Aging Resistance Research Articles

Study of the Cold Curing Characteristics of Isocyanate-Modified Asphalt.

Isocyanate esters are widely recognized for their superior curing capabilities. Leveraging this attribute, the current research formulated a modified cold-mixed asphalt blend using 4,4'-methylene diphenyl diisocyanate (MDI). Tests and analyses of the MDI-modified asphalt with varying inclusion percentages of MDI revealed that a mixture containing 15% rock asphalt and 15% MDI-modified asphalt exhibited a more balanced, comprehensive performance. We also conducted an examination of the role and properties of MDI in asphalt modification using molecular dynamics simulations. The cold-curing properties of MDI-modified asphalt as compared to petroleum asphalt were evaluated based on its density, free volume analysis, cohesive energy density, and glass transition temperature. Implementing the LB-13 gradation-a cold-mixed asphalt gradation with a nominal particle size of 13.2 mm recommended by Chinese specifications-we prepared MDI-modified cold-mixed asphalt and carried out analyses of its mechanical characteristics, high-temperature performance, and water damage resistance. The results demonstrated that MDI-modified asphalt showcases excellent ductility, flexibility, and aging resistance, surpassing the performance of petroleum asphalt. The stability, high-temperature rutting, and water damage resistance of the MDI-modified cold-mixed asphalt exceeded the requirements for hot-mixed asphalt. This research provides theoretical and experimental support for isocyanate ester applications in asphalt engineering, presenting significant value for practical engineering applications.

Research on Strengthening Fragile Paper with Polyvinylamine.

Paper documents are an important carrier of information related to human civilization, with the reinforcement and protection of fragile paper documents being a key aspect of their protection. This research utilized amphoteric polyvinylamine polymer as a paper reinforcement agent, strengthening the Xuan paper commonly used in paper documents. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), solid-state 13C NMR, and other analytical methods were employed to compare the physical properties, micro-morphology, crystallinity, and aging resistance of the paper before and after reinforcement. Research was conducted on the effects of reinforcement, the aging resistance, and the effects on the fiber structure. The results indicate that polyethylenimine has a filling and bridging effect between the paper fibers. After treatment with polyethylenimine, there was a significant improvement in the folding endurance and tensile strength of the paper. Additionally, the paper maintains a good mechanical strength even after undergoing dry heat and humid aging.

Effects of Different Antioxidant Intercalated Layered Double Hydroxides on Anti-Aging Properties of Asphalt Binders

This research aims to prepare different antioxidant intercalated layered double hydroxides (LDHs) and compare the thermal oxidation and ultraviolet (UV) aging resistances of different modified asphalts. The ion exchange technique was used to intercalate three different antioxidants: 3-(3,5-di-tert-butyl-4-carboxyphenyl) propionic acid, antioxidant 1222, and sodium dibutyl dithiocarbamate (rubber accelerator TP) into the interlayer of LDHs. The morphology, structures, UV blocking, and free radical scavenging properties of different antioxidant intercalated LDHs were characterized, respectively. The effects of the anti-aging agents on the physical properties (penetration, softening point, ductility, and viscosity); rheological behaviors (complex modulus and phase angle); and functional groups (C=O and S=O) of asphalt both before and after thermal oxidation aging and UV aging were systematically investigated. The results of the crystal structure and functional group analysis show that the three different antioxidants can be successfully inserted into the interlayer of LDHs without destroying their layered structures. Antioxidant intercalated LDHs exhibit a remarkable capacity for absorbing UV rays, coupled with a moderate ability to reflect UV light. Moreover, the inclusion of antioxidants into the interlayers of LDHs confers upon them the ability to scavenge free radicals. After 2 h of reaction, the free radical scavenging rates of LDHs-3, LDHs-1222, and LDHs-TP were 57.7%, 35.6%, and 17.1%, respectively. With an increase in the content of the antioxidant intercalated LDHs, the performance of the modified asphalt varies, and 4% is the optimal content of the anti-aging agents. Asphalts with the three antioxidant intercalated LDHs all had favorable storage stability, and their physical and rheological properties were improved after aging compared to LDHs-modified asphalt. The LDHs-3-modified asphalt showed the best anti-ultraviolet aging effect, while LDHs-1222-modified asphalt showed the best anti-thermal oxidation aging effect. This research lays the foundation for developing aging-resistant asphalt and improving the durability of asphalt pavement.

