Melamine cyanurate-microencapsulated red phosphorus flame retardant unreinforced and glass fiber reinforced polyamide 66

A novel microencapsulated red phosphorus (RP) was prepared through the molecular self-assembly of melamine cyanurate (MCA). Compared with the conventional encapsulated RP, MCA-encapsulated RP (MERP) shows simpler and more environment-friendly preparation process higher thermal stability and lower moisture absorption. With MERP filled in unreinforced polyamide 66 (PA66) and glass fiber (GF) reinforced PA66, flame retardant materials with satisfactory flame retardancy and mechanical performance can be obtained. The influence of the MCA/RP ratio on the flame retardancy as well as the condensed phase of MERP flame retardant PA66 was investigated to reveal the nitrogen-phosphorus (N-P) synergistic flame retarding effects between MCA and RP.     

MPP/PER/APP系统阻燃的PA6/OMMT纳米复合材料的燃烧特性

以聚磷酸蜜胺(MPP)／季戊四醇(PER)／聚磷酸铵(APP)三元膨胀型阻燃剂(IFR)(其中P／PER／三聚氰胺(MA)的摩尔比为4．1／1．0／1．1)对聚酰胺6(PA6)／有机蒙脱土(OMMT)纳米复合材料(wOMMT=0．03)进行阻燃，测定了阻燃PA6／OMMT的极限氧指数(LOI)及垂直燃烧阻燃性(UL94)，以锥形量热仪(CONE)测定了材料诸多与火灾安全性有关的阻燃参数，包括释热速率、有效燃烧热、总释热量、质量损失速率、比消光面积及引燃时间等，并与PA6、阻燃PA6及PA6／OMMT进行了比较，用扫描电镜(SEM)观察了由CONE测试所得残炭的形态。     

Preparation, properties and characterizations of halogen-free nitrogen-phosphorous flame-retarded glass fiber reinforced polyamide 6 composite

Halogen free nitrogen-phosphorous flame retardants (PMOP) were prepared through reaction of melamine and polyphosphoric acid in the presence of flame retardant modifier CM with silicotungistic acid as a catalyst in aqueous solution. FT-IR, XRD, DSC and TGA techniques were used to characterize the reaction product PMOP. The obtained flame retardants were then used to prepare flame retardant (FR) polyamide 6 (PA6) composite reinforced with glass fiber (GF) and the factors affecting the flame retardancy of the material were also investigated. The FR GF reinforced PA6 composite and the obtained charred layers were analyzed by utilizing TGA, SEM, FT-IR and XRD. The properties of the charred layer were connected with the flame retardancy of the corresponding material to reveal the flame retarding mechanism of FR GF reinforced PA6 composite. The experimental results show that PMOP flame retardant consists of melamine polyphosphate, melamine phosphate and possible melamine pyrophosphate. The presence of CM was found to improve the flame retardancy of FR GF reinforced PA6 composite. It was experimentally found that PMOP flame retardant, which is comparatively stable in the range of processing temperatures of PA6, is particularly suitable for flame retarding PA6 reinforced with GF. With increasing the flame retardant content, the flame retardancy of the FR reinforced material is not improved so obviously. However, the increase in the GF content greatly improves the flame retardancy of the composite, because GF greatly increases the char yield of material, decreases the maximal thermal decomposition rate, promotes the formation of charred layer with (PNO)_x structure and greatly increases the strength of the charred layer. The prepared FR GF reinforced PA6 composites have good comprehensive properties with flame retardancy 1.6 mm UL 94 V-0 level, tensile strength 76.8 MPa, Young's modulus 11.7 GPa, Izod notched impact strength 4.5 kJ/m², flexural strength 98.0 MPa and flexural modulus 7.2 GPa, showing a better application prospect.     

