Melamine cyanurate surface treated by nylon of low molecular weight to prepare flame‐retardant polyamide 66 with high flowability

In the present research, a nitrogen‐based flame‐retardant, melamine cyanurate (MCA) was surface‐treated with low‐molecular‐weight nylon through a solvent process to further improve its flowability and dispersion. The surface energy and flow energy of the modified MCA were investigated. The properties of polyamide 66 (PA66) prepared with surface‐treated and with conventional MCA were evaluated and compared. Because of lower surface energy and flow energy for modified MCA, its agglomeration degree and flow resistance are obviously decreased compared with conventional MCA, thus achieving finer and more homogenous dispersion in the PA66 matrix. Moreover, the low‐molecular‐weight nylon resin encapsulating MCA surface will melt at lower temperature during compounding with PA66; hence, it serves as a lubricant and carrier to further improve the flowability and dispersion of the flame retardants. Based on these advantages, the modified MCA flame‐retardant PA66 achieves much better flame retardancy, flowability, and mechanical properties compared with conventional MCA/PA66 under the same loading level of flame retardant (10 wt%).     

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     

Highly dispersed melamine cyanurate flame‐retardant epoxy resin composites

Ultrafine dispersion of flame retardants in polymer matrices favors improving the performance of flame‐retardant polymers, but is still a challenge on most occasions. In the present research, an efficient method was employed to realize satisfactory dispersion of a nitrogen flame retardant, melamine cyanurate (MCA), in epoxy resin (EP) composites, and meanwhile integrated the synthesis of MCA with the preparation of the flame‐retardant composites. In the conventional technology, EP pre‐polymer glue with added MCA powder (synthesized in water, then dried and pulverized) is used to coat glass fabrics, which are compressed into laminated boards. Here, MCA was synthesized in a good solvent for EP, and then EP pre‐polymer was directly dissolved in the MCA suspension to obtain the in situ synthesized flame‐retardant glue. In this way, MCA could keep perfect dispersion whether in the glue or cured resin. Compared with the conventional addition system easily resulting in the aggregation of MCA particles, the in situ synthesized MCA flame‐retardant system exhibited much better stability of the coating glue, and markedly improved flame retardancy and mechanical properties. © 2016 Society of Chemical Industry     

改性MCA的固相合成及其在PA6中的应用

本实验选用一种新的方法合成改性三聚氰胺氰尿酸盐(MCA),将三聚氰胺(MA)、氰尿酸(CA)和极少量水混合成膏状物并使其在室温下反应一定时间,再加入少量MCA和二氧化硅(Si O2)溶胶使其继续反应以制备改性MCA(mMCA)阻燃剂。将制备的mMCA与尼龙6(PA6)熔融共混制备阻燃PA6复合材料。用FTIR、XRD和TG对所制mMCA进行了表征,对阻燃PA6复合材料的阻燃性能和力学性能进行了测试。结果表明:所制mMCA的FTIR、XRD特征峰与MCA的特征峰一致;m MCA的最大热失重温度有了较大的提升达到465.2℃。在PA6复合材料中,当阻燃剂含量为13%时,阻燃PA6复合材料的极限氧指数(LOI)达到33%,阻燃性能为UL-94 V0级,锥形量热测试的PHRR降低了26.3%。随着阻燃剂含量的增加,复合材料的力学性能有所提高。与传统大量水体系制备mMCA方法相比,此法具有工艺简单、不需加热、耗水量极低,没有污水排放等优点。     

The effect of morphology on the flame‐retardant behaviors of melamine cyanurate in PA6 composites

