Effect of cerium salt-activated ceria on the UV degradation resistance of waterborne epoxy coatings

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Effect of Polypyrrole on the Electrical, Dielectric and Mechanical Properties of Waterborne Epoxy Coatings

In this context, conducting composite based on waterborne epoxy system and polypyrrole (PPy) was investigated. The polypyrrole was synthesized by chemical oxidation polymerization. Its morphology and chemical structure were confirmed by using field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). Then, PPy was well-dispersed in the epoxy coating and had a good compatibility with the matrix. The effects of PPy on dielectric, electrical and mechanical properties of epoxy/PPy composites was examined. The dielectric constant and electrical conductivity of the coatings increased with addition of PPy fillers. Over to 15 wt. % of PPy loading, the volume resistivity of samples slightly decreased from 6.7 × 1010 to 1.5 × 1010 Ω cm. In contrast, the presence of PPy diminished both impact and abrasion resistance of the epoxy/PPy composites, down to 160 kg cm and 10.2 L/mil, respectively, but they stayed acceptable for the coatings. The results reveal that the epoxy containing polypyrrole is suitable for various electrical and dielectric applications

DOES DEMOGRAPHICS MATTER IN LIFELONG LEARNING? A RESEARCH CONTEXT OF VIETNAM

Objective: Lifelong learning (LLL) has lately attracted significant attention from the society in general, universities and corporations in particular. For the case of Vietnam, the Government has pledged to create a Lifelong Learning Society. A number of initiatives have been launched to help achieve this goal, including the Southeast Asian Ministers of Education Organization Centre for Lifelong Learning (SEAMEO CELLL) and "Book Day", a day dedicated to encouraging reading and raising awareness of its importance in the development of knowledge and skills. Lifelong learning (LLL) programs are also being adopted at libraries, museums, cultural centers, and clubs in Vietnam. In addition to the effort done by the Vietnamese government, a number of non-governmental, non-profit organizations and educational institutions have started to take action to encourage literacy and lifelong learning. It can be said that education and educational reforms are always the top concern of each country. This study is to investigate about lifelong learning of community with 4 aspects: (1) Learning Competencies; (2) Learning Contexts; (3) Learning Contents and (4) Learning Goals as well as examining the differences in the opinion about lifelong learning between categorical variables. The second purpose of the study is to examine the relationship between an individual's perspective on lifelong learning and their actual learning capacity, as well as learning motive. Methods: The paper deploys primary data collecting from 270 people in different sectors and different occupations. Standard statistical techniques such as mean analysis, OLS multivariable analysis are used to find the answer for proposed hypotheses. Results: Using a sample of 270 respondents varying in age, gender, and employment status, the authors found that there are differences on the attitudes towards lifelong learning, the motivations and skills needed for this “journey”. Conclusion: From the findings, researchers proposed recommendations to promoting and fostering lifelong learning of community with the case of Vietnam

Elements affecting primary school teachers' digital competency in Vietnam’s northern mountainous areas

This study aims to identify the elements that contribute to the digital competencies of primary school teachers working in the mountainous region of Northern Vietnam and assess the significance of these factors. The research sample consisted of 260 primary school teachers from this region. Exploratory factor analysis (EFA) and multivariate regression methods are used. The results of this research indicate that seven characteristics have a substantial impact on the digital abilities of teachers: ability to incorporate digital technology into teaching,  conditions for digital transformation in teaching and learning activities are found to be influential, ability to create digital resources is highlighted as an important factor,  ability to select teaching content with opportunities for technology usage,  professional development needs of teachers,  school policy  and ability to select digital resources. These results offer education administrators a comprehensive understanding of the factors influencing primary teachers' digital competencies and  enable them to implement strategic changes and prioritize each element. Moreover, this study provides a valuable reference for future researchers seeking to explore new research directions in this field and analyze the correlation between factors to propose solutions to develop digital competencies of primary school teachers suitable to specific contexts and conditions

Perceived Audit Quality, Earnings Management and Cost of Debt Capital: Evidence from the Energy Listed Firms on Vietnam's Stock Market

This study examines the impact of perceived audit quality and accrual-based earnings management on cost of debt capital of the energy listed firms on Vietnam's stock market. Our data set includes 29 energy companies on Vietnam stock markets (HNX and HOSE) in the period from 2010 to 2016. We used FEM and REM estimator to test our hypotheses. The results confirm that there is no significant statistical association between accrual-based earnings management and cost of debt. There is a negative association between audit quality, firm size, return on assets and cost of debt while firm leverage and the tangible asset has a positive association. Moreover, global financial crisis has no statistically significant influence on the cost of debt capital. The research results have implications for regulators and investors about the stability of the economy in emerging markets. Keywords: cost of debt, earnings management, audit quality, energy enterprises, Vietnam. JEL Classifications: M42; G32 DOI: https://doi.org/10.32479/ijeep.699

Using fly ash treated by NaOH and H2SO4 solutions for Hg2+ and Cd2+ ion adsorption.

