Improved fire retardancy of thermoset composites modified with carbon nanofibers

Abstract

Multifunctional thermoset composites were made from polyester resin, glass fiber mats and carbon nanofiber sheets (CNS). Their flaming behavior was investigated with cone calorimeter under well-controlled combustion conditions. The heat release rate was lowered by pre-planting carbon nanofiber sheets on the sample surface with the total fiber content of only 0.38 wt.%. Electron microscopy showed that carbon nanofiber sheet was partly burned and charred materials were formed on the combusting surface. Both the nanofibers and charred materials acted as an excellent insulator and/or mass transport barrier, improving the fire retardancy of the composite. This behavior agrees well with the general mechanism of fire retardancy in various nanoparticle-thermoplastic composites.     

Fire performance of composite laminates embedded with multi-ply carbon nanofiber sheets

In this study, free-standing carbon nanofiber sheets (CNS) were incorporated into glass fiber reinforced polyester composites through resin transfer molding (RTM) process. These sheets were made of vapor grown carbon nanofibers. The composite laminates consisted of eight plies of CNS and eight plies of glass fiber mats. The fire retarding performance of the laminates was evaluated with cone calorimeter tests with an external radiated heat flux of $50\text{kW}/{\text{m}}^2$. The test results indicated that there was significant improvement in the fire retardancy of composite laminates due to the incorporation of CNS. It was found that the CNS plies survived the test except the one on the top surface of the laminates. The formation of compact char materials was observed on the surface of the CNS residues. The improvement in fire retarding performance was achieved through the barrier and insulator effects of the CNS and charred materials by restricting the migration of flammable products to the top surface of the laminates and preventing the transmission of external heat to the underlying polyester resin.     

Fire retardancy of clay/carbon nanofiber hybrid sheet in fiber reinforced polymer composites

In this paper, two kinds of clay/carbon nanofiber hybrid sheets containing 0.05 wt% and 0.20 wt% of Cloisite Na⁺ clay, were fabricated through a high-pressure filtration system. These sheets were integrated onto the surface of laminated composites like traditional continuous fiber mats through vacuum-assisted resin transfer molding process. The fire performance of the laminated composites was evaluated with cone calorimeter tests under an external radiant heat flux of 50 kW/m². Their residues were analyzed with scanning electron microscopy and thermal gravimetric analyses. It was found that the clay/nanofiber hybrid sheets survived on the combustion surface of composites and significantly reduced the heat release rate by 60.5%. The protective clay layer reduces the heat release rates and the nanofiber network reinforces the clay layer against the air bubbling and melt flow of the products degraded from the polymer resin. The clay/carbon nanofiber hybrid sheet combines the barrier and insulator effects of the clays with the re-emitting heat effect of carbon nanofibers on the combustion surface of composites.     

混杂纤维布加固钢筋混凝土梁抗弯性能试验及理论研究

该文提出了碳/芳纶/玻璃三种纤维混杂思路,高强、高弹模碳纤维提高承载能力,高延伸率玻璃纤维改善延性,而芳纶纤维使应力从碳纤维向玻璃纤维平稳转移。通过对11根钢筋混凝土梁的抗弯试验,研究了不同混杂方式、混杂结构、纤维布层数对梁抗弯性能的影响。结果表明:如果应力转移不平稳,混杂纤维布将与混凝土发生局部剥离,导致混杂纤维布加固效果降低;在相同纤维布层数条件下,与单一碳纤维布加固梁相比,碳/芳纶/玻璃层间混杂纤维布加固梁的初裂、屈服、峰值和极限荷载分别降低了22%、12%、12%和16%,而位移延性系数提高了20%,表明碳/芳纶/玻璃层间混杂纤维布能够显著降低单一碳纤维布的脆性。在试验研究的基础上,采用弹塑性截面分析法计算了混杂纤维布加固梁的承载力,理论计算值与试验值吻合良好。     

