Plastic transition parameters

For updating with the smaller-amplitude data set, Pec, estimates of inter-story stiffnesses are fairly well-constrained, and close to the actual values. However, since there is relatively little non-linear behavior, there are larger uncertainties associated with the strength and elastic-to-plastic transition parameters, and especially the breaking ductility ratio in model class Mi, since there is very little deterioration in the actual system. Figure 4 shows the posterior samples obtained by updating model class Mi... 

PAT should be used for such studies only when other techniques fail to reveal clearly a given phase transition. Thus, in Figure 4.13, it is interesting to note that the liquid/plastic transition is not detected through the PALS and DB parameters, although it is easily seen by direct observation. On the opposite, the plastic/solid transition is well marked, although it is not easily seen by using conventional techniques. 

From the results of yield stress which represents the transition from elastic to plastic deformation, it could be seen that this transition is mainly dependent on whether the sample is crosslinked or not. Ihe values of obtained in this study increase with fiber content up to a maximum of 20 wt% for imcrosslinked and 10 wt% for cross-linked films however, for the crosslinked films they are considerably higher than those for imcrosslinked ones, which indicates that the influence of the crosslinking agent is determining the values of this mechanical parameter. The same trend is observed for the tensile stress, which indicates that both the elastic to plastic transition and the plastic deformation are determined by the crosslinking. It is important to notice that the maximum values of these parameters, observed for the crosslinked films with 10 wt% of fibers = 9.9 1.7MPa = 13.2 1.3 MPa), are higher than the maximum... 

Plasticizers and Processing Aids. Petroleum-based oils are commonly used as plasticizers. Compound viscosity is reduced, and mixing, processing, and low temperature properties are improved. Air permeabihty is increased by adding extender oils. Plasticizers are selected for their compatibihty and low temperature properties. Butyl mbber has a solubihty parameter of ca 15.3 (f /cm ) [7.5 (cal/cm ) ], similar to paraffinic and naphthenic oils. Polybutenes, paraffin waxes, and low mol wt polyethylene can also be used as plasticizers (qv). Alkyl adipates and sebacates reduce the glass-transition temperature and improve low temperature properties. Process aids, eg, mineral mbber and Stmktol 40 ms, improve filler dispersion and cured adhesion to high unsaturated mbber substrates. 

The model of Condo permits the determination of the limiting pressure at which the glass state exists, on the basis of a reduced number of parameters (only the glass transition temperature of the pure polymer is needed to calibrate the energy parameter) for this reason, it seems particularly useful for the prediction of the plasticizing effects. 

For miscible blend phases, these parameters need to be described as a function of the blend composition. In a first approach to describe the behavior of the present PPE/PS and SAN/PMMA phases, these phases will be regarded as ideal, homogeneously mixed blends. It appears reasonable to assume that the heat capacity, the molar mass of the repeat unit, as well as the weight content of carbon dioxide scale linearly with the weight content of the respective blend phase. Moreover, a constant value of the lattice coordination number for PPE/PS and for SAN/PMMA can be anticipated. Thus, the glass transition temperature of the gas-saturated PPE/SAN/SBM blend can be predicted as a function of the blend composition (Fig. 17). Obviously, both the compatibilization by SBM triblock terpolymers and the plasticizing effect of the absorbed carbon dioxide help to reduce the difference in glass transition temperature between PPE and SAN. 

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... 

All PALS and DB (AC) parameters can be sensitive to phase transitions and PAT have been commonly used for such studies [125, 126], A typical example is shown in Figure 4.13, for I3 in the case of sulfolan similar changes are observed for x3 and fwhm [23], With a roundish molecular shape, this compound forms a plastic phase below the melting temperature and before forming a brittle solid phase. In the plastic phase, the molecules can still rotate around their axis, but not move in a translational mode. 

Kambour et al. performed extensive studies on the mechanisms of plasticization [18-25]. The correlation observed between the critical strain to craze and the extent of the glass-transition temperature (Tg) depression speaks strongly in favor of a mechanism of easier chain motion and hence easier void formation. In various studies on polycarbonate [19,24], polyphenylene oxide [20], polysulfone [21], polystyrene [22], and polyetherimide [25], Kambour and coauthors showed that the absorption of solvent and accompanying reduction in the polymer s glass-transition temperature could be correlated with a propensity for stress cracking. The experiments, performed over a wide range of polymer-solvent systems, allowed Kambour to observe that the critical strain to craze or crack was least in those systems where the polymer and the solvent had similar solubility values. The Hildebrand solubility parameter S [26] is defined as... 

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