Dimeric Liquid Crystalline Epoxy Resins Containing Azo Group: Mesogenic Behavior and Curing with Anhydride

2010 ◽  
Vol 123-125 ◽  
pp. 955-958
Author(s):  
De Wen Zhou ◽  
Li Yan Liang ◽  
Man Geng Lu
Keyword(s):  
Epoxy Resins ◽  
Liquid Crystalline ◽  
Cure Kinetics ◽  
X Ray Diffraction ◽  
Melting Points ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Azo Group ◽  
Kinetics Of

A series of dimeric liquid crystalline (LC) epoxy monomers containing azo groups with different length of central spacers were synthesized. The mesogenic behavior of these monomers was characterized by differential scanning calorimetry(DSC), polarized optical microscopy (POM) and wide-angle X-Ray diffraction(WAXS). Like other dimeric LC epoxy monomers, the melting points, clear points and mesophase of these compounds were influenced by the carbon numbers of the central spacers. Cure kinetics of these monomers with anhydride was studied by non-isothermal DSC at different heating rates. With the increasing of conversion, the values of activation energy show a tendency to decrease. The formation and development of LC phase during curing were also studied by POM. Finally LC thermosets with nematic phase were obtained.

scholarly journals Hydrogen desorption kinetics of MgH2 synthesized from modified waste magnesium

2014 ◽  
Vol 32 (3) ◽  
pp. 385-390
Author(s):  
Aysel Kantürk Figen ◽  
Bilge Coşkuner ◽  
Sabriye Pişkin
Keyword(s):  
Hydrogen Desorption ◽  
Nitrogen Atmosphere ◽  
Desorption Kinetics ◽  
X Ray Diffraction ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Xrf Scanning ◽  
Isothermal Kinetic ◽  
Kinetics Of

AbstractIn the present study, hydrogen desorption properties of magnesium hydride (MgH2) synthesized from modified waste magnesium chips (WMC) were investigated. MgH2 was synthesized by hydrogenation of modified waste magnesium at 320 °C for 90 min under a pressure of 6 × 106 Pa. The modified waste magnesium was prepared by mixing waste magnesium with tetrahydrofuran (THF) and NaCl additions, applying mechanical milling. Next, it was investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) techniques in order to characterize its structural properties. Hydrogen desorption properties were determined by differential scanning calorimetry (DSC) under nitrogen atmosphere at different heating rates (5, 10, and 15 °C/min). Doyle and Kissenger non-isothermal kinetic models were applied to calculate energy (Ea) values, which were found equal to 254.68 kJ/mol and 255.88 kJ/mol, respectively.

Study on Curing Mechanism of Azo-Containing Twin Liquid Crystalline Epoxy Resins with Anhydride

2013 ◽  
Vol 702 ◽  
pp. 119-122
Author(s):  
Teng Fei Shen ◽  
Fa Chao Wu ◽  
Ying Juan Sun
Keyword(s):  
Differential Scanning Calorimetry ◽  
Epoxy Resins ◽  
Liquid Crystalline ◽  
Curing Kinetics ◽  
Scanning Calorimetry ◽  
Curing Reaction ◽  
Azo Group ◽  
Liquid Crystalline Epoxy ◽  
Curing Mechanism ◽  
Kinetics Of

A series of novel azo-containing twin liquid crystalline (LC) epoxy monomers were cured with anhydrides without extra catalyst and the curing kinetics was investigated by non-isothermal differential scanning calorimetry (DSC) technique. The effect of Azo group on the Curing Kinetics of Epoxy/anhydride System was investigated and the result showed that Azo group served as a catalyst to accelerate the curing reaction. The curing mechanism was confirmed by the UV-Vis spectrum.

