Enhanced Mechanical and Antibacterial Properties of Nanocomposites Based on Poly(vinyl Alcohol) and Biopolymer-Derived Reduced Graphene Oxide

Functionalized graphene-polymer nanocomposites have gained significant attention for their enhanced mechanical, thermal, and antibacterial properties, but the requirement of multi-step processes or hazardous reducing agents to functionalize graphene limits their current applications. Here, we present a single-step synthesis of thermally reduced graphene oxide (TrGO) based on shellac, which is a low-cost biopolymer that can be employed to produce poly(vinyl alcohol) (PVA)/TrGO nanocomposites (PVA-TrGO). The concentration of TrGO varied from 0.1 to 2.0 wt.%, and the critical concentration of homogeneous TrGO dispersion was observed to be 1.5 wt.%, below which strong interfacial molecular interactions between the TrGO and the PVA matrix resulted in improved thermal and mechanical properties. At 1.5 wt.% filler loading, the tensile strength and modulus of the PVA-TrGO nanocomposite were increased by 98.7% and 97.4%, respectively, while the storage modulus was increased by 69%. Furthermore, the nanocomposite was 96% more effective in preventing bacterial colonization relative to the neat PVA matrix. The present findings indicate that TrGO can be considered a promising material for potential applications in biomedical devices

Atrasentan and renal events in patients with type 2 diabetes and chronic kidney disease (SONAR): a double-blind, randomised, placebo-controlled trial

Background: Short-term treatment for people with type 2 diabetes using a low dose of the selective endothelin A receptor antagonist atrasentan reduces albuminuria without causing significant sodium retention. We report the long-term effects of treatment with atrasentan on major renal outcomes. Methods: We did this double-blind, randomised, placebo-controlled trial at 689 sites in 41 countries. We enrolled adults aged 18–85 years with type 2 diabetes, estimated glomerular filtration rate (eGFR)25–75 mL/min per 1·73 m 2 of body surface area, and a urine albumin-to-creatinine ratio (UACR)of 300–5000 mg/g who had received maximum labelled or tolerated renin–angiotensin system inhibition for at least 4 weeks. Participants were given atrasentan 0·75 mg orally daily during an enrichment period before random group assignment. Those with a UACR decrease of at least 30% with no substantial fluid retention during the enrichment period (responders)were included in the double-blind treatment period. Responders were randomly assigned to receive either atrasentan 0·75 mg orally daily or placebo. All patients and investigators were masked to treatment assignment. The primary endpoint was a composite of doubling of serum creatinine (sustained for ≥30 days)or end-stage kidney disease (eGFR <15 mL/min per 1·73 m 2 sustained for ≥90 days, chronic dialysis for ≥90 days, kidney transplantation, or death from kidney failure)in the intention-to-treat population of all responders. Safety was assessed in all patients who received at least one dose of their assigned study treatment. The study is registered with ClinicalTrials.gov, number NCT01858532. Findings: Between May 17, 2013, and July 13, 2017, 11 087 patients were screened; 5117 entered the enrichment period, and 4711 completed the enrichment period. Of these, 2648 patients were responders and were randomly assigned to the atrasentan group (n=1325)or placebo group (n=1323). Median follow-up was 2·2 years (IQR 1·4–2·9). 79 (6·0%)of 1325 patients in the atrasentan group and 105 (7·9%)of 1323 in the placebo group had a primary composite renal endpoint event (hazard ratio [HR]0·65 [95% CI 0·49–0·88]; p=0·0047). Fluid retention and anaemia adverse events, which have been previously attributed to endothelin receptor antagonists, were more frequent in the atrasentan group than in the placebo group. Hospital admission for heart failure occurred in 47 (3·5%)of 1325 patients in the atrasentan group and 34 (2·6%)of 1323 patients in the placebo group (HR 1·33 [95% CI 0·85–2·07]; p=0·208). 58 (4·4%)patients in the atrasentan group and 52 (3·9%)in the placebo group died (HR 1·09 [95% CI 0·75–1·59]; p=0·65). Interpretation: Atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease who were selected to optimise efficacy and safety. These data support a potential role for selective endothelin receptor antagonists in protecting renal function in patients with type 2 diabetes at high risk of developing end-stage kidney disease. Funding: AbbVie

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Department of Mechanical Engineeringclos

