In the original publication, there was a mistake in Figure 7 as published [...].
In the original publication, there was a mistake in Figure 7 as published [...].
This research addresses the study of the combined effect of two abiotic treatments, a thermo-oxidative treatment followed by a photo-oxidative treatment with ultraviolet light, on the physicochemical properties of commercially available low-density polyethylene films with an oxo-degradant additive (OXOLDPE) and without (LDPE). The change in the oxidized film properties was characterized using FTIR, XRD, TGA, GPC, and SEM analytical techniques. The results indicated that the increment in carbonyl index (CI) and crystallinity percentage (XXRD) was higher for those films that received the combined oxidative treatments compared with those that received only one of them, thermo- or photo-oxidative treatment. Moreover, the combined oxidative treatments produced more ester and carboxylic groups on the degradation products than the other single treatments. An analysis of variance (ANOVA) was carried out, and a synergistic effect was observed between the thermo- and photo-oxidative treatments for both ester and carboxylic degradation products. TGA results revealed that the loss of thermal stability in the films was more significant after their exposure to the combined thermo- and photo-oxidative treatments compared with those which received only one. The GPC results showed that the combined oxidative treatment is necessary to decrease the Mz and Mz+1 average molecular weight of degraded films containing an oxo-degradant additive to the same extent as MW and Mn. The SEM surface appearance of the films changed more drastically after their exposure to the combined thermo- and photo-oxidative treatments, and they seemed to erode with the presence of inorganic fillers (CaCO3). These results suggest that the combined oxidative treatments produced degradation products with lower molecular weight and greater content of ester and carboxylic groups that should enhance its environmental biodegradability.
Laser reduction of graphene oxide (GO) is a promising approach for achieving flexible, robust, and electrically conductive graphene/polymer composites. Resulting composite materials show significant technological potential for energy storage, sensing, and bioelectronics. However, in the case of insulating polymers, the properties of electrodes show severely limited performance. To overcome these challenges, we report on a post-processing redox treatment that allows the tuning of the electrochemical properties of laser-induced rGO/polymer composite electrodes. We show that the polymer substrate plays a crucial role in the electrochemical modulation of the composites' properties, such as the electrode impedance, charge transfer resistance, and areal capacitance. The mechanism behind the reversible control of electrochemical properties of the rGO/polymer composites is the cleavage of polymer chains in the vicinity of rGO flakes during redox cycling, which exposes rGO active sites to interact with the electrolyte. Sequential redox cycling improves composite performance, allowing the development of devices such as electrolyte-gated transistors, which are widely used in chemical sensing applications. Our strategy enables the engineering of the electrochemical properties of rGO/polymer composites by post-treatment with dynamic switching, opening up new possibilities for flexible electronics and electrochemical applications having tunable properties.
The aim of the work was to study the effect of additive concentration on changes in the adhesive and cohesive strength of bitumen. To evaluate the effectiveness of modifiers in the composition of binary and triple bitumen systems in relation to mineral fillers of two grades, the method of determination of the adhesive efficiency and thermodynamic calculations of adhesion and cohesion work were used. The following compounds were used as additives: AS-2 synthesized from the oil refining waste and AG-4I (waste sealing liquid). Adhesion-cohesion processes in modified bitumen systems are limited by the wetting effect of crushed stone and the intensity of intermolecular forces in the condensed phase of the binder. In the binary compositions, the addition of modifiers into bitumen significantly improves the cohesive strength and adhesive efficiency in relation to crushed stone. The introduction of AS-2 into bitumen compositions with AG-4I increases adhesion efficiency and thermodynamic work of adhesion in relation to the filler surface. The adhesion efficiency and thermodynamic work of adhesion in the "bitumen-AG-4I-AS-2" system reach their maximum at CAG-4I = 3.0 g/dm3 and CAS-2 = 1.5 g/dm3. In these concentration modes, the composition ensures maximum increase in adhesion efficiency (AKS = 65.18%; AKA = 48.11%) and the greatest increase in thermodynamic work of adhesion (WA(KS) = 15.79 mN/m; WA(KA) = 14.13 mN/m).
Ammonia is commonly used as a preservative in the production of concentrated natural rubber latex (CNRL) and latex products; however, it poses a serious risk to human health and the environment. In this study, we investigated a thioacetamide derivative (TD) as a preservative of ammonia-free CNRL and the optimization of a stabilization system comprising potassium hydroxide (KOH), lauric acid (LA), and sodium dodecyl sulfate (SDS) to enhance its preservation effect. The results revealed that an optimal amount of TD (0.03%) can effectively maintain the stability of CNRL, inhibit the increase in volatile fatty acid number (VFA number), maintain stable viscosity values, and improve the mechanical stability time (MST). However, increasing the TD dosage results in an increase in both the viscosity and VFA number and a decrease in MST. KOH was used to regulate the pH value of CNRL. It was also found that it can enhance considerably the mechanical properties of CNRL dry films and accelerates the vulcanization of vulcanized film; however, an excessive amount causes latex thickening. LA proved essential for improving the MST and reducing latex viscosity, thereby substantially enhancing the stability and processability of pre-vulcanized latex, but an excessive amount is detrimental to the curing speed and final mechanical strength. SDS can rapidly improve the MST and reduce the viscosity, but it negatively affects the surface molding of dry rubber films. In conclusion, KOH, LA, and SDS at appropriate dosages play a balancing and complementary role in the preparation of ammonia-free CNRL. Upon analyzing diverse performance metrics of CNRL, it has been determined that the optimal TD dosage ranges from 0.02 to 0.03% for maximum efficacy. The KOH dosage should be maintained within 0.1-0.15% to achieve the most favorable outcome, while the LA dosage is advisable to be kept between 0.06 and 0.1%.
