Synergistic effect of melamine polyphosphate with macromolecular charring agent novolac in wollastonite filled PA66

In this article, macromolecular charring agent linear novolac (NA) was served as a synergist with nitrogen‐phosphorous flame retardant melamine polyphosphate (MPP) for the flame‐resistance of wollastonite (WT) filled polyamide 66 (PA66). The investigations showed that MPP/NA system possessed obvious synergistic effects by increasing the charring rate and amount, therefore, showing much higher flame retardancy than the filled PA66 flame retarded with MPP alone. The corresponding char layer structure of MPP/WT/PA66 and MPP/NA/WT/PA66 was investigated and their difference was analyzed. In addition, as a multifunctional additive, NA could act as a compatibilizer and lubricant in the system, and endowed the material with improved mechanical performance and processability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Properties of talc/wollastonite/polyamide 6 hybrid composites

In this study, it was aimed to investigate the mechanical, thermal, and morphological properties of PA6 hybrid composites containing talc and wollastonite. Talc and wollastonite filled single and hybrid composites were prepared with melt compounding in a twin screw extruder. The filler content was 40% by weight and the wollastonite/talc ratio was 40/0, 30/10, 20/20, 10/30, and 40/0. The melt flow rate measurements showed that incorporation of fillers into the polyamide 6 (PA6) resulted in an increment in melt viscosity of composites. The presence of a homogeneous dispersion of fillers in the matrix was obtained from morphological analysis. It was revealed from the mechanical tests that in most cases, mechanical properties of 20/20 hybrid composites were significantly higher than that of the single and the other hybrid composites. Heat deflection temperature of the composite was markedly improved by the addition of fillers. Differential scanning calorimeter analysis showed that talc and wollastonite acted as a nucleating agent for PA6. POLYM. COMPOS., 36:739–746, 2015. © 2014 Society of Plastics Engineers     

Influence of morphology and ammonium polyphosphate dispersion on the flame retardancy of polystyrene/nylon‐6 blends

The influences of the distribution of ammonium polyphosphate (APP) in polystyrene/nylon‐6 [PS/polyamide‐6 (PA6)] blends and the continuity of the (PA6 + APP) phase on flame retardancy were investigated. The flame retardant properties were evaluated by limiting oxygen index (LOI), vertical flammability test and cone calorimeter tests. The results showed that APP is exclusively dispersed in the PA6 phase, and (PA6 + APP) phase formed a continuous state when the content of PA6 in PS/PA6 blends was higher than 32% (w/w). For blends with a continuous (PA6 + APP) phase, the decrease of PA6 content caused an increase in LOI values from 26% to 33% and a reduction of peak heat release rate. The improvement of flame retardancy was attributed to the increase of APP concentration in the PA6 phase, which benefited the fast formation of a continuous intumescent charred layer. The transformation of (PA6 + APP) phase morphology from a continuous state to a discontinuous state at a PA6 content of below 32% (w/w) caused a decrease in LOI. Results of thermo‐gravimetric and cone calorimeter tests indicated that the discontinuous intumescent charred layer thus formed could be responsible for the deterioration of flame retardant properties, which was also confirmed by scanning electron microscopy. Copyright © 2013 John Wiley & Sons, Ltd.     

成炭剂和分子筛协同MPP对PA6的阻燃性研究

将聚磷酸三聚氰胺(MPP)作为阻燃剂阻燃PA6,研究了高效成炭(剂CFA)和4A分子筛对MPP阻燃PA6性能的影响,并通过热失重分(析TGA)对材料进行了表征。结果表明:CFA和4A分子筛对MPP具有协效阻燃作用,加速了PA6阻燃时的成炭化学反应,改善了炭层结构。当阻燃体系中添加26%的MPP、4%的CFA和2%的4A分子筛时P,A6的氧指数可达到35%,垂直燃烧通过UL94 V—1级。     

Effect of Phosphorus-Based Flame Retardants and PA6 on the Flame Retardancy and Thermal Degradation of Polypropylene

The investigation mainly focuses on the effect of polyamide 6 (PA6) and phosphorus based flame retardants (FRs) on improving the flame retardancy of polypropylene (PP). The flame retardant properties have been studied by limiting oxygen index, vertical burning test tests and cone calorimeter testing. The results demonstrate that PA6 and FRs can greatly improve the flame-retardant and thermal properties of PP. It’s found that the addition of PA6/APP/FRs can promote the formation of stable intumescent char layers. Those indicate that the flame retardancy of PA6/APP/FRs/PP composites is improved by the condensed-phase action of PA6/APP/FRs.     