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

Three different boron containing materials, zinc borate (ZnB), borophosphate (BPO₄), and boron and silicon containing oligomer (BSi), were used to improve the flame retardancy of melamine cyanurate (MC) in a polyamide‐6 (PA‐6) matrix. The combustion and thermal degradation characteristics were investigated using limiting oxygen index (LOI), UL‐94 standard, thermogravimetric analysis‐Fourier transform infrared spectroscopy (TGA‐FTIR), differential scanning calorimeter (DSC), and scanning electron microscopy (SEM). All the three boron compounds showed no synergistic effect with MC, and only BPO₄ at high loadings showed comparable LOI values by increasing the dripping rate. For ZnB and BSi glassy film and char formation decreases the dripping rate and sublimation of melamine and give rise to low LOI. According to TGA‐FTIR results, addition of boron compounds does not alter the gaseous product distribution of both MC and PA‐6. The addition of boron compounds affects flame retardancy through physical means. It was noted from the TGA data that boron compounds reduced the decomposition temperature of both MC and PA‐6, also affecting the flame retardancy negatively by premature degradation of MC at low temperatures. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and characterizations of inherent flame retarded polyamide 66 containing the phosphorus linking pendent group

Polyamide 66 (PA66) containing the phosphorus linking pendent group with inherent flame retardancy property was prepared by condensation polymerization of hexamethylene diammonium adipate (AH salt) and 9,10‐dihydro‐10‐[2,3‐di(hydroxycarbonyl)propyl]‐10‐phosphaphenanthrene‐10‐oxide (DDP) as a co‐monomer. Prior to condensation polymerization, DDP was reacted with hexamethylene diamine (HMDA), which made DDP easier to react with AH salt. Then, the DDP‐HMDA was introduced into AH salt solution to prepare inherent flame retarded PA66 (FRPA66). Fourier transform infrared spectra, nuclear magnetic resonance spectra, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, tensile test, vertical burning test, limiting oxygen index test, cone calorimetry, and scanning electron microscopy were utilized to investigate the properties of FRPA66. Experimental results indicated that the bulky pendent phosphorus group tended to destroy the structure regularity of FRPA66 and the molecular weight, crystallinity, and thermal stability reduced. The tensile strength of FRPA66 containing 5 wt% of DDP was 58.44 MPa, and it can achieve a V‐0 rating according to the vertical burning test with the limiting oxygen index value of 33.2%. This indicated that the inherent flame retarded PA66 expanded the application of PA66 materials.     

A novel phosphorus-containing copolyester/montmorillonite nanocomposites with improved flame retardancy

A novel phosphorus-containing flame-retardant copolyester/montmorillonite nanocomposite (PET-co-HPPPA/O-MMT) was synthesized by the in situ intercalation polycondensation of terephthalic acid, ethylene glycol, and 2-carboxyethyl(phenylphosphinic) acid (HPPPA) with montmorillonite (O-MMT). The morphology was characterized by wide-angle X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The effects of organoclay on the thermal properties and melting behaviors of the nanocomposites were investigated by thermogravimetric analysis and differential scanning calorimetry. The flammability of the nanocomposites was characterized by the limiting oxygen index test and the UL-94 vertical test. The results showed that a small amount of organoclay was able to improve the thermal stabilities and the flame retardancy of PET-co-HPPPA copolyesters, and however there was no significant increase in the melting points of nanocomposites when the content of diethylene glycol was controlled as a certain value. The overall crystallization rate of the nanocomposites is greater than that of neat copolyester. The nanocomposites have better flame retardancy than PET-co-HPPPA.     

Polyamide 6 with a flame retardant encapsulated by polyamide 66: Flame retardation, thermo-decomposition and the potential mechanism

A novel encapsulated flame retardant containing phosphorus-nitrogen(MSMM-Al-P) was prepared by encapsulating with polyamide 66(PA66-MSMM-Al-P) for the flame retardation of polyamide 6(PA6).The structure and thermal properties of PA66-MSMM-Al-P were characterized by Fourier-transform infrared spectroscopy,X-ray photoelectron spectroscopy and thermogravimetric analysis.The flammability of PA6 containing flame retardants(MSMM-Al -P and PA66-MSMM-Al-P) was investigated by the limiting oxygen index test,vertical burning test and cone calorimeter. The flame retardancy and cone calorimetric analyses suggested a synergistic effect between PA66 and MSMM-Al-P in the flame-retardant PA6.Thermal stability of the flame-retardant PA6 was also investigated.     

