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The penetration of external stimuli (microorganisms, ions, etc.) following to the pore is the key reason for the deterioration of cement and concrete structures. Although the traditional methods such as improving the chemical composition of cement and concrete materials can delay the erosion rate, the inevitable pore structure still makes its deterioration a challenge. Based on this, we reported a protective coating for cementitious materials based on phenol and Ti3C2 MXene-modified polyacrylate (MXene-PG/PA). The introduction of phenols enhanced the waterproof properties of polyacrylate by increasing the interaction among molecular chains. Moreover, the introduction of Ti3C2 MXene also endows the MXene-PG/PA coating with good light-induced antimicrobial properties. Beneficial to these designs, the MXene-PG/PA coating exhibited good waterproof properties (the water absorption ratio in seawater decreased by 58.2%) and antimicrobial properties (inhibition of E. coli and S. epidermidis activity under light). These results not only confirm that the MXene-PG/PA coating is a potential candidate of protective coating for cement-based materials, but also provide a new strategy for the design of multifunctional protective coatings. [ABSTRACT FROM AUTHOR]

Helical springs are indispensable mechanical parts widely used in industry. Lightweight is one of the development trends of helical springs. In this study, three kinds of lightweight polymer matrix composite helical springs (PMCHSs) with unidirectional, multistrand, and wrapped textile structural reinforcement (PMCHS-U, PMCHS-M, and PMCHS-W) were designed, manufactured, and evaluated. The performance of these PMCHSs and the relationship between their performance and their corresponding polymer matrix composite spring wire rods (PMCRs) were studied through the torsion test of the PMCRs and the compression and resilience tests of the PMCHSs. The results showed that the performance of the PMCHSs could be effectively improved by using the wrapped structure as the reinforcement. The compression capacity of PMCHS-W was 72.6% and 137.5% higher than that of PMCHS-M and PMCHS-U, respectively. The resilience performance of the PMCHSs decreased with the increase in the spring constant. The performances of the PMCHSs and a steel spring were compared. The results showed that the spring constant of the steel spring could be achieved when the masses of PMCHS-U, PMCHS-M, and PMCHS-W were only 75%, 63%, and 49% of the mass of the steel spring, respectively. This research is of great significance to the improvement in lightweight spring performance. [ABSTRACT FROM AUTHOR]

Although poly vinyl alcohol-poly acrylic acid (PVA-PAA) composites have been widely used for biomedical applications, their incorporation into double-layer assembled thin films has been limited because the interfacial binding materials negatively influence the water uptake capacity of PVA. To minimize the effect of interfacial binding, a simple method for the fabrication of a double-layered PVA-PAA hydrogel was introduced, and its biomedical properties were evaluated in this study. Our results revealed that the addition of PAA layers on the surface of PVA significantly increased the swelling properties. Compared to PVA, the equilibrium swelling ratio of the PVA-PAA hydrogel increased (p = 0.035) and its water vapour permeability significantly decreased (p = 0.04). Statistical analysis revealed that an increase in pH value from 7 to 10 as well as the addition of PAA at pH = 7 significantly increased the adhesion force (p < 0.04). The mechanical properties--including ultimate tensile strength, modulus, and elongation at break--remained approximately untouched compared to PVA. A significant increase in biocompatibility was found after day 7 (p = 0.016). A higher release rate for tetracycline was found at pH = 8 compared to neutral pH. [ABSTRACT FROM AUTHOR]

Customarily, retarders serve as the setting time regulators of cement-based composites to meet the demands of various construction environments. However, the limited ability to adjust the setting time restricts the application of polysaccharides in special environments. In this study, we reported a naturally high-efficiency retarder, konjac glucomannan (KGM), and studied the mechanism of its effect on the hydration of ordinary Portland cement. Incorporating KGM could significantly prolong cement hydration without strength damage. Furthermore, the active hydroxyl group (−OH, rich in KGM) could chelate with Ca2+ (released from cement hydration) to form a cross-linking network, which is adsorbed on the surface of cement clinker, thereby being conducive to delaying the process of cement hydration and reducing the heat of hydration. The findings of this study are critical to the ongoing efforts to develop polysaccharide-cement-based composite materials for application in various special environments. [ABSTRACT FROM AUTHOR]