Preparation of polyamide resin‐encapsulated melamine cyanurate/melamine phosphate composite flame retardants and the fire‐resistance to glass fiber‐reinforced polyamide 6

In this study, melamine cyanurate (MCA)/melamine phosphate (MP) composite flame retardants were synthesized in the solution of phosphoric acid/polyamide 6 (PA6). Phosphoric acid acted as the solvent of PA6, catalyst of melamine‐cyanurate self‐assembly reaction and reactant of melamine‐phosphoric acid reaction. With the consumption of the acid, the pH value of the system increased, and the solved PA6 precipitated on the surface of the flame retardant particles to form polymeric encapsulation. This technology realized the synthesis and surface modification of the flame retardants in one process. The catalyst and solvent, phosphoric acid, was finally converted into the product MP, and need no an additional removing process. The encapsulated MCA/MP (EMCMP) composite flame retardants were successfully applied in the fire‐resistance to glass fiber (GF)‐reinforced PA6. Because the encapsulated layer of EMCMP was also PA6, good interfacial compatibility and effective dispersion of EMCMP in PA6 resin can be obtained, and the corresponding flame retardant materials showed excellent flame retardancy and mechanical performance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1773–1779, 2006     

玻璃纤维增强尼龙66改性研究进展

阐述了玻璃纤维增强尼龙66在增韧改性、阻燃改性、耐溶剂改性、耐磨改性、界面改性、复合改性和制备工艺改进等方面的研究进展。指出玻璃纤维增强尼龙66目前常用的增韧方法是与弹性体和高韧性聚烯烃共混,而阻燃改性的有效手段是添加微胶囊化红磷和P-N型阻燃剂。     

Preparation of microencapsulated red phosphorus through melamine cyanurate self‐assembly and its performance in flame retardant polyamide 6

A novel technology was developed to prepare microencapsulated red phosphorus (RP) with a coating of melamine cyanurate (MCA) serving as both a nitrogen‐containing flame retardant and as a solid lubrication agent. We took advantage of the self‐thickening effects during the MCA self‐assembly process to realize effective encapsulation on the surface of predispersed RP powder. The technology described in this article can overcome several drawbacks of current microencapsulation processes including (1) relatively complicated preparation processes, (2) use of formaldehyde or other noxious modifiers, and (3) poor compatibility with flame retardant fillers and polymer matrix resulting in poor physical properties. Additionally, this novel technology can also modify various properties of RP with regard to lubrication performance, ignition point, moisture absorption ratio, and color. As a composite system of flame retardant phosphorus encapsulated by a nitrogen‐containing flame retardant, the microencapsulated RP showed nitrogen‐phosphorus (N‐P) synergism with further improved flame retardancy. The action and mechanisms of the microencapsulated RP flame retardant polyamide 6 (PA6) were investigated by limiting oxygen index, vertical burning experiment (UL94), thermogravimetric analysis, and scanning electron microscope observations. The results indicated that the flame retardant PA6 possessed desired flame retardancy because of effective char‐formation of the condensed phase and it also showed satisfactory mechanical properties as the result of the good compatibility between flame retardant and PA6 resin. POLYM. ENG. SCI., 46:1548–1553, 2006. © 2006 Society of Plastics Engineers     

Effect of melamine polyphosphate on thermal degradation of polyamides: a combined X-ray diffraction and solid-state NMR study

The effect of melamine polyphosphate (MpolyP) on the thermal degradation of both polyamide 66 (PA66) and polyamide 6 (PA6) was studied using a combination of solid-state techniques. The mixtures of MpolyP with polyamides were heated for different times at 350 and 450 °C. The residues were then analyzed by X-ray diffraction and both solid-state ¹³C NMR and ³¹P NMR. The chemical structures formed in these oven experiments were used to study the chemical changes that take place during a standard flammability test. The mixtures of MpolyP with polyamides were also characterized by frequency-dependent rheological experiments. It was shown that MpolyP could induce significant cross-linking in PA66 and leads to dramatic depolymerization of PA6. These results were used to explain the performance of MpolyP as a flame retardant in these polyamides.     