Dispersion of graphene oxide and its flame retardancy effect on epoxy nanocomposites

Graphene oxide was prepared by ultrasonication of completely oxidized graphite and used to improve the flame retardancy of epoxy.The epoxy/graphene oxide nanocomposite was studied in terms of exfoliation/dispersion,thermal stability and flame retardancy.X-ray diffraction and transmission electron microscopy confirmed the exfoliation of the graphene oxide nanosheets in epoxy matrix.Cone calorimeter measurements showed that the time to ignition of the epoxy/graphene oxide nanocomposite was longer than that of neat epoxy.The heat release rate curve of the nanocomposite was broadened compared to that of neat epoxy and the peak heat release rate decreased as well.     

Flame retardancy mechanisms of poly(1,4‐butylene terephthalate) containing microencapsulated ammonium polyphosphate and melamine cyanurate

The flame retardancy mechanisms of poly(1,4‐butylene terephthalate) (PBT) containing microencapsulated ammonium polyphosphate (MAPP) and melamine cyanurate (MC) were investigated via pyrolysis analysis (thermogravimetric analysis (TGA), real‐time Fourier transform infrared (FTIR), TG‐IR), cone calorimeter test, combustion tests (limited oxygen index (LOI), UL‐94), and residue analysis (scanning electron microscopy (SEM)). A loading of 20 wt% MC to PBT gave the PBT composites an LOI of 26%, V‐2 classification in UL‐94 test and a high peak heat release rate (HRR) in cone calorimeter test. Adding APP to PBT/MC composites did not improve their flame retardancy. In comparison with the addition of ammonium polyphosphate (APP) to PBT, MAPP with silica gel shell and MAPP with polyurethane shell both promoted the intumescent char‐forming and improved the flame retardancy of PBT through different mechanisms in the presence of MC. These two halogen‐free PBT composites with V‐0 classification according to UL‐94 test were obtained; their LOI were 32 and 33%, respectively. Copyright © 2010 John Wiley & Sons, Ltd.     

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

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

Preparation of graphene oxide modified glass fibers and their application in flame retardant polyamide 6

In order to improve the flame retardancy of glass fibers (GFs) reinforced polyamide 6 (PA6) composites and eliminate the “wicking effect,” the preparation and application of graphene oxide (GO) modified GFs were investigated in this work. Flame retardant PA6 was prepared by blending graphene oxide modified GFs reinforced PA6 and aluminum diethyl phosphonate. For the GFs reinforced PA6, the limiting oxygen index of the composite increased from 20.6% to 22.3%, and peak heat release rate decreased by 37.2% in cone calorimeter test via introducing graphene oxide onto the surface of GFs. Comparing PA6/GF30/ADP15 and PA6/GF‐GO30/ADP15, LOI of the later increased to 31.2%, the vertical burning test (UL‐94) reached V‐0, and the peak heat release rate decreased by 18.0%. The interface compatibility was greatly improved after the introduction of GO. The sheet structure of the GO on the GFs surface could block the combustible gas spillage and the flow of melt along the GFs, thus significantly attenuating the “wicking effect” and improving the flame retardancy of composites.     

Synergistic flame‐retardant effect of DOPO‐based derivative and organo‐montmorillonite on glass‐fiber‐reinforced polyamide 6 T