晶硅炉热场用碳材料在硅蒸汽中的腐蚀行为研究

对晶硅炉热场用三种碳材料(石墨、C/C复合材料、硬质碳毡)在不同腐蚀条件下进行了硅蒸汽腐蚀实验, 研究了不同碳材料的硅化腐蚀行为。结果表明: 三种材料的结构组成不同, 导致三种碳材料在高温环境下与硅蒸汽发生硅化腐蚀的程度不同, 硅蒸汽主要通过材料的孔洞以及缺陷扩散进入材料内部进行腐蚀, 腐蚀造成材料表面产生大量的裂纹, 并且会造成C/C复合材料以及硬质碳毡材料内部严重的破坏。材料中碳纤维的存在方式以及纤维强度对硅化腐蚀程度有较大影响, C/C复合材料中的腐蚀主要是碳基体和碳纤维的剥离以及碳纤维的缩颈、劈裂等; 而由强度较差的短碳纤维为主要组成的硬质碳毡材料的腐蚀最严重, 其内部碳纤维出现了明显的碎断、粉化。腐蚀参数对材料硅化腐蚀的程度具有较大影响, 随着腐蚀温度的升高以及腐蚀时间的延长, 三种碳材料的硅化腐蚀程度均增加。     

MoSi2-SiC 抗氧化涂层对碳/碳复合材料弯曲性能的影响

在C/C 复合材料表面制备了MoSi₂-SiC 抗氧化涂层, 分析了涂层工艺对C/C 复合材料组织的影响, 测试了材料的室温弯曲力学性能。结果表明, 该工艺在C/C 复合材料表面生成抗氧化涂层的同时, 基材内部的层间和纤维束界面, 以及孔隙周围也被硅化。C/C 复合材料经涂层工艺处理后, 弯曲断裂行为发生改变, 弯曲强度明显升高,塑性有一定程度的降低。      

微胶囊红磷和聚苯醚对高抗冲聚苯乙烯的协同阻燃作用

利用微胶囊红磷(MRP)和聚苯醚(PPO)来提高高抗冲聚苯乙烯(HIPS)的阻燃性能, 通过熔融共混法制备了一系列不同组成的MRP-PPO/HIPS复合材料。采用水平燃烧、垂直燃烧、氧指数、锥形量热分析、高温热分解实验等方法研究了复合材料的阻燃性能。研究表明, 阻燃剂用量相同时, 在HIPS基体中同时加入MRP和PPO得到的复合材料比单独加入MRP或PPO得到的复合材料具有更好的阻燃性能。当MRP-PPO/HIPS的质量比为10:20:70时, 复合材料的氧指数为23.9%, 水平燃烧级别达到FH-1级, 垂直燃烧级别达到FV-0级, 阻燃性能达到最佳。MRP用量过多时, 复合材料的阻燃性能下降。研究认为, PPO和MRP对HIPS具有较强的协同阻燃作用。两者以适当比例并用时能够使复合材料在燃烧时的热释放速率和燃烧热大幅度减小, 降低了气相燃烧区的温度, 起到气相阻燃作用。同时, 复合材料在热分解和燃烧时能够生成连续和致密的炭层, 抑制了燃烧过程中的热量传递和物质交换, 起到凝聚相阻燃作用。因此, 复合材料的阻燃性能显著改善。     

热压碳/铜复合材料的制造工艺与性能

研究了用作连续碳纤维增强铜-5%锡基复合材料的制造工艺,实验表明:热压能使碳纤维与铜粉、锡粉良好地复合,在给定的工艺条件下,制成了碳纤维的体积含量V_f=10～50%的接近完全致密的碳铜复合材料,碳纤维均匀地分布于基体中并具有随机的取向。对该材料的硬度、电阻率、弯曲强度、摩擦磨损等多种性能进行了测试,讨论了碳纤维的含量对材料性能的影响,并对弯曲断口及磨面进行了扫描电镜分析。      

表面改性对聚丙烯/纳米氢氧化镁复合材料性能的影响

研究了表面处理剂(钛酸酯和硅烷偶联剂)对聚丙烯/纳米氢氧化镁(MH)阻燃复合材料性能的影响。通过高压毛细管流变仪、LO I、力学测试、DSC和SEM对PP/纳米MH复合体系的结构与性能进行了研究。结果表明,所选偶联剂能有效地降低复合体系的表观黏度,改善体系的流动性。未改性的纳米MH对PP基体有异相成核作用;而表面改性剂能削弱填料对基体的异相成核作用。改性后的纳米MH粒子以独立形式均匀分散在基体中,PP与纳米MH界面的粘接力得到了加强,复合材料的拉伸性能和冲击强度有较大幅度的提高,阻燃性能也得到了改善。     