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     

Synthesis of novolac‐based char former: Silicon‐containing phenolic resin and its synergistic action with magnesium hydroxide in polyamide‐6

Novel novolac‐based char former silicon‐containing phenolic resin (SCPR) was synthesized by the reaction of novolac with γ‐aminopropyltriethoxysilane in ethanol via a dehydration reaction, and the synthesized SCPR was characterized by Fourier transform infrared (FT‐IR) spectra, proton nuclear magnetic resonance (¹H NMR) spectroscopy, and thermogravimetric analysis (TGA). Serving as a synergist of magnesium hydroxide (MH) for the flame retardancy of polyamide 6 (PA6), it shows that the introduction of silicon in the structure of novolac molecule can greatly increase the charring performance of phenolic resin, and effectively eliminate the melt drips of PA6, thus improving the flame retardancy of the PA6. Compared with conventional novolac, the thermal oxidative stability of SCPR was obviously enhanced in the presence of MH due to the decrease of phenol hydroxide groups sensitive to oxidation, as well as the high energy Si–O bond introduced in the molecular structure. Copyright © 2010 John Wiley & Sons, Ltd.     

次磷酸盐⁃环四硅氧烷双基化合物复配二乙基次磷酸铝对PA6的阻燃性能研究

将次磷酸盐?环四硅氧烷双基化合物（MVC?AlPi）与二乙基次磷酸铝（AlPi）复配阻燃聚酰胺6（PA6）。目的是考察外加的富磷酸铝化合物中磷酸铝基团和环四硅氧烷基团之间的配比对PA6阻燃效率的影响。结果表明, PA6/8.8 %AlPi/2.2 %MVC?AlPi具有协同屏障效应,可使复合材料的极限氧指数（LOI）值提高到31.5 %,并通过UL 94 V?0级别。相比于纯PA6,PA6/8.8 %AlPi/2.2 %MVC?AlPi的热释放速率峰值（PHRR）降幅近50 %、总热释放量（THR）也降低了15 %,PA6/8.8 %AlPi/2.2 %MVC?AlPi的残炭率虽略低于11 %MVC?AlPi,却形成了内层坚硬,外层类陶瓷化的双层炭层结构,MVC?AlPi、AlPi与PA6的相互作用可以锁定更多P、C碎片,促进由含硅富磷残渣组成的屏障保护炭层的形成。在阻燃剂添加总量不变的情况下,通过调节各组分的比例,发挥出更好的协同阻燃效果。     

Highly thermally stable novolac derivatives and their properties in epoxy composites

Two diazo‐coupling novolac derivative resins (carbonyl phenyl azo novolac resin and carbonyl phenol–biphenylene azo novolac resin) were used as flame retardants. The cured resins exhibited elevated glass‐transition temperatures from 115°C (blank) to 195 and 167°C, respectively. The char yield at 800°C was increased, which elaborated the effectiveness of flame retardancy with evaluated limiting oxygen indices around 36 to 40. This was mainly attributed to the increased crosslink densities and highly aromatic contents in the modified phenol novolac derivative resins, which exhibited higher thermal degradation energies. Furthermore, the more effective flame retardancy was expected because of the loss of nitrogen during combustion. Through the evaluation of the cooperative flame retardancy in the organic/inorganic hybrid with char yield and increasing limiting oxygen index percentage, the effects of the filler showed cooperative flame retardancy only with the appropriate addition and with a difference in the crosslinking densities. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Flame retardant properties of polyamide 6 with piperazine pyrophosphate

