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To meet the environmental protection and flame retardancy requirements for epoxy resins (EPs) in certain fields, in this study, a novel triazine-ring-containing DOPO-derived compound (VDPD), derived from vanillin, 2,4-Diamino-6-phenyl-1,3,5-triazine, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), was synthesized using a one-pot method. Flame-retardant epoxy resin (FREP) was prepared by adding various ratios of VDPD to EP and curing with 4,4-diaminodiphenylmethane (DDM). The curing behavior, thermal stability, mechanical properties, and flame-retardant properties of the FREP were examined in various tests. According to the results, when the amount of VDPD added to the EP increased, the glass transition temperature of the FREP decreased linearly, and the flame-retardant properties gradually improved. With a 0.4 wt.% P content, the vertical burning rating of EP/DDM/VDPD-0.4 (according to the theoretical content of VDPD) reached the V-0 level, and the LOI value reached 33.1%. In addition, the results of a CCT showed that the peak heat release rate (PHRR) of EP/DDM/VDPD-0.4 decreased by 32% in comparison with that of the EP. Furthermore, compared with those of the EP, the tensile strength of EP/DDM/VDPD-0.4 decreased from 80.2 MPa to 74.3 MPa, only decreasing by 6 MPa, and the tensile modulus increased. Overall, VDPD can maintain the mechanical properties of EP and effectively improve its flame-retardant properties. [ABSTRACT FROM AUTHOR]

To improve the efficient use of nitrogen and decrease the environmental pollution of N losses, a novel and biodegradable composite hydrogel was prepared by chemical cross-linking synthesis using gelatin (Gel), chitosan (CS) and polylactic acid (PLA) as raw materials. Urea as the nitrogen source was loaded into this new biodegradable hydrogel using the solution immersion method. The chemical structures of the composite hydrogels were characterized and their properties were analyzed by XRD and XPS. The regulation of urea loading and the swelling behavior of the composite hydrogel under different temperature conditions were investigated; the release behavior and release model of the composite hydrogel in the aqueous phase was explored. The results show that the loading of urea is controllable in aqueous urea solution with different concentrations. In the water phase, it shows a three-stage sustained release behavior, that is, the initial release rate of urea is relatively fast, and the medium release rate of urea gradually slows down, and finally the nutrient release rate tends to be flat. The release behavior in the water phase fits to the Ritger–Peppas model. Within 10 min, 180 min and 900 min, the cumulative nutrient release rate of gelatin/chitosan/PLA-urea (GCPU) composite hydrogel is 20%, 70% and 86%, respectively. Compared with pure urea, The urea diffusion time of GCPU was extended by 1350-times. In addition, the GCPU also has good water absorption and water retention properties, in which average water content can reach as high as 4448%. All of the results in this work showed that GCPU hydrogel had good water absorption and retention and N slow-release properties, which are expected to be widely used in sustainable agriculture and forestry, especially in arid and degraded land. [ABSTRACT FROM AUTHOR]

Achilles tendon rupture is a severe injury, and its optimal therapy remains controversial. Tissue engineering scaffolds play a significant role in tendon healing and tissue regeneration. In this study, we developed tri-layered doxycycline/collagen/bupivacaine (DCB)-composite nanofibrous scaffolds to repair injured Achilles tendons. Doxycycline, collagen, and bupivacaine were integrated into poly(lactic-co-glycolic acid) (PLGA) nanofibrous membranes, layer by layer, using an electrospinning technique as healing promoters, a 3D scaffold, and painkillers, respectively. After spinning, the properties of the nanofibrous scaffolds were characterized. In vitro drug discharge behavior was also evaluated. Furthermore, the effectiveness of the DCB–PLGA-composite nanofibers in repairing ruptured Achilles tendons was investigated in an animal tendon model with histological analyses. The experimental results show that, compared to the pristine PLGA nanofibers, the biomolecule-loaded nanofibers exhibited smaller fiber size distribution and an enhanced hydrophilicity. The DCB-composite nanofibers provided a sustained release of doxycycline and bupivacaine for over 28 days in vivo. Additionally, Achilles tendons repaired using DCB-composite nanofibers exhibited a significantly higher maximum load-to-failure than normal tendons, suggesting that the biomolecule-incorporated nanofibers are promising scaffolds for repairing Achilles tendons. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) composites have been widely used for strengthening or constructing structures due to their excellent corrosion resistance and high tensile strength. An emerging hybrid structural member form with FRP composites—which consist of a steel section as internal reinforcement, an external FRP wrap/tube, and concrete filled between them (referred to as FRP-confined steel-reinforced concrete (FCSRC) systems)—has attracted increasing research interest. To date, the concept has been adopted to strengthen/repair steel structures or used as new hybrid structural members (e.g., hybrid columns or beams, including buckling restrained braces (BRBs)). The FRP confinement and composite action between the three components in FCSRCs result in the excellent performance of the hybrid member. This paper presents a state-of-the-art review of FCSRCs for structural applications. The gaps in knowledge and future research opportunities on FCSRC structural members are also identified. [ABSTRACT FROM AUTHOR]

In this study, we developed biodegradable lidocaine–/vancomycin–/ceftazidime–eluting poly(d,l–lactide–co–glycolide) (PLGA) nano/microparticulate carriers using an electrospraying process, and we evaluated the release behaviors of the carriers in knee joints. To prepare the particles, predetermined weight percentages of PLGA, vancomycin, ceftazidime, and lidocaine were dissolved in solvents. The PLGA/antibiotic/lidocaine solutions were then fed into a syringe for electrospraying. After electrospraying, the morphology of the sprayed nano/microparticles was elucidated by scanning electron microscopy (SEM). The in vitro antibiotic/analgesic release characteristics of the nano/microparticles were studied using high-performance liquid chromatography (HPLC). In addition, drug release to the synovial tissues and fluids was studied in vivo by injecting drug-loaded nano/microparticles into the knee joints of rabbits. The biodegradable electrosprayed nano/microparticles released high concentrations of vancomycin/ceftazidime (well above the minimum inhibition concentration) and lidocaine into the knee joints for more than 2 weeks and for over 3 days, respectively. Such results suggest that electrosprayed biodegradable nano/microcarriers could be used for the long-term local delivery of various pharmaceuticals. [ABSTRACT FROM AUTHOR]