MgO-微胶囊红磷/高抗冲聚苯乙烯复合材料的阻燃性能

通过熔融混合方法把MgO和（或）微胶囊红磷（MRP）加入高抗冲聚苯乙烯（HIPS）基体中制备了一系列不同组成的MgO-MRP/HIPS复合材料。采用极限氧指数（LOI）、垂直燃烧（UL-94）、锥形量热分析、TGA、SEM、XRD、FTIR等方法研究了复合材料的阻燃性能。结果表明,MgO和MRP单独使用时对HIPS的阻燃作用较小,但是当二者以适当比例共同使用时对HIPS有明显的协同阻燃作用。当MgO∶MRP∶HIPS的质量比为35∶15∶100时,复合材料的LOI为24.7%,UL-94级别达到V-0级,热释放速率和总热释放量显著降低,表现出良好的阻燃性能。MgO-MRP/HIPS复合材料在无氧条件下热分解时,MgO、MRP与HIPS之间无相互作用。但是,在空气中热分解或燃烧时,MgO和MRP均能够促进HIPS成炭。MgO-MRP/HIPS复合材料燃烧时能够在材料表面生成连续致密的炭层,起到防火屏障作用,提高材料的阻燃性能,燃烧残余物主要由结晶性MgO和含磷的无定形碳组成。此外,MgO-MRP/HIPS复合材料燃烧时MRP在气相也起到了一定的阻燃作用。     

PP/纳米SiO2/氮磷阻燃剂复合材料的研究

目的研究聚丙烯复合材料的燃烧行为和纳米SiO_2含量对复合材料力学性能的影响。方法采用熔融共混方法,将聚丙烯、氮磷复配阻燃剂及表面改性的纳米SiO_2制备成聚丙烯复合材料。结果在燃烧过程中纳米SiO_2对阻燃性能有一定影响,氮磷复配阻燃剂是影响复合材料阻燃性能的关键因素。随着纳米SiO_2含量的增加,复合材料的极限氧指数先增加后降低,当纳米SiO_2质量分数为1%时,复合材料的极限氧指数最大。随着纳米SiO_2含量的增加,复合材料的拉伸、冲击、弯曲强度和弯曲模量呈现先增大后减小的现象。结论氮磷复配阻燃剂与纳米SiO_2对于复合材料有一定的协同阻燃效果。当纳米SiO_2质量分数为1%时,复合材料的阻燃及力学性能最优。     

A Comparative Investigation of the Tribological Behavior of Short Fiber Reinforced Polyimide Composites Under Dry Sliding and Water-Lubricated Condition

The friction and wear behavior of high performance polyimide (PI) and its composites reinforced with short cut fibers such as carbon fiber, glass fiber and quartz fiber was comparatively evaluated under dry sliding and water-lubricated condition, aiming at selecting matching materials for the pumps of pure water power transmission. The wear mechanisms of the composites under the two different sliding conditions were also comparatively discussed, based on scanning electron microscopic examination of the worn composite and steel counterpart surfaces. As the results, the PI composites reinforced with carbon fiber have the best mechanical and tribological properties compared with glass fiber and quartz fiber. PI composites sliding against stainless steel register lower friction coefficients and wear rates under water-lubricated condition than under dry sliding though the transfer of PI and its composites was considerably hindered in this case. PI and its composites are characterized by plastic deformation, micro cracking, and spalling under both dry-and water-lubricated sliding. Such plastic deformation, micro cracking, and spalling is significantly abated under water-lubricated condition. The glass and quart2 fibers were easily abraded and broken when sliding against steel in water environment, the broken fibers transferred to the mating metal surface and increase the surface roughness of mating stainless steel. This is probably the cause of the increased wear rate of glass fiber and quartz fiber PI composites in this case.     

