetric analysis data indicated that the IFR effectively enhanced the temperature of the main thermal degradation peak of the IFR–O‐SEBS/PP composites because of the formation of abundant char residue. The flammability parameters of the composites obtained from cone calorimetry testing demonstrated that water treatment almost did not affect the flammability behavior of the composite. The morphological structures of the char residue and fractured surfaces of the composites were not affected by the water treatment. This was attributed to a small quantity of IFR extracted from the composite. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39575.     

Rheology of a low‐filled polyamide 6/montmorillonite nanocomposite

The rheological properties of a polyamide 6/clay nanocomposite with a low loading of clay (1 wt %) were studied. Linear viscoelastic measurements in oscillatory and steady shear with small strain amplitudes were carried out. The nanocomposite exhibited a higher elastic modulus, viscous modulus, and complex viscosity than neat polyamide 6 during dynamic and steady shear tests. Moreover, the addition of clay resulted in a reduction of the critical strain amplitude, an increase of the loss angle, and a reduction of the frequency at the intersection of the elastic and viscous moduli. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Enhancement of flame retardancy and mechanical properties of polyamide 6 by incorporating melamine cyanurate combined with attapulgite

In this study, the nanocomposites are prepared which used polyamide 6 (PA6) composite as matrix, melamine cyanurate (MCA) as fire retardant and attapulgite (AT) as synergistic agent. The mathematical model between MCA content, AT content, and limited oxygen index (LOI) is established by multiple linear regression fitting. The polymer materials are characterized using Fourier transform infrared spectroscopy, X-ray diffraction, Thermogravimetric Analysis, and scanning electron microscopy. Through response surface methodology, the important variables (polymerization time, the content of MCA, and the content of AT) affecting the mechanical strength of composites are modeled. Results demonstrate that when the t is 0.6 h, the AT content is 6.2%, and the MCA content is 11.5%, the mechanical properties of the PA6/MCA/AT composite are up to 44.81 MPa, and the sample passes the UL-94 V-0 flammability rating, and the LOI reaches 27.9%. Therefore, polymers with highly effective flame retardancy and optimal mechanical properties are prepared. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47298.     

Role of caged bicyclic pentaerythritol phosphate alcohol in flame retardancy of PA6 and mechanism study

A series of PA6/PEPA composites were prepared by mixing caged bicyclic pentaerythritol phosphate alcohol (PEPA) and polyamide 6 (PA6) at different feed ratios by the melt‐blending method in a twin‐screw extruder. The influence of PEPA on the flame‐retardant properties of PA6 was investigated using the limiting oxygen index (LOI), the Underwriters Laboratories UL‐94 test, and the cone calorimeter method. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, X‐ray photoelectron spectroscopy, thermogravimetry (TG), and TG‐FTIR were conducted to study the influence of PEPA on the thermal decomposition and the mechanism of performance of PA6 from products of condensed and gaseous phases. The results show that the LOI value and the content of residual char of PA6/PEPA composites increased with increasing PEPA content, and an LOI value of 38% could be reached when the feed ratio of PEPA was 30 wt %. The average heat release rate and total heat release drastically decreased with increasing content of PEPA, and the amount of carbon residue increased by 52.9% over neat PA6 after TG tests. The inorganic acid produced by PEPA during combustion can be used as an acid source to promote the dehydration of PA6 and the processes of esterification crosslinking, arylation, and carbonization. Moreover, there was less CO₂ released than by PA6, and more carbon‐containing compound remained in the composites so that a stable carbon layer structure was formed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46236.     

Flame retardancy and mechanical properties of EVA nanocomposites based on magnesium hydroxide nanoparticles/microcapsulated red phosphorus

The flame retardancy and mechanical properties of ethylene vinyl acetate (EVA) polymer nanocomposite based on magnesium hydroxide (MH) nanoparticles with lamellar‐shape morphological structures and synergistic agent microcapsulated red phosphorus (MRP) have been studied by limiting oxygen index (LOI), cone calorimeter test (CCT), UL‐94 test, tensile strength (TS), and elongation at break (EB). Results showed that LOI values of lamellar‐like nanosized MH (50 × 350 nm²) samples were 1–7 vol. % higher than those of the common micrometer grade MH (1–2 μm) in all additive levels. When 1–3 phr MRP substituted for nanosized MH filler, LOI value increased greatly from original 37 to 55, and met the V‐0 rating in the UL‐94 test. The values of TS for MH nanoparticles composites increased from 10.4 to 17.0 MPa as additive loading levels increased from 80 to 150 phr, respectively, while the corresponding values for common micrometer MH composites decreased steadily from 9.7 to 7.1 MPa. Thermogravimetric analysis (TGA) and dynamic Fourier‐transform infrared spectroscopy (FTIR) results revealed two‐step flame‐retardant mechanism. First, MH particles decompose endothermically with the release of 30.1% hydration water in the 320–370°C temperature range. Second, MRP promote the formation of compact charred layers slowly in the condensed phase in the 450–550°C temperature range. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Flame retardancy and mechanical properties of pet‐based composites containing phosphorus and boron‐based additives

