多壁碳纳米管的化学修饰及其增强环氧树脂复合材料的性能

研究原生多壁碳纳米管和己二胺修饰的多壁碳纳米管分别对环氧树脂的增强作用。用SEM、FT-IR及XPS对修饰前后的碳纳米管进行的表征表明,所用的方法可以在碳纳米管的表面接上己二胺。研究发现,修饰后的碳纳米管比原生碳纳米管对环氧树脂有更明显的增强作用。修饰后的碳管含量为2%时,拉伸强度、断裂伸长率和冲击强度比纯环氧树脂分别提高79.7%、160.4%和188.2%。     

含多芳香环嵌段聚合物PS-b-PAH对碳纳米管的修饰

以芘丁酸为原料通过酯化反应制备了含芘丁单元的苯乙烯基单体,再利用原子转移自由基聚合法（ATRP）合成了分子量可控的嵌段聚合物PS-b-PAH,采用凝胶渗透色谱（GPC）、核磁共振（1H-NMR）等测试手段对产物进行了表征。采用聚合物对碳纳米管表面修饰,比较了聚苯乙烯PS和嵌段聚合物PS-b-PAH修饰碳纳米管后在THF...     

聚丙烯接枝马来酸酐修饰碳纳米管增强聚丙烯复合材料的制备及性能

采用混合溶剂的溶液法技术,对聚丙烯接枝马来酸酐(PP-g-MAH)包覆碳纳米管(MWNTs)与聚丙烯(PP)纳米复合材料的电学和力学性能进行了研究。PP-g-MAH包覆MWNTs在二甲苯溶液中呈现良好的分散性,红外结果表明,酸化碳纳米管后表面官能团如羟基、羧基与马来酸酐发生氢键作用。场发射扫描电镜(FESEM)也证明了PP-g-MAH修饰MWNTs在PP基体中分散良好,并且相容性也得到了明显改善。复合材料的拉伸强度和电导率都有较大的提高,其中导电性相比未处理碳管/聚丙烯提高了两个数量级。     

Studies on preparation and properties of the multi-walled carbon nanotubes (MWNTs)/epoxy nanocomposites

The MWNTs were coated with polyaniline (PANI) by in situ chemical oxidation polymerization method. FTIR spectroscopy, scanning electron microscope (SEM) and X-ray diffraction (XRD) indicated that the MWNTs were coated with PANI. The MWNTs/epoxy nanocomposites were fabricated by using the solution blending method. Differential scanning calorimetry (DSC), tensile testing, HP 4294A impedance analyzer and SEM were used to investigate the properties of the nanocomposites. The results showed that the modified carbon nanotubes were well dispersed in the polymer matrix. The nanocomposites have enhancements in mechanical, thermal and dielectric properties compare with the neat epoxy resin. The nanocomposites were proven to be a good polymer dielectric material.     

多壁碳纳米管/聚亚苯基苯并二噁唑复合材料的微结构与性能

以甲基磺酸(MSA)为溶剂通过溶液共混法制备了不同多壁碳纳米管(MWNTs)含量的多壁碳纳米管/聚亚苯基苯并二噁唑(MWNTs/PBO)复合材料, 用扫描电镜(SEM)对热处理前后复合材料的微结构进行了分析, 并对其导电、力学和耐热性能进行了研究。结果表明: MWNTs能均匀地分散在聚合物基体中, 并能形成一定的网络结构, 热处理后的复合材料较热处理前的结构更致密, 导电性能和力学性能都有所改善, 其中MWNTs质量分数为10％的热处理后复合材料与纯PBO聚合物相比, 体积电阻率降低约9个数量级, 而拉伸强度和拉伸模量分别提高了95％和53％, 耐热性能也有一定的提高。      

Preparation and properties of poly (p-phenylene sulfide)/multiwall carbon nanotube composites obtained by melt compounding

In this paper, electrical and mechanical properties of Poly (p-phenylene sulfide) (PPS)/multi-wall carbon nanotubes (MWNTs) nanocomposites were reported. The composites were obtained just by simply melt mixing PPS with raw MWNTs without any pre-treatment. The dispersion of MWNTs and interfacial interaction were investigated through SEM &TEM and Raman spectra. The rheological test and crystallization behavior were also investigated to study the effects of MWNTs concentration on the structure and chain mobility of the prepared composites. Though raw MWNTs without any pre-treatment were used, a good dispersion and interaction between PPS and MWNTs have been evidenced, resulting in a great improvement of electrical properties and mechanical properties of the composites. Raman spectra showed a remarkable decrease of G band intensity and a shift of D bond, demonstrating a strong filler–matrix interaction, which was considered as due to π–π stacking between PPS and MWNTs. The storage modulus (G′) versus frequency curve presented a plateau above the percolation threshold of about 2–3 wt% with the formation of an interconnected nanotube structure, indicative of ‘pseudo-solid-like’ behavior. Meanwhile, a conductive percolation threshold of 5 wt% was achieved and the conductivity of nanocomposites increased sharply by several orders of magnitude. The difference between electrical and rheological percolation threshold, and the effect of critical percolation on the chain mobility, especially on crystallization behavior of PPS, were discussed. In summary, our work provides a simple and fast way to prepare PPS/MWNTs nanocomposites with good dispersion and improved properties.     