阻燃型木塑复合材料热解燃烧特性及产物研究

以改性天然碳水化合物结合碱式硫酸镁晶须(MHSH)混杂纤维为协效剂,结合膨胀阻燃剂(IFR)制备了阻燃型聚丁二酸丁二醇酯(PBS)木纤维复合材料。利用极限氧指数和垂直燃烧测试研究了复合材料的阻燃性能,并采用TG/DTA-MS对复合材料的热解过程、吸放热量和热解燃烧气体产物进行了分析。结果表明,5%的木薯渣作为碳源代替PBS提高了材料的阻燃性能。IFR/木薯渣/MHSH阻燃剂能够有效提高PBS的燃烧初始温度,并缩小燃烧温度范围。阻燃材料燃烧时,首先是IFR受热分解产生不可燃气体氨气在材料表层形成第一层阻燃保护层;其次,材料迅速燃烧产生的炭层形成第二层阻燃保护层;最后,在高温段MHSH分解形成第三层协效阻燃保护层。因此,最终形成了由外层不可燃气体氨气和内层天然碳水化合物MHSH膨胀炭层构成的气-固阻燃屏障,从而有效地提高了复合材料的阻燃性能。     

黄麻纤维/聚酯纤维复合材料的阻燃改性

应用两种水性磷系阻燃剂——磷酸铵类阻燃剂(DAG-50)和磷酸酯类阻燃剂(DAG-80)及其复配阻燃剂对天然黄麻纤维进行阻燃改性,并与皮芯结构聚酯纤维制备成黄麻纤维/聚酯纤维复合材料,通过燃烧测试、SEM、红外、热失重、热失重-红外联用等技术分析了此两种阻燃剂及复配阻燃剂对黄麻纤维及其黄麻纤维/聚酯纤维复合材料的阻燃效果及阻燃机制,并筛选出适合黄麻纤维/聚酯纤维复合材料产业化的阻燃改性配方。结果表明,阻燃剂DAG-50阻燃改性效果良好,但容易析出于黄麻纤维表面。阻燃剂DAG-80能较为均匀地包覆在黄麻纤维表面,阻燃改性效果好,但其价格较高。DAG-50与DAG-80形成的复配阻燃剂,阻燃效果好,既避免了单独使用DAG-50时阻燃剂易析出问题,且复配阻燃剂接近中性,避免设备腐蚀。综合考虑成本与阻燃性能,使用DAG-50与DAG-80复配阻燃剂比例为2∶1且浓度为55wt%时,可达到黄麻纤维/聚酯纤维复合材料B1级阻燃。     

热处理对炭/炭-铜复合材料载流磨损行为的影响

为探明炭/炭(C/C)多孔体热处理对炭/炭-铜(C/C-Cu)复合材料载流磨损行为的影响,采用化学气相渗透法(CVI)增密的C/C多孔体,再通过压力熔渗法制备C/C-Cu复合材料.采用载流动态磨损试验机测试C/C-Cu复合材料载流磨损行为,利用数字式三维视频显微镜和扫描电子显微镜观察复合材料磨损前后的表面形貌,研究了C/C多孔体经过2 000℃热处理对C/C-Cu复合材料载流磨损行为的影响.结果表明:C/C-Cu复合材料的质量磨损率和线磨损率比C/C多孔体未经热处理的复合材料分别降低了34.42%和17.84%;C/C多孔体经过2 000℃热处理,石墨化度提高,片层劈裂阻力减小,在载荷的作用下石墨片层易于劈裂形成细小的石墨微晶碎片,迅速填充修复表面缺陷,形成具有一定润滑作用、平整的摩擦膜,有效抑制了局部非均匀磨损的扩大,减弱了磨粒磨损和电弧放电引起的烧蚀、粘着、氧化磨损之间的循环交替磨损,载流磨损性能提高.     

