Synergistic effect of hyperthermal atomic oxygen beam and vacuum ultraviolet radiation exposures on the mechanical degradation of high-modulus aramid fibers

The synergistic effect of atomic oxygen and vacuum ultraviolet (VUV) radiation exposures was investigated on the mechanical properties of high-modulus aramid fibers. Tensile tests were performed on single fibers. It was found that both tensile strength and Young's modulus decreased significantly due to the simultaneous exposures of atomic oxygen and vacuum ultraviolet radiation. In contrast, the surface of aramid fiber exposed to ultraviolet alone showed no change in tensile strength and Young's modulus. X-ray photoelectron spectroscopy showed that atomic oxygen exposure leads to oxidization and decomposition of amid groups, that only VUV exposure does not change the fiber surface, and that VUV exposure decreased oxidized components on the oxidized fiber surface exposed to atomic oxygen and ultraviolet simultaneously. Scanning electron microscopy revealed that the diameter of the fiber was not influenced so much by atomic oxygen and ultraviolet exposures, but the fiber surface became substantially rougher than the aramid fiber surface exposed to atomic oxygen alone.     

两种对位芳纶纤维本体性能的对比研究

采用SEM、AFM和红外光谱对F-12芳纶纤维和国产芳纶Ⅲ纤维表面微观形态以及纤维化学结构进行了测试分析;通过芳纶复丝性能测试考核了两种纤维本体的力学性能。结果表明:两种芳纶纤维结构和化学成分相似,都具有"皮-芯"结构,表面具有较多的微观缺陷,且F-12芳纶纤维表面比国产芳纶Ⅲ纤维表面粗糙;两种芳纶纤维都是全芳香族聚酰胺结构;F-12芳纶复丝拉伸强度和断裂伸长率比国产芳纶Ⅲ纤维分别高出33.6%和62.5%但,拉伸弹性模量比国产芳纶Ⅲ纤维低11.9%。     

RETRACTED ARTICLE: Surface modification of aramid fibers with novel chemical approach

Friedel–Crafts Reaction as a simple and convenient approach to the surface modification of aramid fiber was introduced in this paper. Epoxy chloropropane was chosen as the treatment reagent to modify aramid fibers surface via Graft reaction. After the modification, the interfacial properties of aramid/epoxy composites were investigated by the single fiber pull-out test (SFP), and the mechanical properties of aramid fibers were investigated by the tensile strength test. The results showed that the interfacial shear strength (IFSS) value of aramid/epoxy composites was enhanced by about 50%, and the tensile strength of aramid fibers had no obvious damage. The crystalline state of aramid fibers was determined by X-ray diffraction instrument (XRD), and the results showed that there were not any distinct crystal type varieties. The surface elements of aramid fibers were determined by X-ray photoelectron spectroscopy (XPS), the analysis of which showed that the oxygen/carbon ratio of aramid fiber surface increased obviously. The possible changes of the chemical structure of aramid fibers were investigated via Fourier transform infrared spectrum (FTIR), and the analysis of which showed that the epoxy functional groups were grafted into the molecule structure of aramid fibers. The surface morphology of aramid fibers was analyzed by Scanning electron microscope (SEM), and the SEM results showed that the physical structure of aramid fibers was not etched or damaged obviously. The surface energy of aramid fibers was investigated via the dynamic capillary method, and the results showed that the surface energy was enhanced by 31.5%, and then the wettability degree of aramid fiber surface was enhanced obviously too. All of the results indicated that this novel chemical modification approach not only can improve the interfacial bonding strength of aramid/epoxy composites remarkably, but also have no negative influence on the intrinsic tensile strength of aramid fibers.     

Biocomposites based on sea algae fibers and biodegradable thermoplastic matrices

Composites were prepared by mixing thermoplastic biodegradable polymers with sea algae fibers. Tensile mechanical properties were analyzed as a function of fiber concentration. The effect of processing, such as compression molding and calendering, on the mechanical properties of the materials was investigated. Composites showed higher elastic modulus and lower strength than the matrix components. Fiber damaging, characterized by a reduction of both length and diameter, was observed in the composites. Films, prepared by calendering operations, showed anisotropic properties due to fiber alignment. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 583–592, 1999     

紫外老化对芳纶／环氧复合材料性能和结构的影响

通过紫外老化试验（温度（40±5）℃,湿度40％）,研究了芳纶、环氧及其复合材料的力学性能、玻璃化转变温度、失重随老化时间的变化,并用红外光谱分析了芳纶的结构变化。结果表明：经紫外老化后,芳纶／环氧的拉伸强度、失重率有明显的变化,芳纶结构和复合材料的玻璃化转变温度无明显的变化。     