Inferring Mycobacterium Tuberculosis Drug Resistance and Transmission using Whole-genome Sequencing in a High TB-burden Setting in China

ObjectiveChina is among the 30 countries with a high burden of tuberculosis (TB) worldwide, and TB remains a public health concern. Kashgar Prefecture in the southern Xinjiang Autonomous Region is considered as one of the highest TB burden regions in China. However, molecular epidemiological studies of Kashgar are lacking. MethodsA population-based retrospective study was conducted using whole-genome sequencing (WGS) to determine the characteristics of drug resistance and the transmission patterns. ResultsA total of 1,668 isolates collected in 2020 were classified into lineages 2 (46.0%), 3 (27.5%), and 4 (26.5%). The drug resistance rates revealed by WGS showed that the top three drugs in terms of the resistance rate were isoniazid (7.4%, 124/1,668), streptomycin (6.0%, 100/1,668), and rifampicin (3.3%, 55/1,668). The rate of rifampicin resistance was 1.8% (23/1,290) in the new cases and 9.4% (32/340) in the previously treated cases. Known resistance mutations were detected more frequently in lineage 2 strains than in lineage 3 or 4 strains, respectively: 18.6% vs. 8.7 or 9%, P < 0.001. The estimated proportion of recent transmissions was 25.9% (432/1,668). Multivariate logistic analyses indicated that sex, age, occupation, lineage, and drug resistance were the risk factors for recent transmission. Despite the low rate of drug resistance, drug-resistant strains had a higher risk of recent transmission than the susceptible strains (adjusted odds ratio, 1.414; 95% CI, 1.023–1.954; P = 0.036). Among all patients with drug-resistant tuberculosis (DR-TB), 78.4% (171/218) were attributed to the transmission of DR-TB strains. ConclusionOur results suggest that drug-resistant strains are more transmissible than susceptible strains and that transmission is the major driving force of the current DR-TB epidemic in Kashgar.

Thermally rearranged OH-containing polyimide composite membranes with enhanced gas separation performance and physical aging resistance

Gas separation membranes play a pivotal role in various industrial processes, demanding continuous improvement in their efficiency and durability. This study focuses on thin-film composite (TFC) membranes based on polyimide, utilizing a hydroxyl-containing polyimide selective layer for its processability and selectivity. A complete and smooth surface for the selective layer in the composite membranes was achieved by exclusively selecting a 10% concentration of the polyimide spin-coating solution. Subsequent thermal rearrangement at 430°C induced the formation of a rigid polybenzoxazole structure, enhancing gas permeance. Optimal separation performance was achieved through a two-hour rearrangement, resulting in a more than 30-fold increase in gas permeance while preserving selectivity. The study also delved into anti-physical aging performance. The thermally treated PI-10 wt%−2 h membrane exhibited a 10% reduction in CO2 and O2 permeance over 90 days, with O2/N2 and CO2/N2 selectivities nearly maintaining their initial levels. This research provides valuable insights for the development of efficient and durable gas separation membranes.