Three types of melamine cyanurate (MCA) with micrometer‐size sphere‐like, micrometer‐scale rod‐like, and nanometer‐scale flake‐like morphologies were synthesized by changing the chemical circumstances of the reactions. The microcosmic morphologies of MCA were characterized via scanning electron microscopy and X‐ray diffraction. After the MCAs with different morphologies were incorporated into polyamide 6 (PA6), the flame‐retardant properties of the MCA/PA6 composites were investigated using the limited oxygen index (LOI), UL94, and cone calorimeter tests. The MCA/PA6 composites with nanometer‐scale flake‐like MCA obtained an LOI value of 29.5% and a UL94 V‐0 rating, which were higher than those with micrometer‐size sphere‐like and rod‐like MCAs. However, the different morphologies did not affect the heat release rate, total smoke release, average carbon monoxide yield, and average carbon dioxide yield based on the cone calorimeter. The flame‐retardant mechanism of MCAs with different morphologies was investigated via thermal gravimetric analysis (TGA) and TGA‐Fourier transform infrared spectra. The results show that the different morphologies of MCA resulted in different dispersed evenness of MCA. Further, the nanometer‐scale flake‐like morphology of MCA brought more interactions of hydrogen bond between MCA and PA6, which resulted in the delay of MCA decomposition and the enhancement of MCA flame‐retardant effect. The nanometer‐scale flake‐like MCA had a better performance compared with the other samples because of the delaying and even release of flame‐retardant effect by the decomposition of evenly dispersed MCA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40558.     

Preparation and characterization of flame‐retardant melamine cyanurate/polyamide 6 nanocomposites by in situ polymerization

This article focuses on an improved method, i.e., improved in situ polymerization of ε‐caprolactam in the presence of melamine derivatives to prepare flame‐retardant melamine cyanurate/polyamide 6 (MCA/PA6) nanocomposites. The chemical structures of these synthetic flame retardant composites are characterized by Fourier‐transform infrared spectroscopy and X‐ray diffraction. Morphologies, mechanical properties, and thermal properties also are investigated by the use of transmission electron microscopy, mechanical testing apparatus, differential scanning calorimetry, and thermogravimetric analysis, respectively. Through transmission electron microscopy photographs, it can be found that the in situ‐formed MCA nanoparticles with diametric size of less than 50 nm are nanoscaled, highly uniformly dispersed in the PA6 matrix. These nanocomposites, which have good mechanical properties, can reach UL‐94 V‐0 rating at 1.6‐mm thickness even at a relatively low MCA loading level. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of in situ encapsulated intumescent flame retardant and the flame retardancy in polypropylene

In this article, a nitrogen–phosphorus composite flame retardant, melamine phosphate (MP), was synthesized in a solution of phosphoric acid/macromolecular charring agent, polyamide 6 (PA6). With the progress of the phosphoric acid–melamine reaction producing MP, the acidity of this system decreased and the originally dissolved PA6 resin precipitated on the surface of MP particles to obtain the MP in situ encapsulated by PA6. This encapsulated MP was incorporated with a small molecular charring agent, pentaerythritol (PER), composed of an intumescent system to flame retard polypropylene (PP). As a result of the isolation effects of PA6 resin, the esterfication reaction between MP and PER was effectively suppressed at the processing temperature of PP, thus remarkably improving the thermal stability of such an intumescent system while maintaining the mechanical performance of the flame retardant PP. Additionally, encapsulated MP/PER system showed better charring properties when compared with MP/PER and therefore possessed a higher efficiency in flame retarding PP. The corresponding charring mechanisms of the former, including either a macromolecular charring agent or small molecular one, were investigated. POLYM. COMPOS., 28:163–167, 2007. © 2007 Society of Plastics Engineers     

Effect of halloysite nanotubes on thermal and flame retardant properties of polyamide 6/melamine cyanurate composites

In this study, polyamide 6 (PA6) with various contents of halloysite nanotubes (HNTs) and melamine cyanurate (MCA) were prepared by a twin‐screw extruder. The flame retardant and physical properties of PA6 composites were examined. X‐ray diffraction (XRD) patterns of PA6/HNTs and PA6/MCA/HNTs composites showed that HNTs as a nanoscale material dispersed in PA6 whether with MCA or not. Thermo gravimetric analyzer (TGA) results showed the presence of HNTs can improve thermal stability of PA6 and PA6/MCA composites. The incorporation of HNTs seemed to result the increase of crystallinity of PA6 and PA6/MCA composites from the differential scanning calorimetry (DSC) results. The combined of HNTs and MCA that leads to further improvements limiting oxygen index (LOI) value of PA6 to 31.7% exerted a positive effect on flame retardancy of PA6. What's more, some mechanical enhancements of PA6 with adding of HNTs were achieved and HNTs also made the tensile properties of PA6/MCA composites improved. POLYM. COMPOS., 36:892–896, 2015. © 2014 Society of Plastics Engineers     