Atomistic simulations of functionalization of aramid fiber-epoxy nanocomposite

Owing to its high degree of crystallinity and orientation, the surface of aramid fiber is smooth, causing its low bonding strength with polymer matrix. This has restricted the application of aramid fiber in reinforced polymer materials. Effective methods are by introducing functional groups through surface modification and by increasing its surface roughness thereby greatly improving its bonding strength with the polymer. In this work, molecular dynamics (MD) simulation study fiber functionalized with hydroxyl (OH), carboxyl (COOH), and the silane coupling agent as nanofillers for polymer nanocomposites. The interfacial characteristics and the mechanical behavior of polymer nanocomposites are investigated. The results show that the functionalization can enhance the interfacial shear stress and tensile strength. The functional group not only provides a stronger interface, but also provides additional mechanical interlocking effect, which effectively improves load-bearing transmission capacity. The analysis of the micro-mechanism from the energy level also provides new insights for the functionalized design of nanocomposites.     

芳纶Ⅲ与芳纶Ⅱ防弹性能研究

选用两种不同型号芳纶,通过单向复合工艺分别制造成靶板。以NIJⅢA标准通过弹道试验,测试出两种靶板的弹坑凹陷深度与子弹穿透层数差异,并进一步通过测试两种芳纶SEA值比较其防弹性能差别,结果表明,芳纶Ⅲ抗弹性能比芳纶Ⅱ提高近30%。最后讨论了纤维力学性能对其防弹性能的影响,指出更高的拉伸强度和断裂伸长率是芳纶Ⅲ抗弹性能更优的主要原因,并预测芳纶Ⅲ的抗弹性能还有进一步提升的空间。     

芳纶纤维/AFR树脂复合材料界面粘结性能的研究

为了改善芳纶纤维复合材料的界面粘结性能,合成了一种新型树脂(AFR)作为基体,以未经任何表面处理的芳纶纤维作增强材料,制备了芳纶纤维/AFR复合材料。采用测定表面能、接触角、层间剪切强度、横向拉伸性能和扫描电镜观察形貌等方法,从宏观和微观等方面研究了芳纶纤维/AFR复合材料的界面粘结性能。结果表明,AFR树脂与芳纶纤维有相近的表面能,AFR树脂溶液与芳纶纤维的接触角为42.8°,而环氧树脂(EP)与芳纶纤维的接触角为68°,说明AFR树脂对芳纶纤维的润湿性优于EP树脂;芳纶/AFR复合材料的层间剪切强度、横向拉伸强度和纵向拉伸强度分别为74.64MPa、25.34MPa和2256MPa,比芳纶/EP复合材料的相应强度分别提高了28.7%、32.5%和13.4%,其复合材料破坏面的形貌也说明芳纶纤维与AFR树脂之间的界面粘结性能较好。     

磷酸酯偶联剂改性芳纶纤维增强聚丙烯复合材料的性能研究

采用磷酸酯偶联剂对芳纶纤维表面进行接枝改性,研究了实验条件和纤维含量对芳纶纤维增强聚丙烯(PP)复合材料力学性能的影响,并用电子扫描显微镜观察了PP复合材料的微观形态结构。结果表明:磷酸酯偶联剂成功接枝到芳纶纤维表面上,使芳纶纤维和PP的界面黏结性能得以明显改善。芳纶纤维可以显著地提高PP复合材料的力学性能当,其含量为20%时复,合材料的综合性能最优。     

热处理对国产对位芳纶AFS-920结构与性能的影响

以国产对位芳纶AFS-920为研究对象,通过热处理装置对芳纶进行增强改性。采用纤维强伸度仪、扫描电子显微镜、同步辐射广角X射线衍射等表征方法,系统地研究了热处理时间、温度、张力对芳纶性能的影响以及结构与性能之间的演变规律。结果表明:随着热处理温度的上升、张力的加大及停留时间的延长,强度和模量均有比较明显的提高然后又下降。最佳的热处理工艺为:处理温度500℃,张力0.3 c N/dtex,处理时间10 s。结构分析发现:无定形区的改善有利于提高纤维的力学性能,模量和强度提高的原因是纤维取向度及结晶度增大。     

表面处理对玻纤/碳纤增强橡胶基密封复合材料性能的影响

采用压延成张工艺制备碳纤维和玻璃纤维混杂增强非石棉橡胶基密封复合材料(NAFC),以横向抗拉强度作为表征混杂增强橡胶基密封材料中纤维与橡胶界面粘结性能的指标.通过扫描电镜(SEM)对材料横向拉伸试样断口进行形貌分析,及对材料的耐油、耐酸、耐碱性能进行测试,探讨了不同表面处理工艺对纤维与基体界面粘结效果的影响.研究结果表明,对玻璃纤维采用偶联剂KH-550浸渍后涂覆环氧树脂涂层,对碳纤维在空气氧化后涂覆环氧树脂涂层,可有效增强纤维、基体的界面粘结,所制得的混杂纤维增强复合材料具有较好的机械性能和耐介质性能.     

