Study of the Behavior of Some Polyheteroarylenes Treated with Supercritical Carbon Dioxide

2009 ◽  
Vol 21 (5) ◽  
pp. 562-578 ◽  
Author(s):  
Inga A. Ronova ◽  
Lev N. Nikitin ◽  
Ekaterina A. Sokolova ◽  
Ion Sava ◽  
Maria Bruma
Keyword(s):  
Carbon Dioxide ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Supercritical Carbon Dioxide ◽  
Hydrogen Bonds ◽  
Polymer Matrix ◽  
Residual Solvent ◽  
Before And After ◽  
Supercritical Carbon

Various polyheteroarylenes have been studied with regard to their physical properties before and after treatment with supercritical carbon dioxide (sc-CO 2). Thus, the study of dependence of glass transition temperature and free volume of polymer matrix on the conformational rigidity showed that the process of swelling in sc-CO2 is influenced by the residual solvent and by the formation of possible hydrogen bonds between CO2 and amide groups in the polymer chain.

Study of the effect of the reinforcement direction on the identification of relaxation transitions of moisture-saturated carbon fiber VKU-25

2021 ◽  
Vol 87 (9) ◽  
pp. 38-43
Author(s):  
O. G. Ospennikova ◽  
P. S. Marakhovsky ◽  
N. N. Vorobyov ◽  
E. V. Nikolaev ◽  
A. I. Gulyaev ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Carbon Fiber ◽  
Polymer Matrix ◽  
Structural Parameters ◽  
Polymer Materials ◽  
Thermal Coefficient ◽  
Initial State ◽  
Relaxation Transitions

Thermodilatometric methods of analysis are used to study the structural parameters of polymer materials, however, when studying moisture-saturated compositions certain difficulties arise in their identification. The results of thermophysical tests of VKU-25 carbon fiber samples in the initial state and after moisture saturation are presented. It is shown that heat treatment of materials affects the recorded values of the glass transition temperature of the epoxy matrix. When the samples are exposed in water or above the water surface, the sorbate penetrates into the polymer at the same rate, which is confirmed by almost identical values of water absorption at the same exposure time. The estimates of the thermal coefficient of linear expansion (TCLE) of the samples in the range of 20 - 250°C are given. Moreover, it is shown that the glass transition temperature of the plasticized polymer matrix depends on the direction of fiber reinforcement. In the case of moisture-saturated carbon fiber (CF)heated to 210°C, the formation of main cracks occurs mainly at the fiber-matrix interface. The glass transition temperature (GTT) of the material in the dry state (176 - 177°C), appeared almost independent on the heating rate, whereas for water-saturated samples, GTT changes significantly and can be described by a polynomial of the 2nd order. After exposure of the carbon fiber under conditions of high temperature and humidity, two relaxation transitions corresponding to the systems occur in the polymer matrix: epoxidian oligomer— amine hardener and polyfunctional resin— amine hardener. The glass transition temperature is 132 and 159°C in the first and in the second, respectively. The results obtained can be used in the development of new polymer composite materials.

scholarly journals Effects of Residual Solvent on Glass Transition Temperature of Poly(methyl methacrylate)

2018 ◽  
Vol 46 (3) ◽  
pp. 117-121 ◽  
Author(s):  
Asae Ito ◽  
Viknasvarri Ayerdurai ◽  
Azusa Miyagawa ◽  
Akikazu Matsumoto ◽  
Haruki Okada ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Methyl Methacrylate ◽  
Residual Solvent ◽  
Poly Methyl Methacrylate

Macroscale Mechanical and Microscale Structural Changes in Chinese Wufeng Shale With Supercritical Carbon Dioxide Fracturing

SPE Journal ◽  
2017 ◽  
Vol 23 (03) ◽  
pp. 691-703 ◽  
Author(s):  
Qing-You Liu ◽  
Lei Tao ◽  
Hai-Yan Zhu ◽  
Zheng-Dong Lei ◽  
Shu Jiang ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Shale Gas ◽  
Structural Changes ◽  
Triaxial Tests ◽  
Upper Ordovician ◽  
Sem Images ◽  
Bedding Planes ◽  
Before And After ◽  
Supercritical Carbon

Summary Waterless fracturing for shale-gas exploitation using supercritical carbon dioxide (scCO2) is both effective and environmentally friendly, and has become an extensive research topic. Previous researchers have focused on the chemical and physical properties and microstructure of sandstone, carbonate, and shale caprock, rather than on the properties of shale-gas formations. The macroscale mechanical properties and microscale fracture characteristics of Wufeng Shale exposed to scCO2 (at greater than 31.8°C and 7.29 MPa) are still not well-understood. To study the macroscale and microscale changes of shale subjected to scCO2, we obtained Chinese Wufeng Shale crops (Upper Ordovician Formation) from Yibin, Sichuan Basin, China. The shale samples were divided into two groups. The first group was exposed to scCO2, and the second group was exposed to nitrogen (N2). Scanning-electron-microscope (SEM) and X-ray-diffraction (XRD) images were taken to study the original microstructure and mineral content of the shale. To study the macroscale mechanical changes of Wufeng Shale immersed in scCO2 or N2 for 10 hours, triaxial tests with controlled coring angles were conducted. SEM and XRD images were taken after the triaxial tests. In the SEM images, tight bedding planes and undamaged minerals (with sharp edges and smooth surfaces) were found in N2-treated samples both before and after testing, indicating that exposure to N2 did not affect the microstructures. However, the SEM images for the microstructure scCO2-treated samples before and after testing were quite different. The bedding planes were damaged, which left some connected microfractures and corrosion holes, and some mineral types were broken into small particles and left with uneven mineral surfaces. This shows that scCO2 can change rock microstructures and make some minerals (e.g., calcite) fracture more easily. The complex microscale fractures and the decrease in strength for scCO2-treated shale aid the seepage and gathering of gas, enhancing shale-gas recovery. Knowledge of the multiscale physical and chemical changes of shale exposed to scCO2 is not only essential for scCO2 fracturing, but it is also important for scCO2 jets used to break rock and for the geological storage of CO2.

Effects of Complexation on the Glass Transition Temperature of Polymers

1990 ◽  
Vol 215 ◽  
Author(s):  
Michael F. Roberts ◽  
Samson A. Jenekhe
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Hydrogen Bonds ◽  
Intermolecular Interactions ◽  
Lewis Acid ◽  
Dominant Effect ◽  
Intermolecular Hydrogen Bonds ◽  
Aromatic Polyamides ◽  
Rigid Chain

AbstractThe effects of Lewis acid complexation on the glass transition temperature (Tg) of several polymers with strong intermolecular interactions was investigated. The decrease in the Tg due to GaCl3 complexation of aliphatic and aromatic polyamides was 40–600° C and 148° C, respectively, and was shown to originate from scission of the intermolecular hydrogen bonds. The reduction in the Tg due to GaCl3 complexation of rigid–chain polymers was greater that 325° C and can be explained by the mitigation of the otherwise strong van der Waals forces in the pristine polymers. Thus, the dominant effect of intermolecular interactions on the Tg of several polymers has been probed by Lewis acid complexation.

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