Owing to highly tunable topology and functional groups, hyper-branched polymers are a potential candidate for toughening agents, for achieving supramolecular interactions with hydrogel networks. However, their toughening effects and mechanisms are not well understood. Here, by means of tensile and pure shear testings, we characterise the mechanics of a nanoparticle–hydrogel hybrid system that incorporates a hyper-branched polymer (HBP) with abundant hydroxyl end groups into the matrix of the polyacrylic acid (PAA) hydrogel. We found that the third and fourth generations of HBP are more effective than the second one in terms of strengthening and toughening effects. At a HBP content of 14 wt%, compared to that of the pure PAA hydrogel, strengths of the hybrid hydrogels with the third and fourth HBPs are 2.3 and 2.5 times; toughnesses are increased by 525% and 820%. However, for the second generation, strength is little improved, and toughness is increased by 225%. It was found that the stiffness of the hybrid hydrogel is almost unchanged relative to that of the PAA hydrogel, evidencing the weak characteristic of hydrogen bonds in this system. In addition, an outstanding self-healing feature was observed, confirming the fast reforming nature of broken hydrogen bonds. For the hybrid hydrogel, the critical size of failure zone around the crack tip, where serious viscous dissipation occurs, is related to a fractocohesive length, being about 0.62 mm, one order of magnitude less than that of other tough double-network hydrogels. This study can promote the application of hyper-branched polymers in the rapid evolving field of hydrogels for improved performance. [ABSTRACT FROM AUTHOR]

Three-dimensional braided composite has a unique spatial network structure that exhibits the characteristics of high delamination resistance, damage tolerance, and shear strength. Considering the characteristics of braided structures, two types of high-performance materials, namely, aramid and carbon fibers, were used as reinforcements to prepare braided composites with different hybrid structures. In this study, the longitudinal and transverse shear properties of 3D braided hybrid composites were tested to investigate the influences of hybrid and structural effects. The damage characteristics of 3D braided hybrid composites under short beam shear loading underwent comprehensive morphological analysis via optical microscopy, water-logging ultrasonic scanning, and X-ray micro-computed tomography methods. It is shown that the shear toughness of hybrid braided composite has been improved at certain degrees compared with the pure carbon fiber composite under both transverse and longitudinal directions. The hybrid braided composites with aramid fiber as axial yarn and carbon fiber as braiding yarn exhibited the best shear toughness under transverse shear loading. Meanwhile, the composites with carbon fiber as axial yarn and aramid fiber as braiding yarn demonstrated the best shear toughness in the longitudinal direction. Due to the different distribution of axial and braiding yarns, the transverse shear property of hybrid braided structure excels over the longitudinal shear property. The failure modes of the hybrid braided composite under the two loading directions are considerably different. Under transverse loading, the primary failure mode of the composites is yarn fracture. Under longitudinal loading, the primary failure modes are resin fracture and fiber slip. The extensive interfacial effects and the good deformation capability of the hybrid braided composites can effectively prevent the longitudinal development of internal cracks in the pattern, improving the shear properties of braided composites. [ABSTRACT FROM AUTHOR]

Controllable feature and size, good mechanical stability and intelligent release behavior is the capsule products relentless pursuit of the goal. In addition, to illustrate the quantitative relationship of structure and performance is also important for encapsulation technology development. In this study, the sphericity and size of millimeter-scale calcium sodium alginate capsules (mm-CaSA-Caps) with aqueous core were well tuned by manipulating the viscosity, surface tension, and density of CaCl2/carboxyl methyl cellulose (CMC) drops and sodium alginate (SA) solution. The well-tuned mm-CaSA-Caps showed significant mechanical and control-releasing property effects. The results showed that the prepared mm-CaSA-Caps were highly monodispersed with average diameter from 3.8 to 4.8 mm. The viscosity of the SA solution and the viscosity and surface tension of the CaCl2/CMC solution had significant effects on the mm-CaSA-Caps sphericity. Uniform and spherical mm-CaSA-Caps could be formed with high viscosity CaCl2/CMC solution (between 168.5 and 917.5 mPa·s), low viscosity SA solution (between 16.2 and 72.0 mPa·s) and decreased surface tension SA solution (by adding 0.01 wt.% poloxamer 407). The diameter of the mm-CaSA-Caps could be predicted by a modified Tate's law, which correlated well with the experimental data. The Caps with sphericity factor (SF) < 0.07 had better mechanical stability, with the crushing force 2.91–15.5 times and the surface Young's modulus 2.1–3.99 times higher than those of the non-spherical Caps (SF > 0.07). Meanwhile, the spherical Caps had a more even permeation rate, which was helpful in producing uniform and sustained releasing applications in foodstuff, medicine, agriculture and chemical industry. [ABSTRACT FROM AUTHOR]

