Polyamide‐12/Functionalized Carbon Nanofiber Composites: Evaluation of Thermal and Mechanical Properties

This work aims at improving the interfacial bonding between polyamide‐12 and CNFs. CNFs were oxidized and dispersed in polyamide‐12 giving rise to polymer nanocomposites. The oxidation caused an increase in the specific surface area and structural defects of the fibers, as indicated by surface area and Fourier‐transform Raman spectroscopy. The nanocomposites exhibited improved thermal and thermo‐oxidative stabilities. The oxidized nanofibers had marginal effect on the crystallinity and crystallization of the polyamide‐12. An over‐proportional enhancement of stiffness due to the fibers could be achieved. In spite of these improvements the fiber/polymer adhesion should be further improved.

     

Impact of Filler Functionalisation on the Crystallinity,Thermal Stability and Mechanical Properties of Thermoplastic Elastomer/Carbon Nanotube Nanocomposites

In the present work, the functionalisation of oxidised SWCNTs and MWCNTs is studied. The functionalised fillers are characterised by Raman spectroscopy and TGA. The functionalised fillers are dispersed in a PBT‐PTMO thermoplastic elastomer matrix via in situ polymerisation. The functionalisation causes a fine filler dispersion right at beginning of nanocomposite manufacturing. The fillers act as nucleating agents for crystallisation and evidences for a grafting from PBT at the surface of the functionalised nanotubes are found. An outstanding reinforcement effect by the functionalised CNTs is confirmed by tensile tests.

     

Chemical Functionalization and Dispersion of Carbon Nanofibers in Waterborne Polyurethane Adhesives

Waterborne polyurethane adhesives (WBPU) reinforced with carbon nanofibers (CNFs), to make them also conductive to static electricity, were prepared and their properties were evaluated as a function of content (0.1–1 wt%). The incorporation of carbon nanofibers to waterborne polyurethane adhesives implies a great difficulty because of their tendency to form aggregates, which prevents an efficient dispersion. In this sense, it is necessary to insert functional groups on the surface of the nanofibers to improve their interaction with any polymer. In this research, the surfaces of carbon nanofibers were previously oxygenated by chemical functionalization to enhance their stability in waterborne polyurethane adhesives. The obtained results showed that the chemical treatment used to functionalize the carbon nanofillers was adequate, as well as the experimental procedure carried out for their incorporation into the polyurethane, since stable dispersions were obtained. Moreover, the addition of the nanofibers to the waterborne polyurethanes contributed to improving their rheological and viscoelastic properties, imparting an increase in the viscosity and changes in the crystallisation kinetics.     

静电纺丝PA66纳米纤维束的拉伸性能

利用静电纺丝技术,采用两个间隔一定距离的针头作为收集装置制备PA66纳米纤维束,其中一个接收针头静止,另一个以不同转速旋转。通过调节针头转速得到纳米纤维不同排列方式的纳米纤维束。利用扫描电镜（SEM）、广角X射线衍射（WAXD）、差示扫描量热法（DSC）、拉伸试验等对纳米纤维束的微观结构和拉伸性能进行表征,并研究了接收针头转速对纳米纤维束的微观结构和力学性能的影响。结果表明：旋转条件下制备的纳米纤维束的拉伸强度和断裂伸长率均大于静止条件下制备的纤维束。     

相容剂对PP／PS形态与力学性能的影响

研究了苯乙烯-乙烯／T-烯-苯乙烯共聚物（SEBS）、聚丙烯与苯乙烯接枝共聚物（PP—g-PS）、沙林（Surlyn）对聚丙烯／聚苯乙烯（PP／PS）形态和力学性能的影响。结果表明：SEBS对PP／PS的冲击强度有比较明显的提高，但拉伸强度有所下降；PP-g-PS使PP／PS相界面变得模糊，分散相微粒尺寸变小，分布变窄，PP／PS相容性得到改善；Surlyn使PP／PS力学性能略微下降，增容作用不显著。     