Improvement of the properties of PC/LCP blends in the presence of carbon nanotubes

Polycarbonate (PC)/liquid crystalline polymer (LCP)/Multiwall carbon nanotube (MWNTs) nanocomposites containing as-received and modified (COOH-MWNT) carbon nanotubes were prepared through melt process in extruder and then compression molded. The chemical modification of MWCNT enhances the compatibility as well as miscibility between Polycarbonate and LCP in the concerned composites. Incorporation of functionalized MWCNTs improves the thermal, mechanical dynamic mechanical and electrical properties of the composites. Storage modulus and glass transition temperature increases in a remarkable fashion due to the enhanced interfacial adhesion between the PC/LCP/COOH-MWCNT. Field emission microscopy (FESEM) and HRTEM exhibit LCP fibrillation and fine dispersion of COOH-MWCNT throughout the matrix highlighting the miscibility between LCP and PC matrix.     

碳纳米管／聚氨酯纳米复合材料的制备及性能

采用可逆加成-断裂链转移(RAFT)聚合方法在碳纳米管表面接枝聚甲基丙烯酸甲酯和聚苯乙烯嵌段共聚物MWNT-P(MMA-b-St),对碳纳米管进行改性。采用直接共混法制备碳纳米管/水性聚氨酯纳米复合材料。通过红外光谱(FT-IR)和透射电镜(TEM)对嵌段共聚物的结构进行了表征。碳纳米管加入对乳液成膜性影响不大。热失重分析(TGA)和力学性能测试结果表明,当改性后的碳纳米管含量为聚氨酯固体份的0.75%时,复合材料的热稳定性、拉伸强度和断裂伸长率均较聚氨酯有所提高。     

Preparation and properties of the polyimide/multi-walled carbon nanotubes (MWNTs) nanocomposites

The polyimide/multi-walled carbon nanotubes (MWNTs) nanocomposite films were prepared by mixing of poly(amic acid) (PAA) solution and MWNTs/DMAc suspension follow by mixture casting, evaporation and thermal imidization. To increase the chemical compatibility between polyimide matrix and MWNTs, MWNTs were modified with mixed strong acid. The results show that the dispersion of the MWNTs is improved greatly in the polyimide matrix after acid modification. The modified MWNTs are dispersed homogeneously in the polyimide matrix while the structure of the polyimide and MWNTs structures is stable in the preparation process. With the incorporation of MWNTs, the mechanical properties of the resultant nanocomposite films were greatly improved due to the strong interfacial interaction between the modified MWNTs and the polyimide matrix. The thermal stability of the nanocomposites was lower a little than pure polyimide because of the drop of thermostability of MWNTs through acid-treatment. The electrical conductivity and the dielectric constant of the nanocomposites were also having sharp increase, which is favorable for practical use in anti-static materials and embedded capacitors.     

The matrix stiffness role on tensile and thermal properties of carbon nanotubes/epoxy composites

In this study, randomly oriented single-walled carbon nanotubes (SWCNTs)/epoxy nanocomposites were fabricated by tip sonication with the aid of a solvent and subsequent casting. Two different curing cycles were used to study the role of the stiffness of the epoxy matrix on the tensile and thermal behavior of the composites. The addition of a small amount of SWCNTs (0.25 wt.%) in rubbery, i.e., soft matrices, greatly increased Young’s modulus and tensile strength of the nanocomposites. The results showed that the tensile properties of soft epoxy matrices are much more influenced by the addition of carbon nanotubes than stiffer ones. The significant improvement in tensile properties was attributed to the excellent mechanical properties and structure of SWCNTs, an adequate dispersion of SWCNTs by tip sonication, and a stronger SWCNT/matrix interfacial adhesion in softer epoxy matrices. A slight improvement in the thermal stability of the nanocomposites was also observed.     

