No abstract

Rubber particles were dipped into NaOH solution in order to wipe the zinc stearate generated in the process of preparation of rubber power. Rubber with different particle diameters and mixing amount (sand replaced in equal volume percentage) was adopted to produce rubberized concrete specimens. A series of tests including compressive strength tests, flexural strength tests, elastic modulus tests and ultimate strain ratio tests were done respectively. The results of tests showed that the value of the compressive strength, flexural strength and elastic modulus decreased with the increase of the mixing amount of rubber, while the decrease amplitude was different from each other. The value of ultimate strain increased a little and the ability of toughness and deformation of rubberized concrete were enhanced obviously through dipping rubber particles into NaOH solution.

Cationic nanopolystyrenes (CNPSs) were prepared by the polymerization of styrene with a cationic polymerizable emulsifier, N‐(2‐(methacryloyloxy)ethyl)‐N,N‐dimethyltetradecane‐1‐ammonium bromide (MDTB), in the presence of 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (APPH). The polymerization kinetics was investigated through monomer conversion versus polymerization time. 1H NMR spectra and FTIR spectra were used to confirm the structures of MDTB and nanopolymers. The particle size, ζ‐potential, molecular weight, and thermal stability were also investigated by Zetasizer, gel permeation chromatography, and thermogravimetric analysis, respectively. The antibacterial activities of the obtained products were evaluated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Staphylococcus aureus ATCC 29913 (S. aureus, a Gram‐positive bacterium) and Escherichia coli ATCC 25922 (E. coli, a Gram‐negative bacterium). The results indicated that the polymerization has the characteristics of microemulsion polymerization, all nanopolystyrenes are cationic and can be stored in the form of a microemulsion in aqueous phase, CNPSs present stable chemical structure at 190 °C, and their MIC and MBC reach 0.0625 and 0.125 mg mL−1 for E. coli, 0.0325 and 0.0625 mg mL−1 for S. aureus, respectively. Therefore, CNPSs are a promising new type of polymer antimicrobial agent, which can be used in the development of antimicrobial polymer materials and their products. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48405.

Due to the particularity of the ancient city wall, the collapse damage of ancient city wall earthen ruins is different from general soil slope failure. Through on-site observations and theoretical analysis, collapse failure process and mechanism of ancient city wall earthen sites under the action of capillary water is studied, and protection measures are proposed. Collapse failure process of earthen sites under the action of capillary water has the characteristics of particularity, diversity and stage. Capillary water reduces the stability of ancient city wall by changing the soil physical properties, chemical and ice split role. Finally, the effect of capillary water is illustrated through a specific project example.

The flexible biodegradable polymer hydrogels have attracted increasing attention in the exploration of multifarious biomedical applications. However, conveniently achieving the synergistic characteristics of favorable mechanical performance, anti-swelling behavior, antibacterial activity and conductivity into a biodegradable hydrogel remains a significant challenge. In this aspect, we report a facile one-pot approach to prepare the multiple-crosslinked PVA (PVA/PA-Fe) hydrogels assisted by phytic acid (PA) and ferric trichloride. Firstly, PVA polymer chains and PA molecules form hydrogen bonds, meanwhile PA molecules interact with Fe 3+ ions by ionic coordinations. Then, PVA polymer chains are crystallized by forming hydrogen bonds after cyclic freezethaw process. Based on the synergistic interactions of multiple hydrogen bonds and ionic coordinations in hydrogel system, PVA/PA-Fe hydrogels possess favorable tensile strength (1222.72 kPa), toughness (1.82 MJ/m 3 ) and antiswelling properties. Moreover, the introduction of PA and ferric trichloride successfully endows hydrogel with outstanding antimicrobial activity. Furthermore, the existence of H + ions ionized by PA, Fe 3+ and Cl À ions originating from ferric trichloride provides hydrogel with ionic conductivity (4.91 S/m) and strain responsiveness. Thus, the facile one-pot preparation approach basing on the multiple-crosslinked strategy would broaden the path for preparation of multifunctional hydrogels with promising biomedical applications, particularly smart flexible strain sensors.