复合材料中碳纤维的铺设方式对吸波性能的影响

实验采用东华大学自制的碳纤维作为吸波剂，在基体环氧树脂中平行排列，制备出了吸波复合材料。采用矢量网络分析仪在2~18GHz波段，对复合材料的吸波性能进行测试。结果表明：复合材料的吸波性能不仅与碳纤维含量有关，还与碳纤维在基体中的排列方式有关，当碳纤维含量为3．2％（质量分数）时，吸波复合材料最大反射衰减为-18．64dB，反射率〈-10dB的频率带宽为2．6GHz，同时采用电磁理论对材料的吸收机理进行了探讨。     

Wear and mechanical properties of carbon fiber reinforced copper alloy composites

The mechanical properties and wear behavior of lead-free metal matrix composite, and carbon fiber reinforced copper alloy composites were studied, and compared with a common leaded copper (Cu-6wt.%Zn-6wt.%Sn-3 wt.%Pb) alloy. The effects of carbon fibers and alloy element Sn on these properties were investigated. Carbon fiber/Cu–Sn–Zn composites showed higher hardness and bending strength than the leaded copper alloy when carbon fibers content is less than 12 vol.%. Tribological tests were conducted with disks made from these materials, and tested against a steel counterface. The carbon fiber/Cu–Sn–Zn composites showed higher wear resistance than the leaded copper alloy under a constant load of 50 N. Observations on surface morphology were utilized in understanding the wear properties of these materials. The results show that the wear mechanism of the leaded copper alloy is adhesive wear, while it is mainly adhesive wear accompanied by oxidative wear for the 12 vol.% carbon fiber/Cu–Sn–Zn composites. The 12 vol.% carbon fiber/Cu–Sn–Zn composites are likely to provide optimum substitutes for the leaded copper alloy under the load of 50 N.     

Wood–plastics composites with better fire retardancy and durability performance

This study concerns the preparation and study of wood–plastic composites (WPCs). The matrix used was high density polyethylene. Results showed that the addition of wood fibres increased mechanical properties (tensile, flexural and compression) of the neat plastic remarkably. Additives such as fire retardants and light stabilizers were added to improve properties like fire retardancy and durability performance. The addition of fire retardants could lead to auto-extinguishing materials when ammonium polyphosphate or aluminium hydroxide were used. Outdoor durability depended on both the light stabilizer and the fire retardant added to the formulation. The fire retardant worsened the outdoor durability. However, stabilized fire retarded-WPCs showed much lower fading than non-stabilized non-fire retarded composites and several industrial samples. Stabilized composites with aluminium hydroxide as fire retardant showed the best overall results with a fading degree even lower than the stabilized non-fire retarded composite.     

Investigation into hybrid configuration in electrospun nafion/silica nanofiber

Organic–inorganic composites with nanostructure could exhibit a diverse range of multi-functional properties. In this study, nafion/silica composite nanofibers were successfully fabricated by using electrospinning technique with nafion coated surface. The tunable wettability of composite nanofiber was controlled by addition of nafion or flame-treatment. The thermal stability of nafion has been improved as it hybridized with silica nanofiber. Interestingly, the hydrophobic behavior still existed after heat-treatment with 500 °C for 2 h. The fire resistant property of composite nanofiber has been characterized. The effect of nafion polymer and post treatment on the morphology and wettability of composite nanofiber was evaluated. The mechanism of formation of nafion/silica composite nanofiber during electrospinning process has been proposed. The results of this study improve the understanding of the structure rearrange in organic–inorganic sols during high voltage field.     

(壳聚糖-聚磷酸铵)/剑麻纤维素微晶层层自组装复合材料的热性能和阻燃性能

采用层层自组装法（LBL）,在剑麻纤维素微晶（SFCM）表面交替吸附壳聚糖（CH）和聚磷酸铵（APP）构筑CH-APP阻燃涂层,成功制备（CH-APP）_n/SFCM阻燃复合材料。通过Zeta电位分析仪、FTIR、TGA、POM、垂直燃烧法（VFT）、SEM手段对复合材料的结构和性能进行表征。FTIR、Zeta电位结果表明,CH和APP在SFCM表面电位正负交替变化,CH-APP涂层成功包覆在SFCM表面; POM和SEM结果显示,组装后（CH-APP）_n/SFCM复合材料表面变得粗糙,其表面包覆了一层较厚涂层; TGA结果表明,随着吸附CH-APP组装层数的增加,（CH-APP）_n/SFCM复合材料的初始分解温度（T_5%）由279.4℃降低至243.1℃,残炭率由11.24%提高至32.06%; VFT测试结果表明,随着组装层数的增加,（CH-APP）_n/SFCM复合材料阻燃性能明显提高,组装10层的（CH-APP）₁₀/SFCM复合材料甚至可以达到离火自熄的程度。