The Mechanical Properties of Particulate-filled Aramid and Polyethylene Laminates

Some mechanical properties of particulate-filled polyethylene/epoxy and aramid/epoxy laminates are reported, following earlier work with particulate-filled glass/epoxy laminates. The behaviour of the organic fibre laminates was different from that of glass fibre ones, investigated and reported earlier. There was an increase in compression strength with increasing filler content, with both kinds of organic fibre reinforcement. The interlaminar shear strength values were significantly lower for the polyethylene laminates than the aramid ones at all filler concentrations, and they fell to little more than 10MPa at high filler levels. However, the impact damage zone in drop weight tests was generally smaller for the polyethylene laminates, and the visible crack damage was less apparent than in the aramid ones. The flexural strength and modulus values are also reported. © of SCI.     

左旋多巴胺处理对芳纶表面结构与性能的影响

利用L-3,4-二羟基苯丙氨酸(L-DOPA)的氧化自聚合,在杂环芳纶表面修饰聚L-3,4-二羟基苯丙氨酸(PDOPA)活性涂层来提高芳纶的表面活性及耐紫外辐照性能。结果表明:改性后芳纶表面粗糙度显著提高,同时,PDOPA涂层上大量的羧基、羟基等活性单元均有利于增强与环氧树脂的机械锁合力,改性后芳纶/环氧树脂复合材料的界面剪切强度提高了32.0%。此外,上述改性过程对杂环芳纶本身力学性能影响较小,纤维的拉伸强度保持率可以达到100%,基本实现了无损改性。同时,由于PDOPA的保护作用,改性后芳纶的耐紫外辐射性能显著提高;经过168 h紫外线辐照处理后,其拉伸强度保持率可达到92.5%,显著提升了杂环芳纶的耐紫外线辐照特性。     

Orientation microstructure and properties of poly(propylene carbonate)/poly(butylene succinate) blend films

The blends of high molecular weight poly(propylene carbonate) (PPC) and poly(butylene succinate) (PBS) were melt blended using triphenylmethane triisocyanate (TTI) as a reactive coupling agent. TTI also serves as a compatibilizer for the blends of PPC and PBS. The blend containing 0.36 wt % TTI showed that the optimal mechanical properties were, therefore, calendared into films with different degrees of orientation. The calendering condition, degree of orientation, morphologies, mechanical properties, crystallization, and thermal behaviors of the films were investigated using wide‐angle X‐ray diffraction, scanning electron microscopy, tensile testing, and differential scanning calorimetry (DSC) techniques. The result showed that the as‐made films exhibited obvious orientation in machine direction (MD). Both tensile strength in MD and the tear strength in transverse direction (TD) increased with increasing the degree of orientation. The orientation of the film also increased the crystallinity and improved the thermal properties of the PPC/PBS blend films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

纳米SiO2改性EP对基体力学性能和芳纶纤维/EP复合材料界面性能的影响

研究了纳米SiO2对环氧树脂(EP)基体力学性能的影响,并进一步采用对位芳纶纤维(F-12)增强环氧树脂,制备了NOL环复合材料,通过复合材料层间剪切性能测试考核了F-12与环氧树脂之间的界面粘接性能.结果表明:环氧树脂中添加适量的纳米SiO2能够有效提高环氧树脂浇注体的拉伸强度、拉伸弹性模量、冲击强度.纳米SiO2的加入,可以有效改善F-12与环氧树脂基体之间的界面粘接性能,降低复合材料的空隙率,F-12/纳米SiO2(6%)-EP复合材料的层间剪切强度(ILSS)提高约60.3%.     