Morphological evolution and property changes of acrylate rubber/polyacetal thermoplastic vulcanizates during dynamic vulcanization process

AbstractA new type of thermoplastic vulcanizates (TPV) that is resistant to hot oil, high temperature, and aging was prepared using acrylate elastomer (ACM) and polyoxymethylene (POM) as raw materials. The phase transition process and micromorphology development of the blends with the change of dynamic vulcanization (DV) time, and to illustrate the effects of the phase transition and the degree of elastomer phase crosslinking on the macroscopic properties of TPV were investigated. It was shown that ACM crosslinking occurs continuously during 0–8 min of DV, whereas the phase inversion process occurs predominantly during 0–3 min. In contrast, the cross‐section of the blends after phase inversion is flat, The constant elongation stress under small deformation, hardness, and permanent deformation after break are reduced, and the elongation at break, nonrelaxable modulus, and aging resistance are improved. The increase in the degree of vulcanization of the ACM phase resulted in a significant increase in the modulus of the blends under large deformation, an increase in the nonrelaxable modulus and relaxable modulus, an increase in the aging resistance, and a decrease in the elongation at tear were observed.

Influence of environmentally friendly curing system on properties of railway rubber pad

AbstractImproving the aging resistance and elasticity of rubber materials can increase the service life of rubber pads and reduce railway operation costs. The purpose of this work was to improve aging resistance, decrease compression set and ratio of dynamic stiffness to static stiffness (Rd/s) of railway rubber pads by using environmentally friendly accelerators N‐t‐butyl‐2‐benzothiazole sulfenimide (TBSI) and tetrabenzylthiuram disulfide (TBzTD). The influence of the curing system on the properties of rubber pads was assessed using multiple techniques. Compared to sulfur/tetramethylthiuram disulfide (TMTD) /N‐cyclohexyl‐2‐benzothiazole sulfenamide (CZ), compression set of S/TBSI/TBZTD decreased to 29.5% from 35.7%, retention of elongation at break after hot air aging increased to 77.7% from 66.1%, and Rd/s decreased to 1.82 from 1.85. Thermogravimetry (TG) and derivative thermogravimetry (DTG) analysis indicated that maximum thermal decomposition temperature of TBSI/TBZTD was higher, which was the reason for the good aging resistance and low compression set results. Rubber processing analysis (RPA) demonstrated that the loss factor of TBSI/TBZTD was smaller. The rubber cured by TBSI/TBZTD had a higher crosslinking density and smaller loss factor, which decreased the Rd/s. This study provides a reference for preparing of environmentally friendly rubber pads with a low Rd/s and long service life.

The role of inorganic nanoparticles in photo-oxidation ageing resistance of the thermochromic asphalt binder

The aim of this research is to reveal the role of inorganic nanoparticles concerning silicon dioxide (SiO2), zinc oxide (ZnO) and titanium dioxide (TiO2) in retarding the photodegradation of thermochromic microcapsules for extending the serviceability of thermochromic cool pavement material. Thermochromic asphalt binders (TABs) with and without inorganic nanoparticles were prepared. The varying trends of physical, rheological, chemical and morphological properties with the extended ultraviolet irradiation (UV) ageing duration were compared among asphalt binders. The effects of inorganic nanoparticles on the long-term cooling effects of TABs were evaluated. The results indicate that differing from regular asphalt binder, TABs present an inversely-age hardening phenomenon due to the photodegradation of thermochromic microcapsules. ZnO shows the best efficiency in retarding the photodegradation of thermochromic microcapsules, followed by TiO2 and SiO2. The addition of ZnO or TiO2 can effectively mitigate the impacts of long-term UV ageing on the cooling effects shown by TAB.

Enhancing capillary action of acidified paper to achieve uniform deacidification and long-lasting aging resistance

Deacidification is a necessary and urgent means of protecting acidified paper documents. However, the contradiction between deacidification efficiency and uniformity in existing aqueous or organic phase deacidification methods has not been resolved yet, which is mainly attributed to the differences in capillary action of paper on solvents with different polarities. In this work, a strategy of two-phase deacidification was proposed to achieve efficient and uniform deacidification and long-lasting aging resistance. Impregnation of nano magnesium oxide organic dispersion of deacidified paper achieved efficient batch deacidification and sufficient alkali reserve. Using ultrasonic atomization of saturated calcium hydroxide aqueous solution, the penetration of alkaline substances into paper promoted uniform deacidification based on strong capillary action. Meanwhile, microstructural reinforcement of paper fibers was achieved based on the multiple interactions. This method can endow the treated paper with better thermal stability and long-lasting aging resistance. After artificial accelerated aging for 30 d, the treated paper samples still maintained the highest tensile index (18.46 Nm/g), folding endurance (8.5 times), tear index (3.95 mN·m2/g) and displayed negligible chromatic aberration (∆E = 2.46 ± 0.21). This method greatly extends the lifespan of acidified paper, which has significant value for the protection of paper documents.