Facile preparation,characterization and performance of noncovalently functionalized graphene/epoxy nanocomposites with poly(sodium 4-styrenesulfonate)

Graphene was noncovalently functionalized with poly(sodium 4-styrenesulfonate) (PSS) and then successfully incorporated into the epoxy resin via in situ polymerization to form functional and structural nanocomposites. The morphology and structure of PSS modified graphene (PSS-g) were characterized with transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The effects of PSS-g additions on tensile, electrical and thermal properties of the epoxy/graphene nanocomposites were studied. Noncovalent functionalization improved interfacial bonding between the epoxy matrix and graphene, leading to enhanced tensile strength and modulus of resultant nanocomposites. The PSS-g additions also enhanced electrical properties of the epoxy/PSS-g nanocomposites, resulting in a lower percolation threshold of 1.2 wt%. Thermogravimetric and differential scanning calorimetric results showed the occurrence of a two-step decomposition process for the epoxy/PSS-g nanocomposites.     

Thermo-physical properties of epoxy nanocomposites reinforced with amino-functionalized multi-walled carbon nanotubes

The modification of multi-walled carbon nanotubes (MWNTs) with amine groups was investigated by FTIR, Raman spectroscopy and XPS after such steps as carboxylation, acylation and amidation. Nanotube-reinforced epoxy polymer composites were prepared by mixing amino-functionalized MWNTs with epoxy resin and curing agent. DSC, TGA, SEM and flexural test were used to investigate the thermal and mechanical properties of the composites. The results showed that amino-functionalized MWNTs could enhance the interfacial adhesion between the nanotubes and the matrix, thus greatly improve the thermal and mechanical properties of the resin epoxy bulk material.     

Mechanical and thermal properties of epoxy nanocomposites reinforced with amino-functionalized multi-walled carbon nanotubes

The functionalized multi-walled carbon nanotubes (MWNTs) with amino groups were prepared after such steps as oxidation, the addition of carboxyalkyl radicals, acylation and amidation. Besides oxidated-MWNTs/epoxy nanocomposites, amino-functionalized MWNTs/epoxy nanocomposites, in which MWNTs with amino groups acted as a curing agent and covalently attached into the epoxy matrix, were fabricated. Subsequently, the effects of MWNT content on the mechanical and thermal properties for the two systems were investigated. It is found that both the tensile strength and impact strength enhance with the increase of MWNT addition, and the most significant improvement of the tensile strength (+51%) and especially impact strength (+93%) is obtained with amine-treated MWNTs at an 1.5 wt.% content. Moreover, the thermal stability of the nanocomposites also distinctly improves. The improvement of the properties of the amine-treated MWNTs system is more remarkable than those of o-MWNTs system. The reasons for these changes were discussed.     

Study on thermal and mechanical properties of nano-calcium carbonate/epoxy composites

A study on evaluating the effect of nano-CaCO₃ particles on thermal and mechanical properties of epoxy resin cast was performed by TGA and mechanical tests. A silane coupling agent KH550 as an interfacial modifier was introduced into nanocomposites through preparing KH550/nano-CaCO₃ master batch. It is revealed that epoxy resin cast filled with nano-CaCO₃ particles represents higher thermal stability and mechanical strength. The improvement of thermal and mechanical properties is attributed to the surface modification of nano-particles, which can enhance the interfacial properties between nano-CaCO₃ fillers and epoxy resin. The mechanical properties of nano-CaCO₃/epoxy/carbon fibres composites based on the modified epoxy matrix are also enhanced.     

Study on dispersion and electrical property of multi-walled carbon nanotubes/low-density polyethylene nanocomposites

Sonication is one of the promising approaches to disperse nanoparticles into the base material thoroughly. Furthermore, coupling treatments for MWNTs and polymer matrix also contribute to homogenous dispersion of MWNTs among polymer matrix. In this paper, MWNTs and KH-550 were dispersed with acetone via sonication method, then, the MWNTs/low density polyethylene (LDPE) composites was prepared by using melt blending process. Effects of MWNTs and LDPE coupling treatment on dispersion and electrical property of the MWNTs/LDPE nanocomposites were investigated. SEM observation on fracture surfaces of the nanocomposites explained the functions of sonication and coupling treatment on the dispersion, and electrical conductivity of the nanocomposites was measured by four-contact scheme. The results displayed that the optimum sonication temperature was 70 °C and the optimum sonication amount of MWNTs particles in 200 ml KH-550 acetone solution was 20 g. Moreover, dispersion of the nanocomposites was improved with increasing sonication power amplitude. Furthermore, dispersion and electrical conductivity of the nanocomposites with coupling treatment LDPE were better than those of the nanocomposites with uncoupling treatment LDPE. The good dispersion and electrical conductivity enhancement are based on the strong bonding and coupling reaction of MWNTs and LDPE matrix, which associated greatly with sonication and coupling treatment.     

