Degradation of flame retardance: A comparison of ethylene-vinyl acetate and low-density polyethylene cables with two different metal hydroxides

The durability of flame retardancy is a challenge for cables over long lifetimes. The degradation of flame retardance is investigated in two kinds of exposures, artificial weathering and humidity. In this basic study, typical mineral flame retardants in two polymers frequently used in cable jackets are investigated to get the fundamental picture. Aluminum hydroxide (ATH) and magnesium hydroxide (MDH) are compared in ethylene-vinyl acetate (EVA), and further in EVA and linear low-density polyethylene (LLDPE) cables containing the same ATH. The changes in chemical structure at the surface are studied through attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), the formation of cracks, and changes in color are investigated. The cone calorimeter and a bench scale fire testing cable module are utilized to evaluate the fire behavior of the cables. Although the flame retardancy deteriorated slightly, it survived harsh exposure conditions for 2000 h. Compared to EVA/MDH and LLDPE/ATH, the fire behavior of EVA/ATH is the least sensitive. Taken together, all of the results converge to estimate that there will be no problem with flame retardancy performance, for materials subjected to natural exposure for several years; the durability of fire retardancy is questionable for longer periods, and thus requires further investigation.     

阻燃EVA热熔胶的制备及其在线缆修复中的应用研究

选取二乙基次膦酸铝、焦磷酸二三聚氰胺和氢氧化铝为阻燃剂,制备了用于老化线缆快速修复的阻燃乙烯-醋酸乙烯酯共聚物（EVA）热熔胶,并对热熔胶材料的阻燃性能及线缆修复后的阻燃性能和绝缘性能等进行了测试和表征。结果表明,当3种阻燃剂的质量比为1:1:3,总添加量为50%（质量分数,下同）时,阻燃热熔胶通过垂直燃烧测试UL 94 V-0级且测试过程中无滴落,极限氧指数为27.1%;与纯热熔胶相比,阻燃热熔胶的热释放速率和总热释放量均大幅降低,阻燃体系发挥了很好的协同阻燃作用;修复后线缆的体积电阻率为1.15×1015Ω·m,热熔胶在线缆表面具有良好的成膜性和黏附力,线缆弯折过程中热熔胶不开裂、不脱落;燃烧过程中,修复后的线缆表面形成了膨胀的炭层,能有效保护线缆。     

碱式碳酸镁基复合阻燃剂的制备及其阻燃性能研究

采用硅烷表面处理的碱式碳酸镁纳米片和氢氧化镁以及氢氧化铝为复合阻燃剂,通过密炼模压法制备了一系列复配阻燃剂协效阻燃EVA的复合材料。利用拉伸性能测试仪、熔融指数仪、垂直燃烧测试仪和锥形量热仪分别测试了复合材料的力学性能、加工流动性能和阻燃性能,利用热重分析仪测试了复配阻燃剂的热分解行为。结果表明,复配阻燃剂以适当比例协效阻燃EVA在更宽的燃烧温度范围内发生分解,能够起到更好的阻燃效果。并且复配阻燃剂/EVA复合材料的热释放速率和烟释放率大幅度降低,分别为181.06 kW/m²和0.032 m²/s。另外,复配阻燃剂/EVA复合材料的拉伸强度达到9.73 MPa,断裂伸长率为155.07%,每10 min熔融指数为1.00 g,符合电线电缆行业标准。     

Effect of sulfur in different valence on flame retardance of epoxy resin for light emitting diode

A novel phosphorus/nitrogen-containing flame retardant (DOPO-AM) was synthesized by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and acrylamide (AM) and its chemical structure was characterized. DOPO-AM was added into diglycidyl ether of bisphenol-A (DGEBA) with curing agent m-xylylenediamine (MXDA)to prepare flame retarded epoxy resin to reduce the possibility of fire. The compounds with different valences sulfur respectively replace partial DGEBA resin to study the effects of sulfur valences on the flame retardance of epoxy resins. The results indicated that DOPO-AM had excellent flame retardance for epoxy resin. When phosphorus content was only 0.75%, DGEBS resin containing DOPO-AM achieved the limiting oxygen index value of 34.55% and vertical burning test (UL-94) V-0 rating. Although sulfur element is help for refractive index of epoxy resin, sulfur element in three kinds of valences all weaken the flame retardant of epoxy resin. Improving phosphorus content is help for the synergistic effect of P N and P N S. Moreover, the flame retardance is not proportional to sulfur valence, sulfide with +2 valence had the best flame retardance. However, +6 valence sulfonic with strong oxidation effect worsen the flame retardant. Simultaneous thermal analysis of thermogravimetric analyzer and differential scanning calorimeter and scanning electronic microscopy photographs verified the above conclusion.     

