Surface characteristics of fluorine-modified PAN-based carbon fibers

Different fluorination methods were applied to modify the surface properties of carbon fibers. The relationship between the degree of fluorination and the physicochemical properties of carbon fibers was studied using a combination of mechanical tests, elemental analysis (EA), X-ray photoelectron spectrometry (XPS), and X-ray diffraction (XRD). EA and XPS analyses of fluorinated carbon fibers showed that treatment with mixtures of F₂/O₂ introduced a much higher fluorine concentration than that with F₂ only. However, XRD analysis showed that there was no increase in the interlayer distance, due to the mild fluorination condition applied. Consequently, the oxyfluorination was one of the more effective methods to increase surface polarity of carbon fibers, which probably played an important role in improving the tensile properties of the fibers in the epoxy resin system.     

Effect of fiber types on relevant properties of porous asphalt

The research was conducted to evaluate the effects of cellulose and polyester fibers on the properties of porous asphalt mixes, using the tests of draindown, abrasion, volumetric properties, rutting, and moisture damage. Images of scanning electron microscopy and X-ray computerized tomography were adopted to identify the microstructure of the fiber and inner stone skeleton of porous asphalt. The influence of rutting parameter （G＊/sin δ） of asphalt modified by different fibers on the rutting resistance of the mixes was investigated. Based upon MOHR-COULOMB theory, the cohesion and the angle of internal friction of the mixes were derived from both indirect tension and unconfined compression strength. The experimental results indicate that fibers mainly stabilize asphalt binder and thicken asphalt film around aggregates. Furthermore, they result in the improved mechanical strength of porous asphalt mixes at high temperature slightly. From comparison analysis, cellulose fibers appear to perform better than polyester fibers in porous asphalt mixes.     

Study on the long‐term thermal‐oxidative aging behavior of polyamide 6

The long‐term thermal‐oxidative aging behavior of polyamide 6 (PA6) was studied by comparison with the stabilized sample in this work. The variation of mechanical properties of the pure and the stabilized samples of PA6 with aging time at 110°C, 130°C, and 150°C were investigated, respectively. The aging mechanism of PA6 under heat and oxygen was studied in terms of the reduced viscosity, crystallization behavior, dynamic mechanical behavior, and chemical composition through the methods of polarized light microscopy (PLM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X‐ray photoelectron energy spectrum (XPS), and so on. The results indicated that at the initial stage of aging, the molecular crosslinking reaction of PA6 dominated resulting in the increase of the mechanical strength, reduced viscosity, and the glass transition temperature of the sample. And the molecular degradation dominated in the subsequent aging process resulting in the decrease of the melting temperature, the increase of the crystallinity, and the formation of the oxides and peroxides products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of the amount of ferromagnetic addition on the rheological properties of spinning solutions,the structure,the strength,and thermal properties of polyacrylonitrile fibres

The rheological properties of spinning solutions of polyacrylonitrile in dimethyl formamide (DMF) containing various amounts of a ferromagnetic nanoaddition were investigated. The porous structure, the strength and thermal properties of fibers obtained from these solutions were assessed, as well as the uniformity of the nanoaddition distribution on the fiber surface was estimated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A comparative study of short nylon fiber—Natural rubber composites prepared from dry rubber and latex masterbatch

A novel method for the preparation of short nylon fiber–natural rubber composites was developed in which short fibers chopped to approximately 6 mm were incorporated in the latex stage and processed into sheet form. By this method, mixing cycle time was reduced without compromising the fiber dispersion. Fiber breakage during mixing was reduced. The new composites when compounded with a dry bonding system based on hexamethylenetetramine, resorcinol and hydrated silica (HRH) showed improved modulus, tensile strength and abrasion resistance compared to conventional composites. Tear strength, resilience, and compression set were similar to the conventional composites. SEM analysis indicated better interaction between matrix and fibers in the case of latex master batch. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Evaluation of improvement of physical and mechanical properties of bamboo fibers due to alkali treatment

