Macromol. Mater. Eng. 10–11/2007

Journal of Nanomaterials, 2008

A successful integration of two independent phases with good adhesion is imperative for effective translation of superior carbon nanofiber filler properties into a physically superior carbon nanocomposite. Carbon nanofibers were subjected to electrochemical oxidation in 0.1 M nitric acid for varying times. The strength of adhesion between the nanofiber and an epoxy matrix was characterized by flexural strength and modulus. The surface functional groups formed and their concentration of nanofibers showed a dependence on the degree of oxidation. The addition of chemical functional groups on the nanofiber surface allows them to physically and chemically adhere to the continuous resin matrix. The chemical interaction with the continuous epoxy matrix results in the creation of an interphase region. The ability to chemically and physically interact with the epoxy region is beneficial to the mechanical properties of a carbon nanocomposite. A tailored degree of surface functionalization was found to increase adhesion to the matrix and increase flexural modulus.

Journal of Materials Science, 2013

The effect of carbon nanofiber (CNF) functionalization on the thermo-mechanical properties of polyamide-12/CNF nanocomposites was investigated. Three main different surface treatments were performed to obtain CNF-OH (OH rich), CNF-Silane (C 6 H 5 Si-O-), and CNF-peroxide. CNF modified with poly-(tert-butyl acrylate) chains grown from the surface via ATRP (atom transfer radical polymerization) were also prepared and tested. The modified CNFs and neat CNFs were used as fillers in polyamide-12 nanocomposites and the properties of the ensuing materials were characterized and compared. Universal tensile tests demonstrated a substantial increase (up to 20 %) of the yield strength, without reduction of the final elongation, for all functionalized samples tested within 1 wt% filler content. Further evidences of mechanical properties improvement were given by dynamic mechanical thermal analyses. CNFs functionalized with poly-(tert-butyl acrylate) and silane exhibited the best performance with stiffening and strengthening at low (B1 wt%) filler loadings, via a partial decrease of the intensity of b-transitions attributed to favorable interactions between the functional groups on the surface of functionalized CNFs and polyamide-12. CNFs treated with peroxide proved to be the most simple preparation technique and the ensuing nanocomposites exhibited the highest storage modulus at high (5 wt%) filler content. Theoretical simulations using the micro-mechanics model were used to predict the Young modulus of the composites and compare them with experimental data. The results obtained suggest a synergistic effect between the matrix and the filler enhanced by surface functionalization.

Bioresources

The aim of this work was to explore how various surface treatments would change the dispersion component of surface energy and acidbase character of hemp nanofibers, using inverse gas chromatography (IGC), and to investigate the effect of the incorporation of these modified nanofibers into a biopolymer matrix on the properties of their nanocomposites. Bio-nanocomposite materials were prepared from poly (lactic acid) (PLA) and polyhydroxybutyrate (PHB) as the matrix, and the cellulose nanofibers extracted from hemp fiber by chemo-mechanical treatments. Cellulose fibrils have a high density of -OH groups on the surface, which have a tendency to form hydrogen bonds with adjacent fibrils, reducing interaction with the surrounding matrix. It is necessary to reduce the entanglement of the fibrils and improve their dispersion in the matrix by surface modification of fibers without deteriorating their reinforcing capability. The IGC results indicated that styrene maleic anhydride coated and ethylene-acrylic acid coated fibers improved their potential to interact with both acidic and basic resins. From transmission electron microscopy (TEM), it was shown that the nanofibers were partially dispersed in the polymer matrix. The mechanical properties of the nanocomposites were lower than those predicted by theoretical calculations for both nanofiber-reinforced biopolymers.

Composites Science and Technology, 2005

The reinforcement of rubbery matrices by vapour grown carbon nanofibres (VGCFs) is studied in the case of a rubbery epoxy and a styrene butadiene rubber (SBR). In the case of epoxy, the VGCF were introduced in the hardener and blended with the prepolymer. Nanocomposites were produced by subsequent polymerization. For the second matrix, samples were prepared by casting of a mixture of SBR latex and a water suspension of VGCF. Evaluation of mechanical performances revealed a linear increase of the modulus measured above and below the glass transition temperature for nanofibre content up to 10 wt%. This increase is low, but in good agreement with the estimation based on mechanical coupling models. In the case of epoxy matrix, the ultimate stress and strain are largely increased, even for very low fibre content (i.e. 1 wt%). However, this improvement is not observed in the case of nanocomposites based on SBR matrix, due to the non-optimized dispersion of the fibres.

