体育器材用CFRPA6复合材料的制备及其性能

采用碳纤维(CF)改性聚酰胺(PA)6,从而获得PA 6/CF复合材料。结果表明:CF被浓硝酸氧化后,表面会引入碳氮、碳氧等极性基团,增加了PA 6与CF的界面反应活性;CF经浓硝酸处理后表面有许多沟槽出现,增大的表面积对PA 6与CF间机械锁合有利;随着浓硝酸处理CF时间的延长,复合材料的悬臂梁缺口冲击强度略有提高,拉伸强度提高较大;CF被过度氧化时,复合材料的缺口冲击强度、拉伸强度均降低;经浓硝酸氧化处理后,增强了CF界面黏结效果,CF被PA 6紧密包覆,断裂时两者有黏结现象发生;未经浓硝酸处理的样条在纤维拔出后会留下大量空洞,经浓硝酸处理后CF表面极性基团增加,提高了CF与基体树脂的黏结强度。     

The mechanical and tribological properties of nitric acid‐treated carbon fiber‐reinforced polyoxymethylene composites

The carbon fibers have been exposed to nitric acid oxidation treatments and introduced into polyoxymethylene composites (POM/CF). The nitric acid treatment increases the number of the flaws, roughness of the surface, and disorder of carbon atoms on fiber, as well as introduces reactive functional groups, which could lead to a better mechanical bonding between fiber and the matrix. It is shown that the impact strength and fiber‐matrix adhesion in composites (POM/mCF) are superior to those for POM/CF composites. Simultaneously, the addition of mCF improves flexural strength and modulus relative to virgin POM significantly. Average friction coefficient values of POM/CF composites are lower than that of POM/mCF composites. As the percentage of fiber increases, the trend of wear ratio of the composites goes down initially and bumps up afterwards. The results indicate that the proper contents of CF and mCF in composites range from 5 wt % to 20 wt %. Scanning electron microscopy of worn surface morphology has revealed that the main wear mechanism of the composites were adhesive wear and ploughing wear. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41812.     

Effect of adding carbon fiber on conductive stability of acrylonitrile‐butadiene rubber composites

In this work, the conductive composites of acrylonitrile‐butadiene rubber (NBR) and conductive carbon black (CCB) were prepared. The volume resistivity of NBR/CCB composites became stable when the addition content of CCB reached 12 wt %. However, when carbon fiber (CF) was added into the composites, the volume resistivity of NBR/CCB/CF composites continued to decrease with the increase of CF addition, which resulted from the formation of the three‐dimensional conductive network in composite matrix. In addition, the effect of acid oxidation of CF surface on the mechanical proprieties and conductive stability of NBR/CCB/CF composites was studied. The results indicated the acid oxidation of CF surface improved the bond structure between NBR and CF, which further decreased the resistance and significantly improved the mechanical properties of the composites. It was demonstrated that the conductive stability of NBR composites after cyclic mechanical and temperature fatigues was remarkably enhanced with the addition of CF. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46668.     

Preparation and tribological properties of carbon fibre reinforced poly(vinylidene fluoride) composites

Abstract

The current study examines the tribological performance of poly(vinylidene fluoride) (PVDF) and carbon fibre reinforced poly(vinylidene fluoride) (CF/PVDF) under dry sliding condition. Different contents of carbon fibres (CFs) were employed as reinforcement. All filled and unfilled polyimide composites were tested against CGr15 ball and representative testing was performed. The effects of CF content on tribological properties of the composites were investigated. The worn surface morphologies of neat PVDF and its composites were examined by scanning electron microscopy and the wear mechanisms were discussed. Moreover, all filled PVDFs have superior tribological characteristics to unfilled PVDFs. The optimum wear reduction was obtained when the content of CF is 20 vol.-%.     