三聚氰胺氰尿酸阻燃尼龙6的抗熔滴燃烧性研究

考察传统抗滴落剂聚四氟乙烯（PTFE）微粉和氮磷复合型阻燃剂三聚氰胺磷酸盐（MP）对三聚氰胺氰尿酸（MCA）阻燃尼龙6抗熔滴燃烧性的影响。结果表明,PTFE与MCA之间有对抗效应,加入PTFE后材料的阻燃性能有所降低;而MP可显著增强其凝聚相过程,有效降低材料的熔滴燃烧性,提高材料的阻燃性能。     

Enhanced mechanical properties and fire retardancy of polyamide 6 nanocomposites based on interdigitated crystalline montmorillonite–melamine cyanurate

Polyamide 6 (PA6)–montmorillonite (MMT)–melamine cyanurate (MCA) nanocomposites were prepared by the incorporation of interdigitated crystalline MMT–MCA. Their morphologies were assessed by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal stability measurement by thermogravimetric analysis, mechanical properties measurement by tensile tests, and fire retardancy measurement by limiting oxygen index testing and vertical burning testing (UL‐94). The results indicate that MMT–MCA was homogeneously nanodispersed in PA6. Compared with PA6–MCA, the PA6–MMT–MCA nanocomposites showed enhanced thermal stability. The mechanical properties and fire retardancy show that the PA6–MMT–MCA nanocomposites with 5 wt % total loading of MMT–MCA reached UL‐94 V‐2 rating (3.2 mm) and significantly increased the tensile strength of PA6 up to 24.8 % with only 1 wt % MMT in PA6. Through the control the weight ratio of MMT and MCA in MMT–MCA, the Young's modulus of PA6 could be adjusted in a very wide range (300–1100 MPa) because of the dual role of the rigid MMT and nonrigid MCA layers. The reinforced mechanism of the mechanical properties was also investigated. Consequently, the PA6–MMT–MCA nanocomposites with a good nanodispersing ability, improved thermal stability, excellent mechanical properties, and good flame retardancy were obtained and could provide broad prospects for wider applications for PA6 materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46039.     

尼龙基MCA母粒的制备及其在阻燃尼龙的应用

针对三聚氰胺氰尿酸盐(MCA)粉体对尼龙(PA)进行阻燃改性时,MCA分散性差,材料阻燃性能不稳定的问题,运用特殊的包覆工艺成功制得了PA基MCA母粒。将制得的MCA母粒及MCA粉体分别与PA6或PA66共混挤出,制得阻燃PA材料。对比分析了MCA母粒及MCA粉体阻燃PA6或PA66的垂直燃烧性能和力学性能。结果表明,与MCA粉体相比,MCA母粒可在MCA含量较低的情况下使厚度为0.8 mm及1.6 mm的阻燃PA6或PA66试样的垂直燃烧等级达到V–0级。MCA母粒及粉体对阻燃PA6的弯曲强度和PA66的拉伸强度影响很小,MCA母粒阻燃PA6的拉伸强度较粉体阻燃的高,而阻燃PA66的弯曲强度低;MCA母粒使阻燃PA的缺口冲击强度降低,而MCA粉体对PA的缺口冲击强度影响较小,当MCA含量较低时,MCA母粒阻燃PA的缺口冲击强度明显高于MCA粉体阻燃的PA。制备的MCA阻燃母粒对PA的阻燃效果不受黑色母料的影响,且具有较好的阻燃稳定性。     

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     

聚酰胺表面改性三聚氰胺氰尿酸盐及其阻燃聚酰胺6研究

以聚酰胺树脂的无机酸溶液为介质进行三聚氰胺-氰尿酸分子自组装合成三聚氰胺氰尿酸盐(MCA),并同时实现聚酰胺树脂对阻燃剂的表面包覆改性,集MCA的合成及表面改性于一体。该阻燃剂与目标阻燃树脂聚酰胺6 的相容性良好,阻燃剂粒子与聚酰胺6(PA6)树脂基体之间相界面基本消失。聚酰胺6中添加7％该阻燃剂即达到 UL94-1．6mm V0级别,成功解决了传统MCA阻燃PA6燃烧熔滴易引燃脱脂棉的问题,其极限氧指数高达34％,阻燃效率远高于传统MCA。材料力学性能良好,具有较好的市场应用前景。     

Synergistic effect of expandable graphite and melamine phosphate on flame‐retardant polystyrene