Effect of SBS/SBR/component molecular compatibility on anti-aging properties for asphalt binder

To explain the effect of SBS/SBR/component molecular compatibility on anti-aging properties for asphalt binder, the micro-aging behavior of SBS/SBR composite modified asphalt binder was studied by molecular simulation, scanning electron microscopy (SEM) and infrared spectroscopy (IR). First, the micro-models of SBS molecule, SBR molecule and component molecule (asphaltene, resin, saturation, aromatic) were established, and the molecule number was determined by component test. Additionally, the characteristics of micro-model were analyzed, and the change characteristics of molecular compatibility for unaged asphalt binder and aged asphalt binder were obtained. Lastly, the rationality of molecular compatibility simulation results of SBS/SBR/component was demonstrated by SEM and IR tests, respectively. The results show that there is a close relationship between SBS/SBR/component molecular compatibility and asphalt binder anti-aging performance. The change of molecular space structure leads to the increase of asphalt binders density and the decrease of intermolecular distance. The study revealed the anti-aging properties of asphalt binder from the aspect of SBS/SBR/component molecular compatibility, which provided a theoretical foundation for the improvement of its aging resistance.

Effects of two antioxidants with different degrees of steric hindrance on the thermal‐oxidative aging properties of ABS resin

AbstractABS resin is easily oxidized and deteriorated during use or processing. The addition of antioxidants is an effective method for improving ABS oxidation. The hindered phenol antioxidant DBHMIE and the asymmetrically hindered 245 were added separately or together to ABS; the oxidation induction temperature of ABS increased by 10.6, 12.1 and 14°C, with the addition of DBHMIE, 245 and their combination, respectively, and the initial decomposition temperature T3% increased by 29.7, 16.2 and 51.3°C, respectively. The addition of these two antioxidants to ABS did not greatly affect the mechanical properties of the material, but the impact strength increased by 2.24 kJ/m2 when both antioxidants were added together. During the thermal aging test, the decomposition temperature of the ABS splines prepared with the combined antioxidants increased during the first few cycles. The impact strength of the splines prepared with the combined antioxidants was the highest, with the smallest decrease of only 5.18%. The yellow index of the spline prepared with the combined antioxidants was between those of splines prepared with the antioxidants added alone. The combination of DBHMIE and 245 induced synergistic effects, improved thermal‐oxidative aging resistance, and improved and protected the toughness of ABS resin.

Novel Lignin-Functionalized Waterborne Epoxy Composite Coatings with Excellent Anti-Aging, UV Resistance, and Interfacial Anti-Corrosion Performance.

Developing high-performance lignin anti-corrosive waterborne epoxy (WEP) coatings is conducive to the advancement of environmentally friendly coatings and the value-added utilization of lignin. In this work, a functionalized biomass waterborne epoxy composite coating is prepared using quaternized sodium lignosulfonate (QLS) as a functional nanofiller for mild carbon steel protection. The results showed that QLS has excellent dispersion and interface compatibility within WEP, and its abundant phenolic hydroxyl, sulfonate, quaternary ammonium groups, and nanoparticle structure endowed the coating with excellent corrosion inhibition and superior barrier properties. The corrosion inhibition efficiency of 100mgL-1 QLS in carbon steel immersed in a 3.5wt% NaCl solution reached 95.76%. Furthermore, the coating maintained an impedance modulus of 2.29×106Ωcm2 (|Z|0.01Hz) after being immersed for 51 days in the high-salt system. In addition, QLS imparted UV-blocking properties and thermal-oxygen aging resistance to the coating, as evidenced by a |Z|0.01Hz of 1.04×107Ωcm2 after seven days of UV aging while still maintaining a similar magnitude as before aging. The green lignin/WEP functional coatings effectively withstand the challenging outdoor environment characterized by high salt concentration and intense UV radiation, thereby demonstrating promising prospects for application in metal protection.

