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Solid Polymer Electrolyte Membranes
Published in Asit Baran Samui, Smart Polymers, 2022
Swati S. Rao, Manoranjan Patri
Thermal stability of the membranes is determined through a thermogravimetric analyzer. Typically, the membranes are dried till constant weight before the test. They are then subjected to heating from ambient temperature to 800°C in an air/nitrogen atmosphere. The initial decomposition temperature is measured from the TGA plot. It was obtained from the first point of inflection in the primary thermogram. This gives an approximate estimate of the degradation temperature of the membrane since the temperature may differ under actual fuel cell conditions due to the influence of other electrochemical and physical factors. Another important parameter that is taken into consideration while designing membrane materials is the glass transition temperature. This is important in terms of the procedure used for making the membrane electrode assembly, wherein the membrane is usually hot-pressed along with the electrodes. The thermal stability, as well as the mechanical stability, is crucial under these circumstances to achieve defect-free MEAs. The values of the glass transition temperature are recorded from the DSC thermograms or in some cases from the plot obtained during dynamic mechanical analysis.
Hybrid Natural Fibers Reinforced Polymer Composite: Thermal Analysis
Published in Sajith Thottathil, Sabu Thomas, Nandakumar Kalarikkal, Didier Rouxel, Advanced Polymeric Materials for Sustainability and Innovations, 2018
The damping or Tan δ of the polymer materials is the ratio of loss modulus and storage modulus. It is related to the degree of molecular mobility in polymer material.26 Temperature corresponding to the Tan δ peak represents the glass transition temperature of the composites. The glass transition temperature is the temperature range where the state of polymer materials changes from glassy (hard, rigid) to rubbery (flexible, yielding). The effect of damping parameter on epoxy and hybrid composites as a function of temperature is shown in Figure 7.3. The maximum value of Tan δ (0.617) for epoxy shows better damping properties as compared to all the other composites. The hybrid composite J50S50 shows lower value (0.278) of Tan δ which shows good load bearing capacity due to strong adhesion between fibers and matrix. The value of Tg obtained from the curve for epoxy and composites are given in Table 7.3.
1 Properties of Electronic Packaging Materials
Published in Mitel G. Pecht, Rakesh Agarwal, Patrick McCluskey, Terrance Dishongh, Sirus Javadpour, Rahul Mahajan, Electronic Packaging: Materials and Their Properties, 2017
Mitel G. Pecht, Rakesh Agarwal, Patrick McCluskey, Terrance Dishongh, Sirus Javadpour, Rahul Mahajan
Glass transition temperature, Tg. The glass transition temperature is a material property of polymers that is generally not exhibited by metals or ceramics. The glass transition temperature is the temperature at which a material changes from a hard, brittle, “glass-like” form to a softer, rubberlike consistency. The change in state occurs over a range of temperature for amorphous polymers. Crystalline polymers such as polytetrafluroethelene (PTFE) exhibit a unique melting point rather than passing through stages of decreasing viscosity with increased temperature. Typical TgS for common resin materials are listed in Table 5. The test method for glass transition temperature is covered in ASTM E1363.
Imidazole and benzoimidazole derived new ionic liquid crystal compounds: synthesis, characterisation, mesomorphic properties and DFT computations
Published in Liquid Crystals, 2021
AbdulKarim-Talaq Mohammad, Omar S. Khalefa, H. T. Srinivasa, Wissam Ahmed Ameen
The differential scanning calorimetry (DSC) has been used to identify the transition temperature by heating and cooling scans, with their corresponding enthalpies. The polarising optical microscopy (POM) has been used to determine the mesophases type by analysing the mesophase textures. Table 1 is dedicated to provide summary regarding the phase transitions and their associated enthalpy values of compounds 5a-i, 6a-i, 7a-i and 8a-i.
Fabrication of a novel PVDF based silica coated multi-walled carbon nanotube embedded membrane with improved filtration performance
Published in Chemical Engineering Communications, 2022
Elif Demirel, Sakhavat Dadashov
Viscoelastic behavior of fabricated membranes was measured with respect to the temperature using dynamic mechanical analysis and results were interpreted in terms of storage modulus, loss modulus and tan delta values. As shown in Figure 16(a), three regions were captured representing different viscoelastic behaviors of membranes. The first region corresponds to the glassy region, in which the modulus values are high, and the segmental motion is restricted; the second region is the transition region, in which storage modulus decreases gradually with increased temperature and the third region is as known as plastic region, in which the modulus values initially decreases sharply and then becomes steady and consequently the membrane exhibits fluid like properties (Komalan et al. 2007). The storage moduli of all fabricated membranes reduced with increasing temperature as a result of the polymeric molecular segmental agitation ability. The vibration of molecules at low temperature results in higher storage modulus; whereas with increasing temperature an enhanced molecular segmental agitation causes the free volume within the matrix leading to a decline in storage modulus (Mathur and Arya 2018). The lowest storage modulus value was observed for the pristine membrane, and it increased sharply with incorporation of SiO2-CNT nanoparticles into the membrane matrix. Storage modulus can be regarded as a measure of material stiffness and it was reported in the literature that silica provided stiffness and strength due to the strong interfacial interactions between PVDF chains and nanoparticles (Saha et al. 1999; Young and Mauritz 2001). Glass transition temperature of a material is defined as the temperature at which the material transforms from glassy to a rubbery state or undergoes a softening process and can be obtained from either tan delta or loss modulus data. In the tan delta versus temperature graph, the temperature corresponding to the maximum tan delta value is the glass transition temperature (Komalan et al. 2007; Saha et al. 1999; Sgreccia et al. 2010; Zhu et al. 2019). As can be seen in Figure 16(c), the glass transition temperature of pristine PVDF membrane was −44.1 °C, while those of M1 and M2 membranes were −35.7 and −33.8 °C, respectively (Zhang et al. 2020; Zhu et al. 2019). The increase in glass transition temperature of pristine PVDF membrane after the addition of 0.5% SiO2-CNT nanoparticles could be attributed to the improved strength and stiffness of the membrane matrix due to restrained polymer chain movement resulted from the enhanced polymer nanoparticle interaction leading to a more elastic structure (Young and Mauritz 2001). The results demonstrated that SiO2-CNT/PVDF nanocomposite membranes were mechanically more stable than pristine PVDF membrane indicating that the pore integrity of nanocomposite membranes was likely maintained under applied pressure.