This is an editorial article. It has no abstract.
Maleic anhydride functionalized graphene oxide (MAH-GO) was synthesized and then introduced into carbon fiber (CF) reinforced bismaleimide (BMI) composites, with the aim of improving the interfacial adhesion strength between CF and BMI resin. Various characterization techniques including Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectra (XPS) and thermogravimetric analysis (TGA) demonstrated that the maleic anhydride has been successfully grafted onto the GO surfaces. The study showed that the interlaminar shear strength (ILSS) and flexural properties of CF/BMI composites were all improved by the incorporation of GO and MAH-GO, and the MAH-GO showed the substantially improved effect due to the strong interaction between the MAH-GO and the resin matrix. The maximum increment of the ILSS, flexural strength and flexural modulus of composites were 24.4, 28.7 and 49.7%, respectively. Scanning electron microscope (SEM) photographs of the fracture surfaces revealed that the interfacial bonding between CF and resin matrix was significantly strengthened by the addition of MAH-GO. The results suggest that this feasible method may be an ideal substitute for the traditional method in the interfacial modification of composites.
Cadmium sulfide (CdS) nanoparticles have been synthesized by hydrothermal method and dispersed in poly vinyl alcohol (PVA) matrix in varying amounts by weight. Subsequently, PVA/CdS nanocomposites have been synthesized with the objective of investigating the effect of CdS nanoparticles on structural and electrical properties of PVA films. Structural properties were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Differential scanning calorimetry (DSC) was used to investigate thermal properties of PVA/CdS nanocomposites. Electrical properties were measured by using high frequency LCR meter and were found to be strongly dependent on frequency and nano CdS content. Dielectric constant decreased with increase in frequency and with increase in nanofiller concentration. AC conductivity and dielectric loss increased with frequency and decreased with increase in nano CdS content.
Nanosized particles have attractive characteristics, which have received considerable attention in the last decade. Polymeric nanoparticles (PNP)s are solid particles or particulate dispersions with size in the range of 10–1000 nm. Due to the very small size, the surface area is very large so the percentage of atoms or molecules on the surface is significantly increased, which is expected to have extensive applications in various fields such as drug delivery systems, biosensors, catalysts, nanocomposites, agriculture and environment. The aim of the present paper is to critically review enhancement in the field of synthesis and different application of novel PNPs in various area from drug delivery to composite fabrication. Literature sources were mainly taken from the publications of 2011 and later; though, for a basic depiction of the structural principles, older publications have also been cited.
This study focuses on the transfer of the healing functionality of supramolecular polymers (SP) to fibre reinforced composites through interleaving. SPs exhibiting self-healing based on hydrogen bonds were formed into films and were successfully incorporated into carbon fibre composites. The effect of the SP interleaves on in-plane fracture toughness and the subsequent healing capability of the hybrid composites were investigated under mode II fracture loading. The fracture toughness showed considerable increase since the maximum load (Pmax) of the hybrid composite approximately doubled, and consequently the mode II interlaminar fracture toughness energy (GIIC) exhibited an increase reaching nearly 100% compared to the reference composite. The healing component was activated using external heat. Pmax and GIIC recovery after activation were measured, exhibiting a healing efficiency after the first healing cycle close to 85% for Pmax and 100% for GIIC, eventually dropping to 80% for Pmax while GIIC was retained around 100% even after the fourth healing cycle. Acoustic Emission activity during the tests was monitored and was found to be strongly reduced due to the presence of the SP.