表面处理碳纤维改性聚酰亚胺复合材料的机械性能

采用硅烷偶联剂KH-550、高温氧化和超声波+偶联剂复合方法(简称超声复合方法)分别对碳纤维(CF)进行表面处理,制备不同表面处理的CF改性热塑性聚酰亚胺(PI)复合材料,研究表面处理CF对CF/PI复合材料力学和摩擦磨损性能的影响,利用扫描电子显微镜对PI复合材料磨损表面进行观察。结果表明:与纯PI相比,CF的加入提高了PI复合材料的机械性能,经超声复合处理的CF的增强效果较好;磨损表面表明:超声复合处理CF改性PI复合材料磨损表面的犁沟和磨屑较少,且平整。     

Ethylene–(vinyl acetate) copolymer/carbon fiber conductive composite: effect of polymer–filler interaction on its electrical properties

Ethylene–(vinyl acetate) (EVA)/carbon fibre (CF) composites were prepared by changing the content of CF in the composite. To investigate the effect of the interaction between EVA and CF on the electrical properties of the composite, the CF was treated in nitric acid. The interaction between EVA and CF was examined by a solvent-extraction method. It was found that the interaction of EVA with CF was enhanced due to the chemical absorption of EVA on CF. The correlation of CF content, electrical properties and the formation of polymer–filler gel for the composite with oxidized CF was studied. Although the composites filled with treated CF exhibit a slightly higher resistivity than those filled with untreated CF at room temperature, they show the improved electrical properties, including elimination of the negative-temperature-coefficient (NTC) effect, high electrical reproducibility after thermal cycles, and independence of the conductivity on time, which improves the practical applications of positive-temperature-coefficient (PTC) materials. Copyright © 2004 Society of Chemical Industry     

Bulk and surface chemical functionalities of type III PAN-based carbon fibres

PAN-based carbon fibres carbonised at relatively low temperature, i.e. type III carbon fibres, were submitted to heat treatment at 2300 °C (GR) or oxidation in nitric acid. The samples were characterised by XPS, FTIR, wetting measurements, gas adsorption, elemental analysis and acid/base titration. While oxidation only slightly affects the nitrogen concentration, it produces an appreciable change in the nature of the chemical functions, namely the conversion of pyridine-type nitrogen and quaternary nitrogen into aliphatic functions. Oxidation treatment modifies all the material constituting the fibre, the oxygen concentration being about 1.5 times higher at the fibre external surface compared with the whole material. Three components (531.2, 532.6 and 533.8 eV) are clearly identified in the oxygen XPS peak, allowing a comparison to be made between the whole material and the external surface regarding chemical species. The acidic groups are mainly carboxyl. Fibres submitted to extensive oxidation also show a high basicity, attributed mainly to calcium carboxylate. Although the acidic and basic groups present in the whole material can be titrated with aqueous solutions, the fibres develop only a very small surface area and no microporosity as determined by krypton adsorption. The material may be viewed as a sponge, collapsed when dry but able to swell in water and developing a high cation-exchange capacity.     

Processing and properties of Cfibre/SiCfillers/SiOC composites using solvent free liquid polysiloxane as matrix source

Abstract

Carbon fibre reinforced SiOC composites (denoted as C_fibre/SiC_fillers/SiOC) were prepared by slurry coating and polymer infiltration pyrolysis (PIP) process. Low viscosity liquid polysiloxane (PSO) and SiC powder were combined at a 1∶1 weight ratio to produce a blend (S-PSO), which was employed as matrix source. Heat treated carbon fibre fabric was adopted as the reinforcement. The lamination process was determined on the basis of cure and rheology investigations on S-PSO. The effects of PIP cycles and temperature of heat treatment of the carbon fibre on the mechanical properties of C_fibre/SiC_fillers/SiOC were examined. The results indicate that composites using carbon fibres annealed at 1700°C as reinforcement reached a maximum flexural strength of 300 MPa after six PIP cycles. The resistance of the C_fibre/SiC_fillers/SiOC composite to oxidation was also evaluated. Without any protective coatings, the composite retained 60% of its strength after oxidation at 800°C for 3 h in a static air environment.     