Enhanced Mechanical and Antibacterial Properties of Nanocomposites Based on Poly(vinyl Alcohol) and Biopolymer-Derived Reduced Graphene Oxide

Functionalized graphene–polymer nanocomposites have gained significant attention for their enhanced mechanical, thermal, and antibacterial properties, but the requirement of multi-step processes or hazardous reducing agents to functionalize graphene limits their current applications. Here, we present a single-step synthesis of thermally reduced graphene oxide (TrGO) based on shellac, which is a low-cost biopolymer that can be employed to produce poly(vinyl alcohol) (PVA)/TrGO nanocomposites (PVA–TrGO). The concentration of TrGO varied from 0.1 to 2.0 wt.%, and the critical concentration of homogeneous TrGO dispersion was observed to be 1.5 wt.%, below which strong interfacial molecular interactions between the TrGO and the PVA matrix resulted in improved thermal and mechanical properties. At 1.5 wt.% filler loading, the tensile strength and modulus of the PVA–TrGO nanocomposite were increased by 98.7% and 97.4%, respectively, while the storage modulus was increased by 69%. Furthermore, the nanocomposite was 96% more effective in preventing bacterial colonization relative to the neat PVA matrix. The present findings indicate that TrGO can be considered a promising material for potential applications in biomedical devices

Fabrication and Characterization of Carbon Nanotube/Carbon Fiber/Polycarbonate Multiscale Hybrid Composites

Multiscale hybrid composites, which consist of polymeric resins, microscale fibers and nanoscale reinforcements, have drawn significant attention in the field of advanced, high-performance materials. Despite their advantages, multiscale hybrid composites show challenges associated with nanomaterial dispersion, viscosity, interfacial bonding and load transfer, and orientation control. In this paper, carbon nanotube(CNT)/carbon fiber(CF)/ polycarbonate(PC) multiscale hybrid composite were fabricated by a solution process to overcome the difficulties associated with controlling the melt viscosity of thermoplastic resins. The dependence of CNT loading was studied by varying the method to add CNTs, i.e., impregnation of CF with CNT/PC/solvent solution and impregnation of CNTcoated CF with PC/solvent solution. In addition, hybrid composites were fabricated through surfactant-aided CNT dispersion followed by vacuum filtration. The morphologies of the surfaces of hybrid composites, as analyzed by scanning electron microscopy, revealed the quality of PC impregnation depends on the processing method. Dynamic mechanical analysis was performed to evaluate their mechanical performance. It was analyzed that if the position of the value of tan ?? is closer to the ideal line, the adhesion between polymer and carbon fiber is stronger. The effect of mechanical interlocking has a great influence on the dynamic mechanical properties of the composites with CNTcoated CF, which indicates that coating CF with CNTs is a suitable method to fabricate CNT/CF/PC hybrid composites.clos

Fabrication and Characterization of Graphene Oxide/Thermoplastic Composites Prepared by In-situ Interfacial Polymerization

Today, graphene oxide (GO)/thermoplastic composites have been researched actively to improve the interfacial properties between polymer and GO. In these nanocomposites, dispersion of GO in polymer matrix and the interfacial bonding between GO and polymer are key factors that govern the interfacial properties. Accordingly, polymer has been grafted onto GO by various chemical reactions. Furthermore, modification of GO surface can enhance the dispersion and interfacial properties through attachment of specific functional groups on GO. In this study, GO was functionalized with thionyl chloride (SOCl2) to enhance interaction between matrix and GO. The acyl chloride-functionalized GO (AGO) was used as the reinforcement in the nanocomposites. AGO/Nylon 6,6 composites were fabricated using interfacial polymerization of Nylon 6,6, which involves synthesis of AGO/Nylon 6,6 interphase at the interface between organic and aqueous phases. Furthermore, CNTs were dispersed into AGO solution resulting in Nylon 6,6 composites containing hybrid fillers, such as AGO and CNT. The morphology and chemical state of AGO were analyzed using TEM, SEM, XRD, Raman and FT-IR. Meanwhile, the CNT-based Nylon 6,6 composites showed higher peak intensity of amide 1 than that of AGO-based composites, which was indicative of the activated formation of hydrogen bonding. In terms of crystallinity, AGO-based composites were more effective than CNT-based composites due to the graphene sheets serving as strong nucleating agents and their large surface area where the Nylon 6,6 chains need more time to adjust their conformation

