Adhesion and Wettability Characteristics of Chemically Modified Banana Fibre for Composite Manufacturing

In this work banana fibre was chemically modified using various chemical agents. The surface energy of the fibre is an important parameter and one which governs the interaction of fibre with polymeric matrices. This paper describes the influence of various chemical treatments on the surface energy of the banana fibre investigated by contact angle measurements, spectroscopic analysis and surface morphology studies. The surface energy, work of adhesion, polarity, spreading coefficient, interfacial energy and interaction parameter were determined in the case of raw and chemically modified fibres. Chemical modification has been found to have a profound effect on the surface energy. The polar and dispersive components of the surface energy were also found to be dependent on the chemical treatment involved. The chemical modifications done in this work were: alkali treatment, silanation, benzoylation, formylation, potassium permanganate treatment and acetylation. Of all the modifications, the relative surface energy was found to be a maximum for alkali treated fibre and minimum for silanated fibre. Contact angle measurements were found to be an effective tool in predicting the possible interaction of the fibres with phenol formaldehyde matrix resin. Atomic force microscopy roughness analysis revealed a significant decrease in surface roughness for the chemically modified fibre. An increase both in fibre/matrix adhesion and interfacial shear strength has been observed for all surface modified fibres except for those modified by benzoylation and acetylation.     

AFM observations of silane coupling agent layers having a vinyl group deposited on a mica surface

The topography of silane layers deposited on an inorganic surface was observed using atomic force microscopy. For this purpose, cleaved mica plates were treated with some silane coupling agents at various conditions. Silanes having a vinyl group as the organic functional group with mono-, di- and trialkoxy structures were used. Four different solvents for silane solutions, 2-propanol, 2-propanol/water mixture, water and toluene, were used. The pH of the aqueous solution was controlled. As a result, the suitable solvent and pH were identified in order to obtain a smooth silane layer. The solubility of silane in the solution, the wettability of silane onto the inorganic surface and the depression of the self-condensation of silane molecules in the solution were found to be important parameters for this purpose.     

Surface structure of silane-treated glass beads and its influence on the mechanical properties of filled composites

The surface treatment of glass beads, chosen as a model filler, was carried out using four different silane coupling agents with multilayer coverage. For this purpose, silanes having an aminopropyl or a methacryloxypropyl group as an organofunctional group with di- or tri-alkoxy structures were used. The amount of silane detected on the bead surface was four to six times that required for a monolayer coverage. The topography of the silane layer on the bead surface was observed using an atomic force microscope. The topography was strongly affected by the composition of the silane solution and the number of alkoxy groups in the silane. The effects of the organofunctional group and the number of alkoxy groups of the silanes on the mechanical properties of bead-filled poly(vinyl chloride), chosen as a typical ductile polymer, were investigated. A higher yield stress was observed for the silane with an aminopropyl group than for that with a methacryloxypropyl group. Furthermore, for each organofunctional group, the yield stress was higher for the silane with a dialkoxy structure than for that with a trialkoxy structure. However, their effects on the elongation-at-break were contrary to the above tendencies.     

Aging of fluorocarbon thin films deposited on polystyrene from hyperthermal C3F+5 and CF+3 ion beams

Fluorocarbon films grown on polystyrene (PS) in vacuum from 25-100 eV CF⁺ ₃ and C₃F⁺ ₅ ions are aged by exposure to atmosphere for 4 and 8 weeks, then analyzed by X-ray photoelectron spectroscopy, atomic force microscopy, and water contact angle measurements. These fluorocarbon films oxidize with time, showing an increase in their oxygen/ carbon ratio and a decrease in their fluorine/carbon ratio. The decrease in fluorine/carbon ratio with aging is due not only to increased oxygen content, but also to surface restructuring and release of low molecular weight oxidized material from the surface. The higher oxidation and surface restructuring observed upon aging for 100 eV C₃F⁺ ₅ and 50 eV CF⁺ ₃ ion-modified PS can be additionally attributed to higher surface bond breakage and active site formation. 100 eV C₃F⁺ ₅ and 50 eV CF⁺ ₃ ion-modified PS surfaces are rougher than the 50 eV C₃F⁺ ₅ ion-modified PS. Overall, the aging process of these ion-deposited films appears similar to that of plasma-deposited films.     

The effect of liquid-induced adhesion changes on the interfacial shear strength between self-assembled monolayers

Friction between chemically-modified tips and surfaces has been studied with chemical force microscopy (CFM) to evaluate the effect of changing solid/liquid free energy on energy dissipation in sliding tip-surface contact. Well-controlled conditions were necessary to attain a single asperity contact in these experiments. We found that in a series of methanol- water mixtures the interfacial shear strength between CH3-terminated surfaces of the siloxane self-assembled monolayers (SAMs) was independent of the adhesion force. The shear strength value of 10.2 ± 1.0 MPa found for this interface under methanol-water media is consistent with the previous studies of similar systems under dry gas conditions. A comparison to available data on interfacial shear strengths demonstrated that siloxane monolayers were much more effective in reducing friction than various carbon coatings.     