无卤阻燃EVM/EPDM并用胶的性能研究

试验研究乙烯-乙酸乙烯酯橡胶（EVM）/EPDM并用胶的性能。结果表明,随着EPDM用量的增大,EVM/EPDM并用胶的物理性能变化不大,热空气老化后并用胶的邵尔A型硬度和拉伸强度增大,拉断伸长率减小,耐低温性能提高；EVM或EVM/EPDM并用胶的阻燃性能明显优于EPDM；添加阻燃剂和增塑剂的EVM/EPDM并用胶的相容性较未添加阻燃剂和增塑剂的并用胶有所改善。     

阻燃剂对热固性酚醛树脂阻燃性能影响的研究

通过氧指数、垂直燃烧等级及产烟率测定研究了氢氧化铝(ATH)、氢氧化镁(MH)、膨胀石墨(EG)、膨胀型阻燃剂(IFR)等以单一或协同复配的形式对酚醛树脂(PF)体系阻燃性能的影响,并采用差热分析(DTA)对体系的微观热行为进行了研究。结果表明,放热量最小的体系为ATH/MH/EG/PF,ATH/MH/EG/IFR/PF体系的氧指数最大,达到96。ATH/MH/PF体系的产烟率最低(72%)。添加阻燃剂后,体系的垂直燃烧等级可提高到UL94V-0级。     

聚合物成炭阻燃新进展

根据协效阻燃、硅氧烷阻燃、聚合物纳米阻燃和本质阻燃的方法和机理综述了聚合物阻燃在成炭方面的研究新进展。提高与聚合物基体的相容性、降低聚合物材料的性能损失、提高聚合物的成炭阻燃效率、兼顾对环境友好已成为聚合物阻燃的研究重点。综合使用多种阻燃方法正成为聚合物阻燃的研究方向。     

茶皂素基膨胀型阻燃剂的制备及其在涂料中的应用

采用多羟基、多羧基的活性天然产物茶皂素为原料,与聚磷酸铵和季戊四醇在一定条件下反应,制备一种聚磷酸酯类茶皂素基三位一体新型环保膨胀型阻燃剂。采用傅里叶红外分析技术对阻燃剂进行了结构表征,采用综合热分析仪对阻燃剂的热降解性能进行了研究。结果表明,茶皂素与聚磷酸铵、季戊四醇发生反应,生成聚磷酸酯类茶皂素基膨胀型阻燃剂,且该阻燃剂具有良好的热稳定性,降解热释放较小,高温残留率高,最终的质量残留率高达30.77%。将制备阻燃剂用于阻燃涂料中,并采用氧指数测试仪和锥形量热仪研究了阻燃涂料的阻燃性能和热解性能。研究表明,茶皂素基三位一体膨胀型阻燃剂能显著提高涂料的阻燃性能,阻燃涂料的氧指数值高达34.2%,耐火时间为11.1 min,且锥形量热实验中,该阻燃涂料试样的平均热释放速率（m-HRR）为36.18 kW/m2,总热释放量（THR）为5.25 kJ/m2,平均有效燃烧热（m-EHC）为5.11 kJ/kg,与含复合型阻燃剂的阻燃涂料试样相比,阻燃性能得到极大提高。该制备阻燃剂不含卤素,集三源一体,具有阻燃性能优越,相容性能良好,高效环保等优点。     

涤纶磷系共聚阻燃剂及阻燃聚酯制备方法

描述了膦菲共聚阻燃剂的特性。介绍了由 H CA( 9,10 -二氢 -9-氧 -10 -氧杂膦菲 )、衣康酸、乙二醇反应制备新型磷化合物磷系共聚阻燃剂 ,以及用该阻燃剂制备阻燃聚酯的方法。所制备的阻燃聚酯具有优异的阻燃性能 ,极限氧指数 30～ 32。     

聚苯乙烯的无卤阻燃研究

采用正交设计法分析了聚磷酸胺(APP)、季戊四醇(PER)、三聚氰胺(MEL)作为一种混合体系对聚苯乙烯(PS)的阻燃作用。实验表明,酸源、炭源、气源组成的膨胀型阻燃剂有良好的阻燃效果,PER对PS阻燃性能的影响显著。各个因子对材料力学性能和加工性能的影响不同:PER用量是影响拉伸强度、弯曲强度和流动性的主要因素;APP用量是影响无缺口冲击强度的主要因素;MEL用量是影响缺口冲击强度的主要因素。当APP、PER、MEL 的用量分别为30,20,5摩尔份时,阻燃PS获得较好的综合性能。     