Crude glycerol (CG), a major biodiesel production by-product, is the focus of ongoing research to convert it into polyhydroxyalkanoate (PHA). However, few bacterial strains are capable of efficiently achieving this conversion. Here, 10 PHA-producing strains were isolated from various media. Among them, Burkholderia sp. Oh_219 exhibited the highest polyhydroxybutyrate (PHB) production from glycerol and was therefore characterized further. Burkholderia sp. Oh_219 demonstrated significant tolerance to major growth inhibitors in CG and metabolized the fatty acids present as impurities in CG. Furthermore, the Oh_219 strain was genetically engineered using phaCBP-M-CPF4 and phaJPa to enable the fatty acid-based production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), a component of CG. The resulting strain produced PHBHHx containing 1.0-1.3 mol% of 3HHx from CG. Further supplementation with capric and lauric acids increased the 3HHx molar fraction to 9.7% and 18%, respectively. In a 5 L fermenter, the Oh_219 strain produced 15.3 g/L PHB from 29.6 g/L biomass using a two-stage fermentation system. This is the highest yield reported for PHA production from glycerol by Burkholderia spp. Additionally, PHB produced from CG had a lower melting point than that from pure glycerol and fructose. Taken together, Burkholderia sp. Oh_219 is a promising new candidate strain for producing PHA from CG.
This study developed a scientific process parameter setup based on nozzle pressure and screw position, with the process parameter search sequence being injection speed, V/P switchover position, packing pressure, and packing time. Unlike previous studies, this study focuses on the scientific process parameter setup of experiments and simulations, as well as on the implementation of calibration. Experiments and simulations had the same trend of results in the scientific process parameter setup. Although the experiments and simulations had the same trend, the machine response caused parameter errors. After setting the time constant of the simulations, injection speed profiles from the experiments and simulations became closely aligned. The simulation results for the injection speed and V/P switchover position became closer to the experiment results than the results of the uncalibrated simulation. The error between the simulated and experimental injection speed was reduced from 20% to 6% after applying time constant calibration. The V/P switchover point error was also reduced from 11% to 5%, highlighting the effectiveness of the time constant to calibrate the simulation.
The substantial waste generated during the processing of hides and skins as well as at other stages of manufacturing is a recurring issue in the leather industry that this article attempts to address. To investigate the mechanical and thermal characteristics of the resultant composites, this study suggests using leather waste from the bovine leather industry, analyzes the tanning process, and assesses the viability of mixing this waste with natural rubber (TSR-20). Without the inclusion of leather waste, the resulting composites had exceptional tensile strength, surpassing 100% of rubber's strength. The effective interaction of the recycled leather particles with the natural rubber matrix was evidenced using the Lorentz-Park equation. This better performance points to a competitive relationship between rubber and leather waste. The samples' density was 10% greater than that of polybutadiene elastomers and 10% greater than that of natural leather, while the hardness was comparable to that of PVC, which is frequently utilized in the design of general-purpose soles. This suggests that waste from the leather industry can be efficiently utilized in sustainable applications, particularly in the production of leather goods and shoes, helping to valorize waste that is typically discarded. Furthermore, by encouraging the use of recycled resources in the creation of new compounds, this plan provides the rubber sector with a sustainable option. To optimize this proposal, perhaps will be necessary to identify different vulcanization systems to improve the physical mechanical properties and other uses derived from the optimizations realized. This composite can be applied in the fashion industry in order to develop new trends around the application of waste and residues for a natural design line. Through the research process, it was possible to integrate the residues into the natural rubber matrix, as evidenced in the characterization process.
An original design of a simple bioreactor was used to fabricate two tubular, 200 cm long BC structures by culturing Komagataeibacter sucrofermentans B-11267 on a molasses medium. In addition, a tubular BC-based biocomposite with improved mechanical properties was obtained by combining cultivation on the molasses medium with in situ chemical modification by polyvinyl alcohol (PVA). Moreover, the present study investigated the BC production by the K. sucrofermentans B-11267 strain on the media with different molasses concentrations under agitated culture conditions. The dynamics of sugar consumption during the cultivation were studied by HPLC. The structure and physicochemical properties of BC and tubular BC structures were characterized by FTIR spectroscopy and X-ray diffraction (XRD). Thus, the findings indicate that K. sucrofermentans B-11267, when cultivated in a molasses medium, which is such a cheap waste product in the sugar industry, forms a significant amount of BC with a high crystallinity degree. The BC tubular structures demonstrated great potential for their application in biomedicine as artificial blood vessels and conduits for nerve regeneration.
In this research, fully biobased composites consisting of poly(butylene 2,5-furandicarboxylate) (PBF) and cellulose nanocrystals (CNC) were successfully prepared through a common solution and casting method. The influence of CNC on the crystallization behavior, mechanical property, and hydrophilicity of PBF was systematically investigated. Under different crystallization processes, the crystallization of PBF was obviously promoted by CNC as a biobased nucleating agent. The Ozawa equation was not suitable to fit the nonisothermal melt crystallization kinetics of PBF and PBF/CNC composites. The nucleation activity of CNC was quantitatively calculated by the Dobreva method; moreover, the nucleation efficiency of CNC was further evaluated through the self-nucleation procedure. The isothermal melt crystallization kinetics of PBF and PBF/CNC composites was well described by the Avrami method; moreover, the crystallization mechanism and the crystal structure of PBF remained unchanged despite the presence of CNC. CNC also greatly enhanced both the mechanical property and hydrophilicity of PBF in the composites. In sum, low loadings of CNC simultaneously improved the crystallization, mechanical property, and hydrophilicity of PBF, which should be of significant importance and interest in fully biobased polymer composites from a sustainable viewpoint.
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