Cure Kinetics of Epoxy/DDS/ Epoxy-Grafted Nano-Aluminum Oxide

2011 ◽  
Vol 236-238 ◽  
pp. 2058-2062
Author(s):  
Hong Jun Zhou ◽  
Guo Qiang Yin ◽  
Miao Hong Zhuang ◽  
Jian Fang Ge ◽  
Xuan Lin
Keyword(s):  
Aluminum Oxide ◽  
Epoxy Resins ◽  
Cure Kinetics ◽  
Ozawa Method ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Autocatalytic Model ◽  
Chain Mobility ◽  
Málek Method ◽  
Kinetics Of

The cure kinetics of epoxy/epoxy-grafted nano-aluminum oxide using 4, 4'-diaminodiphenylsulphone (DDS) as the curing agent was studied by nonisothermal differential scanning calorimetry (DSC) at different heating rates. The activation energy (Ea) was determined by Flynn-Wall-Ozawa method, and kinetic model was predicted by Málek method. TheEa values of epoxy/nano-aluminum oxide/DDS systems are generally higher than those of epoxy /DDS. These imply that the addition of nano-aluminum oxide would inhibit the chain mobility of the epoxy resins. Furthermore, autocatalytic model was found to be appropriate to describe the kinetics of above mentioned reactions. The predicted curves fit well with the experimentally obtained curves.

Highly luminescent crystals of a novel linear π-conjugated thiophene–phenylene co-oligomer with a benzothiadiazole fragment

2019 ◽  
Vol 75 (6) ◽  
pp. 1076-1085 ◽  
Author(s):  
Valery A. Postnikov ◽  
Nataliya I. Sorokina ◽  
Artem A. Kulishov ◽  
Maria S. Lyasnikova ◽  
Vadim V. Grebenev ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Liquid Crystalline ◽  
Photoluminescence Spectra ◽  
X Ray Diffraction ◽  
Growth From Solutions ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Kinetics Of ◽  
Thermal Stability Of

The synthesis, growth from solutions and structure of crystals of a new linear thiophene–phenylene co-oligomer with a central benzothiadiazole fragment with a conjugated core, (TMS-2T-Ph)2-BTD, are presented. Single-crystal samples in the form of needles with a length of up to 7 mm were grown and their crystal structure was determined at 85 K and 293 K using single-crystal X-ray diffraction. The conformational differences between the crystal structures are insignificant. The parameters of melting and liquid crystalline phase transitions of (TMS-2T-Ph)2-BTD were established using differential scanning calorimetry and the thermal stability of the crystals was investigated using thermogravimetric analysis. The optical absorption and photoluminescence spectra of the solutions and crystals of (TMS-2T-Ph)2-BTD were obtained, and the kinetics of their photodegradation under the action of UV radiation were studied.

Effects of additives on the cure kinetics of vinyl ester pultrusion resins

2021 ◽  
pp. 002199832110015
Author(s):  
Alexander Vedernikov ◽  
Yaroslav Nasonov ◽  
Roman Korotkov ◽  
Sergey Gusev ◽  
Iskander Akhatov ◽  
...  
Keyword(s):  
Vinyl Ester ◽  
Mean Squared Error ◽  
Cure Kinetics ◽  
Zinc Stearate ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Different Temperatures ◽  
Predicted Values ◽  
Kinetics Of ◽  
Final Degree

Pultrusion is a highly efficient composite manufacturing process. To accurately describe pultrusion, an appropriate model of resin cure kinetics is required. In this study, we investigated cure kinetics modeling of a vinyl ester pultrusion resin (Atlac 430) in the presence of aluminum hydroxide (Al(OH)3) and zinc stearate (Zn(C18H35O2)2) as processing additives. Herein, four different resin compositions were studied: neat resin composition, composition with Al(OH)3, composition comprising Zn(C18H35O2)2, and composition containing both Al(OH)3 and Zn(C18H35O2)2. To analyze each composition, we performed differential scanning calorimetry at the heating rates of 5, 7.5, and 10 K/min. To characterize the cure kinetics of Atlac 430, 16 kinetic models were tested, and their performances were compared. The model based on the [Formula: see text]th-order autocatalytic reaction demonstrated the best results, with a 4.5% mean squared error (MSE) between the experimental and predicted data. This study proposes a method to reduce the MSE resulting from the simultaneous melting of Zn(C18H35O2)2. We were able to reduce the MSE by approximately 34%. Numerical simulations conducted at different temperatures and pulling speeds demonstrated a significant influence of resin composition on the pultrusion of a flat laminate profile. Simulation results obtained for the 600 mm long die block at different die temperatures (115, 120, 125, and 130 °C) showed that for a resin with a final degree of cure exceeding 95% at the die exit, the maximum difference between the predicted values of pulling speed for a specified set of compositions may exceed 1.7 times.

