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Synthesis of Amido-quinoline Hafnium and Zirconium Complexes with Improved Performances toward Ethylene/1-Octene Copolymerization

Abstract

A cost-effective and straightforward route has been developed to synthesize amidoquinoline-supported hafnium and zirconium complexes. The new Hf (Hf1-Hf4) and Zr (Zr1) complexes show high thermal stability, high activity, and excellent 1-octene incorporation capability, and thus have been successfully employed in high-temperature solution-phase polymerization to prepare polyolefin elastomers (POEs). It is interesting that both the activity and the 1-octene incorporation by the Hf complex are much higher than those by the Zr analogue bearing the same ligand under otherwise identical conditions, revealing a significant metal center effect on catalytic performances. Moreover, the nature of the ligands also greatly influences the catalysis, and those with electron-donating substituents are favorable for copolymerization. In particular, the Hf complex (Hf1) with Pr-i-substituents shows an activity as high as 78150 kg(POE)mol(-1)(Hf)h(-1) toward ethylene/1-octene copolymerization at 120 degrees C and produces POE with a high molecular weight (M-w = 20.2 x 10(4) gmol(-1)), narrow distribution (& Dstrok; = 2.2), and high incorporation of 1-octene (49.6 mol %).

article Article

date_range 2024

language English

link Link of the paper

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Zhang Xingwang

Zhang Mengxue

Liu Shaofeng

Li Zhibo

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Assessment of reinforced concrete building damages following the Kahramanmaraş earthquakes in Malatya, Turkey (February 6, 2023)

Abstract

Earthquakes of magnitude Mw = 7.7 and Mw = 7.6 hit the city of Kahramanmaraş (Turkey) on 6 February 2023. These earthquakes caused serious damage in 11 provinces in Turkey resulting in over 50,000 deaths and huge economic losses with the collapse of thousands of buildings. Two consecutive devastating earthquakes have severely damaged the reinforced concrete building stock located in Malatya. There are many reasons reinforced concrete structures suffer damage under the influence of seismic loads. These reasons can be listed as material and section properties that do not comply with earthquake codes, workmanship defects, ground parameters that are not considered and design errors, as seen in field investigations after earthquakes in Turkey in the past. In this research, a field study was conducted on reinforced concrete buildings damaged after the earthquakes in Malatya province. The causes of structural damages in reinforced concrete buildings between 6–26 years of age were assessed in terms of design and material defects. The structural damages were mainly caused due to insufficient stirrups in structural members, short column, strong beam–weak column, failures of infill walls, soft story type collapse, poor concrete quality, and reinforcement corrosion. In addition to the field investigation, the spectrum relationships created using raw acceleration data obtained from DEMP (Disaster and Emergency Management Presidency) stations in Malatya province were compared with the design response spectra.

article Article

date_range 2024

language English

link Link of the paper

Collapsed buildings

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