This paper presents the results of adsorption ability of heavy metal ions (Hg2+ and Cd2+) by fly ash (FA) before and after treatment using NaOH and H2SO4 solutions.  Original- and treated FA were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscope (SEM). Specific surface area of FA before and after treatment was calculated by Brunauer – Emmett – Teller (BET) isotherm equation. The obtained results indicated that the morphology and specific surface area of FA changed clearly after treatment by acid or alkaline solutions. Adsorption capacity the Hg2+ and Cd2+ ion by FA was determined from data of UV-Vis spectra. After treatment, the adsorption capacity of ions by FA increased remarkably in comparison with non-treated FA. The FA treated by NaOH solution has the adsorption capacity higher than FA treated by H2SO4 solution. The maximum adsorption capacity of the FA treated by NaOH solution for Cd2+ and Hg2+ ions at room temperature is 28.97 and 14.60 mg/g, respectively. The equilibrium adsorption data were described by the Langmuir and Freundlich isotherm models. The results showed that equilibrium data were fitted well to the Langmuir isotherm. Keywords. Fly ash, treatment, adsorption capacity, heavy metal, Langmuir isotherm

PREPARATION AND FTIR STUDIES OF PMMA/PVC POLYMER BLENDS, PVC-g-PMMA GRAFT COPOLYMERS AND EVALUATING GRAFT CONTENT

This study presents the qualitative and quantitative analyses of Fourier Transform Infrared (FTIR) spectra of poly(methyl methacrylate)/poly(vinyl chloride) blends (PMMA/PVC), as well as PVC-g-PMMA graft copolymers. Graft copolymerizations of methyl mathacrylate (MMA) onto PVC macromolecules were carried out mixture of cyclohexanone/N,N-dimethylformamide as solvents, dibenzoyl peroxide as initiator and nitrogen medium. FTIR spectra of PMMA/PVC blends showed that there were molecular interactions between C=O groups of PMMA and C-Cl groups of PVC. Assignments of infrared absorption bands for specific groups of PMMA/PVC blends have been contributed. Using regression method, linear calibration curve between PMMA mole content and peak areas of C=O groups in FTIR spectra of the blends has been found when C=O peak areas were multiplied by an appropriate factor. PMMA grafted content and total PMMA formed content in PVC-g-PMMA graft copolymers have been evaluated. The results showed that grafted PMMA content was increased since PVC was initiatly dechlorinated by NaOH solution. The grafted PMMA content and total formed PMMA content were 5.05 wt.% and 11.25 wt.% respectively when MMA monomers were grafted onto neat PVC and modified PVC molecules

HIGH PROTECTION PERFORMANCE OF COATING SYSTEMS BASED ON ZINC RICH PRIMER AND FLUOROPOLYMER COATING

Coating systems based on zinc rich primer and fluoropolymer top coat were exposed for 8 years at different atmospheric stations in Vietnam: Hanoi, Ha Long and Nha Trang. For comparison the coating system with zinc rich primer and polyurethane topcoat was also tested. The degradations of coating systems were evaluated by gloss measurement and electrochemical impedance spectroscopy. The obtained results show that coating systems with zinc rich primer and top coatings based on fluoropolymer  and polyurethane topcoats show very high weather resistance and corrosion protection performance, but the systems with fluoropolymer are better than coating system with polyurethane topcoat

Chemical composition and antimicrobial activity of the essential oil from twigs and leaves of Magnolia macclurei (Dandy) Figlar from Ha Giang Province, Vietnam

The chemical composition of the essential oil obtained by hydrodistillation of the twigs and leaves of Magnolia macclurei collected in Hoang Su Phi, Ha Giang Province, Vietnam was analyzed using GC/MS. A total of 38 compounds were detected in essential oil, accounting for 94.49% of the oil, in which 37 compounds were identified accounting for 93.33%. cis-β-Elemene (14,30%), bicyclogermacrene (18,57%), and 10-epi-ᵧ-eudesmol (16,86%) were the main components of essential oil. The minor components present with rather high amount were: Germacrene D (2,12%), guaiol (8,52%), hinesol (2,34%), valerianol (6,76%), and bulnesol (2,93%). Antibiotic activity of the essential oil sample was tested against a Gram positive bacteria Staphylococcus aureus, a Gram negative bacteria Escherichia coli, and a yeast Candida albicans using an agar disk diffusion method. All three microorganisms tested are resistant to the oil from twigs and leaves of M. macclurei. That is exhibited through the inhibitory zone diameters ranging from 4 to 12 mm

ADSORPTION OF MERCURIC ION FROM AQUEOUS SOLUTIONS USING MODIFIED FLY ASH

In this study, fly ash was treated with NaOH solution (FAN) before modifying with (3-mercaptopropyl) triethoxysilane - MPTMS (FAMPS). By using FTIR, FESEM, XRD, EDX, and BET techniques, the change in structure, composition and morphology of FAN and FAMPS was evaluated. The FTIR spectra of FAN and FAMPS showed that there is no chemical reaction between the MPTMS and FAN. After modification, the FAMPS has a rough surface with composition difference from the FAN. Mercuric ion adsorption behavior as well as adsorptionisotherm models (Langmuir and Freundlich) of the FAN and FAMPS were also investigated and discussed. Thanks to FAN modification, the mercuric ion removal percent of the FAMPS was higher than that of the FAN. Owing to the adsorption data, Freundlich isotherm modelwas fitted for the mercuric ion adsorption process