Bamboo strips treated with caustic solutions of different concentrations, e.g., 5%, 10%, 15%, 20%, 25%, and 50%, were subjected to mechanical testing giving stresses on tensile strength, percent elongation at break, flexural strength, flexural modulus, and toughness. The change in average density was ?15%, and the weight loss value shows a maximum of 21.94% at 50% alkali treatment. The mechanical properties of bamboo strips increase steadily with increasing concentration of caustic soda, showing a comparable increased value at 15 and 20%, and then exhibiting a gradual fall. The percent elongation at break corroborates these observations showing a continuous decreasing trend. The properties under investigation exhibit a clear transition in between 15 and 20% alkali concentration. The morphology of strips was studied by scanning electron microscope and polarizing light microscope. The crystal structure of both untreated and treated strips was compared by XRD analysis. In both cases, the breakdown of the crystal structures of the cellulose fibers and the recrystallization or reorientation of the degraded chains that are devoid of hemicellulose are quite apparent. However, at a very high concentration (to the extent of 25%) the breakdown of structure predominates much more over the reorientation or recrystallization. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nitrogen plasma modification of viscose-based activated carbon fibers

Viscose-based activated carbon fibers (VACFs) were treated by a dielectric-barrier discharge plasma at different conditions. Nitrogen was used as the feed gas to create nitrogen radicals. The textural characteristics were analyzed by SEM, BET and XRD. The surface chemical functional groups were analyzed by XPS. The results show that after nitrogen plasma modification (NPM), the external surface of the VACFs was etched and became rougher, the surface area and pore volume decreased, the average micropore width barely changed, the PSD of the VACF became narrower and the graphitic crystallites of VACF had been destroyed slightly. XPS revealed that NPM could remarkably change the distribution of the oxygen functional groups on the VACFs surface and there were more nitrogen atoms incorporated into the aromatic ring. A tentative explanation for the modification process is proposed.     

氧气液相氧化一元取代甲苯制备芳香醛

研究了在酸碱不同体系下气氛液相氧化对氯甲苯、邻硝基甲苯制取相应芳香醛的反应 ,比较了反应温度、反应时间、氧气流量、底物浓度对各自反应的影响。初步研究了反应在酸碱不同条件下的反应机理 ,认为在醋酸体系下是自由基反应 ,而在有机胺体系下应是碳负离子反应。     

"Recovery of spatial alternation deficits following selective hippocampal destruction with kainic acid": Correction to Kesslak and Gage (1986).

Reports an error in "Recovery of spatial alternation deficits following selective hippocampal destruction with kainic acid" by J. Patrick Kesslak and Fred H. Gage (Behavioral Neuroscience, 1986[Apr], Vol 100[2], 280-283). In the aforementioned article, the degrees of freedom reported in the Results section are incorrect. In the sixth paragraph on page 281, the second sentence should read as follows: Results of the ANOVA indicated a significant effect for surgical treatments. F(2, 25)=25.44, p1986-21445-001.) Examined whether the sympathetic ingrowth of superior cervical ganglion (SCG) fibers sprouting into the hippocampus following kainic acid (KA) lesion of CA3 and CA4 pyramidal cells in male Sprague-Dawley rats would contribute to behavioral recovery. 31 Ss were trained on a forced-choice task. After reaching criterion performance levels, Ss received either KA (8 nM/0.4 μl) or saline injections into the hippocampus and were again tested on the forced-choice task. Half of the Ss had their SCG removed 35 days after injections, and all were again tested on the forced-choice task. Analysis of variance (ANOVA) showed Ss receiving KA took significantly longer to reach criterion following injections. Removal of the SCG after recovery reintroduced the performance deficit of KA-treated Ss on the alternation task; no other group showed any effect for SCG removal. Results indicate that the SCG may have a modulatory effect in behavioral recovery, although other mechanisms may also be operating. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)