多组分协效低烟无卤阻燃电缆料的研究

以Al(OH)_3为主阻燃剂,聚硅氧烷为副阻燃剂,低密度聚乙烯为基础树脂,配合适当比例的乙烯-乙酸乙烯酯共聚物和乙烯-丙烯酸乙酯共聚物制备了综合性能优良的无卤阻燃电缆料。采用多步混合造粒工艺,并采取了对无机阻燃剂实施表面处理及加入适量的高分子相容剂等方法解决了无机阻燃剂高填充时出现的分散不均匀问题,同时,添加润滑剂可以改善复合体系的流动性能。     

Investigation on effects of aluminum and magnesium hypophosphites on flame retardancy and thermal degradation of polyamide 6

Two hypophosphites, aluminum hypophosphite (AlHP) and magnesium hypophosphite (MgHP), were applied to obtain flame retardant polyamide 6 (FR-PA6) composites. UL-94 and limiting oxygen index results indicated that AlHP contributed both good flame retardance and antidripping ability for PA6, while MgHP did not. Based on thermogravimetric analysis (TGA), AlHP and MgHP presented the different thermal degradation behavior. That is, the quick decomposition of AlHP took place at lower temperature than that of MgHP. AlHP promoted the early thermal degradation of PA6 and formed more char residue. The thermal decomposition mechanisms of AlHP and MgHP in nitrogen or air were suggested. Scanning electron microscope and X-ray photoelectron spectroscopy indicated that in the existence of AlHP, the morphological structures of char residue were more homogenous, and compact, and more char residue was formed. These results well illustrated the difference of the flame retardancy between AlHP and MgHP. Mechanical properties of PA6/AlHP and PA6/MgHP were also obtained. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

膨胀型阻燃剂在聚丙烯中的应用

对自制的膨胀型阻燃剂(IFR)进行了预处理并添加了协效阻燃剂等助剂,形成一种高效的膨胀型阻燃体系。通过氧指数、热重分析和扫描电子显微镜等检测手段,考察了该阻燃体系的阻燃性能和添加量。IFR、硼酸锌和其他助剂最佳质量比为25：2：2。改进后的膨胀型阻燃体系用于聚丙烯,不仅阻燃性能优良,同时还具有较好的力学性能。     

Structural characterization of LDPE/EVA blends containing nanoclay‐flame retardant combinations

The combination of different types of organo‐modified montmorillonite (MMT) with aluminum hydroxide (aluminum trihydrate—ATH), as a flame retardant system for polyethylene‐ethylene vinyl acetate (LDPE/EVA), blends were studied. Five different types of organically modified montmorillonite clays, each with different modifier, were used. The structural characterization was carried out by X‐ray diffraction (XRD) and scanning electron microscopy in transmission mode (STEM). The mechanical and rheological properties were also evaluated. The XRD analysis showed a clear displacement of the d₀₀₁ signal, which indicates a good degree of intercalation, especially for the MMT‐I28 and MMT‐20, from Nanocor and Southern Clay Products, respectively. The presence of ATH and the compatibilizer did not have any effect on the exfoliation of the studied samples. The thermal stability and flame retardant properties were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI—ASTM D2863), and flammability tests (Underwriters Laboratory—UL‐94). The effect of different compatibilizers on the clay dispersion and exfoliation was studied. The results indicated that the addition of montmorillonite makes it possible to substitute part of the ATH filler content while maintaining the flame retardant requirements. The thermal stability of MMT/ATH‐filled LDPE/EVA blends presented a slight increase over the reference ATH‐filled LDPE/EVA blend. Compositions with higher clay content (10 wt %) showed better physicochemical properties. The increased stability of the higher clay content compositions results from the greater inorganic residual formation; this material has been reported to impart better performance in flammability tests. The mechanical properties and flame retardancy remained similar to those of the reference compound. The reduced ATH content resulted in lower viscosities and densities, facilitating the processing of the polymer/ATH/clay compounds. Extrusion of these compounds produced a lower pressure in the extrusion head and required reduced electrical power consumption. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synergistic flame retardant effects of Fe-OMMT with LDH in EVA/LDH composites

Abstract

The synergistic effects of Fe organic modified montmorillonite (Fe-OMMT) with layered double hydroxides (LDHs) in ethylene vinyl acetate copolymer/LDH (EVA/LDH) composites have been studied using thermal analysis [thermogravimetric analysis (TGA)], limiting oxygen index (LOI), UL-94 test and cone calorimeter test (CCT). The results showed that the addition of a given amount of Fe-OMMT apparently increased the LOI value and the rating in the UL-94 test. The results from the LOI and UL-94 tests show that Fe-OMMT can act as flame retardant synergistic agents in EVA/LDH composites. The CCT data indicated that the addition of Fe-OMMT in the EVA/LDH system can greatly reduce the heat release rate. The TGA data show that Fe-OMMT, as an excellent flame retardant synergist of LDH, cannot increase the thermal degradation temperature and the charred residues.     