Piperazine pyrophosphate (PAPP) was mixed in polyamide 6 (PA6) to investigate its flame retardant properties. The PAPP was characterised by Fourier transform infrared (FT-IR), elemental analysis, proton nuclear magnetic resonance (1H-NMR) spectroscopy and thermogravimetric analysis (TGA). The elemental analysis and TGA results of PAPP indicated it had a high P element content and good thermal stability. The flame retardancy of PA6/PAPP was also characterised by TGA, limiting oxygen index (LOI), UL-94 vertical test and microscale combustion calorimetry (MCC). The TGA results showed that the PAPP increased the stability of the PA6/PAPP and resulted in a significant increase of char residue. PA6/PAPP passed the UL94 V-0 rating with a LOI value of 42 vol %. The MCC test indicated that the PAPP can greatly decrease the peak heat release rate (PHRR) and total heat release (THR). The results of scanning electron microscope (SEM) illustrated that PAPP can promote the formation of compact char layer.     

Mechanical properties and morphology of nylon‐6 hybrid composites

In this investigation, the influence of filler type and filler content on the mechanical properties of nylon‐6 is investigated. The mineral fillers were selected on the basis of their shape and size: flake‐like kaolin and talc, spherical glass beads or fibrous wollastonite. These fillers were added to nylon‐6 individually or in mixed combinations. They were added at different percentages varying between 10 and 30% w/w. Samples of the composites were prepared by the injection moulding process. Uniaxial tensile, Izod impact and flexural tests were carried out. Tensile strength, elongation at break, modulus of elasticity and impact energy were obtained and compared. In case of single fillers the results showed that the tensile strength, modulus of elasticity and their flexural values for nylon‐6 composite improve with the increase in filler content while mixed compounds showed no significant changes above 15% + 15% w/w filler. However, for single and mixed filler up to 10% w/w, the impact strength and maximum elongation at break showed significant decrease. In general, the maximum improvement in mechanical the addition of 10–15% w/w filler. Copyright © 2003 Society of Chemical Industry     

The investigation on the flame retardancy mechanism of nitrogen flame retardant melamine cyanurate in polyamide 6

Melamine cyanurate (MCA) flame retardant polyamide 6 (PA6) shows good flame retardancy, but the corresponding mechanisms have not been completely understood. In this paper, Fourier transform infrared spectra (FTIR), elemental analysis (EA), scanning electronmicroscope (SEM), energy dispersive scanning (EDS), thermogravimeric analysis (TGA) and pyrolysis-gas chromatogram-mass spectrometer (Py-GC-MS) were conducted to investigate the processes including melt-drip phase, gaseous phase and condensed phase of MCA/PA6 system. Compared with original PA6, it is found that MCA flame retardant PA6 mainly undergoes predominant weak bond-breakage degradation forming oligomers rather than oxidative degradation producing low-boiling point fuel as original PA6 does. The produced oligomers can accelerate the formation of the melt drips which effectively removes the combustion heat and latent fuel, also the self-condensation of these oligomers is advantageous to form stable cross-linking structure, thus greatly consolidating the char layer.     

无卤膨胀阻燃PP/PA6合金性能研究

研究了以聚磷酸铵（APP）、三聚氰胺（MA）和层状复合金属氢氧化物（LDH）复配得到的膨胀阻燃剂（IFR）对聚丙烯／尼龙6（PP／PA6）合金性能的影响，分析了不同阻燃体系对PP／PA6合金的阻燃性能、力学性能、热性能和微观形态的影响。结果表明，当APP／MA／LDH为21．0／7．5／1．5（质量比）时，PP／PA6合金具有较好的阻燃性能并能保持较高的力学性能。LDH可以提高阻燃材料的热稳定性和残炭量，而且SEM照片显示炭层微观形态为“面包”状的膨松状。     

Synergistic effects of ammonium polyphosphate/melamine intumescent system with macromolecular char former in flame-retarding polyoxymethylene

