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        Effects of Diamines on the Optical Properties of Poly(ether imide)s Derived from 2,2-Bis[4-(3,4-dicarboxyphenoxy)phenyl]propane Dianhydride (BPADA)

        Linshuang Li,Yong Xu,Jianfei Che,Xiaohong Liu,Wei Zhao,Zhifeng Ye 한국고분자학회 2019 Macromolecular Research Vol.27 No.9

        The objective of this study was to investigate the effects of diamines with ether group or/and trifluoromethyl (-CF3) group on the optical properties of polyimides. A series of poly(ether imide)s (PEIs) (III) were prepared from 2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl]propane dianhydride (BPADA) with various aromatic diamines (Ia-h) including non-fluorinated diamines (Ia-d) and the corresponding trifluoromethyl-substituted diamines (Ie-h). The fluorinated PEIs IIIe-h based on fluorinated diamines were nearly colorless with cutoff absorption wavelength (λ0) below 370 nm and with solubility higher than that of the corresponding CF3-free analogues (IIIa-d). Meanwhile, they had lower dielectric constants in the range of 2.91-3.21 at 1 MHz coupled with water absorptions below 0.70% and contact angles against water beyond 108o. The III series had tensile strength of 84.3-94.4 MPa, modulus of elasticity of 3.6-8.9 GPa and elongation at break of 9.4-25.3%, together with temperatures of 5% weight loss (T5%) beyond 510 °C. Compared to the IV series based on 4,4’-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), the corresponding III series exhibited better thermal and mechanical properties coupled with good optical properties, especially the fluorinated PEIs IIIe-h.

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        Experimental Study on Cyclic Lateral Loaded Circular CFST Members with Initial Imperfections

        Haiqing Zhu,Hang Zhang,Linshuang Liu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.8

        To study the influence of an initial imperfection on the cyclic performance of concrete-filled steel tubular (CFST) members, twelve specimens were cast with different notch lengths, notch widths, notch orientations and notch locations. These specimens were implemented in a lateral quasi-static test, and the test details, damage modes, load-deflection responses and strain histories were detailed and recorded. The measured and theoretical equivalent elastic flexural stiffness, displacement ductility coefficient, maximum lateral load, and measured and theoretical bending capacity of all the specimens were collected and analysed. The research results showed that all specimens mainly experienced flexural damage with different damage levels. Good agreement was observed between the measured and theoretical elastic flexural stiffness as well as the bending capacity for the intact specimens (specimen 1 and specimen 2). The mid-span notch weakened the equivalent elastic flexural stiffness, displacement ductility and flexural capacity of the CFST specimens. Furthermore, a horizontal mid-span notch resulted in greater impact on the specimen behaviour than a vertical notch or a quarter-span notch, an observation that deserves particular attention.

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