Herein, a bridged 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) derivative (PN‐DOPO) in combination with organ‐montmorillonite (OMMT) was used to improve the flame retardancy and mechanical properties of glass‐fiber‐reinforced polyamide 6 T (GFPA6T). The flame retardancy and thermal stabilities of the cured GFPA6T composites were investigated using limiting oxygen index, vertical burning (UL‐94) test, cone calorimeter test, and thermogravimetric analysis (TGA). The morphological analysis and chemical composition of the char residues after cone calorimeter tests were characterized via scanning electron microscopy and energy dispersive spectrometry. The results indicate that 2 wt% OMMT combined with 13 wt% PN‐DOPO in GFPA6T achieved a V‐0 rating in UL‐94 test. The peak heat release rate and total smoke release remarkably decreased with the incorporation of OMMT as compared to those of GFPA6T/15 wt% PN‐DOPO. The TGA results show that the thermal stability and residual mass of the samples effectively increased with the increase in OMMT content. The morphological analysis and composition structure of the residues demonstrate that a small amount of OMMT could help form a more thermally stable and compact char layer during combustion. Also, with the incorporation of OMMT, the layers consisted of more carbon‐silicon and aluminum phosphate char in the condensed phase. Furthermore, GFPA6T/PN‐DOPO/OMMT composites exhibited excellent mechanical properties in terms of flexural modulus, flexural strength, and impact strength than the GFPA6T/PN‐DOPO system. The combination of PN‐DOPO and OMMT has improved the flame retardancy and smoke suppression of GFPA6T without compromising the mechanical properties.     

Great enhancement of efficiency of intumescent flame retardants by titanate coupling agent and polysiloxane

Modified intumescent flame retardants (MIFRs) and polysiloxane (APID) have been used in combination to enhance the flame retardancy of polypropylene (PP). The IFR system was composed of melamine (MEL), ammonium polyphosphate (APP) and pentaerythritol (PER). Aimed to improve the thermal stability of the IFR and its dispersivity in PP, titanate coupling agent NDZ‐201 was used to modify the IFRs via ball milling. MIFRs and APID have a cooperative effect on the flame retardant properties of PP. With 25 wt.% of MIFR and APID, the flame retardant sample (PPMA) was rated V0 for UL‐94, the LOI value was 34.3%, and the peak heat release rate (PHRR) was reduced by 80% in cone calorimeter test. In addition, APID could improve the compatibility of MIFR with the PP matrix, thereby increasing the mechanical properties of PP blends. The flame retardant effect of APID and MIFR in PP was presented in the condensed phase resulting in a rigid, thermally stable and expanded carbon layer due to different char structures.     

Flame‐retardant behavior of bi‐group molecule derived from phosphaphenanthrene and triazine groups on polylactic acid

The flame‐retardant polylactic acid (PLA) has been prepared via mixing the flame retardant TGIC‐DOPO derived from phosphaphenanthrene and triazine groups into matrix. The flame retardancy of TGIC‐DOPO/PLA composites was characterized using the limiting oxygen index (LOI), vertical burning test (UL94), and cone calorimeter test. Results reveal that the 10%TGIC‐DOPO/PLA composite obtained 26.1% of LOI and passed UL94 V‐0 rating. The flame‐retardant mechanism of PLA composites was characterized via thermogravimetric analysis (TGA), pyrolysis gas chromatography/mass spectroscopy, and TGA‐Fourier transform infrared. It discloses that TGIC‐DOPO promoted PLA decomposing and dripping early, and it also released the fragments with quenching and dilution effects. These actions of TGIC‐DOPO contribute to reducing the burning intensity and extinguishing the fire on droplets, thus imposing better flame retardancy to PLA. When TGIC‐DOPO was partly replaced by melamine cyanuric with dilution effect and hexa‐phenoxy‐cyclotriphosphazene with quenching effect in composites respectively, the results confirm that TGIC‐DOPO utilize well‐combination in dilution effect and quenching effect to flame retard PLA. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of surface chemical modification for aluminum hypophosphite with hexa‐(4‐aldehyde‐phenoxy)‐cyclotriphosphazene on the fire retardancy,water resistance,and thermal properties for polyamide 6

