Transition temperature glass, in polymers

Keddie, J. L, Jones, R. A. L. and Cory, R. A. (1994) Size-Dependent Depression of the Glass-Transition Temperature in Polymer-Films. Europhys. Lett., 27, 59-64. 

Lodge TP, McLeish TCB (2000) Self-concentrations and effective glass transition temperatures in polymer blends. Macromolecules 33(14) 5278—5284... 

Keddie J, Jones RAL, Cory RA (1994) Size-dependent depression of the glass transition temperature in polymer films. Europhys Lett 27 59-64... 

Painter, P.C., Graf, J.F., and Coleman, M.M. (1991) Effect of hydrogen bonding on the enthalpy of mixing and the composition dependence of the glass transition temperature in polymer blends. Macromolecules, 24, 5630-5638. 

Near the glass transition temperature in polymers, decreases. This decrease has been explained by the extra free volume created by thermal expansion, which leads to the Williams-Landel-Ferry (WLF) equation (Ferry, 1980). This equation describes the viscosity at temperature 7 in terms of viscosity at some reference temperature T,. 

Another interesting application of NC-AFM is in the detection of thermal events such as melting and glass transition temperature in polymers on heating. The technique uses FM detection with the tip fixed above the surface as the polymer temperature is ramped underneath [162]. The mechanism behind this technique is not well understood. 

Dang A, Hui CM, Ferebee R, Kubiak J, Li T, Matyjaszewski K, Bockstaller MR (2013) Thermal properties of particle brush materials effect of polymer graft architecture on the glass transition temperature in polymer-grafted colloidal systems. Macromol Symp 331-332 (1) 9-16... 

Polycarbonates are an unusual and extremely useful class of polymers. The vast majority of polycarbonates are based on bisphenol A [80-05-7] (BPA) and sold under the trade names Lexan (GE), Makrolon (Bayer), CaUbre (Dow), and Panlite (Idemitsu). BPA polycarbonates [25037-45-0] having glass-transition temperatures in the range of 145—155°C, are widely regarded for optical clarity and exceptional impact resistance and ductiUty at room temperature and below. Other properties, such as modulus, dielectric strength, or tensile strength are comparable to other amorphous thermoplastics at similar temperatures below their respective glass-transition temperatures, T. Whereas below their Ts most amorphous polymers are stiff and britde, polycarbonates retain their ductiUty. 

The glass-transition temperature in amorphous polymers is also sensitive to copolymerization. Generally, T of a random copolymer falls between the glass-transition temperatures of the respective homopolymers. For example, T for solution-polymerized polybutadiene is —that for solution-polymerized polystyrene is -HlOO°C. A commercial solution random copolymer of butadiene and styrene (Firestone s Stereon) shows an intermediate T of —(48). The glass-transition temperature of the random copolymer can sometimes be related simply as follows ... 

T and are the glass-transition temperatures in K of the homopolymers and are the weight fractions of the comonomers (49). Because the glass-transition temperature is directly related to many other material properties, changes in T by copolymerization cause changes in other properties too. Polymer properties that depend on the glass-transition temperature include physical state, rate of thermal expansion, thermal properties, torsional modulus, refractive index, dissipation factor, brittle impact resistance, flow and heat distortion properties, and minimum film-forming temperature of polymer latex... 

It should be pointed out that the view of the glass transition temperature described above is not universally accepted. In essence the concept that at the glass transition temperature the polymers have a certain molecular orientation time is an iso-elastic approach while other theories are based on iso-viscous. 

As described in several review articles [409,452-454] and books [10,13,15], this is basically due to the inherent features of the d -p bond in phosphazenes, which allows the permanent overlapping of the 2pj orbital of the skeletal nitrogens with any one of the 3p orbitals of the phosphorus atoms [455]. Such a high chain flexibihty generated very low glass transition temperatures in these polymers, which can reach values of about -100 °C when suitable flexible substituent groups (e.g. n-butanol) are present on the skeletal phosphorus [274]. 

Amorphous polymers convert reversibly between the rubbery and glassy states as their temperature rises or falls. Below their glass transition temperature, amorphous polymers exist in a glassy state. Above their glass transition temperature they are rubbery. We can demonstrate this easily with a racquet ball, which is made of an amorphous polymer. At room temperature, as we all know, the ball bounces at this temperature it is in the rubbery state. If we immerse the ball in liquid nitrogen it becomes brittle and will shatter when we drop it, i.e., it has become a glass, If we were to allow the frozen ball to warm up to room temperature, it would become rubbery once more. We can freeze and thaw the same ball repeatedly with no loss of its properties at room temperature. 

Chemical structure factors affect the melting point and glass transition temperature in much the same manner. A good empirical rale for many polymers is (142-144)... 

In general, the miscibility between two polymers can be predicted by thermal characterization of the blends [36], One of the most simple and effective ways to predict miscibility between two polymers is to consider the behavior of the glass transition temperature in the blend systems, which is known as the Tg method. In miscible blend systems, only a single 7 g intermediate between two components appears in the amorphous state. Therefore, we studied the change of... 

The glass transition temperature in the polymer containing a few percent of 5-triethoxysilanenorbomene for dielectric applications can be lowered by increasing the amount of 5-decylnorbomene (see Figure 10.33). 

Fluorinated poly(imide-ether-amide)s are readily soluble in organic solvents like dimethylformamide (DMF), N-methylpyrrolidone (NMP), pyridine or tetrahydrofu-ran (THF) and give flexible films by casting of such solutions. These polymers exhibit decomposition temperatures above 360°C, and glass transition temperatures in the 221-246° C range. The polymer films have a low dielectric constant and tough mechanical properties. 

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