Poly glass transition parameters

Figure 2 shows the d3mamic modulus (E ) and the loss tangent (tan 6) at 0% RH as a function of temperature for unoriented and oriented (5.5X) poly(ethylene terephthalate), (PET) fibers. The glass transition parameters (a peak temperature, tan 6 ax and... 

TABLE 2.2. Glass Transition Parameters of Poly(ethylene Terephthalate) (PET), Poly(ethyIene 2,6-NaphthalenedicarboxyIate) (PEN), and Poly(phenylene Snifide) (PPS)... 

The thermal glass-transition temperatures of poly(vinyl acetal)s can be determined by dynamic mechanical analysis, differential scanning calorimetry, and nmr techniques (31). The thermal glass-transition temperature of poly(vinyl acetal) resins prepared from aliphatic aldehydes can be estimated from empirical relationships such as equation 1 where OH and OAc are the weight percent of vinyl alcohol and vinyl acetate units and C is the number of carbons in the chain derived from the aldehyde. The symbols with subscripts are the corresponding values for a standard (s) resin with known parameters (32). The formula accurately predicts that resin T increases as vinyl alcohol content increases, and decreases as vinyl acetate content and aldehyde carbon chain length increases. 

A new class of hydrophilic polyamides, poly(tetrahydropyran-2,6-diylimino-carbonyl) 1 was prepared by the anionic polymerization of a bicyclic oxalactam (abbreviated as BOL, 2) 38-42). The resulting polyamide / has glass transition, fusion, and decomposition points at 130,260-285, and 315 °C, respectively, and its membrane can be obtained by casting from a polyBOL solution. The solubility parameter... 

Fig. 2. Correlation of experimental values of the Langmuir capacity parameter (Sq) for C02 at 35 °C with the glass transition temperature of the polymer25) [cf. Eq. (10)]. Pure polymers (PSF = a poly-sulphone 231 COP = a copolyester 26) remaining abbreviations as in the text). Miscible polymer blends O PPO-PS 65> O PC-COP 26>...

Unformulated poly (vinyl acetal) resins form hard, unpliable materials which are difficult to process without using solvents or plasticizers. The solubility parameter ranges for some commercially available PVF and PVB resins are listed in Table 1. Plasticizers not only aid resin processing but also lower the glass-transition temperature, T, and can profoundly change other physical properties of the resins. For example, the mechanical glass-transition... 

In the vicinity of glass transition, both Eqs. (47) and (48) become Eqs. (42) and (43), respectively. The calculated dependence of the physical aging rate on temperature for polystyrene (PS), poly(vinyl chloride) (PVC), and poly(vinyl acetate) (PVAc) is shown in Fig. 17. There are five parameters (e, p, f xr, 7 ) in Eqs. (23), (2), (15) and (19). We have chosen p = 1/2. ft = 1/30, and xr = 30 min for these linear polymers in our theoretical calculation. The other two parameters r. = h and Tr are listed in Table 1. The calculation reveals that the Struik exponent (p) increases from zero above 7 to a constant below Tg, and then decreases to zero at 200 K below Tg. The three polymers all show a similar type of temperature dependence of physical aging rate, which compares well with the reported observations (see Fig. 15 of Ref. 2). 

Early fundamental studies of gas transport in polymers were almost entirely confined to hydrocarbon materials above their glass transition temperatures. The essentially nonpolar structures of the elastomers led to a number of reasonably successful attempts to correlate gas transport parameters with various physical characteristics of the gases and the polymers. These have been summarized and discussed in a number of papers In addition to studies with hydrocarbon elastomers a few studies of other amorphous polymers above their glass transition temperatures have dealt with polyvinyl acetate silicones and fluorocarbon polymers Recent studies have also dealt with poly(methyl aciylate) poly-(vinyl methyl ether) and poly(vinyl methyl ketone) With these more... 

Molecular dynamics calculations have been carried out to simulate a conformational model and vibrational spectra of poly(dichlorophospha-zenes). Molecular dynamics similations for [NP(OCH2CF3)2] and the isomers [NP(OBu")2] , [NP(OBu )2] and [NP(OBu )2] show a reasonable agreement between the calculated and experimental values of density and glass transition temperature as well as for gas transport parameters in these polymers.Small molecule models have been used for a theoretical approach of poly(thionylphosphazenes). ... 

A solid-state C NMR study of the intermolecular hydrogen bonding formation in a blend of phenolic resin and poly(hydroxyl ether) of bisphenol A was reported by Wu et at) " The presence of a single glass transition temperature for all of the blend samples with different composition as disclosed by the DSC measurements demonstrates that the blends are thermodynamically miscible. The solid state NMR parameters, including chemical shift, efficiency of cross-polarization and Ti, confirm the presence of more free OH groups when one of the polymers is the minor component. 

Blends of poly(trimethylene terephthalate) (PTT) and PEN are miscible in the amorphous state over a wide range of eompositions. This is evidenced by a single, composition-dependent glass transition temperature (7 ). The variation of the Tg with composition can be predicted by the Gordon-Taylor equation, with the fitting parameter being 0.57. 

Glass transitions involve mainly the onset or freezing of cooperative, large-amplitude motion and can be studied using thermal analysis. Temperature-modulated calorimetry, TMC, is a new technique that permits to measure the apparent, fiequency-dependent heat capacity. The method is described and a quasi-isodiermal measurement method is used to derive kinetic parameters of the glass transitions of poly(ethylene terephthalate) and polystyrene. A first-order kinetics expression can describe the approach to equilibrium and points to the limits caused by asymmetry and cooperativity of the kinetics. Activation energies vary from 75 to 350 kJ/mol, dependent on thermal pretreatment. The preexponential factor is, however, correlated with the activation energy. 

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