Effect of Ultrasonic Dispersion Methods on Thermal and Mechanical Properties of Organoclay Epoxy Nanocomposites

This report highlights the importance of nanocomposite formation and dispersion upon improvements in properties for high performance epoxy based layered silicate nanocomposites. This is achieved through the preparation of epoxy nanocomposites with varying clay concentrations using ultrasonic and solvent based fabrication and standard shear mixing procedures. Ultrasonication (combined with a solvent), in comparison to shear mixing methods, produces superior nanoscale dispersion according to SEM and TEM. As a result of the improvements in nanoscale dispersion, the corresponding improvements in fracture toughness, strength, strain to failure (compressive and flexural) and char stability are presented. TGA shows that while the initial thermal decomposition process is not affected, the stability of the char layer formed during decomposition increases with improved nanoscale dispersion as well as increasing concentration. The effect of moisture upon the dynamic mechanical thermal analysis of the epoxy nanocomposites displays some dependence upon the clay dispersion with a modest increase in plasticisation for the sonicated samples. Overall, this work shows that for a high performance epoxy anhydride resin system, significant improvements in key properties can be achieved at low levels of addition if appropriate sonicated dispersion methods can be utilised.

     

交联聚苯乙烯的合成及力学性能研究

以苯乙烯为单体,二乙烯基苯为交联剂,采用自由基交联共聚合的方法合成出交联聚苯乙烯热固性塑料,并运用红外光谱、差示扫描量热分析对其进行了表征。研究了交联剂用量及后期热处理对其力学性能的影响。结果表明,交联聚苯乙烯的力学性能随着二乙烯基苯用量的增加呈先增后减变化,其含量在1.6～1.8 质量%时交联聚苯乙烯具备最佳综合力学性能,适当的后期热处理使得交联聚苯乙烯的拉伸强度及断裂伸长率分别提高12 %和20 %。     

阻燃聚苯乙烯板的力学性能

以阻燃涂料对可发性聚苯乙烯板(EPS)进行内部包覆和外部涂刷,制备阻燃EPS板。对涂覆涂料的阻燃EPS板进行抗弯压缩、高低温尺寸稳定性以及吸水率的测试结果表明,在阻燃EPS板极限氧指数达34.7%、垂直燃烧达UL94 V–0级及水平燃烧达HF–1级标准时,其力学性能及其它性能均能达到国家要求的保温材料标准,由此表明,阻燃涂料在改善EPS板的阻燃性能的同时,也能保证阻燃EPS板的力学性能。     

Improving Mechanical Properties of Carbon/Epoxy Composite by Incorporating Functionalized Electrospun Polyacrylonitrile Nanofibers

Electrospun functionalized polyacrylonitrile grafted glycidyl methacrylate (PAN‐g‐GMA) nanofibers are incorporated between the plies of a conventional carbon fiber/epoxy composite to improve the composite's mechanical performance. Glycidyl methacrylate (GMA) is successfully grafted onto polyacrylonitrile (PAN) polymer powder via a free radical mechanism. Characterization of the electrospun PAN and PAN‐g‐GMA nanofibers indicates that the grafting of GMA does not significantly alter the tensile properties of the PAN nanofibers but results in an increase in the diameter of nanofibers. Statistical analysis of the mechanical characterization studies on PAN‐carbon/epoxy hybrid composites conclusively shows that the composite reinforced with functionalized PAN nanofibers has greater mechanical properties than that of both the neat PAN nanofiber enriched hybrid composite and control composite (without nanofibers). The improved performance is attributed to the grafted glycidyl groups on PAN, leading to stronger interactions between the nanofibers and the epoxy matrix. PAN‐g‐GMA nanofiber reinforced composite outperforms their neat PAN counterparts in tensile strength, short beam shear strength, flexural strength, and Izod impact energy absorption by 8%, 9%, 6%, and 8%, respectively. Compared to the control composite, the improvements resulting from the PAN‐g‐GMA nanofiber incorporation are even more pronounced at 28%, 41%, 32%, and 21% in the corresponding tests, respectively.

