Band 41, Heft 5

Nylon composites are of evolving interest due to their good strength, toughness, and low coefficient of friction. Various fillers like micro- and nanoparticulates of metals and metal compounds were used to enhance the mechanical and tribological properties of nylons for many years by researchers. In this paper, an overall understanding of composites, filler materials, especially particulate filler materials, application areas of polymer composites, wear of polymers, and the effect of various fillers on tribo-mechanical properties of nylons have been discussed. The detailed review is limited to micro- and nanoparticulate fillers and their influence on the mechanical and tribological properties of various nylon matrices.

In this paper, the effects of filler content and the use of hybrid nanofillers on agglomeration and nanocomposite mechanical properties such as elastic moduli, ultimate strength and elongation to failure are investigated experimentally. In addition, thermoset epoxy-based two-phase and hybrid nanocomposites are simulated using multiscale modeling techniques. First, molecular dynamics simulation is carried out at nanoscale considering the interphase. Next, finite element method and micromechanical modeling are used for micro and macro scale modeling of nanocomposites. Nanocomposite samples containing carbon nanotubes, graphene nanoplatelets, and hybrid nanofillers with different filler contents are prepared and are tested. Also, field emission scanning electron microscopy is used to take micrographs from samples’ fracture surfaces. The results indicate that in two-phase nanocomposites, elastic modulus and ultimate strength increase while nanocomposite elongation to failure decreases with reinforcement weight fraction. In addition, nanofiller agglomeration occurred at high nanofiller contents especially higher than 0.75 wt% in the two-phase nanocomposites. Nanofiller agglomeration was observed to be much lower in the hybrid nanocomposite samples. Therefore, using hybrid nanofillers delays/prevents agglomeration and improves mechanical properties of nanocomposite at the same total filler content.

Anhydride cured epoxy vitrimers usually exhibit desired mechanical strength but poor toughness and slow transesterification rate. Therefore, the repairing property of the material was restricted. In this paper, polyurethane modified epoxy vitrimer (PU-Epv) was prepared. PU was introduced into the vitrimer system of tetrahydrophthalic anhydride cured epoxy to improve the toughness of the material. Meanwhile, because of the presence of amino ester, the transesterification reaction was promoted and the activation energy of the transesterification was only 33.59 kJ/mol. In the thermal welding experiment, the material could be welded at least five times, and scratches on the surface of the samples could be efficiently repaired within 30 min. The toughness of the material was improved without damaging the strength. Meanwhile, the hard thermosetting epoxy was endowed with excellent repairing properties to increase the service life of the material.

Here, the role of simvastatin-loaded graphene oxide embedded in polyurethane-polycaprolactone nanofibers for bone tissue engineering has been investigated. The scaffolds were physicochemically and mechanically characterized, and obtained polymeric composites were used as MG-63 cell culture scaffolds. The addition of graphene oxide-simvastatin to nanofibers generates a homogeneous and uniform microstructure as well as a reduction in fiber diameter. Results of water-scaffolds interaction indicated higher hydrophilicity and absorption capacity as a function of graphene oxide addition. Scaffolds’ mechanical properties and physical stability improved after the addition of graphene oxide. Inducing bioactivity after the addition of simvastatin-loaded graphene oxide terminated its capability for hard tissue engineering application, evidenced by microscopy images and phase characterization. Nanofibrous scaffolds could act as a sustained drug carrier. Using the optimal concentration of graphene oxide-simvastatin is necessary to avoid toxic effects on tissue. Results show that the scaffolds are biocompatible to the MG-63 cell and support alkaline phosphatase activity, illustrating their potential use in bone tissue engineering. Briefly, graphene-simvastatin-incorporated in polymeric nanofibers was developed to increase bioactive components’ synergistic effect to induce more bioactivity and improve physical and mechanical properties as well as in vitro interactions for better results in bone repair.

In our previous research, the utilization of Gemini surfactants to control the dispersion and interaction of HNTs aerogels (HCAs) in the concrete matrix had obtained positive research results. In order to further deepen the research in this field, in this work, a Gemini surfactant with a new structure was synthesized, the surface modification characteristics of HCAs in a series of concrete systems were also investigated. Microstructures and properties of the composites were characterized by using scanning electron microscope (SEM), Fourier transform infrared (FTIR), Thermogravimetric analysis (TGA), and so on. The results showed that the newly synthesized Gemini surfactants had an ideal modification effect on the surface of HCAs. Compared with other traditional surfactants, Gemini had better hydrophobic and mechanical properties. Different molecular layers with hydrophilicity or hydrophobicity were constructed on the HCAs surface. The introduction of the modified HCAs could significantly improve the heat insulation performance and mechanical strength of concrete. The improvement of the above comprehensive properties could not have significant difference due to the different types of concrete matrix.

Extensional mixing elements (EMEs) that impose extension-dominated flow via stationary single-plane or double-plane hyperbolic converging-diverging channels were previously designed for twin-screw and single-screw extruders (TSE and SSE, respectively). In a recently published work by the authors, reactive extrusion was performed on PS/PA6 polymer blends TSE using EMEs and a crystalline phase transition of the minor phase in these droplets was observed as the size of droplet decreases from micron to submicron. Herein, we expand upon this work to SSE and study: a) The ability of the EMEs to improve dispersive mixing in the same blends; b) Assess the possibility of achieving the same crystalline phase transition in SSEs. The final blends were characterized by DSC, rheologically and morphologically via SEM, and the results show that while EME-based SSE leads to much improved mixing, better than non-EME TSE, the reduction in size of the PA6 disperse phase is not enough to induce the phase transition observed in EME-based TSE.

High-performance rubber composites can be obtained by combining the strength of fiber with the high elasticity of rubber. In this article, environmentally friendly natural rubber (NR)/carbon (CB) composites reinforced by maleic anhydride (MAH) grafted hemp fiber (HF) in the presence of polyhydric hyper-branched polyester (PHP) were studied. The grafting of MAH on the surface of HF (HF-MAH) improves the roughness of fibers, the introduced C=C participates in rubber covulcanization with NR matrix at high temperature, thus enhancing the physical locking and chemical crosslinking between HF and NR matrix. The bridge effect was produced between HF-MAH and rubber matrix by PHP, and the interfacial adhesion was further enhanced. As a result, the tensile strength, tear strength, and elongation at break were improved by approximately 14.5, 26.2, and 10.8%, respectively. The 100 and 300% constant elongation stress was increased by 134 and 113%, and the cutting resistance was also improved obviously.

In this study, a novel PVC/tourmaline ultrafiltration membrane was fabricated by phase inversion method in order to improve anti-fouling performance and water quality. FESEM was used to examine the changes in the morphology of pure PVC and PVC/tourmaline hybrid membranes. The introduction of tourmaline resulted in the increase of porosity and mean pore size. EDX images indicated that tourmaline particles were homogeneously dispersed in the membranes when the amount were less than 1.0 wt%. The hybrid membranes exhibited lower contact angle (78.7°) and higher water flux (121.3 L/m 2  h) than the pure PVC membrane. The anti-fouling performance of the membranes were studied by filtration of BSA solution. The results demonstrated that the hybrid membrane with 1.0 wt% tourmaline particles exhibited the best anti-fouling performance and the highest BSA rejection. In addition, the pH and conductivity of the filtered water were measured by pH meter and electrical conductivity meter. And the results showed that the quality of the filtered water was improved after treating through the hybrid membranes.