scholarly journals Flexible Nanocomposites Based on Polydimethylsiloxane Matrices with DNA-Modified Graphene Filler: Curing Behavior by Differential Scanning Calorimetry

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2301 ◽  
Author(s):  
Elisa Toto ◽  
Susanna Laurenzi ◽  
Maria Gabriella Santonicola
Keyword(s):  
Differential Scanning Calorimetry ◽  
Deoxyribonucleic Acid ◽  
Isoconversional Methods ◽  
Activation Energies ◽  
Scanning Calorimetry ◽  
Curing Behavior ◽  
Model Free ◽  
Lower Viscosity ◽  
Modified Graphene

Novel silicone-based nanocomposites with varied elastic properties were prepared by blending standard polydimethylsiloxane (PDMS) with a lower viscosity component (hydroxyl-terminated PDMS) and integrating a graphene nanoplatelets (GNP) filler modified by strands of deoxyribonucleic acid (DNA). The curing behavior of these nanocomposites was studied by dynamic and isothermal differential scanning calorimetry. The activation energies of the polymerization reactions were determined using the Kissinger method and two model-free isoconversional approaches, the Ozawa–Flynn–Wall and the Kissinger–Akahira–Sunose methods. Results show that the complex trend of the curing behavior can be described using the isoconversional methods, unveiling lower activation energies for the nanocomposites with standard PDMS matrices. The role of the DNA modification of graphene on the curing behavior is also demonstrated. The curing reactions of the nanocomposites with the PDMS matrix are favored by the presence of the GNP–DNA filler. PDMS/PDMS–OH blends generate softer nanocomposites with hardness and reduced elastic modulus that can be tuned by varying the amount of the filler.

SOĞUK HADDELENMİŞ AA3105 VE AA5005 LEVHALARIN DSC ANALİZİ İLE YENİDEN KRİSTALLENME KİNETİĞİ

2021 ◽  
Vol 8 (17) ◽  
pp. 80-85
Author(s):  
Atae RAOUGUI ◽  
Ion GRECU ◽  
Volkan Murat YILMAZ ◽  
Kenan YILDIZ
Keyword(s):  
Differential Scanning Calorimetry ◽  
Aluminum Alloy ◽  
Activation Energies ◽  
Isothermal Kinetics ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Recrystallization Kinetics ◽  
Model Free ◽  
Cold Rolled ◽  
Kinetics Of

In this study, the non-isothermal recrystallization kinetics of cold rolled AA3105 and AA5005 aluminum alloy sheets obtained from ASAŞ Aluminum located in Akyazı-Sakarya was studied by using differential scanning calorimetry (DSC). The non – isothermal kinetics was performed by using Kissenger, Boswell, Ozawa and Starink methods known as model – free methods. The recrystallization temperatures on DSC graphics at different heating rates (β) were deduced and the activation energies were calculated from the slopes from Y – 1/T diagrams. Y is ln(β/T2) for Kissenger, ln(β/T) for Boswell, ln(β) for Ozawa and ln(β/T1.92) for Starink. The results showed that the activation energies of recrystallization are in the range of 194 – 206 kJ/mol for cold rolled AA5005 sheet and in the range of 235 – 257 kJ/mol for cold rolled AA3105 sheet, according to four non-isothermal kinetics model.

Crystallization kinetics mechanism investigation of sol–gel-derived NaYF4:(Yb,Er) up-converting phosphors

CrystEngComm ◽  
2017 ◽  
Vol 19 (34) ◽  
pp. 4992-5000 ◽  
Author(s):  
C. Bartha ◽  
C. E. Secu ◽  
E. Matei ◽  
M. Secu
Keyword(s):  
Differential Scanning Calorimetry ◽  
Crystallization Kinetics ◽  
Sol Gel ◽  
Model Fitting ◽  
Crystallization Mechanism ◽  
Differential Scanning Calorimetry Analysis ◽  
Scanning Calorimetry ◽  
Model Free

The crystallization mechanism of sol–gel-derived NaYF4:(Yb,Er) up-converting phosphors has been studied by differential scanning calorimetry analysis using both model-free and model fitting approaches.

scholarly journals Heat Curing Behavior of Light-cured Composite Resins Investigated by Dynamic Differential Scanning Calorimetry

1990 ◽  
Vol 9 (2) ◽  
pp. 153-162,228 ◽  
Author(s):  
Seiji BAN ◽  
Yosifumi TAKAHASHI ◽  
Hiroaki TANASE ◽  
Jiro HASEGAWA
Keyword(s):  
Differential Scanning Calorimetry ◽  
Composite Resins ◽  
Scanning Calorimetry ◽  
Curing Behavior ◽  
Heat Curing