Current challenges highlight the need for polymer research using renewable natural sources as a substitute for petroleum-based polymers. The use of polyols obtained from renewable sources combined with the reuse of industrial residues such as lignin is an important agent in this process. Different compositions of polyurethane-type materials were prepared by combining technical Kraft lignin (TKL) with castor oil (CO) or modified castor oil (MCO1 and MCO2) to increase their reactivity towards diphenylmethane diisocyanate (MDI). The results indicate that lignin increases the glass transition temperature, the crosslinking density and improves the ultimate stress especially for those prepared from MCO2 and 30% lignin content from 8.2 MPa (lignin free) to 23.5 MPa. Scanning electron microscopy (SEM) micrographs of rupture surface after uniaxial tensile tests show ductile-to-brittle transition. The results show the possibility to develop polyurethane-type materials, varying technical grade Kraft lignin content, which cover a wide range of mechanical properties (from large elastic/low Young modulus to brittle/high Young modulus polyurethanes).
Epoxy resins are used as high-performance thermosetting linings to protect substrates under corrosive environments. However, in a severe corrosive chemical solution, such protective layers may degrade with long time due to penetrations of solvent and solute molecules into resin network. In this regard, the terahertz time-domain spectroscopy (THz-TDS) is a promising tool for non-destructive evaluation of the penetrant amounts due to high transparency of such plastic materials and high sensitivity to the molecular vibrations in terahertz spectral range. In this work, the complex refractive indexes n and κ of epoxy specimens were measured after immersion into sulfuric acid solutions and compared with penetrated mass fractions of water and acid ions. It was found that n and κ depended linearly with water and sulfuric acid mass fraction in specimens, and κ of sulfuric acid immersed specimens was lager at higher frequency. While the calculated Δκ agreed well with THz-TDS measurement by THz-TDS, the calculated Δn was higher than the measurement. The difference may be attributed to the water and sulfuric states in the specimen.
Composite coating with synergistic effect of biomimetic epoxy thermoset morphology and incorporated superhydrophobic silica for corrosion protection
W. F. Ji, C. W. Li, W. J. Huang, H. K. Yu, R. D. Chen, Y. H. Yu, J. M. Yeh, W. C. Tang, Y. C. Su
Vol. 10., No.11., Pages 950-963, 2016
Vol. 10., No.11., Pages 950-963, 2016
In this work, potential anticorrosive coating resulted from the composite with synergistic effect of biomimetic epoxy thermoset (BET) morphology and incorporated superhydrophobic silica microspheres was presented. First of all, superhydrophobic methyl-modified silica (MS) microspheres were synthesized by performing the conventional base-catalyzed sol-gel process of MTMS and APTMS. The as-prepared MS microspheres were identified as having an average particle size of ~1 µm in diameter. The as-prepared MS microspheres were characterized by Fourier transform infrared spectrometry (FTIR), 29Si and 13C solid-state nuclear magnetic resonance (NMR) spectroscopy. Morphological properties of MS microspheres and BET-silica composite coating were studied by scanning electron microscopy (SEM). Subsequently, 3 wt% of MS microspheres were incorporated into an epoxy slurry of DGEBA/T-403 in dimetyl acetamide (DMAc), followed by performing the programmed heating through nanocasting technique with PDMS as soft template materials for pattern transfer by using leaf of Xanthosoma Sagittifolium as natural template, leading to the formation of artificial biomimetic composite coating. The appearance/dispersion capability of silica microspheres in BET coating was confirmed by the energy dispersive X-ray spectroscopy (EDX) and Si-mapping. The roughness level of BET and BEC-3% were detected by AFM. The BETsilica composite was found to exhibit a contact angle (CA) of ~153°, revealing the synergistic effect of biomimetic epoxy morphology and incorporated superhydrophobic MS microspheres, which is found to be more hydrophobic than that of neat epoxy thermoset (CA = 81°). Corrosion protection of as-prepared coatings was demonstrated by performing a series of electrochemical measurements (Tafel, Nyquists and Bode plots) upon CRS electrodes in saline condition. It should be noted that the BET coatings upon CRS electrode revealed an effectively enhanced corrosion protection as compared to that coatings without biomimetic morphology. Moreover, the BET coating with superhydrophobic MS microspheres upon CRS electrode was found to exhibit better corrosion protection as compared to a counterpart coating without MS microspheres.