填充油对聚苯乙烯-b-聚〔乙烯-(乙烯-丙烯)〕-b-聚苯乙烯结构与性能的影响

研究了油品的种类及环烷烃油用量对聚苯乙烯-b-聚〔乙烯-(乙烯-丙烯)〕-b-聚苯乙烯(SEEPS)加工性能、物理机械性能、微观结构及玻璃化转变温度的影响。结果表明,环烷烃油和石蜡油均能明显改善SEEPS的加工流动性;环烷烃油填充SEEPS的物理机械性能优于石蜡油填充者;新疆和天津产环烷烃油填充SEEPS的物理机械性能相近,但天津产环烷烃油挥发分含量略高。填充100质量份Nyflex 222 B环烷烃油(NNO)的SEEPS具有较好的塑化成型性和物理机械性能。在此基础上再增加填充油量,SEEPS的定伸应力、拉伸强度和撕裂强度降低,扯断伸长率增大,但永久变形变化不大。NNO可均匀地渗入SEEPS弹性段和塑性段微区,其对SEEPS弹性微区的玻璃化转变温度基本没有影响,但会降低SEEPS塑性微区的玻璃化转变温度。     

Microstructure and mechanical properties of Si3N4f/BN composites with BN interphase prepared by chemical vapor deposition of borazine

The boron nitride (BN) interphase of silicon nitride (Si₃N₄) fiber-reinforced BN matrix (Si₃N_4f/BN) composites was prepared by chemical vapor deposition (CVD) of liquid borazine, and the microstructure, growth kinetics and crystallinity of the BN coating were examined. The effects of coating thickness on the mechanical strength and fiber/matrix interfacial bonding strength of the composites were then investigated. The CVD BN coating plays a key role in weakening the interfacial bonding condition that improves the mechanical properties of the composites. The layering structure of the BN coating promotes crack propagation within the coating, which leads to a variety of toughening mechanisms including crack deflection, fiber bridging and fiber pull out. Single-fiber push-out experiments were performed to quantify the fiber/matrix bonding strength with different coating thicknesses. The physical bonding strength due to thermal mismatch was discussed.     

开槽芳纶纸蜂窝芯与有孔芳纶纸蜂窝芯的对比分析

通过压缩性能和剪切性能实验,对同一密度的传统芳纶纸蜂窝芯、开槽芳纶纸蜂窝芯以及有孔芳纶纸蜂窝芯的主要力学性能进行了对比分析。实验表明,同一密度的传统蜂窝芯的压缩性能和剪切性能优于两种特殊蜂窝芯,但两种特殊蜂窝芯的主要力学性能能够达到传统芳纶纸蜂窝芯标准中出厂检验指标值的77%以上,能够满足多数特殊结构的使用要求。对两种特殊芳纶纸蜂窝芯的制造工艺和实际应用进行了对比分析,指出了各自的优势和劣势。两种特殊蜂窝芯的W向剪切模量均高于指标值。开槽蜂窝芯较有孔蜂窝芯制造工艺简单、制造周期短、制造成本低,但有孔蜂窝芯制造精度更高、应用范围更加广泛。     

Short fibers as reinforcement of rubber compounds

The effect of aramid, glass and cellulose short fibers on the processing behavior, crosslinking density and mechanical properties of natural rubber (NR), ethylene‐propylene‐diene terpolymer rubber (EPDM) and styrene‐butadiene rubber (SBR) has been investigated. Two fiber percentages (10 and 20 phr) were added to the rubber. The results have shown that the above‐mentioned fibers, especially aramid fibers, are effective reinforcing agents for these rubbers, giving rise to a significant increase in mechanical properties, such as tensile modulus and strength, and tear and abrasion resistance. Moreover, a significant decrease in the time to reach 97% of curing, t′_c (97) is observed, which indicates that the fibers tend to increase the vulcanization rate, regardless of the rubber used. Fibers give also rise to an increase in crosslinking, especially the aramid fibers.     

碳纤维改性HA/PMMA生物复合材料力学性能的研究

采用原位合成与溶液共混相结合的方法,制备了短切碳纤维增强纳米羟基磷灰石(HA)/聚甲基丙烯酸甲酯(PMMA)生物复合材料。研究了碳纤维的含量和长度对HA/PMMA复合材料结构和力学性能的影响。采用万能材料试验机和扫描电子显微镜对复合材料的力学性能及断面的微观形貌进行了测试和表征。结果表明:碳纤维在HA/PMMA复合材料中分布均匀,有效提高了复合材料的力学性能;碳纤维含量为4%时,复合材料的拉伸强度、弯曲强度、压缩强度和弹性模量等均达到最大值;复合材料的断裂伸长率随碳纤维含量的增加而减小;当碳纤维含量一定时,随其长度的增加,复合材料的拉伸强度、弯曲强度和弹性模量均增加,但断裂伸长率降低。