     

Effect of carbon nanofiber functionalization on the in-plane mechanical properties of carbon/epoxy multiscale composites

In this work, vapor-grown carbon nanofibers (CNFs) were functionalized using an optimized route and dispersed in the matrix of carbon fabric-reinforced epoxy composites to develop multiscale carbon/epoxy composites. Functionalization was carried out through an oxidative treatment with a mixture of HNO₃/H₂SO₄ (1 : 3) using a combination of ultrasonication and magnetic stirring. Functionalized CNFs (F-CNFs) were characterized for their morphology, length, functional groups, and degradation due to oxidative treatment. The results showed that it was possible to efficiently functionalize CNFs without any degradation through proper selection of treatment duration. F-CNFs were dispersed homogeneously into the epoxy matrix using ultrasonication in combination with high-speed mechanical stirring. The incorporation of 0.1 wt % F-CNFs led to a 65% increase in Young's modulus and a 36% in tensile strength of neat carbon/epoxy composites. The fracture surfaces were studied using scanning electron microscopy to understand the property enhancement due to F-CNFs. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

碳布复合材料力学性能研究

测试了两种不同经纬编织密度和不同含胶量的碳布／环氧复合材料的基本力学性能，对碳纤维复丝及碳布在复合材料中的强度利用率作了比较与分析。结果表明：适当增大含胶量有利于改善复合材料的力学性能；经纬编织密度对复合材料力学性能的影响同样不可忽视。     

Effect of Wood Fibers on the Rheological and Mechanical Properties of Polystyrene/Wood Composites

The effects of wood fibers on the rheological and mechanical properties of polystyrene/wood (PS/wood) composites were investigated. The composites with different ratios of PS and wood were prepared by means of internal mixer and, additionally, two different sizes of the wood particles were used, such as ～100 and ～600 µm. The rheological properties were studied using capillary rheometer, apparent shear rate, apparent shear stress, apparent viscosity, power law index, and flow activation energy at a constant shear stress were determined. The rheological results showed that the shear stress–shear rate variations obeyed a power law equation, and the composites exhibited shear thinning. The flow activation energy of the composites increased with the addition of wood particles. Mechanical results showed that stress at break of the composites was higher than that of pure PS, whereas the strain at break and impact strength of the composites were lower than that of PS. In addition, the mechanical properties of the present composites were improved when the small size of wood particles were incorporated.     

Fabrication and Properties of Ethylene Vinyl Acetate-Carbon Nanofiber Nanocomposites

Carbon nanofiber (CNF) is one of the stiffest materials produced commercially, having excellent mechanical, electrical, and thermal properties. The reinforcement of rubbery matrices by CNFs was studied in the case of ethylene vinyl acetate (EVA). The tensile strength was greatly (61%) increased, even for very low fiber content (i.e., 1.0 wt.%). The surface modification of the fiber by high energy electron beam and gamma irradiation led to better dispersion in the rubber matrix. This in turn gave rise to further improvements in mechanical and dynamic mechanical properties of EVA. The thermal conductivity also exhibited improvements from that of the neat elastomer, although thermal stability of the nanocomposites was not significantly altered by the functionalization of CNFs. Various results were well supported by the morphological analysis of the nanocomposites.     

碳纳米管对硅酸盐水泥力学性能的影响研究

研究了用超声分散的碳纳米管对硅酸盐水泥物理力学性能的影响,并利用XRD和SEM等测试手段对碳纳米管改性水泥的水化产物及硬化浆体的形貌进行了分析.结果表明:碳纳米管的掺入改变了水泥净浆的标准稠度用水量和凝结时间,提高了其抗压和劈裂抗拉强度,但并未造成安定性不良.随碳纳米管掺量的增加,水泥净浆的标准稠度用水量逐渐增加,凝结时间不断缩短,标养28天的抗压和疲劳抗拉强度较未掺碳纳米管的硬化浆体分别提高了15.34％和18.44％.XRD分析表明碳纳米管的掺入不仅提高了水泥净浆的水化程度,增加了C-S-H的生成量,而且降低CH的结晶度.SEM证明碳纳米管的掺入较未掺的水泥净浆硬化浆体结构趋于优化,更致密.     

