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Keywords = PSPMA brushes

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19 pages, 7828 KB  
Article
Comparative Study on Macro-Tribological Properties of PLL-g-PEG and PSPMA Polymer Brushes
by Fue Ren, Shuyan Yang, Yang Wu, Feng Guo and Feng Zhou
Polymers 2022, 14(9), 1917; https://doi.org/10.3390/polym14091917 - 8 May 2022
Cited by 10 | Viewed by 3924
Abstract
An ultra-low friction and high load capacity could be obtained on the surfaces grafted by a polymer brush even at relatively slow friction speeds in aqueous lubrication environments, which has attracted widespread attention to study the lubrication mechanism of polymer brushes; however, it [...] Read more.
An ultra-low friction and high load capacity could be obtained on the surfaces grafted by a polymer brush even at relatively slow friction speeds in aqueous lubrication environments, which has attracted widespread attention to study the lubrication mechanism of polymer brushes; however, it has yet to be fully understood. The macroscopic tribological performance of two different polymer brushes, which were prepared by the method of “grafting to” and “grafting from” and named as PLL-g-PEG and PSPMA, respectively, were investigated. The friction results demonstrated that PLL-g-PEG obtained a lower friction coefficient than polymer brush PSPMA, which was ascribed to its unique “self-healing” behavior. The lubrication film was in situ observed and the film thickness induced by the polymer brush was measured using a laboratory set for film thickness measurement apparatus based on interference technology. It was found that PSPMA exhibited excellent lubrication performance not found in PLL-g-PEG, and two film-forming mechanisms highly dependent on velocity were revealed, which may be important to interpret the lubrication mechanism of polymer brushes in aqueous lubricants. Full article
(This article belongs to the Section Polymer Analysis and Characterization)
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15 pages, 2742 KB  
Article
Ultra-Stable Silica Nanoparticles as Nano-Plugging Additive for Shale Exploitation in Harsh Environments
by Lan Ma, Pingya Luo, Yi He, Liyun Zhang, Yi Fan and Zhenju Jiang
Nanomaterials 2019, 9(12), 1683; https://doi.org/10.3390/nano9121683 - 25 Nov 2019
Cited by 44 | Viewed by 5674
Abstract
Owing to the harsh downhole environments, poor dispersion of silica at high salinity and high temperature can severely restrict its application as the nano-plugging agent in shale gas exploitation. The objective of this study is to improve salt tolerance and thermal stability of [...] Read more.
Owing to the harsh downhole environments, poor dispersion of silica at high salinity and high temperature can severely restrict its application as the nano-plugging agent in shale gas exploitation. The objective of this study is to improve salt tolerance and thermal stability of silica. Herein, silica was successfully functionalized with an anionic polymer (p SPMA) by SI-ATRP (surface-initiated atom transfer radical polymerization), named SiO2-g-SPMA. The grafted pSPMA brushes on silica provided sufficient electrostatic repulsion and steric repulsion for stabilizing silica in a harsh environment. The modified silica (SiO2-g-SPMA) had excellent colloidal stability at salinities up to 5.43 M NaCl (saturated brine) and standard API brine (8 wt% NaCl + 2 wt% CaCl2) for 30 days at room temperature. Simultaneously, the SiO2-g-SPMA was stable at 170 °C for 24 h as well as stable in weakly alkali environment. Furthermore, the plugging performance of SiO2-g-SPMA in water-based drilling fluids for low permeate reservoir reached to 78.25% when adding a small amount of 0.5 wt% SiO2-g-SPMA, which effectively hindered the water invasion into formation and protected the reservoir. Full article
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