Mechanical and thermal behavior of non-crimp glass fiber reinforced layered clay/epoxy nanocomposites

Mechanical and thermal properties of non-crimp glass fiber reinforced clay/epoxy nanocomposites were investigated. Clay/epoxy nanocomposite systems were prepared to use as the matrix material for composite laminates. X-ray diffraction results obtained from natural and modified clays indicated that intergallery spacing of the layered clay increases with surface treatment. Tensile tests indicated that clay loading has minor effect on the tensile properties. Flexural properties of laminates were improved by clay addition due to the improved interface between glass fibers and epoxy. Differential scanning calorimetry (DSC) results showed that the modified clay particles affected the glass transition temperatures (T_g) of the nanocomposites. Incorporation of surface treated clay particles increased the dynamic mechanical properties of nanocomposite laminates. It was found that the flame resistance of composites was improved significantly by clay addition into the epoxy matrix.     

Effects of surface-functionalized multi-walled carbon nanotubes on the properties of poly(dimethyl siloxane) nanocomposites

The effects of surface-functionalized multi-walled carbon nanotubes (MWNTs) on the properties of poly(dimethyl siloxane) (PDMS) nanocomposites are investigated in the present study. The surface functionalization of MWNTs is carried out by diphenyl-carbinol functionalization followed by reaction with multifunctional silane, 3-aminopropyltriethoxisilane. Fourier transform infrared spectroscopy (FT-IR) and energy dispersion spectroscopy (EDS) analysis are used to confirm the presence of diphenyl-carbinol and silane on the surface of the MWNTs. The effects of the MWNTs’ surface treatment on the thermal and electrical properties of poly(dimethyl siloxane)-based (PDMS) nanocomposites are also studied. The results show that the grafting of silane molecules onto diphenyl-carbinol-functionalized MWNTs (SD-MWNTs) improves the dispersion of MWNTs in PDMS; this subsequently enhances the thermal conductivity and dynamic mechanical properties as compared to those containing unmodified (U-MWNTs) and diphenyl-carbinol-functionalized MWNTs (D-MWNTs). The electrical conductivity of the nanocomposites is shown to decrease due to the wrapping of MWNTs with non-electrical-conducting organic materials.     

Influence of nanotube content on the mechanical and thermo-mechanical behaviour of –COOH functionalized MWNTs/epoxy composites

Functionalized multi-wall carbon nanotubes (MWNTs) with carboxylic acid group (–COOH) have been utilized for the preparation of epoxy nanocomposites. Composites were synthesized using three different wt% (0.5, 0.75 and 1) of MWNTs via the solution mixing technique followed by ultrasonication. Mechanical and thermo-mechanical properties of the fabricated composites have been experimented for the suitability of this material in a variety of structural applications. The flexural modulus, strength, hardness, impact strength and storage modulus increased upon increasing MWNTs contents. Best results have been observed in nanocomposites with 0.75 wt% nanotubes loading, which showed 101, 166 and 61% enhancement in the flexural modulus, hardness and storage modulus, respectively, compared to neat epoxy. Achievement of uniform dispersion and hence formation of improved interface between nanotubes and epoxy was the reason behind the maximum enhancement at this wt%, which is further evidenced by the fracture surface morphology obtained from microscopical investigations.     

Mechanical,thermal and microstructural characteristics of cellulose fibre reinforced epoxy/organoclay nanocomposites

Epoxy nanocomposites reinforced with recycled cellulose fibres (RCFs) and organoclay platelets (30B) have been fabricated and investigated in terms of WAXS, TEM, mechanical properties and TGA. Results indicated that mechanical properties generally increased as a result of the addition of nanoclay into the epoxy matrix. The presence of RCF significantly enhanced flexural strength, fracture toughness, impact strength and impact toughness of the composites. However, the inclusion of 1 wt.% clay into RCF/epoxy composites considerably increased the impact strength and toughness. The presence of either nanoclay or RCF accelerated the thermal degradation of neat epoxy, but at high temperature, thermal stability was enhanced with increased char residue over neat resin. The failure micromechanisms and energy dissipative processes in these nanocomposites were discussed in terms of microstructural observations.     

Organoclay effect on transverse compressive strength of glass/epoxy nanocomposites

This research focuses on the fabrication of glass fiber/epoxy nanocomposites containing organoclay as well as understanding the organoclay effect on the transverse compressive strength of nanocomposites. To demonstrate the organoclay effect, three different loadings of organoclay were dispersed, respectively, in the epoxy resin using a mechanical mixer followed by sonication. The corresponding glass/epoxy nanocomposites were produced by impregnating dry glass fiber with organoclay epoxy compound through a vacuum hand lay-up procedure. Unidirectional block specimens were employed for transverse compression tests on a hydraulic MTS machine. Experimental observations indicate that glass/epoxy nanocomposites containing organoclay exhibit higher transverse compressive strength than conventional composites. Furthermore, the failure mechanisms for all tested specimens were found to be fiber and matrix debonding. Therefore, results indicate that the increasing characteristic in transverse failure stress may be ascribed to the enhanced fiber/matrix adhesion modified by the organoclay.