阻燃聚烯烃/碳纳米管复合材料研究进展

综述了含碳纳米管(CNT)填料的3种聚烯烃[乙烯-醋酸乙烯酯共聚物(EVA)、聚丙烯(PP)及聚乙烯(PE)]复合材料的研究进展,主要包括含多壁碳纳米管(MWCNT)的材料,也包括了同时含MWCNT及层状硅酸盐(LS)和纳米氢氧化铝(ATH)的材料,从中可看出这几种无机纳米填料间的阻燃协同效应。作为线缆无卤阻燃包覆料,EVA/MWCNT/LS/ATH纳米复合材料显示了很好的应用前景。     

氢氧化铝无卤阻燃乙烯醋酸乙烯共聚物的结构与性能

以表面修饰的氢氧化铝（ATH）作为无卤阻燃剂,以线形低密度聚乙烯接枝物为相容剂制备了阻燃性能和力学性能优良的无卤阻燃乙烯醋酸乙烯（EVA）复合材料。通过扫描电子显微镜、力学性能测试、动态热力学分析、极限氧指数、垂直燃烧测试表征了AHT阻燃EVA复合材料的结构与性能。研究了表面处理及相容剂的引入对ATH在EVA中的分散性和界面相容性的影响,以及AHT粒径大小、添加量对EVA阻燃性能和力学性能的影响。结果表明,界面相容剂和表面处理剂同时使用,能显著提高ATH与基体之间的界面相容性,从而提高了EVA的力学性能和阻燃效果,ATH尺寸越小,阻燃性能越好。     

无机金属氧化物复合羊毛纤维的阻燃机理研究

通过热分析、剩碳率、氧指数和扫描电镜对无机金属氧化物溶胶处理后的羊毛样品的热降解行为进行了表征,并对其阻燃机理作了初步探讨。结果表明,经过阻燃处理的羊毛其氧指数、剩碳率比未处理的羊毛升高,阻燃性明显增强。     

A novel intumescent flame retardant-functionalized montmorillonite: Preparation,characterization, and flammability properties

2,4,8,10-Tetraoxa-3,9-diphosphaspiro[5.5]-undecane-3,9-dioxide-disubstitutio-acetamide-N,N-dimethyl-N-hexadecy-ammonium bromide (PDHAB) containing phosphorus–nitrogen structure was synthesized and characterized. A novel flame retardant, montmorillonite (Mt) modified by PDHAB (PDHAB-Mt), was prepared by ion-exchange of sodium montmorillonite (Na⁺-Mt) with PDHAB. The results of X-ray diffraction (XRD) indicated that PDHAB had intercalated with Na⁺-Mt and exfoliated LDPE/EVA/20% PDHAB-Mt nanocomposites had been obtained by polymer melt intercalation which was further supported by TEM. The flammability of LDPE/EVA/PDHAB-Mt nanocomposites was investigated by the cone calorimeter test. The results showed that the addition of flame retardant PDHAB-Mt enhanced the flame retardancy of LDPE/EVA blend significantly. The results of SEM and TEM indicated that PDHAB-Mt can achieve better dispersion in the chars after combustion and the intumescent char is formed for LDPE/EVA/PDHAB-Mt nanocomposites after combustion. It is found that the char structure plays an important role for PDHAB-Mt in LDPE/EVA blend. The flame retardancy of LDPE/EVA blend was also significantly improved by an addition of PDHAB-Mt in LDPE/EVA blend.     

Preparation of expandable graphite with silicate assistant intercalation and its effect on flame retardancy of ethylene vinyl acetate composite

A halogen‐free intumescent flame retardant expandable graphite composite (EG), with an initial expansion temperature of 202°C and expansion volume of 517 mL g⁻¹, was successfully prepared via a facile two‐step intercalation method, i.e. using KMnO₄ as oxidant and H₂SO₄, Na₂SiO₃·9H₂O as intercalators. The prepared EG flame retardant was characterized by field emission scanning electron microscope, X‐ray diffraction spectroscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. Furthermore, flame retardancy and thermal property of various ethylene vinyl acetate copolymer (EVA) composites, including EVA/EG and EVA/EG/APP (ammonium polyphosphate) specimens, were studied through limiting oxygen index instrument (LOI), vertical combustion UL‐94 rating, thermal gravimetric and differential thermal analysis. The results indicate that the EVA/EG and EVA/EG/APP composites exhibit a better flame retardancy. Addition of EG at a mass fraction of 30% leads LOI of 70EVA/30EG composite improved to 28.7%. Even more, the synergistic effect between EG and APP improves the LOI of 70EVA/10APP /20EG composite to 30.7%. This synergistic efficiency is attributed to the formation of compact and stable layer‐structure, and the prepared EG can make EVA composite reach the UL‐94 level of V‐0. POLYM. COMPOS., 36:1407–1416, 2015. © 2014 Society of Plastics Engineers