Complementarity of Atom Probe, Small Angle Scattering and Differential Scanning Calorimetry for the Study of Precipitation in Aluminium Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 926-932 ◽  
Author(s):  
Frédéric de Geuser ◽  
Thomas Dorin ◽  
Williams Lefebvre ◽  
Baptiste Gault ◽  
Alexis Deschamps
Keyword(s):  
Differential Scanning Calorimetry ◽  
Small Angle ◽  
Atom Probe Tomography ◽  
Aluminium Alloys ◽  
Atom Probe ◽  
Small Angle Scattering ◽  
Precipitation Behavior ◽  
Scanning Calorimetry ◽  
Model Free ◽  
Angle Scattering

Two examples of precipitation studies (in Al-Li-Cu and Al-Li-Mg alloys) are shown to demonstrate the complementarity of atom probe tomography, small-angle-scattering and differential scanning calorimetry for precipitation studies. It will be used to unravel an unexpected two-step precipitation behavior of T1in Al-Li-Cu and to ascertain precipitates size in Al-Li-Mg. through a model free comparison between atom probe and SAXS.

Activation Energies of Liquid Crystalline Thermoset Containing Rigid-Rod Epoxy

2011 ◽  
Vol 378-379 ◽  
pp. 628-631 ◽  
Author(s):  
Seung Hwan Byun ◽  
Seung Hyun Cho
Keyword(s):  
Differential Scanning Calorimetry ◽  
Weight Loss ◽  
Thermogravimetric Analysis ◽  
Liquid Crystalline ◽  
Activation Energies ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
Rigid Rod ◽  
Liquid Crystalline Thermoset ◽  
Weight Loss Process

4,4’-Diglycidyloxy-α-methylstilbene (DOMS) was synthesized and characterized with cross-polarized optical microscopy (POM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Activation energies for decomposition (Ed) by TGA were determined as a function of conversion by weight loss process.

Glass transformation in vitreous As2Se3 studied by conventional and temperature-modulated differential scanning calorimetry

2001 ◽  
Vol 16 (8) ◽  
pp. 2399-2407 ◽  
Author(s):  
S. O. Kasap ◽  
D. Tonchev
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Relaxation Time ◽  
Glass Transition ◽  
Activation Energies ◽  
Temperature Modulation ◽  
Glass Transition Region ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Apparent Activation Energies

We have studied the glass transition behavior of vitreous As2Se3 by carrying out temperature-modulated differential scanning calorimetry (TMDSC) and conventional differential scanning calorimetry (DSC) experiments to measure the glass transition temperature Tg. In TMDSC experiments we have examined the reversing heat flow (RHF), that is the complex heat capacity CP in the glass transition region as the glass is cooled from a temperature above the glass transition temperature (from a liquidlike state) and also as the glass is heated starting from room temperature (from a solidlike state). The RHF, or CP versus T, in TMDSC changes sigmoidally through the glass transition region without evincing an enthalpic peak which is one of its distinct advantages for studying the glass transformations. The Tg measurements by TMDSC were unaffected by the amplitude of the temperature modulation. We have determined apparent activation energies by using Tg-shift methods based on the Tg-shift with the frequency (ω) of temperature modulation in the TMDSC mode and Tg-shift with heating and cooling rates, r and q, respectively, in the DSC mode. It is shown that the apparent activation energies ∆h* obtained from ln ω versus 1/Tg and ln q versus 1/Tg plots are not the same, but nonetheless, they are approximately the same as the apparent activation energy ∆hn of the viscosity over the same temperature range where the empirical Vogel expression of Henderson and Ast, η = 12.9 exp[2940/(T - 335)], was used for the viscosity. The latter observation is in agreement with the assertion that the structural relaxation time Ʈ is proportional to the viscosity h. The apparent activation energy ∆hr obtained from the ln r versus 1/Tg plot during heating DSC scans is lower than ∆h* observed during cooling scans. The results are discussed in terms of a phenomenological Narayanaswamy type relaxation time. It was observed that Tg obtained from TMDSC cooling experiments did not depend on the underlying cooling rate for q ≤ 1 °C min-1; and for temperature amplitudes 0.5–5 °C. The transition due to the temperature modulation was well separated from the transition due to the underlying cooling rate. Further, the apparent activation energies obtained from ln ω versus 1/Tg during cooling and heating scans for q and r ≤ 1 °C min−1 are approximately the same as expected from Hutchison's calculations using a single relaxation time model of TMDSC experiments.

Curing behavior of a novolac-type phenolic resin analyzed by differential scanning calorimetry

2003 ◽  
Vol 90 (6) ◽  
pp. 1678-1682 ◽  
Author(s):  
Eliton S. De Medeiros ◽  
Jos� A. M. Agnelli ◽  
Kuruvilla Joseph ◽  
Laura H. De Carvalho ◽  
Luiz H. C. Mattoso
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phenolic Resin ◽  
Scanning Calorimetry ◽  
Curing Behavior
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