The improvement of the flame retardancy of polyoxymethylene (POM) is a world-wide difficult problem due to its zippered decomposition property. This paper reported the preparation of the flame-retarding (FR) POM with the synergistic combination of ammonium polyphosphate (APP)/melamine (ME) intumescent flame retardant system and macromolecular char former (MC). The UL94 testing, mechanical properties testing, thermogravimetric analysis (TGA), cone calorimetry and scanning electron microscopy (SEM) were used to investigate the corresponding structure, performance and synergistic flame retardant mechanism. The experimental results showed that, in the used macromolecular char formers (novolac, PA6 and TPU), the combination of novolac with APP/ME intumescent system has the best synergism in flame-retarding POM, greatly enhancing the quality of the formed condensed charred layer and hence the corresponding flame retardancy. The obtained FR POM composite could achieve flame retardancy of UL94 3.2 mm V-0 level and remarkably decreased heat release rate relative to pure POM. The synergistic effect of novolac was shown to be the char formed cross-linking reaction of it with APP. Due to the thermodynamic compatibility of novolac and POM, the prepared FR POM composite also has fairly good mechanical performance, having tensile strength of 49.1 MPa and Izod notched impact strength of 2.60 kJ/m².     

Influence of polyamide 6 as a charring agent on the flame retardancy,thermal, and mechanical properties of polypropylene composites

In this work, polyamide 6 (PA6) as a charring agent has been used in combination with thermoplastic polyurethane (TPU)‐microencapsulated ammonium polyphosphate (MTAPP) forming intumescent flame retardants (IFRs) which applies in polypropylene (PP). The effects of the IFRs on the flame retardancy, morphology of char layers, water resistance, thermal properties and mechanical properties of flame‐retardant PP composites are investigated by limiting oxygen index (LOI), UL‐94 test, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and mechanical properties test. The results show that the PP/MTAPP/PA6 composites exhibit much better flame‐retardant performances than the PP/MTAPP composites. The higher LOI values and UL‐94 V‐2 of the PP/MTAPP composites with suitable amount of PA6 are obtained, which is attributed to the thick and compact char layer structure evidenced by SEM. The results from TGA and DSC demonstrate that the introduction of PA6 into PP/MTAPP composites has a great effect on the thermal stability and crystallization behaviors of the composites. Furthermore, the mechanical properties of PP/MTAPP/PA6 composites are also improved greatly due to the presence of PA6 as a charring agent. POLYM. ENG. SCI., 55:1355–1360, 2015. © 2015 Society of Plastics Engineers     

New strategy towards flame retardancy through design,synthesis, characterization,and fire performance of a chain extender in polyamide 6 composites

A novel flame‐retardant chain extension agent (9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide)‐3,5‐triglycidyl isocyanurate defined as DOPO‐TGIC was synthesized, and its chemical structure was well characterized and confirmed. The effect of DOPO‐TGIC as a synergistic agent on the flame retardancy, rheology, thermal and mechanical properties of polyamide 6/aluminum diethylphosphinate (PA6/AlPi) composites were investigated in details. The results demonstrated that PA6/AlPi/DOPO‐TGIC composites (1.6 mm) successfully passed UL‐94 V‐0 rating with the limiting oxygen index value of 30.5% when the total loading amount of AlPi/DOPO‐TGIC was 10 wt%. In order to achieve the equal flame‐retardant level, the individual AlPi was required 14 wt%. The incorporated DOPO‐TGIC improved the complex viscosity of PA6/AlPi/DOPO‐TGIC composites due to the chain extending reaction between epoxide groups in DOPO‐TGIC and the terminal groups of PA6 matrix. The mechanical performance of PA6/AlPi/DOPO‐TGIC composites was also improved compared with that of PA6/AlPi composites. DOPO‐TGIC stimulated to the formation of more sufficient and compact char layer during combustion. The higher melt viscosity and compact char layer of PA6 composites effectively constrained the volatilization of flammable gases, thus the heat release was reduced. Consequently, the introduction of DOPO‐TGIC simultaneously enhanced the flame retardant and mechanical properties of PA6/AlPi/DOPO‐TGIC composites compared with that of PA6/AlPi composites. POLYM. ENG. SCI., 59:E206–E215, 2019. © 2018 Society of Plastics Engineers