Thermal transitions glass transition temperature

Interesting comparisons have been made 17 between dendritic and the hyperbranched structures the thermal properties (glass transition temperature and thermogravimetric analysis) were independent of architecture and their solubilities were comparable, but greater than that shown for linear counterparts. 

Table 1. Thermal analysis glass transition temperatures and crystallization effects (melt temperatures of crystallites)...

Other polymer properties that are often measured are whiteness, color, thermal stability, glass transition temperature (wet and dry), melting point (wet and dry), dope viscosity, and gelation characteristics. Techniques used for characterizing acrylic textile polymers are summarized in Table 12.30. 

Thermal Analysis Glass transition temperatures, Tg s, were obtained by differential scanning calorimetry on a Seiko DSC 210. Scans were run at 10 C per minute and the reported values were obtained from a second heating after quick cooling. The thermooxidative stability was determined by thermogravimetric analysis in air on a Perkin-Elmer TGA-7 at 10 /minute heating rate. 

Figure 9.26 Effects of thermal history. Glass transition temperatures of...

Thermal properties Glass-transition temperature (Tg), °C Melting temperature (Tm), °C Heat-deflection temperature (HDT) at 0.45 or 1.8 MPa, °C D648 75... 

Two copolymers were synthesized with different ratios of the fluorene-based monomer and the fluorenylidene linker. Both polymers were obtained in high yields and high molecular weight with Mw = 55,000-89,500 Da and exhibited excellent thermal stability. Glass transition temperatures ranged from 153 °C to 197 °C with decomposition temperature (5% weight loss measurend by TGA analysis) of 440 to 450 °C. 

The method of irradiation and the dose can influence several properties such as thermal properties (glass transition temperature decomposition temperature T(jeo crystallization temperature Tc, and melting temperature T ) and mechanical properties (tensile strength, modulus at 50% elongation, gel... 

In a wide definition, PBI refers to a large family of aromatic heterocyclic polymers containing benzimidazole units. PBI with different structures can be synthesized from hundreds of combinations of tetraamines and diacids. In a specific way, PBI refers to the commercial product under the trademark Celazole , poly(2,2 -m-(phenylene)-5,5 -bibenzimidazole) (Fig. 4.1). In the context of PBI with different structures, this specific PBI is also named as meia-PBI because phenylene ring is meto-coordinated. As an amorphous thermoplastic polymer, the aromatic nuclei of PBI provide the polymer high thermal stabihty (glass transition temperature, Fg = 425-436 °C), excellent chemical resistance, retention of stiffness and toughness, but poor process-abihty [56-58]. Primarily used in textile fibers, the selection of poly(2,2 -m-(phenyl-ene)-5,5 -bibenzimidazole) as the commercial product was made on the basis of its... 

What are heat capacity, specific heat, thermal conductivity, coefficient of thermal expansion, glass transition temperature, melting temperature, and degradation and decomposition ... 

There are two main types of mechanical thermal analysis instruments, namely thermomechanical analysis and dynamic mechanical analysis, TMA and DMA respectively. The first is a simple technique that has been available for many years and simply records change of sample length as a function of changing temperature. Despite this simplicity it enables the measurement of phase transitions, glass transition temperature and coefficient of thermal expansion. It has the advantage of being simple to use and perhaps more importantly the interpretation of results is quite straightforward. 

The glass-transition temperature, T, of dry polyester is approximately 70°C and is slightly reduced ia water. The glass-transitioa temperatures of copolyesters are affected by both the amouat and chemical nature of the comonomer (32,47). Other thermal properties, including heat capacity and thermal conductivity, depend on the state of the polymer and are summarized ia Table 2. 

The porous electrodes in PEFCs are bonded to the surface of the ion-exchange membranes which are 0.12- to 0.25-mm thick by pressure and at a temperature usually between the glass-transition temperature and the thermal degradation temperature of the membrane. These conditions provide the necessary environment to produce an intimate contact between the electrocatalyst and the membrane surface. The early PEFCs contained Nafton membranes and about 4 mg/cm of Pt black in both the cathode and anode. Such electrode/membrane combinations, using the appropriate current coUectors and supporting stmcture in PEFCs and water electrolysis ceUs, are capable of operating at pressures up to 20.7 MPa (3000 psi), differential pressures up to 3.5 MPa (500 psi), and current densities of 2000 m A/cm. ... 

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