Covalent functionalization of carbon fiber with poly(acrylamide) by reversible addition–fragmentation chain transfer polymerization for improving carbon fiber/epoxy interface

A novel method was developed for grafting poly(acrylamide) (PAAM) on to the carbon fiber (CF) surface via reversible addition–fragmentation chain transfer (RAFT) polymerization to improve the interaction between carbon fibers and epoxy matrix in the composites system. The carbon fibers were first treated with nitric acid and γ‐methacryloxypropyltrimethoxy silane (KH570). Then, the PAAM was grafting onto the carbon fiber surface via RAFT polymerization. The resulted carbon fibers functionalized with PAAM (CF‐PAAM) were characterized by FTIR, XPS, and TGA, and the results revealed that CF‐PAAM were synthesized successfully. The introduction of PAAM chains could make the fiber surface rougher and introduce a large numbers of –NH₂ groups, which can improve the interfacial adhesion in the composites. The microbond test results showed that the interfacial shear strength (IFSS) of the composites reinforced by CF‐PAAM has been enhanced about 107%. POLYM. COMPOS., 38:27–31, 2017. © 2015 Society of Plastics Engineers     

Effects of carbon fiber modification with multiwall CNT on the electrical conductivity and EMI shielding effectiveness of polycarbonate/carbon fiber/CNT composites

The effect of carbon fiber (CF) modification with multiwall carbon nanotube (CNT) on the electrical, mechanical, and rheological properties of the polycarbonate (PC)/CF/CNT composite was investigated. The CF and multiwall CNT (MWCNT) were treated with sulfuric acid and nitric acid (3:1 wt %) mixture, to modify the CF with the CNT. For the PC with acid-treated CNT (a-CNT) modified acid-treated CF (a-CF) (PC/a-CF/a-CNT) composite, the electrical conductivity, and the electromagnetic interference shielding effectiveness (EMI SE) showed the highest values, compared with those of the PC/a-CF and PC/a-CF/CNT composites. The EMI SE of the PC/a-CF (10 wt %)/a-CNT (0.5 wt %) composite was found to be 26 (dB at the frequency of 10.0 GHz, and the EMI SE was increased by 91.2%, compared to that of the PC/a-CF composite at the same amount of total filler content. Among the composites studied in this work, the PC/a-CF/a-CNT composite also showed the highest values of relative permittivity (ε_r) and dielectric loss factor. The above results suggest that the CF modification with the a-CNT significantly affected the electrical conductivity and EMI SE of the composite, and the hybrid fillers of the a-CNT and a-CF resulted in good electrical pathways in the PC/a-CF/a-CNT composite. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47302.     

Effect of Silane Coupling Agent on the Tensile Properties of Carbon Fiber-Reinforced Thermoplastic Polyimide Composites

Silane coupling agent SG-Si900 (SGS) modification and air-oxidation methods were used to improve the interfacial adhesion of the carbon fiber-reinforced polyimide (CF/PI) composite. The interfacial characteristics of the composites reinforced by the carbon fibers treated with different surface modification methods were comparatively investigated. Results showed that both SGS modification and air-oxidation method improved the adhesion between the reinforcement and matrix and SGS modification method was superior to air-oxidation method. For CF/PI composite the optimum interfacial adhesion was obtained at 0.3 wt% SGS concentration. The fracture surfaces of samples were investigated by scanning electronic microscopy (SEM) to analyze the effects of different surface treatment methods.     

Improved tribological properties of polyimide composites by micro–nano reinforcement

The hydroxylate carbon nanotubes (CNTs) were grafted by chemical method on the surface of the oxidized carbon fibers (CF) to improve the mechanical and tribological properties of polyimide (PI). The microstructure and fracture surface of the polyimide composites indicated that CF–CNTs hybrid as a multiscale reinforcement can distribute into the PI matrix homogeneously. Tribo-tests further showed that CF–CNTs hybrid had a better effect on hardness increment, impact strength enhancement, friction reduction, and wear resistance. Compared to the neat PI, the friction coefficient and wear rate of CF–CNTs/PI composite deceased by 23.2 and 55.9%, respectively. In particular, the loading capacity and high speed resistance of CF–CNTs/PI composite were greatly improved. The corresponding wear mechanisms were also discussed by observing the worn surface of the PI composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47900.     

