Shaohua Zeng

Effect of silane hydrolysis on the interfacial adhesion of carbon nanotubes/glass fiber fabric-reinforced multiscale composites

Three types of multiwall carbon nanotubes (MCNTs)/glass fiber fabrics (MGf) were prepared by dispersing industrial-grade MCNTs onto commercial E-glass fiber fabrics (GFfs) through an ultrasonic-assisted impregnation deposition method. The multiscale MGf-reinforced composites were fabricated by the vacuum infusion process. The effect of γ-aminopropyltrimethoxysilane (APS) or APS hydrolysis on the MCNT dispersion and the interfacial bonding between MCNTs and glass fiber were investigated by Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy and their flexural stiffness, respectively. The interfacial adhesion of MGf composites was evaluated by interlaminar shear strength (ILSS) and dynamic mechanical thermal analysis. The results indicated that MCNTs on the MGf surface could form an interpenetrating network and act as anchors to interlock glass fiber with epoxy. The initial storage modulus and glass transition temperature of the MGf composites clearly increased, while the first loss factor of the MGf composites decreased by 30.0–45.0% compared with that of the GFf composite. Whether or not APS was hydrolyzed, it helped the MCNTs disperse on the GFf surface by chemical bonds. The ILSS of the multiscale composite with APS-treated MCNTs was enhanced significantly, while that with hydrolyzed APS-treated MCNTs (MGf-h) had a slight increase. APS hydrolysis increased the flexural rigidity of the MGf-h.

Effect of ultrasonic-assisted impregnation parameters on the preparation and interfacial properties of MWCNT/glass-fiber reinforced composites

Abstract In this study, an ultrasonic-assisted impregnation method was employed to deposit carboxyl multiwalled carbon nanotubes (MWCNTs) onto the E-glass fiber fabric (GFf) for the preparation of the MWCNT-GFf reinforcer. The effects of ultrasonic power, duration and temperature on the dispersion of MWCNTs onto GFf were investigated, and the mechanical properties, interlaminar adhesion, and dynamic viscoelasticity of the resulting MWCNT-GFf-reinforced composites (MGCs) were evaluated. The results indicated that an effective dispersion of MWCNTs onto GFf without obvious breakage of the MWCNTs was achieved under an ultrasonic power of 600 W, duration of 6 min, and processing temperature of about 0°C. Compared with the GFf-reinforced composite, the tensile strength, flexural strength and interlaminar shear strength of the MGCs exhibited maximum increments of 38.4%, 34.6% and 47.1%, respectively. Moreover, the storage moduli and glass-transition temperatures of the MGCs were significantly enhanced. The ultrasonic parameters were of key importance for dispersing MWCNTs onto GFf and improving the interfacial properties of the composites.

Effects of heterionic montmorillonites on flame resistances of polystyrene nanocomposites and the flame retardant mechanism

To improve the flame resistance of polystyrene, three kinds of organophilic heterionic montmorillonites (Na-montmorillonite, Ca-montmorillonite, and Fe-montmorillonite) reinforced polystyrene nanocomposites were prepared by melt dispersion method. The structure and composition of the organo montmorillonites were characterized by using X-ray diffraction and Fourier-transform infrared analysis. The adhesion between organo montmorillonites and polystyrene was investigated by scanning electron microscopy. The flame resistance and thermal stability of the polystyrene/organo montmorillonites were evaluated by cone calorimeter test and thermogravimetric analysis. The interlayer space of organo montmorillonites increased with the increase of the oxidation state of the cations. With the addition of organo montmorillonites, the peak values of all the flame resistance indexes of the polystyrene/organo montmorillonites nanocomposites decreased, among which the PHRR values have decreased the most, compared with those of polystyrene. Their corresponding test times have all been delayed following almost precisely the same trend. Therefore, their flame retardant ability come from their lamellated structures, their charring forming abilities, and the reducing power of Fe3+ in polystyrene/Fe-montmorillonite. Organo montmorillonites mainly act as a kind of intumescent flame retardants. The flame resistance of polystyrene/Na-montmorillonite nanocomposite was the best, and the polystyrene/Ca-montmorillonite came second, which is slightly better than that of polystyrene/Fe-montmorillonite.

Tunable mechanical properties of MWCNT–glass fiber fabric reinforced epoxy composites by controlling MWCNTs dispersing conditions

Abstract A novel, simple and cost-effective method, which is capable of easily tailoring the dispersion of multi-walled carbon nanotubes (MWCNTs), was developed here to fabricate the MWCNT–glass fiber fabric (MWCNT–GFf) multiscale composites with tunable mechanical properties. MWCNTs were dispersed into the commercial GFfs through the combined effect of the ultrasound and amino silane (AS) firstly, followed by a resin infusion process. By tuning the ultrasonic power and AS concentration, it is possible to control the MWCNTs dispersion level and subsequently mechanical properties of resultant composite. Making use of optimal dispersion conditions, which involves the optimal combination of ultrasonic power and AS concentration, the interlaminar shear strength of MWCNT–GFf reinforced composites was dramatically increased by 40.5%, and the storage modulus in the glassy region and rubbery region was improved by 27.7% and 125.0%, respectively. The work demonstrates the great promise of this novel method toward practical, industrial application in manufacturing fiber-reinforced composites with superior mechanical properties.