聚丙烯/纳米碳纤维复合材料微孔注射成型加工与性能研究

将聚丙烯(PP)和纳米碳纤维(CNF)共混后,通过双螺杆挤出制备成不同组份的复合粒料,采用注射成型加工制备实体和发泡试样,研究不同CNF含量对PP基体复合材料性能的影响。结果表明,随着CNF含量的增加,微孔样品中的孔径显著的减小同时泡孔密度增加;注射成型的样品中,添加CNF后的模量和拉伸强度略微降低,但微孔注塑的PP/CNF复合材料的性能呈现出相反的效果。     

Poly(propylene)/Carbon Nanofiber Nanocomposites: Ex Situ Solvent‐Assisted Preparation and Analysis of Electrical and Electronic Properties

CNF‐reinforced PP nanocomposites were fabricated from CNFs dispersed in a boiling PP/xylene solution. Their thermal properties were characterized by TGA and DSC and shown to exhibit improved thermal stability and higher crystallinity. They were further processed into thin films by compression molding. The electrical conductivity and dielectric property of the PP/CNF nanocomposite thin films were studied. Both electric conductivity and real permittivity increased with increasing fiber loading. Electrical conductivity percolation is observed between 3.0 and 5.0 wt.‐% fiber loading. The rheological behavior of the nanocomposite melts were also investigated. It was found that a small fiber concentration affects the modulus and viscosity of PP melt significantly.

     

Effect of Nanoparticles on Mechanical and Flame-retardant Properties of Polyether-Block-Polyamide Polymer Nanocomposites

In this study, polyester elastomer-based thermoplastic (TPEE) nanocomposites were fabricated for flame-retardant applications. Small amounts of graphene and nanoclay were added to the nanocomposites to investigate their effects on the mechanical and thermal properties of the nanocomposites. The addition of a phosphorous flame-retardant additive resulted in a significant improvement of the Young’s modulus and thus yield stress in the synthesized nanocomposites as compared to those made with the virgin TPEE. There was no synergistic improvement in mechanical properties with the addition of graphene and nanoclay to the nanocomposites. However, thermal properties, mainly the heat deflection temperature and fire performance (UL-94 V0), were improved significantly by the addition of graphene and nanoclay and a synergistic effect was observed. Heat distortion temperature and thermogravimetric analysis were used to analyze the thermal properties of the nanocomposites. The UL-94 testing method was used to investigate the fire performance of the nanocomposites. Scanning electron microscopy was used to observe the polymer fracture surface morphology. The dispersion of the graphene and nanoclay particles was confirmed by transmission electron microscopy analysis.     

聚合物接枝纳米碳纤维/聚苯乙烯复合材料的制备与力学性能研究

采用自由基聚合方法,在纳米碳纤维(CNF)表面接枝聚丙烯酸正丁酯(PnBA)和聚苯乙烯(PS),利用接枝的嵌段聚合物作为大分子偶联剂制备CNF/PS复合材料。红外傅里叶变换光谱(FT-IR)研究表明,嵌段聚合物PnBA-b-PS被成功地接枝到CNF表面。扫描电子显微镜(SEM)和力学性能测试结果显示,CNF与PS复合材料界面结合得到改善,力学性能明显提高。     

基于聚丙烯腈/苯并噁嗪的柔性碳纳米纤维薄膜的制备及其电化学性能研究

通过将苯并噁嗪、聚丙烯腈(PAN)和乙酰丙酮铁共同静电纺丝的方式制备了柔性良好的碳纳米纤维薄膜.结果表明,引入结构设计的苯并噁嗪可以有效地将N、O、S等杂元素引入碳纳米纤维薄膜,从而有效地提高电极的赝电容特性及电解质对电极的浸润性.并在此基础上,进一步将环境友好且赝电容特性明显的Fe3O4沉积在所得碳纳米纤维薄膜上,最...