Effect of various methods of pre-treatment of carbon fibers on the mechanical properties of PIP-based ceramics/carbon composites

The purpose of the work was to determine the conditions of CF preparation to obtain carbide composites with favorable mechanical response. The relationships between the interfacial properties of fiber/polymethylsiloxane composite, and mechanical properties of the resulting fiber/carbide composites were investigated. The CF/resin interfacial strength was modified by oxidation of CF surface with nitric acid, silanization, and depositing CNT or a pyrolytic carbon layer (PyC). The study of composite interphases (ILSS and SEM) and surface tests of the modified CF (XPS, FT-IR, wettability measurements) showed different nature of the bonding occurring at the fiber/resin and fiber/ceramics boundary. The CF silanization significantly improved the ILSS between CFs and resin by 38.5%, while reduced flexural properties of carbide composites. The most promising treatment method of CF for PIP-based ceramic composites was modification with PyC, which provided 2 times higher ILSS, 1.5 times higher flexural strength and improved work to fracture (WF) as compared to unmodified CF.     

Evaluation of tribological performance of surface‐treated carbon fiber‐reinforced thermoplastic polyimide composite

The effect of surface treatment [rare earth solution (RES) and air oxidation] of carbon fibers (CFs) on the mechanical and tribological properties of carbon fiber‐reinforced polyimide (CF/PI) composites was comparatively investigated. Experimental results revealed that surface treatment can effectively improve the interfacial adhesion between carbon fiber and PI matrix. Thus, the flexural strength and wear resistance were significantly improved. The RES surface treatment is superior to air oxidation treatment in promoting interfacial adhesion between carbon fiber and PI matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Preparation and properties of T300 carbon fiber‐reinforced thermoplastic polyimide composites

In this study, a series of T300 carbon fiber‐reinforced polyimide (CFRPI) composites were prepared by laminating premolding polyimide (PI) films with unidirectional carbon fiber (CF) layers. On the basis of PI systems design, the effect of CF volume fraction, processing conditions, and PI molecular structure on the properties of CFRPI composites was studied in detail. In addition, two kinds of nano‐particles, including carbon nano‐tube (CNT) and SiO₂ were filled into the premolding PI films with different concentrations. And the effect of nano‐particles on the properties of CFRPI composites was also investigated. The surface characteristic of T300 CF was measured by X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The properties of premolding PI film and CFRPI composites were measured by dynamic mechanical analysis (DMTA), SANS testing machine, scanning electron microscopy (SEM), and so forth. These experimental results showed that the properties of CFRPI composites were mainly affected by the premolding PI film and molding condition. The change of CF volume fraction from 55% to 65% took little effect on the mechanical properties of CFRPI composites. In addition, the incorporation of nano‐particle SiO₂ could further improve the properties of CFRPI composites, but CNT hardly improved the properties of CFRPI composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 646–654, 2006     

High electrical conductivity of nylon 6 composites obtained with hybrid multiwalled carbon nanotube/carbon fiber fillers

The synergetic effect of multiwalled carbon nanotubes (MWNTs) and carbon fibers (CFs) in enhancing the electrical conductivity of nylon 6 (PA6) composites was investigated. To improve the compatibility between the fillers and the PA6 resin, we grafted γ‐aminopropyltriethoxy silane (KH‐550) onto the MWNTs and CFs after carboxyl groups were generated on their surface by chemical oxidation with nitric acid. Fourier transform infrared spectroscopy and thermogravimetric analysis proved that the KH‐550 molecules were successfully grafted onto the surface of the MWNTs and CFs. Scanning electron microscopy and optical microscopy showed that the obtained modified fillers reduced the aggregation of fillers and resulted in better dispersion and interfacial compatibility. We found that the electrical percolation threshold of the MWNT/PA6 and CF/PA6 composites occurred when the volume fraction of the fillers were 4 and 5%, respectively. The MWNT/CF hybrid‐filler system exhibited a remarkable synergetic effect on the electrically conductive networks. The MWNT/7% CF hybrid‐filler system appeared to show a second percolation when the MWNT volume fraction was above 4% and a volume resistivity reduction of two orders of magnitude compared with the MWNT/PA6 system. The mechanical properties of different types of PA6 composites with variation in the filler volume content were also studied. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40923.     

