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An investigation specifically focusing on the relationship among processing parameters, structure, and mechanical properties of solid two-stage die-drawn polypropylene (PP) has been done in this study, which aimed at providing a reliable reference in the choose of appropriate conditions that can be able to meet a specific processing requirement. PP sheets were drawn through a self-design solid two-stage die-drawing apparatus to various drawing ratios (DRs) at different speeds and with different die-exit thicknesses. The results showed that tensile strength, modulus, and the degree of orientation significantly increased with the nominal DR and could be further improved by increasing the drawing speed. While the crystallinity increased prior and decreased to near a constant value when the drawing speed was over 150 mm/min in the researched scope. Larger the die-exit thickness was, lower the orientation degree was but higher the crystallinity could be obtained. Compared with crystallinity, orientation degree plays a leading role in the final product properties during a two-stage solid die-drawing process., INTRODUCTION Polymer and polymer composites have been widely applied in various fields like commodity, engineering, medical materials, and so on [1], As known, the inner structure and morphology are decisive [...]

In this study, poly(butylene adipate‐co‐terephthalate) (PBAT) was introduced to poly(lactic acid) (PLA) matrix to improve its inherent poor toughness. Besides, the orientation structure was also introduced via die drawing process to compensate for strength loss. The results indicate that die drawing process contributes to improve the mechanical properties of PLA. The tensile strength, modulus, and elongation at break of die‐drawn pure PLA increased by 76.6, 36.1, and 1,375.0%, respectively, compared with those of isotropic PLA. Moreover, the tensile strength can be further improved by the addition of PBAT. The die drawing process can remarkably improve crystallinity, and the orientation factor is high when the PBAT content is less than 30 wt%. By combining the PBAT with highly oriented structure imported by die drawing process, it is possible to prepare simultaneously reinforced and toughened materials, which provides a new insight into the modification of PLA. [ABSTRACT FROM AUTHOR]

ABSTRACT: High oriented isotactic polypropylene prepared by self‐designed two‐stage die drawing apparatus was explored through kinds of methods, including differential scanning calorimetry, two‐dimensional wide‐angle X‐ray diffraction, polarized light microscope, and tensile test. The results showed that there was a great difference between the orientation mechanism and structure evolution of two‐stage solid die drawing process and single‐stage solid die drawing process. All samples would undergo free drawing process after die drawing process. Die drawing and free drawing process were of equal importance to single‐stage die drawing process while die drawing process showed an prominent contribution to the two‐stage die drawing process. Drawing speed showed beneficial influence on die drawing process for both single‐ and two‐stage die drawing process routes. Under the same processing condition, tensile strength and modulus of samples prepared by two‐stage die drawing process were higher than those prepared by single‐stage die drawing process and the maximum value could reach 241.93 MPa and 3.57 GPa, respectively. Moreover, two‐stage die drawing samples showed better dimensional stability than single‐stage die drawing samples especially under low draw rate. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46581. [ABSTRACT FROM AUTHOR]

• Al/Mg-Li/Al composite plate with a flat interface. • Expanded the conventional frequency band from 30 to 1500 MHz to 30–6000 MHz. • SE of Al/Mg-Li/Al composite plate was enhanced by adjusting different thickness ratios. Magnesium alloy has good electromagnetic shielding performance, but its shielding effectiveness on high-frequency electromagnetic waves is weak. In order to solve the above problems, aluminum, which is also a lightweight material, is covered on top of Mg. The feasibility of this method is demonstrated by microstructure analysis and measurement of conductivity and electromagnetic shielding effect, and the results show that the Al/Mg-Li/Al-X sandwich structure is improved by nearly 10 dB at 6000 MHz, and the improvement of electromagnetic shielding efficiency is attributed to the absorption loss caused by the addition of Al layer and the reflection loss at the interlayer interfaces. In addition, the alternating arrangement of α-Mg/β-Li in the Mg layer, and the interfaces formed by the Mg 12 YZn hard phase particles and the matrix phase also contribute to the electromagnetic shielding efficiency. [ABSTRACT FROM AUTHOR]

Abstract: SnO2 nanocrystals were synthesized by a precipitation process and then used as the support for Au/SnO2 catalysts preparation via a deposition–precipitation method. The samples were characterized by means of X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM)/energy-dispersive X-ray spectra (EDS) and X-ray photoelectron spectroscopy (XPS). The influence of calcination temperature of SnO2 support, calcination temperature of Au/SnO2 catalysts and Au loading on the catalytic activity of Au/SnO2 catalysts was investigated. The SnO2 samples calcined at 573 and 673K were found to be the suitable support materials for Au/SnO2 catalysts. In all investigated Au/SnO2 catalysts with different Au loading from 0.36 to 5.00wt.%, the catalytic activity of the catalyst with 2.86wt.% Au loading was the highest. The optimum calcination temperature of the Au/SnO2 catalysts was 473K. According to XRD, HRTEM and XPS, the catalytic activity of the Au/SnO2 catalysts was related to the particle size of gold and tin oxide support, the fraction of metallic state Au and the degree of crystallinity of tin dioxide support. [Copyright &y& Elsevier]