Jing Tan

Needleless Melt-Electrospinning of Biodegradable Poly(Lactic Acid) Ultrafine Fibers for the Removal of Oil from Water

As environmentally friendly and degradable material, Poly(lactic acid) (PLA) ultrafine fibers are promising candidates for the removal of oil from water. In this work, a self-established needleless melt-electrospinning process was used to produce PLA ultrafine fibers with diameters in the range of 800 nm–9 µm. In order to obtain ultrafine fibers, three types of hyperbranched polymers were respectively added into the melt for electrospinning. Effects of amount and molecular weight of the added hyperbranched polymers on average fiber diameter and its distribution, and contact angle were investigated. The prepared PLA ultrafine fibers exhibited superhydrophobicity with the contact angle as high as 156°, making it a potential candidate in marine oil spill recovery. The oil sorption capability of these fibers is as high as 159, 118, and 96 g/g for motor oil, crude oil, and diesel, respectively. Even after seven cycles of reuse, the fiber still maintained about 60% of its initial capacity of sorption. The kinetics of oil sorption in the film agrees very well with the pseudo-second-order kinetic model. This work is expected to promote the mass production and application of biodegradable PLA fibers in the treatment of marine oil spill pollution.

Interfacial Diffusion and Bonding in Multilayer Polymer Films: A Molecular Dynamics Simulation.

As a stacked form of ultrathin polymer films, multilayer nanostructures are of great interest in various applications. Coarse-grained molecular dynamics simulations were carried out to understand the behaviors of interfacial diffusion and bonding of multilayer polymer films. We found two obvious stages for the interfacial diffusion of polymers in the multilayer film, and it is 3 times faster in the first stage than in the second one due to the evolution of molecular conformations. The polymers near the interfaces have an in-plane mobility much higher than the out-of-plane one. The strength of interfacial bonding has been characterized by the fast tensile stress-strain curve along the normal direction. It shows multiple yielding points for the multilayer polymer films, which is distinct from the tensile behavior of the bulk. The ultimate tensile stress (UTS) and corresponding separating strain, surprisingly, do not necessarily increase with diffusion time. Because of the dramatic molecular rotation and extension during the first stage of interfacial diffusion, the interlayer interpenetration is nonuniformly distributed in the plane of the interface. Such a nonuniform distribution may be one of the reasons for the decrease of the UTS and separating strain.

Laser induced graphitization of PAN-based carbon fibers

Laser induced graphitization of polyacrylonitrile-based carbon fibers (CFs) was carried out in a self-designed furnace with a CO2 laser source. The microstructures combined with mechanical properties of the irradiated CFs were measured by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and single filament tensile test, respectively. The results exhibited that the hierarchical structures of CFs showed different responses to the CO2 laser. After laser graphitization, the surface and cross-section structure were characterized by Raman spectroscopy. As the power density increased, a profound increase of graphitization degree happened and obvious skin-core structures were observed. Furthermore, the results of XPS measurements indicated that the irradiated CFs showed more conjugated structures. For crystallite structure, the interlayer spacing of the (002) lattice decreased and the thickness of crystallite increased after graphitization. The size of the (002) lattice parallel to the fiber axis changed slightly. The surface morphology was also investigated by SEM, sheet structures and particles could be observed on the surface of CFs. This was attributed to fast energy addition of laser and the characteristics of the material. Further HRTEM investigation revealed that the sheet structure is multilayered graphene. The Youngs modulus of irradiated fibers showed obvious improvements compared to that of as-received ones.

Study on the Acquisition Method of Tire Rubber Parameters Based on Simple Shear Test

Tire simulation gradually becomes an important mean to ensure the quality of the tires. In order to guarantee the reliability of the analysis, the study on the method of obtaining the material parameters is also increasing. According to tire force situation of actual work, the acquisition method of tire rubber parameters based on simple shear test and its application in finite element analysis were studied in this paper. In this research, the international advanced dynamic mechanical analyzer was used to test the tire rubber, and the experimental results were processed by Yeoh hyper-elastic model. The hyper-elastic parameters and thus obtained could be used for finite element analysis of tires, and the simulation results showed that these parameters could be used to simulate the tire performance. In addition, the results could also provide certain guidance for the design and manufacture of tire.

Study on Oil Resistance Properties of Flexible PVC/PNBR Blends

The effects of a combination of polymeric plasticizers and bis(2-etylhexyl) phthalate (DOP) and DOP on mechanical and oil resistance properties of flexible PVC/PNBR blends were investigated. The result showed that the oil resistance of PVC/PNBR blends could be improved obviously by polymeric plasticizer.