Liquid crystalline polyureas with oligo(ethylene glycol) sequences

e-Polymers ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
Shahram Mehdipour-Ataei ◽  
Leila Akbarian-Feizi
Keyword(s):  
Liquid Crystalline ◽  
Spectroscopic Method ◽  
Polymerization Reaction ◽  
X Ray Diffraction ◽  
Subsequent Reaction ◽  
Scanning Calorimetry ◽  
Polar Solvents ◽  
X Ray ◽  
H Nmr ◽  
Ft Ir

AbstractA diamine monomer containing ester, amide and ether functional groups was prepared and its polymerization reaction with different diisocyanates to give main chain poly(ester amide ether urea)s was investigated. The monomer was synthesized via reaction of terephthaloyl chloride with 4-hydroxybenzoic acid and subsequent reaction of the resulted diacid with 1,8-diamino-3,6-dioxaoctane. The polymers were characterized by FT-IR and 1H-NMR spectroscopic method and elemental analysis. The resulting polymers exhibited excellent solubility in polar solvents. Crystallinity of the resulted polymers was evaluated by wide-angle X-ray diffraction (WXRD) method, and they exhibited semi-crystalline patterns. The glass transition temperatures (Tg) of the polymers determined by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) were in the range of 88-112 °C. The temperatures for 10% weight loss (T10) from their thermogravimetric analysis (TGA) curves were found to be in the range of 297-312 °C in air. Also the prepared polyureas showed liquid crystalline character.

Synthesis and Properties of Thermotropic Liquid Crystalline Polyesters with Flexible Polymethylene Spacer

2010 ◽  
Vol 428-429 ◽  
pp. 126-131
Author(s):  
Wei Zhong Lu ◽  
Chun Wei ◽  
Qui Shan Gao
Keyword(s):  
Optical Microscopy ◽  
Liquid Crystalline ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Structure Morphology ◽  
Temperature Ranges ◽  
Ft Ir ◽  
Diffraction Peaks ◽  
Ubbelohde Viscometer

Polymethylene bis(p-hydroxybenzoates) were prepared from methyl p-hydroxybenzoate and different diols by melted transesterification reaction. Three liquid crystalline polyesters were synthesized from terephthaloyl dichloride and polymethylene bis(p-hydroxybenzoates). Its structure, morphology and properties were characterized by Ubbelohde viscometer, Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimetry (DSC), polarized optical microscopy (POM) with a hot stage, and wide-angle X-ray diffraction (WAXD). Results indicated that the intrinsic viscosities were between 0.088 and 0.210 dL/g. Optical microscopy showed that the TLCP has a highly threaded liquid crystalline texture and a high birefringent schlieren texture character of nematic phase and has wider mesophase temperature ranges for all polyesters. DSC analysis were found that the melting point (Tm), isotropic temperature (Ti) of TLCPs decreased and the temperature range of the liquid crystalline phase became wider with increased number of methylene spacers in the polyester. The WAXD results showed that TLCPs owned two strong diffraction peaks at 2θ near 19° and 23°.

