The Hydrophily of Some Lacquers for Electrical Use

2020 ◽  
Vol 57 (1) ◽  
pp. 122-132
Author(s):  
Adriana-Mariana Bors ◽  
Alina-Ruxandra Caramitu ◽  
Dorian Marin ◽  
Iosif Lingvay
Keyword(s):  
Thermal Analysis ◽  
Dielectric Loss ◽  
Water Uptake ◽  
Structural Changes ◽  
Volume Resistivity ◽  
Chemical Processes ◽  
Polar Groups ◽  
Mass Losses ◽  
Different Types ◽  
Maximum Water

Through gravimetric determinations, volume resistivity, dielectric spectroscopy, and comparative thermal analysis (TG, DTA and DTG), the interactions between the distilled water and three different types of alkyd-epoxy-melamine, epoxy and polyurethane lacquers were studied. From the experimental determinations it was found that after 700 h of immersion in water at 20 � 2�C the alkyd-epoxy-melamine based lacquer has a maximum water uptake, respectively 1.76%, followed by the epoxy lacquer 1.4% and polyurethane 0.93%. The thermal analysis sugests that because the water retained by the investigated polymers does not change the TG diagrams in the temperature range up to 150 �C, which suggests that the weight increase of the samples during the immersion could be due to some chemical processes between the water and polymer by which the chemistry structure of the polymer changes. Through electrical measurementes one can observe that after the immersion in water (over 700 hours), dielectric loss increases and the volume resistivity (measured in DC) of the investigated lakes decreases, which is explained by the increasing of polar groups (-OH) in the polymer structure. A comparative analysis of the experimental data reveals that in electrical applications the lacquer LS (polyurethane) is superior to the lacquers L-528 (alkyd-epoxy-melamine) and LG (epoxy), because it has no mass losses (structural changes) up to 280�C it has a volume resistivity of about 21 % higher than L-G, and about 300 % higher than L-528, and has water uptake and dielectric loss substantially lower comparing to L-528 and L-G.

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

2018 ◽  
Vol 69 (5) ◽  
pp. 1139-1144
Author(s):  
Iosif Lingvay ◽  
Adriana Mariana Bors ◽  
Livia Carmen Ungureanu ◽  
Valerica Stanoi ◽  
Traian Rus
Keyword(s):  
Structural Changes ◽  
Oxidation Processes ◽  
High Oleic ◽  
Painting Materials ◽  
Insulating Paper ◽  
Different Types ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Natural Ester

For the purpose of using three different types of painting materials for the inner protection of the transformer vats, their behavior was studied under actual conditions of operation in the transformer (thermal stress in electro-insulating fluid based on the natural ester in contact with copper for electro-technical use and electro-insulating paper). By comparing determination of the content in furans products (HPLC technique) and gases formed (by gas-chromatography) in the electro-insulating fluid (natural ester with high oleic content) thermally aged at 130 �C to 1000 hours in closed glass vessels, it have been found that the presence the investigated painting materials lead to a change in the mechanism and kinetics of the thermo-oxidation processes. These changes are supported by oxygen dissolved in oil, what leads to decrease both to gases formation CO2, CO, H2, CH4, C2H4 and C2H6) and furans products (5-HMF, 2-FOL, 2 -FAL and 2-ACF). The painting materials investigated during the heat treatment applied did not suffer any remarkable structural changes affecting their functionality in the electro-insulating fluid based on vegetable esters.

Lessons Not Learned: Why is There Still a Crisis-Level Shortage of Accounting Ph.D.s?

2014 ◽  
Vol 28 (2) ◽  
pp. 313-330 ◽  
Author(s):  
R. David Plumlee ◽  
Philip M. J. Reckers
Keyword(s):  
Student Perceptions ◽  
Structural Changes ◽  
Ad Hoc ◽  
Doctoral Programs ◽  
Cumulative Impact ◽  
Program Administrators ◽  
Accounting Faculty ◽  
Present Information ◽  
Different Types

SYNOPSIS: In 2005, an ad hoc committee appointed by the American Accounting Association (AAA) documented a crisis-level shortage of accounting Ph.D.s and recommended significant structural changes to doctoral programs (Kachelmeier, Madeo, Plumlee, Pratt, and Krull 2005). However, subsequent studies show that the shortage continues and the cumulative costs grow (e.g., Fogarty and Holder 2012; Brink, Glasscock, and Wier 2012). The Association to Advance Collegiate Schools of Business (AACSB) recently called for renewed attention to the problem (AACSB 2013b). We contribute to the literature by providing updated information regarding responses by doctoral programs and, from the eyes of potential candidates, of continuing impediments to solving the doctoral shortage. In this paper, we present information gathered through surveys of program administrators and master's and Accounting Doctoral Scholars Program (ADS) students. We explore (1) the cumulative impact of the Ph.D. shortage as of 2013, including its impact on accounting faculty composition, across different types of institutions, (2) negative student perceptions of Ph.D. programs and academic accounting careers, which discourage applicants from pursuing Ph.D. programs, and (3) impediments facing institutions in expanding doctoral programs.

