Gordon-Taylor

ET40)/PET blends, and in the 100/0 wt% P(HB80-ET20)/PET blend. This is because of either (a) a high content of rigid rod-like liquid crystalline component, or (b) an enthalpy which was too small to detect. The dependence of Tg on the blend composition can be evaluated by using the Gordon-Taylor Equation [37],... 

Earlier work on chain extended HPLs has shown that these derivatives produce uniform (i.e., single phase) polymers with Tg varying in accordance with the Gordon-Taylor relationship (12). Polyurethanes from chain-extended HPLs were found to be rubber-like at room temperature with modulus declining as lignin content is reduced (8). Star-like structure determines functionality, Tg, viscosity, and several other properties that influence utility as polymer segment. 

Theoretically miscible polymer blends will show Tg values that are intermediate between those of the parent polymers. They follow such models as the Fox or Gordon-Taylor relationships (18,19). However, in the case of HPL/PVA blends, the Tg data did not follow any of these well known models, and Tg values above those of the parent polymers were observed (10). The quotient of the experimental blend-Ttf divided by the predicted (Fox) Tg consistently rose above 1.00 for blends exceeding 5% HPL content (10). This indicates molecular interactions between HPL and PVA. An... 

Glass transition temperature is one of the most important parameters used to determine the application scope of a polymeric material. Properties of PVDF such as modulus, thermal expansion coefficient, dielectric constant and loss, heat capacity, refractive index, and hardness change drastically helow and above the glass transition temperature. A compatible polymer blend has properties intermediate between those of its constituents. The change of glass transition temperature has been a widely used method to study the compatibility of polymer blends. Normally, the glass transition temperatme of a compatible polymer blend can be predicted by the Gordon-Taylor relation ... 

Figure 7.4 shows the glass transition temperatures of PVDF/PMMA blends as a function of PVDF content after a melt process. The results " show agreement with Gordon-Taylor relation up to about 40 wt %, which is much higher than the 20wt % obtained from the annealed blends. This is certainly a result of the increased content of amorphous PVDF matrix in melt-processed blends compared with annealed blends. 

Glass-transition temperatures of the three diblocks and the two homopolymers are plotted against isoprene content in Figure 3. The values plotted in Figure 3 were determined by TMA at a heating rate of 5°C/min. The points fall near a straight line which can be described by a simplified version of the Gordon-Taylor equation (20) ... 

The Gordon-Taylor copolymer equation (Equation 4) has been applied to the Tg data in this study to determine if the blends are single-... 

Figure 3. Tg data for PVC/PCL and NC/PCL blends plotted according to the Gordon-Taylor equation. The lines are fit to the quenched data (1).

Figure 3 shows that the Gordon-Taylor equation fits the quenched data for the PVC/PCL blends quite well. The thermograms for the blends of 25, 35, and 50% PVC display PCL heats of fusion, and conse-... 

Blends of PCL with PVC were shown to exhibit only one glass-transition temperature (Tg), which for blends quenched from the melt could be represented as a function of composition by the Gordon-Taylor Tg equation. By similar criterion, the PCL blends with NC were shown to be compatible for the composition range 0-50% NC by weight. With higher concentrations of NC, both thermal and mechanical testing indicated that multiple amorphous phases were present, even though the films were clear. 

Boessel, Ulf, Baldur Eliasson, and Gordon Taylor. 2003. The Future of the Hydrogen Economy Bright or Bleak Available online at http // www.efcf.com/reports/. Accessed December 10, 2003. 

Figure 7.9. Glass transition temperature of gelatinized WMS as a fiinetion of moisture content compared to the Gordon-Taylor predictions (Reprinted from Carbohyd. Polym., 51, Zimeri and Kokini, Phase transitions of inulin-waxy maize starch systems in limited moisture environments, pp. 183-190, Copyright (2003), with permission from Elsevier.)...

A logarithmic form of this equation is given by Pochan et al. Other expressions include the Wood equation the Kelley-Bueche expression the Gordon-Taylor equation and the DiMarzio-Gibbs equation None of these Equations directly take into account the specific interactions within a blend. 

Fig. 7 Glass transition vs. water content relationship for amorphous indomethacin. Lines show fit to the Gordon-Taylor equation with K values of 0.33 (predicted) and 0.11...

The glass transition temperature of amorphous multicomponent mixtures can be used to determine the miscibility of the components. If the mixture is miscible, then a single glass transition temperature is usually obtained. Various equations can be used to predict the glass transition temperature of miscible mixtures. Examples include the Gordon-Taylor equation [Eq. (11)] or the Fox-Flory equation [Eq. (12)]. 

Calculated using Gordon-Taylor equation with an intrinsic glass transition, 7 of 74°C (347 K) and - 139°C (135 K) for sucrose and water, respectively, and a Gordon-Taylor constant value of 0.13675. 

Glass-transition curve of three model system formulations ( control, O sorbitol, glycerol) expressed vs. (a) water activity or (b) moisture content. Lines indicate the predicted values according to the Gordon-Taylor model (Sherwin and Labuza, 2003). 

The glass-transition temperature curve of the maltodextrin RD-111, MOR-REx 1910, and MOR-REX 1914 were obtained using the Gordon-Taylor equations for binary systems, according to the procedure described by Collares et al. (2004). 

The Tg curves for the water-maltodextrin-sucrose system was plotted using the expanded Gordon-Taylor model (Equation 21.1) for ternary systems, considering the variation in heat capacity for water (ACpi) equal to 1.94 J/g °C (Kalichevsky and Blanshard, 1993) and for sucrose (ACp2) equals to 0.60 J/g °C (Roos, 1993). The value for ACps of 0.24 J/g °C used here for maltodextrin MOR-REX 1910 was estimated from considering the value for k (the ratio of changes in the water and solid heat capacities at Tg) to be equal to 8.055. Table 21.1 shows the parameters used to determine the glass-transition curves for the maltodextrins, with and without additives (sucrose). 

Parameters Used to Determine the Glass-Transition Curves According to the Gordon-Taylor Model... 

Glass-transition curves (Gordon-Taylor model) for maltodextrin MOR-REX 1910 and sucrose. 

In Figure 21.5, the self-detachment conditions for aqueous solutions of the maltodextrin MOR-REX 1910 and sucrose at 5, 10, and 15% (dwb) are compared with the glass-transition curves calculated using the expanded Gordon-Taylor model (Roos, 1993). The self-detachment of the dried films of aqueous solutions of the maltodextrin MOR-REX 1910 and sucrose followed the same pattern of decreasing moisture content of the material with an increase in temperature as observed with the glass-transition data. This process occurred in a temperature range of 20°C below Tg, for 5,10, and 15% sucrose concentrations, as was observed by Collares et al. (2004) for maltodextrin MOR-REX 1910 without the addition of sucrose. 

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