Effect of grain boundary segregation and oxygen vacancy annihilation on aging resistance of cobalt oxide-doped 3Y-TZP ceramics for biomedical applications

Abstract This study aims to investigate the diffusion stabilization process of nano-Co2O3 during the non-precursor transformation of 3Y-TZP. 3Y-TZP was set as the control group, and the experimental groups were 0.1–0.3 mol% nano-Co2O3-doped 3Y-TZP. The samples were prepared by the ball milling process, isostatic cool pressing, and sintering. All samples were hydrothermally treated at 134°C and 2 bar for different time periods. The resistance to low-temperature degradation of nano-Co2O3-doped 3Y-TZP was analyzed by X-ray diffraction. The microstructure of zirconia ceramic samples was determined by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and electron paramagnetic resonance studies. The addition of nano-Co2O3 into 3Y-TZP resulted in higher hydrothermal aging resistance than 3Y-TZP. The addition of 0.2 mol% nano-Co2O3 dopants resulted in the highest hydrothermal aging resistance among nano-Co2O3-doped 3Y-TZP ceramics. The grain sizes of 3Y-0.2Co are smaller than those in the control group. With the increase of cobaltous oxide doping contents, the segregation of Co3+ ions at the crystal boundary increased. The content of oxygen vacancies on the surface of the sample increased with the increase of the Co2O3 doping content. The oxygen vacancy concentrations of 3Y-0.2Co increased obviously after aging. 3Y-0.1Co, 3Y-0.3Co, and the control showed decreased oxygen vacancy concentrations after aging. Trivalent element doping of 3Y-TZP effectively improved the aging resistance of 3Y-TZP. The addition of 0.2 mol% nano-Co2O3 resulted in the highest hydrothermal aging resistance. Improved aging resistance is attributed to the nano-Co2O3 doping resulting in the 3Y-TZP grain size inhibition, grain boundary segregation of cobalt ions, and oxygen vacancy maintenance. This work is expected to provide an effective reference for the development and application of budget dental materials by regulating grain boundary engineering.

Fracture strength of 3-units fixed partial dentures fabricated with metal-ceramic, graphene doped PMMA and PMMA before and after ageing: An in-vitro study

ObjectivesTo evaluate the fracture strength and linear elongation at break of three-units fixed partial dentures (FPDs) fabricated with traditional and new materials for fixed prosthodontics before and after ageing. MethodsSixty models of three-units FPDs were fabricated and cemented onto a Co-Cr model simulating the replacement of a maxillary second premolar. The samples were randomly divided into 3 groups: metal-ceramic (MCR), graphene-doped polymethylmethacrylate (PMMA-GR) and polymethylmethacrylate (PMMA). Half of the samples were directly subjected to fracture test, while the remaining half underwent an ageing process and then a fracture loading test using an electrodynamic testing machine. Fracture load and elongation at break values were taken and statistically analysed. ResultsSignificant differences were detected between the different materials (p<0.05). All groups showed a reduction of the fracture load and elongation at break values after ageing, but not statistically significant, except for PMMA group (p = 2.012e-19) (p = 3.8e-11). ConclusionsMCR and PMMA-GR three-units FPDs showed higher fracture strength and lower elongation at break compared to PMMA. MCR and PMMA-GR had higher resistance to ageing processes compared to PMMA. Clinical significancePMMA-GR could be considered a material for long-term provisional restorations as its mechanical behaviour and ageing resistance are more like MCR than PMMA.