Ultra-High-Performance CNT/Carbon fiber/Polymer Multiscale Hybrid Composites with In-Situ-Polymerized Interface

The interfacial properties in carbon-fiber-reinforced plastics (CFRPs) are very important because they govern the overall mechanical properties of the composites. Modifying the carbon fiber surface with carbon nanotubes (CNTs) is actively researched to reinforce the interface. However, most surface modification methods have limitations of their own, e.g., in CVD growth, high temperature in the range of 600-1000??C should be applied to grow the CNT on carbon fibers, which can lead to damages on the carbon fiber, adversely affecting the mechanical properties. In this study, CNT/carbon fiber/nylon multiscale hybrid composites were fabricated using interfacial polymerization of polyamide 6,10 (PA6,10), which involves synthesis of CNT/PA6,10 interphase at the interface between organic and aqueous phases. Carbon fiber was coated with PA6,10 incorporated with CNTs homogeneously. CNTs were dispersed in organic phase. The degrees of CNT dispersion in composites were analyzed using scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) was used to assess the thermal stability of composites. Furthermore, the adhesion strength between carbon fiber and polymer was measured through fiber pull-out tests. &amp;copy; 2016, The Composites and Advanced Materials Expo (CAMX)

Multi-scale hybrid In situ tow scale carbon fiber reinforced thermoplastic strain sensor

In this study, strain self-sensing of carbon fiber reinforced thermoplastic (CFRTP) composite was investigated using the electrical resistance. The self-sensing researches limited to the thermoset composites motivated the study for the investigations with CFRTP. Additional treatment was performed during the manufacturing to enhance its electromechanical sensitivity and mechanical properties by subtracting carbon fiber tows, in situ interfacial polymerization, and adding graphene oxide (GO) to the polymer. Isolating the sensing tow increased the electromechanical sensitivity because the reduced electrical network was more sensitive to the mechanical deformation. In-plane electrical network to the nearby tows was restricted by eliminating the adjacent carbon fiber tows from the sensing tow. Through-thickness network was controlled by the in situ interfacial polymerization of the sensing tow with polyamide 6,6 (PA 6,6). GO was added to the polymer to enhance the mechanical properties. These additional treatments were converted into equivalent electrical circuit modeling to comprehend the electromechanical behavior of the CFRTPs. The electromechanical sensitivities of the developed CFRTPs increased by 270% compared with control sample. The novel advantages of the proposed method are low cost, easy implementation, in situ integrated smart sensors, and tunable customized electromechanical sensitivity

A study on miscibility properties of polyacrylonitrile blending films with biodegradable polymer, shellac

Polyacrylonitrile (PAN) films blended with shellac, biodegradable polymer, were prepared via simple solution casting method. The miscibility of PAN with shellac polymer was investigated and the optimal concentration of shellac in terms of hydrogen bonding between shellac and PAN chain was determined to be used as a novel biomass carbon precursor. Shellac and PAN chain could exert interaction and the interaction facilitates to loose the crystalline structure of the PAN chain, suggesting that the decrease of the oxidation temperature of the PAN chain in the PAN/shellac blends film by the introduction of shellac segments. The optimal PAN/shellac blends film exhibited outstanding mechanical performances (73.8% higher tensile strength, 60% higher storage modulus compared with control PAN film) showing homogeneous blending state

Direct growth of thermally reduced graphene oxide on carbon fiber for enhanced mechanical strength

In this study, carbon fiber (CF) composites were prepared by synthesizing thermally reduced graphene oxide (TRGO) directly on the surface of CFs in order to reinforce the interface between the CFs and the matrix. The conformal and robust coating of TRGO on the CF surface is achieved by the direct conversion of shellac, a lowcost natural polymer, to TRGO via single-step low-temperature (400-700 degrees C) annealing. X-ray photoelectron spectroscopy, Raman analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, contact angle measurement, and energy dispersive spectrometry results confirmed the synthesis of high-quality TRGO, which prompted hydrogen bonding and mechanical interlocking at the composite interfaces. The CF-TRGO composites showed 60 and 152% higher interlaminar shear strength (ILSS) and flexural strength, respectively than the untreated CF composites. The fracture surface analysis by SEM further reveals that the interfacial bonding between the matrix and the CFs increased significantly with TRGO coating