Xuke Li

Tensile Properties of Epoxy Coated Natural Fabric Hildegardia Populifolia

The natural fabric from the tree of Hildegardia populifolia was coated with epoxy and its tensile strength, elastic modulus, and the percent elongation at break were determined. The effect of sodium hydroxide and a silane coupling agent on the tensile properties of the fabric was also studied. It was observed that the tensile properties increased on alkali treatment but decreased when the silane based coupling agent was used.

Tensile properties of ligno-cellulosic fabrics coated with styrenated polyester resin

Ligno-cellulosic fabrics from the tree Hildegardia populifolia were coated with styrenated polyester resin, and their tensile strength, elastic modulus, and the percent elongation at break were determined. The effects of sodium hydroxide and a silane-coupling agent on the tensile properties of the fabric were also studied. It was observed that the tensile strength and the modulus decreased whereas the percent elongation at break increased with coating. The coupling agent improved the properties of the untreated and polyester-coated fabric, but a reverse trend was observed when the fabric was treated with sodium hydroxide. The possible reasons for this behavior are discussed.

Quasiperiodicity and the nanoscopic morphology of some polyurethanes

When straining polyurethane elastomers (PUEs), it is often observed that the long-period peak of the small-angle X-ray scattering (SAXS) does not shift normally. An explanation is indicated for some PUEs in the real-space chord distribution. It exhibits a sequence of constant long-period bands. The band positions form a Fibonacci sequence. This relates to the underlying chemical synthesis by polyaddition of hard and soft modules, indicating a nearly quasiperiodic setup in sequences of stringed hard domains. These sequences appear to be the probes provided by SAXS for the study of morphology evolution in such PUEs. Should a regular-as-possible arrangement of physical crosslinks optimize a property of the material, then in the synthesis the mole fraction nH of hard modules should be chosen to be nH = τ/(1 + τ) ≃ 0.62, where τ is the golden ratio.

Studying nanostructure gradients in injection-molded polypropylene/ montmorillonite composites by microbeam small-angle x-ray scattering

Abstract The core–shell structure in oriented cylindrical rods of polypropylene (PP) and nanoclay composites (NCs) from PP and montmorillonite (MMT) is studied by microbeam small-angle x-ray scattering (SAXS). The structure of neat PP is almost homogeneous across the rod showing regular semicrystalline stacks. In the NCs the discrete SAXS of arranged crystalline PP domains is limited to a skin zone of 300 μm thickness. Even there only frozen-in primary lamellae are detected. The core of the NCs is dominated by diffuse scattering from crystalline domains placed at random. The SAXS of the MMT flakes exhibits a complex skin–core gradient. Both the direction of the symmetry axis and the apparent perfection of flake-orientation are varying. Thus there is no local fiber symmetry, and the structure gradient cannot be reconstructed from a scan across the full rod. To overcome the problem the rods are machined. Scans across the residual webs are performed. For the first time webs have been carved out in two principal directions. Comparison of the corresponding two sets of SAXS patterns demonstrates the complexity of the MMT orientation. Close to the surface (< 1 mm) the flakes cling to the wall. The variation of the orientation distribution widths indicates the presence of both MMT flakes and grains. The grains have not been oriented in the flowing melt. An empirical equation is presented which describes the variation from skin to core of one component of the inclination angle of flake-shaped phyllosilicate filler particles.

Compact Microstrip Lowpass Filter Using Asymmetric Stepped-Impedance Hairpin Resonator and Slotted Ground Plane

In this paper, a newly compact low pass filter is introduced. This filter is constructed by using novel asymmetric stepped-impedance hairpin resonator and slotted ground plan for size reduction and spurious suppression. Furthermore, the equivalent circuit model of the proposed resonator is set up and analyzed. Additionally, slotted ground plane are adopted to obtain a good stop band characteristics. Finally, this compact filter was designed, fabricated, and measured. The experimental results of the filter have a good agreement with the simulated results.