There is a rising imperative to increase the operational availability of maritime vessels by extending the time between full docking cycles. To achieve operational efficacy, maritime vessels must remain clear of biological growth. Such growth can cause significant increases in frictional drag, thereby reducing speed, range and fuel efficiency and decreasing the sensitivity of acoustic sensors. The impact that various stages of fouling have on acoustic equipment is unclear. It is also unclear to what extent antifouling techniques interfere with the transmission of acoustic signals. In this study, to examine this effect, neoprene samples were coated with three antifouling coatings, namely, Intersmooth 7460HS, HempaGuard X7 and Hempasil X3. Other neoprene samples were left uncoated but were imbedded with the biocide, 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT) during the mixing and curing process. Uncoated nitrile samples that had varying levels of fouling from immersion in Port Phillip Bay, Australia, for 92, 156 and 239 days were also extracted. The acoustic properties of these samples were measured using an acoustic insertion loss test and compared to uncoated neoprene or nitrile to ascertain the acoustic effects of the applications of antifouling coatings as well as the fouling growth itself. A T-peel test was performed on all coated samples in an attempt to understand the adhesive properties of the coatings when applied to neoprene. It was found that the application of antifouling coatings had little effect on the transmission characteristics of the neoprene with approximately 1 dB loss. The embedment of DCOIT, however, has a chance of causing aeration in the neoprene, which can heavily hamper transmission. An assessment of the effect of the fouling growth found that light and medium fouling levels produced little transmission loss, whereas more extreme fouling lead to a 9 dB transmission loss. The adhesion properties of the coatings were investigated but not fully ascertained as tensile yielding occurred before peeling. However, various failure modes are presented and discussed in this study. [ABSTRACT FROM AUTHOR]

This investigation examines the combination of poly (acrylic acid) (PAA) and bacterial cellulose (BC) nanofibers to synthesize hydrogel hybrid composites used for wound dressing application. Amoxicillin (AM) was also grafted onto the composites for drug release. Fourier transform infrared analysis and scanning electron microscopy conducted revealed the structure and porosity of the composite being developed, as well as the successful fabrication of BC-PAA composites. The results of mechanical testing and hygroscopicity revealed that the composite shows higher stability than hydrogels which are currently used worldwide, albeit with a slight reduction in swelling capabilities. However, the composite was revealed to be responsive to a rise in pH values with an increase in composite swelling and drug release. These results together with their morphological characteristics suggest that BC-PAA hydrogel hybrid composite is a promising candidate for wound dressing application. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) cells in vitro culture are becoming increasingly popular in cancer research because some important signals are lost when cells are cultured in a two-dimensional (2D) substrate. In this work, bacterial cellulose (BC)/gelatin hydrogels were successfully synthesized and were investigated as scaffolds for cancer cells in vitro culture to simulate tumor microenvironment. Their properties and ability to support normal growth of cancer cells were evaluated. In particular, the human breast cancer cell line (MDA-MD-231) was seeded into BC/gelatin scaffolds to investigate their potential in 3D cell in vitro culture. MTT proliferation assay, scanning electron microscopy, hematoxylin and eosin staining and immunofluorescence were used to determine cell proliferation, morphology, adhesion, infiltration, and receptor expression. The in vitro MDA-MD-231 cell culture results demonstrated that cells cultured on the BC/gelatin scaffolds had significant adhesion, proliferation, ingrowth and differentiation. More importantly, MDA-MD-231 cells cultured in BC/gelatin scaffolds retained triple-negative receptor expression, demonstrating that BC/gelatin scaffolds could be used as ideal in vitro culture scaffolds for tumor cells. [ABSTRACT FROM AUTHOR]