Processing Effects on Microstructural Charcteristics and Properties of Reactively Ion-Plated Titanium Nitride Coatings

The effects of key processing parameters on the resulting microstructure and mechanical properties of thin TiN coatings, reactively ion-plated on polished aluminum and steel substrates, were investigated experimentally. A deposition procedure was established and a processing scheme for reactive ion plating was developed. Optimization of processing conditions was achieved by means of controlling the principal ion-plating parameters to prevent the growth of species different from TiN, evaporant poisoning, and variations in the coating thickness. Emphasis was placed on identifying the effects of critical independent and dependent processing parameters, such as the rf power density, the deposition rate, and the coating thickness, on the TiN microscopic morphology, crystal structure, surface roughness, microhardness, and deformation behavior arising under static and sliding contact loads. Results from various testing and characterization methods revealed that deposition of hard, strongly adherent, and relatively smooth TiN coatings possessing dense microstructures of fine equiaxed grains with a preferential (200) texture can be accomplished under certain ionplating conditions.     

The effect of chemical modification on the fracture toughness of montmorillonite clay/epoxy nanocomposites

The change in fracture toughness and its dependence on the content of clay nanoplatelets and adhesion at the interface between clay nanoplatelets and anhydride-cured epoxy matrix are discussed. Three clay nanoplatelets with different chemical modifications were used in this investigation. To fabricate nanocomposites, the clay nanoplatelets were sonicated in acetone for 2 h. The role of the clay nanoplatelets in the mechanical/fracture properties was investigated by transmission electron microscopy (TEM). Bright-field TEM micrographs showed excellent dispersion of clay nanoplatelets in epoxy matrix. Both intercalation and exfoliation of clay nanoplatelets were observed depending on clay modification. Compact tension specimens were used for fracture testing. The fracture toughness increased with increasing clay content. The fracture toughness of clay/epoxy nanocomposites varied with the clay morphology in the epoxy matrix. Different morphologies of the fracture surfaces, highly dependent on the morphology of dispersed clay nanoplatelets, were observed using environmental scanning electron microscopy (ESEM). The fracture toughness was found to be correlated with the fracture surface roughness measured by confocal laser scanning microscopy (CLSM).     

The Effect of Radiation Dosages and UV/EB Radiation on the Properties of Nanocomposite Coatings

The aim of this study was to compare the effects of ultraviolet (UV) and electron beam (EB) radiation on the properties of cured nanocomposite coatings. Surface hardness increased with increasing radiation dosages (number of passes) for all samples. This was due to the increase in crosslinking with increasing radiation dosages. Pendulum hardness, gel content, and thumb twist results were analyzed to choose the appropriate curing dosage for both curing techniques. The selected dosages were then used to cure coatings for scratch and abrasion resistance tests. It was found that the UV curing produced coatings with better abrasion resistance, whereas EB curing was more suitable for producing scratch-resistant coatings.     

Study on Tribological Properties of Carbon/Aramid Fabric Coatings Modified by Boron Nitride of Single Layer

Carbon/aramid fabric composite coatings modified with boron nitride of single layer were fabricated through a dip-coating method. The composite coatings were cured with successive heating processes in an oven. The friction and wear properties of those as-prepared coatings were studied on a block-on-ring tester. The obtained results showed that the wear life of the coatings increased obviously after inclusion of boron nitride of single layer; however, the values of friction coefficients of the coatings almost remained constant. The optimal loadings of boron nitride of single layer in our experiments was 5 wt.%, and the wear life of the modified coating increased by ca. 360% compared with that of pristine fabric composite coating. The worn morphology of the sliding surface for both pristine fabric coating and the composite coatings filled with boron nitride of single layer was discussed, and the wear mechanisms were illuminated.     

环氧树脂/蒙脱土纳米复合涂料防腐性能的研究进展

环氧树脂涂料在防腐领域中应用广泛,但仍需进行改性以满足应用需求,一个比较经济、有效的途径就是添加纳米填料。蒙脱土片层分散在环氧树脂基料中时,能有效阻隔腐蚀性介质穿过涂膜,进而提高纳米复合涂料的防腐性能。简单介绍了蒙脱土的结构,环氧树脂/蒙脱土纳米复合涂料的制备方法。综述了近年来环氧树脂/蒙脱土纳米复合涂料防腐性能的研究进展。     

Rod-Like Structure of Cotton Cellulose/Polyvinyl Alcohol/Tellurium Dioxide (TeO2) Hybrid Nanocomposite and Antimicrobial Properties

We report on the in situ synthesis through sol-gel processing of a tellurium dioxide (TeO₂)–cellulose–polyvinyl alcohol (PVA) hybrid composite. The cellulose–PVA hybrid composite was synthesized through chemical graft in the presence of aqueous sodium hydroxide. Field emission scanning electron microscopy, SEM-EDX, high-resolution transition microscopy (FE-TEM) revealed that polycrystalline nanorods were uniformly distributed with sizes of 20?nm in the cotton cellulose–PVA–TeO₂ hybrid nanocomposite. The average size of TeO₂ crystallite was calculated to be 0.292?nm, as shown in the FE-TEM, SAED, and X-ray diffraction analysis. Furthermore, the hybrid nanocomposites were studied for their antimicrobial activity against Bacillus cereus and Escherichia coli strains, which was inhibited at a size of 10–12?mm after 24?h of incubation.