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26 results on '"Li, Naiqiang"'

17. Analysis of OMMT strengthened UV aging-resistance of Sasobit/SBS modified asphalt: Its preparation, characterization and mechanism

Author

Gui Zengjian, Xu Yufeng, Zhang Zhengqi, Li Naiqiang, Hengbin Liu, and Jinqian Xie

Subjects
chemistry.chemical_classification, Materials science, Renewable Energy, Sustainability and the Environment, 020209 energy, Strategy and Management, 05 social sciences, Composite number, 02 engineering and technology, Building and Construction, Polymer, Microstructure, Industrial and Manufacturing Engineering, Rheology, chemistry, Aging resistance, Asphalt, 050501 criminology, 0202 electrical engineering, electronic engineering, information engineering, Composite material, 0505 law, General Environmental Science
Abstract

To promote the application of warm mix asphalt (WMA) technology in strong UV areas, warm mix SBS modified asphalt binders with better UV aging resistance were developed in this study. The conventional physical properties, viscosity-temperature characteristics, rheological properties and storage stability were carried out to analyze the performance of the prepared modified asphalt containing Sasobit and OMMT. Then, TOPSIS method was selected for multi-index optimization to optimize the dosage of OMMT and Sasobit. Subsequently, the warm mix effect, high temperature property and aging resistance of the developed modified asphalt were further evaluated. Finally, the modification mechanism was characterized with FTIR, XRD and FM. Test results show that, Sasobit can significantly improve the construction workability of asphalt, and OMMT can enhance the storage stability and UV-aging resistance. In addition, the two modifiers can both improve the high temperature property of SBS modified asphalt. Based on the multi-index optimization results, it is recommended that the optimal dosage of Sasobit and OMMT is 3% and 2%, respectively. And microstructure characterization test results reveal that the asphalt chains and polymer molecules have been successfully intercalated into the layers of OMMT molecules, and further the exfoliated structure has been formed in the composite asphalt blend, thus improving its road performance. From the above results, it can be concluded that both additives play their own advantages at their optimum dosages.

Published
2021

18. Effects of polyphosphoric acid ( <scp>PPA</scp> ), <scp>styrene‐butadiene‐styrene</scp> ( <scp>SBS</scp> ), or rock asphalt on the performance of desulfurized rubber modified asphalt

Author

Zhuolin Li, Zhengqi Zhang, Hengbin Liu, and Li Naiqiang

Subjects
Materials science, Styrene-butadiene, Polymers and Plastics, General Chemistry, Surfaces, Coatings and Films, Styrene, chemistry.chemical_compound, Natural rubber, chemistry, Rheology, Asphalt, visual_art, Materials Chemistry, visual_art.visual_art_medium, Adhesive, Composite material
Published
2021

19. Synthesis and structure analysis of polyesteramides modified with bio-based diaminopentane hexanedioic salt

Author

Lou Xueqin, Li Naiqiang, Weihai Xu, Wang Xueli, and Liu Xiucai

Subjects
chemistry.chemical_classification, Materials science, Polymers and Plastics, Structure analysis, General Chemical Engineering, Chemical structure, Salt (chemistry), Bio based, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, chemistry, Organic chemistry, Physical and Theoretical Chemistry, 0210 nano-technology
Abstract

Two series of bio-based diaminopentane hexanedioic salt (DHS) modified polyesteramides were successfully synthesized by two different synthesis processes in which DHS reacted with bis-hydroxyethyl terephthalate (BHET) and low molecular weight polyester (LPET), respectively. The intrinsic viscosities of the polyesteramides ranged from 0.62 dl/g to 0.78 dl/g, which correlated greatly with the requirements of subsequent processing such as spinning. The results of the heteronuclear multiple bond correlation (HMBC) indicated that the diaminopentane segment was directly connected with the purified terephthalic acid (PTA) segment. The presence of ester and amide group characteristic peaks in the Fourier transform-infrared (FT-IR) spectroscopy confirmed that the final resultant products were polyesteramides. The results of elemental analysis showed that the ratio of actual nitrogen content to theoretical nitrogen content of two series of polyesteramides was 76%~90%, and the actual nitrogen content in both series was proportional to the addition of DHS.

Published
2016

25. Metabolic engineering combined with site-directed saturated mutations of α-keto acid decarboxylase for efficient production of 6-aminocaproic acid and 1,6-hexamethylenediamine.

Author

Wang T, Ye P, Xu X, Lu M, Zhang X, and Li N

Abstract

6-Aminocaproic acid (6ACA) and 1,6-hexamethylenediamine (HMDA) are key precursors for nylon synthesis, and both are produced using petroleum-based chemical processes. However, the utilization of bio-based raw materials for biological production of monomers is crucial for nylon industry. In this study, we demonstrated that metabolic engineering of Escherichia coli and selected mutations of α-keto acid decarboxylase successfully synthesized 6ACA and HMDA. An artificial iterative cycle from l-lysine to chain-extended α-ketoacids was introduced into Escherichia coli BL21 (DE3). Then, the extended α-ketoacids were decarboxylated and oxidized for 6ACA production. Overexpression of catalase (KatE) combined with the site-directed mutations of α-isopropylmalate synthase (LeuA) contributed synergistic enhancement effect on synthesis of 6ACA, resulting in a 1.3-fold increase in 6ACA titer. Selected mutations in α-keto acid decarboxylase (KivD) improved its specificity and 170.00 ± 5.57 mg/L of 6ACA with a yield of 0.13 mol/mol (6ACA/ l-lysine hydrochloride) was achieved by shake flask cultivation of the engineered strain with the KivD# (F381Y/V461I). Meanwhile, the engineered E. coli could accumulate 84.67 ± 4.04 mg/L of HMDA with a yield of 0.08 mol/mol (HMDA/ l-lysine hydrochloride) by replacing aldehyde dehydrogenase with bi-aminotransferases. This achievement marks a significant advancement in the biological synthesis of 6-carbon compounds, since the biosynthetic pathways of HMDA are rarely identified., (© 2024 Wiley Periodicals LLC.)

Published
2024
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26. [Heterologous expression and characterization of Klebsiella oxytoca lysine decarboxylase].

Author

Li N, Yu L, and Xu Y

Subjects
Bacterial Proteins genetics, Cadaverine, Carboxy-Lyases genetics, Escherichia coli metabolism, Hydrogen-Ion Concentration, Klebsiella oxytoca genetics, Temperature, Bacterial Proteins metabolism, Carboxy-Lyases metabolism, Klebsiella oxytoca enzymology
Abstract

Cadaverine is a biogenic amine that has the potential to become an important platform chemical for the production of industrial polymers, such as polyamides and polyurethanes. We reported here a lysine decarboxylase from Klebsiella oxytoca. The lysine decarboxylase from Klebsiella oxytoca was cloned to Escherichia coli to get the strain LN18. The specific activity of the crude protein from LN18 reached 30 000 U. The molecular weight was about 80 kDa. The optimum temperature and pH of the crude protein were 55 ℃ and 5.5 respectively. The specific activity could keep over 30% at pH 8.0 compared the one at pH 5.5, much difference from Escherichia coli lysine decarboxylase CadA. Mg²⁺ was positive to the specific activity, whereas Fe²⁺, Zn²⁺ and Ca²⁺ were negative.

Published
2016
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