The Effect of Arylboronic Acid Treatment of Carbon Fiber on the Mechanical and Tribological Properties of PA66 Composites

PA66 composites filled with surface-treated carbon fiber were prepared by twin-screw extruder in order to study the influence of carbon fiber surface arylboronic acid treatment on the mechanical and tribological behavior of the PA66 composites (CF/PA66). The mechanical property, friction and wear tests of the composites with untreated and treated carbon fiber were performed and the worn surface morphology was analyzed. The results show that the worn surface area of the treated carbon fiber was far smoother than that of the untreated carbon fiber and there formed a bonding adhesion on the carbon fiber surface after treatment. The tensile strength of CF/PA66 composites with surface arylboronic acid treatment was improved. The friction coefficient and wear of arylboronic acid treated CF/PA66 composites were apparently lower than that with untreated carbon fiber. In conclusion, the surface treatment favored the improvement of the higher interface strength and so had good effect on improving the tribological properties of the composites.     

Effect of electron-beam radiation on thermoplastic composites

Abstract

The effect of electron beam (EB) radiation on carbon fibre reinforced (CF) thermoplastic (PBT, PPS, PA) composites was investigated. To clarify whether crosslinking could take place without or only with the presence of a crosslinking agent, special attention was paid to the incorporation of this agent into polymer sheets with a carbon fibre content of 50% by volume. The thermal and mechanical properties of the materials before and after exposure under different irradiation doses were evaluated. For materials based on PBT, PPS and PA46, no significant changes in properties after irradiation could be observed. However, CF/PA66 exhibited some changes in the presence of a crosslinking agent after irradiation, which could be related to an irradiation-induced crosslinking reaction. The effect of irradiation on the flexural properties was insignificant but an improvement in the creep behaviour was observed. Non-reinforced PA66 plates were also manufactured and a gel content measurement indicated that crosslinking was successfully induced. Additional studies allowed the changes in the polymer due to this crosslink to be quantified.     

Surface composition of carbon fibers subjected to oxidation in nitric acid followed by oxygen plasma

Type II, PAN-based carbon fibers (unsized and commercially treated) have been exposed to nitric acid and oxygen plasma individually and also to combined nitric acid/oxygen plasma treatments and the surface compositions have been determined using angle-resolved X-ray photoelectron spectroscopy (ARXPS) and ion scattering spectroscopy (ISS). Most of the oxygen on the as-received carbon fibers resides within the outermost 10-15 Å of the surface. Fiber exposure to nitric acid at 115°C for 20-90 min enhances the oxygen surface concentration to a point of saturation and the oxygen depth distribution is increased and becomes more uniform within the maximum XPS sampling depth (~60-100 Å). In addition, the fiber surface area is believed to be increased. After treating fibers to various degrees in nitric acid, subsequent exposure to oxygen plasma yields an additional increase in the surface oxygen content, particularly in the outermost fiber layers (10-15 Å). Under the conditions of the investigation, the maximum amount of surface oxidation occurs after sequential fiber exposure to nitric acid at 25°C for 30 s and oxygen plasma. As the extent of initial nitric acid treatment is increased, the synergism with subsequent plasma oxidation decreases, and the oxygen concentration becomes more uniform within the outer layers of the oxidized fibers. Overall, the data are consistent with a proposed oxidation mechanism in which oxygen plasma acts to enhance the surface density of oxygen on roughened and pitted nitric acid-oxidized fiber surfaces. As the duration of nitric acid exposure is increased, it is hypothesized that subsequent exposure to oxygen plasma smoothes the fiber surfaces but the surface density of oxygen remains essentially constant.     

Variable frequency microwave processing of thermoplastic composites

Abstract

The range of applications for variable frequency microwave (VFM) facilities (2–18 GHz) has been extended to thermoplastic composites. Five thermoplastic polymer matrix composites are processed and discussed, including 33 wt-% random carbon fibre reinforced polystyrene [PS–CF (33%)], and low density polyethylene [LDPE–CF (33%)]; 33 wt-% random glass fibre reinforced polystyrene [PS–GF (33%)], low density polyethylene [LDPE–GF (33%)]and Nylon 66 [Nylon 66–GF (33%)]. Bond strengths of lap joints were tested in shear and results were compared with those obtained using fixed frequency (2·45 GHz) microwave processing. The primer or coupling agent used was a 5 min, two part adhesive containing 100%liquid epoxy and 8% amine, which was more readily microwave reactive than the composites themselves. The VFM was operated under software control, which provided automatic data logging facilities. Results indicate that VFM can produce strong bonds for PS and LDPE.