The halogen‐free flame‐retardant polystyrene (PS) composites containing expandable graphite (EG) and melamine phosphate (MP) were prepared successfully, and the thermal degradation behavior and fire performance were investigated by various measurements. The experimental results show that EG and MP have a synergistic effect on flame‐retardant PS, which can catalyze the char formation from PS. PS/MP/EG_(1:2) composite achieves limited oxygen index value of 28.0% and UL‐94V‐0 (1.6 mm) rate. The mass retention at high temperature (800 °C) under air atmosphere of PS composites have a large increase by the introduction of EG and MP. Microscale combustion calorimeter (MCC) and cone calorimetric analysis indicate that the heat release rate and total heat release of PS/MP/EG_(1:2) composite are reduced significantly, because the formed thick char layer has a notable barrier property. The study on the char residue of PS/MP/EG_(1:2) composite by X‐ray photoelectron spectroscopy (XPS) analysis confirms the formation of the stable structures containing P? O? C. Furthermore, the mechanical properties of PS composites were also investigated; compared with neat PS, the addition of flame retardants leads to the decrease of tensile strength and flexural strength, but the impact strength of PS/MP/EG_(1:2) has increased by 44.2%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45474.     

阻燃玻璃纤维增强PA6的紫外光稳定性

分别将三聚氰胺氰尿酸盐、十溴二苯乙烷、溴化聚苯乙烯和次磷酸盐作为阻燃剂对尼龙6(PA6)进行阻燃玻璃纤维增强改性,采用热失重分析仪、水平垂直燃烧测定仪、分光测色仪对PA6复合材料的热降解行为、阻燃性能和紫外光老化后色差值(△E)进行了分析.结果表明,阻燃剂的引入提升了PA6复合材料的阻燃性能,但是降低了复合材料的热稳定...     

Synergistic flame retardancy of ZnO and piperazine pyrophosphate/melamine cyanurate in polypropylene

In order to improve the flame retardant efficiency and smoke-suppression of piperazine pyrophosphate/melamine cyanurate (PPAP/MCA) in PP, the synergism of ZnO and PPAP/MCA was investigated by limiting oxygen index (LOI) determination, UL-94 test, and cone calorimetry test (CCT). It is found that ZnO performs an exceptional synergism in flame retardant effect and inhibition on the flame propagation. Besides, ZnO can significantly inhibit the production of the smoke and CO. The TGA of the PP composites, the component and structure analysis of the heated composites and CCT residues reveal that ZnO performs the synergism primarily by the following modes: ZnO promotes obviously the charring of the composite, and improves the thermal stability as well as the strength of the intumescent layer, which brings about an improved flame retardant property and inhibiting ability on the flame propagation.     

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.     

三聚氰胺氰尿酸盐对聚酰胺6热降解行为的影响

用热失重(TGA和DTG)、差示扫描量热分析(DSC)等热分析手段和傅立叶红外光谱(FTIR)研究了三聚氰胺氰尿酸盐MC对PA6热降解性能的影响和作用本质。结果表明,MC降低了PA6的热稳定性,改变了PA6的热降解途径,促进了PA6的分解。MC分解形成的三聚氰胺可进一步凝缩成热稳定性较高的三嗪类物质,此物质在凝缩相中也具有一定的阻燃作用。而MC主要以吸热的方式在凝缩相分解区和气相反应区发挥阻燃作用。     

EVA/MCA复合体系的燃烧性能与炭层结构

以乙烯-乙酸乙烯酯共聚物(EVA)为基体树脂,以氰尿酸三聚氰胺(MCA)为阻燃剂,研究了EVA/MCA复合体系的燃烧性能,并对燃烧炭层进行了分析.结果表明,MCA改善了EVA/MCA体系的燃烧性能,消除了燃烧滴落现象,抑制了黑烟的产生.随着MCA添加量逐渐增大,氧指数由18.0%提高到26.1%,当MCA添加量为80质量份时,体系成为难燃材料.当MCA添加量分别为50,60,80质量份时,EVA,MCA复合体系的阻燃级别依次可以达到FV-2级,FV-1级,FV-0级.随着MCA添加量的增加,燃烧试样表面的炭层逐渐增多,致密程度提高;随着燃烧时间的增加,燃烧试样内部的孔洞增多,孔径变大.     

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.