A Study on the Red Clay Binder Stabilized with a Polymer Aqueous Solution

In this study, the performance evaluation was performed by adding a polymer aqueous (PA) solution as a new additive of the red clay binder for use in the rammed-earth construction method. The evaluation items were compressive strength, water erosion, shrinkage, crystal structure, and microstructure. As a result of the experiment, the binder was improved by efficiently bonding the silica particles by the polymerized polymer. It was confirmed that adding a PA solution to red clay enhances the compressive strength, which is further improved when 5 wt% poly(Acrylic acid(AA)-co-Acrylamide(AM)) is added to the PA solution. Microstructural analysis indicated that the addition of a PA solution facilitates effective bonding of the silica particles of red clay to form hydrogen bonding with poly(AA-co-AM) and encourages aggregate formation. Therefore, the study confirmed that PA solution can be applied to satisfy the performance requirements of the rammed-earth construction by improving the durability and strength of the binder.

Synthesis and Self-Assembly of Multistimulus-Responsive Azobenzene-Containing Diblock Copolymer through RAFT Polymerization

This paper gathered studies on multistimulus-responsive sensing and self-assembly behavior of a novel amphiphilic diblock copolymer through a two-step reverse addition-fragmentation transfer (RAFT) polymerization technique. N-Isopropylacrylamide (NIPAM) macromolecular chain transfer agent and diblock copolymer (poly(NIPAM-b-Azo)) were discovered to have moderate thermal decomposition temperatures of 351.8 and 370.8 °C, respectively, indicating that their thermal stability was enhanced because of the azobenzene segments incorporated into the block copolymer. The diblock copolymer was determined to exhibit a lower critical solution temperature of 34.4 °C. Poly(NIPAM-b-Azo) demonstrated a higher photoisomerization rate constant (kt = 0.1295 s−1) than the Azo monomer did (kt = 0.088 s−1). When ultraviolet (UV) irradiation was applied, the intensity of fluorescence gradually increased, suggesting that UV irradiation enhanced the fluorescence of self-assembled cis-isomers of azobenzene. Morphological aggregates before and after UV irradiation are shown in scanning electron microscopy (SEM) and dynamic light scattering (DLS) analyses of the diblock copolymer. We employed photoluminescence titrations to reveal that the diblock copolymer was highly sensitive toward Ru3+ and Ba2+, as was indicated by the crown ether acting as a recognition moiety between azobenzene units. Micellar aggregates were formed in the polymer aqueous solution through dissolution; their mean diameters were approximately 205.8 and 364.6 nm at temperatures of 25.0 and 40.0 °C, respectively. Our findings contribute to research on photoresponsive and chemosensory polymer material developments.

Study on the Characteristics of Flow and Heat Transfer of Polymeric-Fluid-Based Cu Nanofluids

In this paper, we propose a new fluid: drag-reducing-fluid-based nanofluids (DRFBN), i.e., nanoparticles are added into polymer aqueous solution. In order to investigate the flow and heat transfer characteristics of this new fluid, the Reynolds stress turbulence model and equivalent viscosity model are used in the simulations. Wall shear stress and Nusselt number (Nu) are chosen to represent the effects of drag reduction and heat enhancement respectively. The numerical studies mainly focus on the effects of different parameters on wall shear stress and Nu. The results show that comparison with water flow, DRFBN flow still has remarkable drag-reducing effect; comparison with polymer aqueous solution flow, DRFBN flow has some improvement on heat transfer. Therefore, DRFBN has duel effects: drag reduction and heat transfer enhancement. Besides, it is found that the parameters of nanoparticle volume fraction, Reynolds number and drag-reducing parameter have remarkable effects on wall shear stress and Nu of DRFBN flow.