The surface chemical modified aluminum hypophosphite (AHP) defined as MAHP was successful prepared through P–H bonds on AHP surface reacted with the aldehyde groups in hexa‐(4‐aldehyde‐phenoxy)‐cyclotriphosphazene made in our lab. The wettability of the flame retardants was evaluated by water contact angle tests, and the water contact angle of the prepared MAHP dramatically increased from 0° for AHP to 145°, which indicated the surface modification made the superhydrophilic AHP into superior hydrophobic MAHP. The prepared MAHP and AHP, respectively, incorporated into polyamide 6 (PA6) matrix to prepare flame retardant PA6 composites and the fire retardancy and thermal degradation behavior of flame retardant PA6 composites were investigated by limiting oxygen index, vertical burning test (UL‐94), cone calorimeter, and thermogravimetric analysis tests. The morphologies and chemical compositions of the char residues for PA6 composites were investigated by scanning electron microscopy and X‐ray photoelectron spectroscopy, respectively. The water resistant properties of flame retardant PA6 composites were evaluated by putting the samples into distilled water at 70°C for 168 hr, and the mechanical properties for flame retardant PA6 composites were investigated by the tensile, flexural, and Izod impact strength tests. The results demonstrated that the PA6/MAHP composites successfully passed UL‐94 V‐0 flammability rating, and the limiting oxygen index value was 27.6% when the loading amount of MAHP was 21 wt%. However, there is no rating in vertical burning tests for PA6/AHP composite with the same amount of AHP, which indicated the surface modification of AHP enhanced the flame retardancy efficiency for PA6 composites. The morphological structures and analysis of X‐ray photoelectron spectroscopy of char residues revealed that the surface modification of AHP benefited to the formation of a sufficient, flame retardant elements rich, more compact and homogeneous char layer on the materials surface during combustion, which prevented the heat transmission and diffusion, limit the production of combustible gases, inhibit the emission of smoke and then led to the reduction of the heat release rate and smoke produce rate. The mechanical properties results revealed that the surface modification of AHP enhanced the mechanical properties, especially the Izod impact strength comparing with that of PA6/AHP composites with the same amount of flame retardant. After water resistance tests, the PA6/MAHP composites remained superior flame retardancy and presented continuous and compact char layer after cone calorimeter tests; however, the fire retardancy for PA6/AHP composite obviously decreased, and the char layer was discontinuous with big hole caused by the extraction of AHP by water during water resistance tests. Copyright © 2017 John Wiley & Sons, Ltd.     

Study of nylon 66–clay nanocomposites via condensation polymerization

Nylon 66–clay (polyamide 66 (PA66)–organophilic montmorillonite (OMT)) exfoliated nanocomposites were synthesized based on nylon 66 salt and organoclay (OMT) modified by hydro-aminocaproic acid via condensation polymerization. And the nanocomposites were characterized by X-ray diffraction and transmission electronic microscopy. Exfoliated morphology with different clay content was obtained. The effects of cation exchange capacity and organic modified agent of OMT on the formation of exfoliated nanocomposites were investigated. It was shown that only suitable cation exchange capacity and organic modified agent could result in the formation of exfoliated morphology under the condition of condensation polymerization. The thermal and flammability properties of the nanocomposites were investigated through thermogravimetry and cone calorimetry experiments. Results indicate that the exfoliated nanocomposites have enhanced thermal stability and flame retardant properties compared with pure PA66.     

Poly(lactic acid) nanocomposites with improved flame retardancy and impact strength by combining of phosphinates and organoclay

To minimize the loading level of the char-forming phosphorus based flame retardants in the poly(lactic acid) (PLA) with reduced flammability, we have developed the flame-retarded PLA nanocomposites by melt blending method incorporating organically modified montmorillonite (OMMT) and aluminium diethylphosphinate (AlPi) additives. The influence of AlPi and OMMT on flame retardancy and thermal stability of PLA was thoroughly investigated by means of the limiting oxygen index (LOI), UL94 test, cone calorimeter, X-ray diffraction (XRD), thermogravimetric analysis and scanning electronic microscopy (SEM). The experimental results show that the PLA/AlPi/OMMT system has excellent fire retardancy. The LOI value increases from 19% for pristine PLA to 28% for the flame-retarded PLA. Cone calorimeter analysis of the PLA/AlPi/OMMT exhibits a reduction in the peak heat release rate values by 26.2%. Thermogravimetric analysis and SEM of cone calorimeter residues indicate that OMMT significantly enhances the thermal stability, promotes char-forming and suppresses the melt dripping. The research of this study implies that the combining of the flame retardant and organoclay results in a synergistic effect. In addition, the flame-retarded PLA nanocomposite also exhibits notable increase in the impact strength and the elongation at break.     