A brand new green coating technology for realizing the regulation of spherical propellant energy release process

To achieve the controllable release of energy of nitrocellulose-based propellants, this paper combines the cellulose-based nanocomposites aqueous coating (Surelease®-NC) with fluidized bed coating equipment to successfully prepare the coated spherical propellant for the first time. The effects of fluidized bed coating temperature, air velocity, flow speed and atomization pressure on the adhesion rate, coating integrity and coating uniformity of the coated spherical propellant were investigated, and the preparation of coated spherical propellant with homogeneous size and structural integrity was achieved for the first time. The microscopic morphology, chemical structure, water vapor adsorption behavior, combustion performance, and ageing resistance property of the coated spherical propellant were systematically investigated by, Fourier transforms infrared spectroscopy (FTIR), Micro confocal raman spectrometer, field scanning electron microscopy (SEM), dynamic vapor adsorption techniques, and closed bomb test, confirming the surface core-shell structure and the tightly bonded interfacial structure of coated spherical propellant. Meanwhile, the coated spherical propellant has good hygroscopic, excellent progressive burning and long storage stability.

Исследование стрессоустойчивости старшеклассников

The article presents the rationale for studying the stress resistance of an individual in high school age, as well as the possibility of influencing its development. The authors’ definition and understanding of personality stress resistance in the context of modern concepts and theories is given. The work itself is devoted to studying the characteristics of stress resistance in high school age using the test by T. Ivanchenko et al. “Inventory of stress symptoms”, the test “Probability of Stress Development” by J.H. Taylor adapted by T.A. Nemchin, self-assessment test of stress resistance by S. Couchen and G. Willianson, methods for determining the dominant state of L.V. Kulikova. The results of diagnostics of high school students’ stress resistance, likelihood of stress development in them, inventory of stress symptoms and dominant states, as well as correlation relations of the studied variables are presented. An analysis of the effectiveness of the program developed by the authors to increase the stress resistance of an individual in high school age, implemented in a secondary school, is pro-vided.

Multiscale characterization of the UV aging resistance and mechanism of light stabilizer-modified asphalt

Abstract To clarify the effect and mechanism of hindered amine light stabilizer (HALS) on the UV aging behavior of asphalt binder, T622-HALS was selected as the modifier for UV aging resistance of asphalt. The physicochemical properties and microstructure of T622 light stabilizer were comprehensively analyzed. The light stabilizer-modified asphalt was prepared and placed in the UV radiation chamber for UV aging treatment. Scanning electron microscope and atomic force microscope were used to analyze the microscopic morphology evolution of light stabilizer-modified asphalt induced by UV radiation. The thermal properties and functional group composition changes in light stabilizer-modified asphalt during UV aging were studied by using the thermogravimetric and infrared spectroscopy combined testing system. The decay laws of the physical and rheological performances of light stabilizer-modified asphalt were studied during UV aging process, and the effect of light stabilizer on the UV aging behavior of asphalt binder was clarified. The research results indicated that HALSs could alleviate the microcracks and roughness change on the surface of asphalt and reduce the content of functional groups such as carbonyl and sulfoxide in asphalt. Furthermore, HALS could reduce the value difference of physical and rheological properties of asphalt before and after UV aging, significantly improving the UV aging resistance of asphalt binder.

Surface modification of zinc oxide and its application in polypropylene with excellent fire performance and ultra-violet resistance

Despite the advantages of easy moulding and excellent mechanical properties, there are still some shortcomings with polypropylene (PP) such as high flammability and poor ultra-violet (UV) resistance. In this work, modified zinc oxide (mZnO) was prepared by reacting zinc oxide nanoparticles (ZnO) with polysiloxanes, and the effect of mZnO on the effectiveness of intumescent flame-retardant and on the UV aging resistance of polypropylene were investigated. By introducing 16 wt% (intumescent flame-retardant /mZnO) and 0.3 wt% maleic anhydride-grafted PP (MAH-g-PP), the limiting oxygen index increased to 32.7 %, and passed UL-94V-0 rating. In comparison to the controls, the peak heat release rate and the peak smoke release rate were 88.5 % and 80 % lower, respectively. In addition, PP samples showed improved mechanical properties, with a 5 % increase in tensile properties compared to the pure PP sample. After 100 h of UV irradiation, the surface of the samples was relatively flat and smooth, and the carbonyl index decreased from 81.1 of neat PP to 26.7. PP composites with 100 h aging treatment still had excellent flame retardancy and mechanical properties. The results showed that mZnO was effective in improving the flame retardancy, mechanical properties and light aging tolerance of PP. This study provides a novel approach to fabricate long-life flame-retardant PP composites with low additive content.