Enhanced thermal stability and lifetime of epoxy nanocomposites using covalently functionalized clay: experimental and modelling

2015 ◽  
Vol 39 (3) ◽  
pp. 2269-2278 ◽  
Author(s):  
Omid Zabihi ◽  
Hamid Khayyam ◽  
Bronwyn L. Fox ◽  
Minoo Naebe
Keyword(s):  
Thermal Stability ◽  
Thermal Degradation ◽  
Structural Changes ◽  
Epoxy Nanocomposites ◽  
Degradation Model ◽  
Different Types

Relationship between thermal degradation model of epoxy nanocomposites containing different types of modified nanoclay and their structural changes is explained.

Thermal analysis of the water uptake by hydrocolloids

1998 ◽  
Vol 322 (2) ◽  
pp. 153-165 ◽  
Author(s):  
Gautam Bhaskar ◽  
James L Ford ◽  
Derek A Hollingsbee
Keyword(s):  
Thermal Analysis ◽  
Water Uptake

THERMAL INVESTIGATION OF SiO2-Bi2O3 HEAVY METAL GLASSES

2005 ◽  
Vol 19 (20) ◽  
pp. 3293-3299 ◽  
Author(s):  
V. SIMON ◽  
M. TODEA ◽  
S. SIMON
Keyword(s):  
Thermal Analysis ◽  
Heavy Metal ◽  
Differential Thermal Analysis ◽  
Silicon Dioxide ◽  
Melting Temperature ◽  
Structural Relaxation ◽  
Structural Changes ◽  
Glass Stability ◽  
Thermal Investigation ◽  
Metal Glasses

Structural changes induced by temperature rising in binary silico-bismuthate glasses are investigated by differential thermal analysis. Several exothermic peaks are recorded for all samples. Progressive substitution of Bi 2 O 3 by SiO 2 contributes to the structural relaxation of vitreous network and leads to diminishing of the melting temperature, even as SiO 2 content reaches 40 mol%. Glass stability is enhanced by addition of silicon dioxide.

In Situ Study of The Exposure of Polycarbonate to an Argon Plasma

1995 ◽  
Vol 385 ◽  
Author(s):  
S. Vallon ◽  
B. Drevillon ◽  
F. Poncin-Epaillard ◽  
J. C. Rostaing
Keyword(s):  
Structural Changes ◽  
Argon Plasma ◽  
Silica Layer ◽  
Molecular Weights ◽  
In Situ Study ◽  
Polar Groups ◽  
Unit Scale ◽  
Two Populations ◽  
Polymer Unit

ABSTRACTThe exposure of polycarbonate to an argon plasma is studied using in situ ellipsometry from the UV to the IR, nuclear magnetic resonance and light scattering measurements. An increase in the refractive index and the existence of two populations of different molecular weights show that structural changes occur in the polymer. They are correlated with modifications at the polymer unit scale, such as formation of new polar groups and decrease in dimethyl groups. Two simultaneous reaction mechanisms must be considered to account for these changes. The adhesion of a silica layer on treated polycarbonate is then discussed.

Thermophysical Properties of Cement Based Composites with Addition of Plastic Fibers and Horse Manure

2018 ◽  
Vol 776 ◽  
pp. 92-97
Author(s):  
Gabriela Pavlendová ◽  
Peter Šín ◽  
Jozefa Lukovičová ◽  
Michal Kopčok
Keyword(s):  
Water Uptake ◽  
Thermophysical Properties ◽  
Structural Changes ◽  
Natural Fiber ◽  
Horse Manure ◽  
The Difference

Effect of different amount of plastic fiber and horse manure addition on thermophysical properties of cement based composite is studied. 1-D process of water uptake, and porosity measurement were carried out to understand the structural changes. Horse manure has high microfiber content, so that the difference between plastic and natural fiber was compared.

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