Nanoclay synergy in flame retarded/glass fibre reinforced polyamide 6

Exfoliated clay nanocomposites of flame retarded/glass fibre reinforced polyamide 6 were prepared by twin-screw extrusion compounding. A flame retardant system based on phosphorus compounds and zinc borate was used at various levels in glass fibre reinforced PA6 and nanocomposites. Thermal stability and combustion behaviours were evaluated by TGA, LOI, UL94 and cone calorimetry. Substitution of a certain fraction of the flame retardant with nanoclays was found to significantly reduce the peak heat release rate and delay ignition in the cone calorimeter. Moreover, remarkable improvements were obtained in LOI along with maintained UL94 ratings. Residue characterization by FTIR, XRD and SEM ascribed the enhanced flame retardancy of nanocomposite formulations to the formation of a glassy boron/aluminium phosphate barrier reinforced by clay layers at the nanoscale. The physically strong and consolidated barriers formed from nanocomposites were much more effective in impeding heat and mass transfer compared to those from conventional formulations.     

Flame‐retardant poly (ethylene terephthalate) enabled by a novel melamine polyphosphate nanowire

A novel strategy was developed for the preparation of melamine polyphosphate (MPP) nanowires to achieve a superior flame‐retardant poly (ethylene terephthalate) (PET). Thanks to the well‐designed nanostructure, the prepared MPP nanowires exhibited great thermal stability and flame retardance. Herein with incorporation of only 1‐wt% MPP nanowires (PET/FR1.0 nanocomposite), the limiting oxygen index (LOI) value was dramatically increased to 29.4% from 20.5%, showing self‐extinguishing behavior. Moreover, PET/FR1.0 nanocomposite passed V‐0 UL‐94 rating in the vertical combustion test. However, PET containing 5‐wt% commercial MPP powder (PET/FR_C5.0) only showed a LOI of 27.9% and ignited the absorbent cotton with flammable melt‐droplets. Cone results also presented that introducing 1‐wt% MPP nanowires brought about a crucial decrease in fire hazard of PET, for instance, 11.1% and 7.7% maximum reduction in heat release rate and total heat release, respectively. Thermogravimetric analysis/infrared spectrometry (TG‐FTIR) result indicated that the main pyrolysis volatiles generated from PET degradation including benzoic acid, aromatic compounds, and carbon dioxide were apparently suppressed after introducing MPP nanowires into PET matrixes, suggesting the outstanding obstructing effect of graphited char residue formed in the combustion. This enhanced flame retardancy rooting in addition of MPP nanowires can be attributed to the combined dilution effect in gaseous phase and catalytic carbonization effect in condensed phase.     

软质聚氨酯泡沫塑料用无卤阻燃剂的研究

本文以羟基苯氧膦丙烯酸(CEPP)和三聚氰胺(MA)为原料合成了一种含磷、氮无卤阻燃剂(CMA),采用FT-IR表征了阻燃剂的化学结构,并将该阻燃剂用于软质聚氨酯泡沫(FPUF)的阻燃。用扫描电镜(SEM)研究了阻燃剂的加入对FPUF的形态的影响,通过LO I和垂直燃烧(Cal.117A)测试研究了该阻燃剂对FPUF的阻燃效果。结果表明,CMA可以有效提高FPUF的阻燃性:当CMA的添加量为10%时,FPUF即可通过Cal.117A测试,其LO I值也从17.3提高到23.0;随阻燃剂添加量的增加,FPUF的阻燃性能也逐渐提高。TG测试结果表明CMA的加入对FPUF的热稳定性没有多大影响。