Investigating the relationship between tack and degree of conversion in DGEBA-based epoxy resin cured with dicyandiamide and diuron

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ali Kuliaei ◽  
Iraj Amiri Amraei ◽  
Seyed Rasoul Mousavi
Keyword(s):  
Epoxy Resin ◽  
Reaction Order ◽  
Theoretical Data ◽  
Cure Kinetics ◽  
Diglycidyl Ether ◽  
Degree Of Conversion ◽  
Ozawa Method ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Kinetics Of

Abstract The purpose behind this research was to determine the optimum formulation and investigate the cure kinetics of a diglycidyl ether of bisphenol-A (DGEBA)-based epoxy resin cured by dicyandiamide and diuron for use in prepregs. First, all formulations were examined by the tensile test, and then, the specimens with higher mechanical properties were further investigated by viscometry and tack tests. The cure kinetics of the best formulation (based on tack test) in nonisothermal mode was investigated using differential scanning calorimetry at different heating rates. Kissinger and Ozawa method was used for determining the kinetic parameters of the curing process. The activation energy obtained by this method was 71.43 kJ/mol. The heating rate had no significant effect on the reaction order and the total reaction order was approximately constant ( m + n ≅ 2.1 $m+n\cong 2.1$ ). By comparing the experimental data and the theoretical data obtained by Kissinger and Ozawa method, a good agreement was seen between them. By increasing the degree of conversion, the viscosity decreased; as the degree of conversion increased, so did the slope of viscosity. The results of the tack test also indicated that the highest tack could be obtained with 25% progress of curing.

scholarly journals Synthesis and mesomorphic properties of calamitic malonates and cyanoacetates tethered to 4-cyanobiphenyls

2012 ◽  
Vol 8 ◽  
pp. 371-378 ◽  
Author(s):  
Katharina C Kress ◽  
Martin Kaller ◽  
Kirill V Axenov ◽  
Stefan Tussetschläger ◽  
Sabine Laschat
Keyword(s):  
Differential Scanning Calorimetry ◽  
Ambient Temperature ◽  
Liquid Crystalline ◽  
X Ray Diffraction ◽  
Cyanoacetic Acid ◽  
Scanning Calorimetry ◽  
Isotropic Liquid ◽  
X Ray ◽  
Nematic Phases ◽  
Mesomorphic Properties

4-Cyano-1,1'-biphenyl derivatives bearing ω-hydroxyalkyl substituents were reacted with methyl 3-chloro-3-oxopropionate or cyanoacetic acid, giving liquid-crystalline linear malonates and cyanoacetates. These compounds formed monotropic nematic phases at 62 °C down to ambient temperature upon cooling from the isotropic liquid. The mesomorphic properties were investigated by differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction (WAXS).

Thermotropic behavior of sodium cholesteryl carbonate

2009 ◽  
Vol 24 (1) ◽  
pp. 156-163 ◽  
Author(s):  
Rabkwan Chuealee ◽  
Timothy S. Wiedmann ◽  
Teerapol Srichana
Keyword(s):  
Phase Behavior ◽  
Chemical Structure ◽  
Liquid Crystalline ◽  
Polarized Light ◽  
Wave Number ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
X Ray Scattering ◽  
C Nmr

Sodium cholesteryl carbonate ester (SCC) was synthesized, and its phase behavior was studied. The chemical structure was assessed by solid-state infrared spectroscopy based on vibration analysis. The wave number at 1705 and 1276 cm−1 corresponds to a carbonyl carbonate and O–C–O stretching of SCC, respectively. Molecular structure of SCC was further investigated with 1H and 13C NMR spectroscopy. The chemical shift, for the carbonyl carbonate resonance appeared at 155.5 ppm. A molecular mass of SCC was at m/z of 452. Differential scanning calorimetry (DSC), video-enhanced microscopy (VEM) together with polarized light microscopy, and small-angle x-ray scattering (SAXS) were used to characterize the phase behavior as a function of temperature of SCC. Liquid crystalline phase was formed with SCC. Based on the thermal properties and x-ray diffraction, it appears that SCC forms a structure analogous to the type II monolayer structure observed with cholesterol esters.

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