Composites Science and Technology, 2008

Carbon nanoparticles (CN), synthesized by a shock wave propagation method from the free carbon of the explosive, were dispersed in isotactic polypropylene (iPP) using a twin screw co-rotating extruder. These materials were analyzed for their tensile properties, crystallization morphology, thermal stability under N 2 , O 2 and air, as well as their permeability rates for N 2 , O 2 and CO 2 . Young's modulus was significantly enhanced, as was the tensile strength at the yield point, although at a smaller extent. However, the tensile strength and elongation at the break point slightly deteriorated with the increase of the Filler's concentration. This behaviour was attributed to the increase tendency of CN to form aggregates into iPP matrix by increasing its content. The size of aggregates, as was evaluated by extended micro-Raman mapping, is ranged from 1 up to 5 lm. The nanoparticles caused a significant reduction of the iPP chain's mobility leading to smaller and less ordered crystallites, with the appearance of c-phase crystallites at CN content 5 wt.%. In inert atmosphere (N 2 ) the presence of the nanoparticles caused a shift of the starting decomposition temperature (T d ), from 368 up to 418.6°C, while, under oxygen, thermal decomposition was more complex, displaying more than two stages. The T d was slightly lowered, up to a filler content of 2.5 wt.%, with the nanoparticles exhibiting a catalytic role at the beginning of the polymer's decomposition. Under air, the degradation behaviour was between those exhibited in inert and O 2 atmospheres. Permeability rates for the gases measured were substantially lowered with increasing filler content.

Ternary non-covalent interactions between carbon nanofibers (CNFs), oxidized carbon nanofibers (ox- CNFs), poly(methyl methacrylate) (PMMA) chains, and benzotriazole-containing UV stabilizers were analyzed using Fourier-transform infra red spectroscopy (FTIR), time-resolved fluorescence emission spectroscopy, and fluorescence lifetime imaging microscopy. The results indicated that PMMA chains form hydrogen bonds both with ox-CNF fibers and the UV stabilizer molecules. It was also determined that UV stabilizers strongly interact with CNF particles via p-p interactions. The extent of p-p and hydrogen bonding interactions was determined to be lower between ox-CNF particles and UV stabilizers due to less perfect graphitic structure of the former. The morphology of the composites indicated that the hydrogen bonds between PMMA chains and ox-CNF particles resulted in highly improved state of filler dispersion in ox-CNF/PMMA composites.

Adsorption Science & Technology, 1996

The peroxidic modification of the surface of a dispersed phase by heterofunctional polymeric peroxides (HFPPs) is discussed. HFPPs are carbochain polymers which have statistically located peroxidic (-00-) and high-polar functional (carboxylic) groups along the main chain. Sharp differences in the polarity of these groups endowes HFPP macromolecules with the capability of interfacial adsorption in various polymeric colloidal systems. The reactions of the functional groups provide chemical bonding of the macromolecules to the interfacial surface. As a consequence of such physical adsorption or chemisorption of HFPP, peroxidation of filler surfaces and the localization of active-00-groups on the interface may be effected. In addition, such-00-groups can facilitate the grafting of matrix polymer macromolecules to the surface of the dispersed phase. Such grafting reactions can be carried out during polymer filling, the curing processes of composites or the vulcanization of a rubber mixture. It has been shown that an improvement in the physical and mechanical properties of polymers and an increase in the e1ectroconductivity and heat conductivity of filled compositions is achieved on modification by HFPP.

Macromolecular Materials and Engineering, 2010

Carbohydrate Polymers, 2015

based polyurethane reinforced with cellulose nanofibers: A comprehensive investigation on the effect of interface, Carbohydrate Polymers (2015), http://dx.

The present study focuses on modeling of carbon nanofibers (CNFs) and evaluating the effect of their reinforcement in polypropylene (PP) matrix. A novel approach for modeling of CNF has been explained in this study. Molecular dynamics (MD) simulation has been used to study the effect of CNF volume fraction (Vf) and aspect ratio (l/d) on mechanical properties of CNF–PP composites. Materials Studio 5.5 has been used as a tool for finding the modulus and damping in composites. CNF composition in PP was varied by volume from 0 to 16%. Aspect ratio of CNF was varied from l/d¼5 to l/d¼100. Results have also been obtained for longitudinal loss factor (11). To the best of the knowledge of the authors, till date there is no study, either experimental or analytical, which predicts 11 for CNF–PP composites at nanoscale. Hence, this will be a valuable addition in the area of nanocomposites. Results show that with only 2% addition by volume of CNF in PP, E11 increases by 748%. Thereafter, the increase is at a lower rate. Increase in E22 is very less in comparison to the increase in E11. With increase in CNF aspect ratio (l/d) till l/d¼60, the longitudinal loss factor (11) decreases rapidly. Thereafter, the decrease is smaller. Results of this study are in agreement with those predicted by Shinichi et al