Flame retardancy of poly(ethylene terephthalate), PET, was improved using different flame retardant additives such as triphenylphosphate, triphenylphosphine oxide, zinc borate, and boron phosphate (BP). Composites were prepared using a twin screw extruder and subsequently injection molded for characterization purposes. The flame retardancy of the composites was determined by the limiting oxygen index (LOI) test. Smoke emission during fire was also evaluated in terms of percent light transmittance. Thermal stability and tensile properties of PET‐based composites were compared with PET through TGA and tensile test, respectively. The LOI of the flame retardant composites increased from 21% of neat PET, up to 36% with the addition of 5% BP and 5% triphenyl phosphate to the matrix. Regarding the smoke density analysis, BP was determined as an effective smoke suppressant for PET. Enhanced tensile properties were obtained for the flame retardant PET‐based composites with respect to PET. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42016.     

Fire retardancy and durability of poly(N‐benzyloxycarbonyl‐3,4‐dihydroxyphenylalanine)‐montmorillonite composite film coated polyimide fabric

Polyimide (PI) fabric was coated with composite films composed of poly(N‐benzyloxycarbonyl‐3,4‐dihydroxyphenylalanine) (PNBD) and montmorillonite (MMT), prepared via layer‐by‐layer assembly. Three coating recipes (changed by altering the concentration of PNBD solution) were used to study the growth of thin films. Scanning electron microscope showed that, after 20 times standard washing, PNBD‐MMT film still coated on PI fiber, while MMT film coated on PI had been almost washed off. Thermogravimetric analysis indicated that, in nitrogen atmosphere at 900°C, the residue of uncoated PI was 36.62%, after 20 times standard washing, residue of PNBD‐MMT coated PI (53.80%) was higher than that of MMT coated PI (50.08%). Vertical flame testing showed that the burning length of PNBD‐MMT coated PI (7 mm) was much shorter than that of uncoated PI (30 mm) and MMT coated PI (17 mm) after 20 times standard washing. These results demonstrated the excellent flame retardancy and durability of PNBD‐MMT film coated PI fabric. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39608.     

Function of the aryl group in bis DOPO phosphonate on reducing fire hazards of polyamide 6 composites

The increased integration interaction of bis 9,10-dihydro-9-oxa- 10-phospaphenanthrene-10-oxide (DOPO) phosphonate (abbreviated as FR) including ethyl-(FR1), phenethyl-(FR2), naphthalene-(FR3) with the aryl group and hexa-phenoxy-cyclotriphosphazene (HPCP) on flame-retardant polyamide 6 (PA6) were investigated. The role of the aryl group in FR on flame-retarding PA6 was analyzed. Results showed that PA6 composites with greatly reduced fire hazards possessed a high-limiting oxygen index value of 34% and achieved a UL-94 V-0 rating and sharply decreased peak heat release rate by simultaneously adding FR and HPCP. Flame inhibition effect acted as the main mechanism for FR and HPCP in flame-retarding PA6. Gas phase action increased with the number of aryl groups. HPCP played a catalytic effect in the condensed phase. Particularly, the result of residue analysis after cone test implied that char surface with network structure was formed, and the structure became compact and continuous with the increase in the number of aryl groups. Furthermore, the aryl group played an important role in aiding the PA6 composites in the construction of a network protective char layer on the surface during combustion.     

Thermal stability,flame retardance,and mechanical properties of polyamide 66 modified by a nitrogen–phosphorous reacting flame retardant

Flame‐retardant polyamide 66 (PA66) was prepared by the polymerization between PA66 prepolymer and N‐benzoic acid (ethyl‐N‐benzoic acid formamide) phosphamide (NENP). Compared with the pure PA66, the flame‐retardant PA66 exhibited better thermal stability, as indicated by thermogravimetric analysis results. The limiting oxygen index was 28% and the UL‐94 test results of the flame‐retardant PA66 indicated a V‐0 rating when the content of the NENP prepolymer was 5 wt %. The flammability and flame‐retardant mechanism of PA66 were also studied with cone calorimetry and scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, respectively. The mechanical properties results show that the flame‐retardant PA66 resin had favorable mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43538.