Mechanical and thermal properties of carbon nanotube- and graphene-glass fiber fabric-reinforced epoxy composites: A comparative study

This study was focused on the comparative effect of tube- and sheet-like nanocarbons on the structure–property relationships of fiber-reinforced composites. Graphene nanosheets and multi-walled carbon nanotubes (MWCNTs) were dispersed into commercial glass fiber fabric (Gf) to obtain multiscale graphene-Gf- and MWCNT-Gf-reinforcing materials, respectively, followed by a vacuum-assisted resin infusion process. The influence of MWCNTs and graphene on the mechanical and thermal performance of multiscale composites were investigated. The experimental results indicated that oxidized MWCNTs or graphene could ensure excellent dispersibility on the fiber surface, and ultimately enhance the mechanical properties and thermal stability of the resultant composites. Graphene oxide (GO), with a wrinkled and roughened texture, was shown to be superior to MWCNTs in terms of toughening the fiber/matrix interface and delaying the deformation or failure of the epoxy matrix. Under the same dosage of nanocarbons, the interlaminar shear strength of GO-Gf-reinforced composites (GO-GfCs) was raised by approximately 12%, and the relevant onset thermal-decomposition temperature was increased by > 11℃, compared with carboxyl MWCNT-Gf-reinforced composites (Mc-GfCs). Meanwhile, the GO-GfCs exhibited superior static and dynamic mechanical properties compared to those of Mc-GfCs.

Interface enhancement of glass fiber fabric/epoxy composites by modifying fibers with functionalized MWCNTs

ABSTRACT Functionalized multi-walled carbon nanotubes (MWCNTs) (with carboxyl, hydroxyl and amino groups, respectively) were grafted onto the surface of glass fiber fabric (GFf) for enhancing interfacial properties of corresponding epoxy-based composites. The effect of introducing various MWCNTs at the fiber/matrix interface was systematically investigated, including on the dispersibility of MWCNTs, interfacial microstructure, interlaminar and mechanical properties. The experimental results showed that the incorporation of functionalized MWCNTs could repair the interface defects, resist the interface debonding, and restrict the mobility of epoxy molecules around the fibers to enhance the interfacial adhesion. Furthermore, the interface layer of resultant composites was broadened with the incorporation of functionalized MWCNTs, and such transition region would transfer mechanical stress uniformly and delay material failure. By choosing the optimal MWCNTs with hydroxyl groups, the interlaminar shear, tensile and flexural strengths of MWCNTs-grafted GFf/epoxy composites were enhanced by 24.0%, 24.9% and 21.1%, respectively; the storage moduli in the glassy and rubbery regions were improved by 17.2% and 153.8%, respectively; the glass-transition temperature also increased by 7.6°C. Graphical Abstract

Properties of MWCNT–glass fiber fabric multiscale composites: mechanical properties, interlaminar adhesion, and thermal conductivity

In this study, multiscale MWCNT–glass fiber fabric (MGFf) preforms with multiwalled carbon nanotubes (MWCNTs) dispersed onto commercial E-glass fiber fabric (GFf) was used to fabricate the MGFf multiscale composites. The mechanical properties, interlaminar shear strength (ILSS), dynamic viscoelasticity and thermal conductivity of MGFf multiscale composites were investigated using a universal material testing machine, dynamic mechanical thermal analyzer and transient plane source method. Furthermore, the reinforcing mechanisms of MWCNTs on interlaminar adhesion of MGFf multiscale composites were explored using scanning electron and transmission electron microscopy and energy dispersive X-ray spectrometry. Compared with the GFf composite, the ILSS and thermal conductivity of MGFf multiscale composites were increased by 40.5% and 55.3%, respectively; both of the tensile and flexural properties of MGFf multiscale composites were significantly enhanced; the glass transition temperature of MGFf multiscale composites was also raised. In addition, the interface thickness was increased with the addition of MWCNTs, and MWCNTs in MGFf multiscale composites behaved as hooked fibers to improve the interlaminar adhesion. The work demonstrates the great promise of MGFf preforms toward practical industrial application in manufacturing multifunctional fiber composites with high strength and modulus, high shear resistance and good thermal conductivity.

Preparation and degradation mechanisms of biodegradable polymer: a review

Polymers are difficult to degrade completely in Nature, and their catabolites may pollute the environment. In recent years, biodegradable polymers have become the hot topic in peoples daily life with increasing interest, and a controllable polymer biodegradation is one of the most important directions for future polymer science. This article presents the main preparation methods for biodegradable polymers and discusses their degradation mechanisms, the biodegradable factors, recent researches and their applications. The future researches of biodegradable polymers are also put forward.