Polymer, thermal property glass transition temperature

The most common backbone structure found in commercial polymers is the saturated carbon-carbon structure. Polymers with saturated carbon-carbon backbones, such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyacrylates, are produced using chain-growth polymerizations. The saturated carbon-carbon backbone of polyethylene with no side groups is a relatively flexible polymer chain. The glass transition temperature is low at -20°C for high-density polyethylene. Side groups on the carbon-carbon backbone influence thermal transitions, solubility, and other polymer properties. 

Spindler and Frechet used 3,5-bis((benzoxy-carbonyl)imino)benzyl alcohol which decomposed thermally in THF solution containing DBTDL as a catalyst [97]. The resulting polymer was found to be insoluble unless an end-capping alcohol was added from the beginning. The end-capping groups determined the properties of the polymers such as glass transition temperature, thermal stability, and solubility. 

Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and infrared spectroscopy are the common techniques used in the characterization of the structure of the congealed solid. Thermal analytic methods, such as DSC and differential microcalorimetric analysis (DMA), are routinely used to determine the effect of solutes, solvents, and other additives on the thermomechanical properties of polymers such as glass transition temperature (Tg) and melting point. The X-ray diffraction method is used to detect the crystalline structure of solids. The infrared technique is powerful in detecting interactions, such as complexation, reaction, and hydrogen bonding, in both the solid and solution states. 

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. 

The mechanical and thermal properties of these polymers can also be varied over a wide range by the selection of starting materials with differing compositions and molecular weights. The tripolymerization of 3,9-h A(ethylidene 2,4,8,10-tetraoxaspiro[5,5]undecane) with mixtures of the rigid diol CDM and the flexible diol HD allows preparation of polymers with controlled glass transition temperature [40] (Fig. 55.6). Other thermal and mechanical properties for P(CDM -co-HD) copolymers are listed in Table 55.1. 

Due to the bulkiness of the carbazole groups the polymer chains are stiff in nature and the polymer has a glass transition temperature of 227 °C [382], which is among the highest known for vinyl polymers. PVK exhibits excellent thermal stability up to at least 300 °C [383-385]. Unfortunately, this property has never been fully utilized because of the extreme brittleness of the material. PVK is soluble in common organic solvents such as benzene, toluene, chloroform, and tetrahydrofuran. 

The thermal and thermomechanical properties of the polymer/HAp composites (glass transition temperature, melting and crystallization behaviour, thermal stability, crosslinking effects, phase composition, modulus, etc.) can be evaluated by thermal analysis methods, like TG, DSC and DMA. Recently, a modulated temperature DSC (MTDSC) technique has been developed that offers extended temperature profile capabilities by, for example, a sinusoidal wave superimposed on the normal linear temperature ramp [326]. The new capabilities of the MTDSC method in comparison with conventional DSC include separation of reversible and non-reversible thermal events, improved resolution of closely occurring and overlapping transitions, and increased sensitivity ofheat capacity measurements [92,327]. 

Furthermore, the supply of thermal energy could also be used to influence the properties of a metallopolymer and to yield the desired effects. For this purpose, Zhou and coworkers utilized phase-separated ruthenium-containing polymers with two glass transition temperatures [71]. The transitions induced the a kind of mobility that is required for the self-healing process [72]. 

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