Production of polyhydroxybutyrate (PHB), a biodegradable polymer from seaweed biomass using novel bacterial isolates

Poly-(3-hydroxybutyrate) (PHB), is a partially crystalline polymer naturally synthesized by microorganisms, and the production of PHB has attracted much attention recently due to its exceptional biodegradable and biocompatible nature. By serving as a copolymer and by being a block copolymer, PHB enhances the mechanical properties of the polymer materials. The materials developed using PHB as a block copolymer are used in numerous applications such as polymer aging resistance, controlled drug delivery, cardiovascular engineering, thin film formation, etc. This study focuses on synthesizing PHB from microbial sources as cell factories. From distinct natural sources two novel bacterial isolates, Bacillus pacificus NAA2 (NAA2) and Klebsiella quasipneumonia NAA4 (NAA4) were screened based on their high PHB synthesizing abilities. To improve the PHB levels, a series of process optimization studies were conducted. The process conditions such as different carbon and nitrogen sources, concentrations, pH levels, temperatures, and incubation periods have been explored and optimized. Under optimized conditions, NAA2 produced 2.92 g/L of PHB (79 %) with glycerol and peptone as carbon and nitrogen sources respectively at pH 7.5 and 35 °C at 48 h. The other isolate, NAA4, produced 2.89 g/L of PHB (73 %) from xylose and urea as equivalent carbon and nitrogen sources respectively with the same pH and temperature after 36 h of incubation. In addition, the replacement of conventional carbohydrates (glucose and/or xylose) with seaweed hydrolysate exhibited almost equivalent levels of PHB 72.7 and 70.7 % of PHB in NAA2 and NAA4 respectively. Fourier Transform Infrared (FTIR) spectroscopy and FE-SEM analysis confirmed the production of a polymer. Though there are several studies reported with other Bacillus sp and Klebsiella sp., this is the only study that used novel strains Bacillus pacificus (NAA2) and Klebsiella quasipneumonia (NAA4) as the microbial cell factories for the effective synthesis of PHB using seaweed as a substrate. Thus, the technology for bioconversion of harmful and waste seaweed biomass into PHB with dual sustainability was developed.

Investigation of Phenolic Resin-Modified Asphalt and Its Mixtures.

This study comprehensively examines the influence of phenol-formaldehyde resin (PF) on the performance of base asphalt and its mixtures for road applications, emphasizing its innovative use in enhancing pavement quality. Optimal PF content was determined through the evaluation of standard indicators and rotational viscosity. In-depth analyses of PF-modified asphalt's high- and low-temperature rheological properties and viscoelastic behavior were conducted using dynamic shear rheometers and bending beam rheometers. Aging resistance was assessed through short-term aging and performance grade (PG) grading. Moreover, Marshall and water stability tests were performed on PF-modified asphalt mixtures. Findings indicate that the uniform dispersion of PF particles effectively inhibits asphalt flow at high temperatures, impedes oxygen penetration, and delays the transition from elasticity to viscosity. These unique properties enhance the high-temperature stability, rutting resistance, and aging resistance of PF-modified asphalt. However, under extremely low temperatures, PF's brittleness may impact asphalt flexibility. Nonetheless, the structural advantages of PF-modified asphalt, such as improved mixture density and stability, contribute to enhanced high-temperature performance, water stability, adhesion, and freeze-thaw cycle stability. This research demonstrates the feasibility and effectiveness of using PF to enhance the overall performance of base asphalt and asphalt mixtures for road construction.