Amorphous phases, miscible

The binary blends of polycarbonate with polybutylene terephthalate (PBT/PC) or polyethylene terephthalate (PET/PC) are now known to be essentially phase separated blend systems exhibiting two glass transition temperatures in each case, one for the polycarbonate-rich phase, and another for the polyester-rich phase. [Murff et ah, 1984 Huang and Wang, 1986 Wahrmund et ah, 1978]. The evaluation of the amorphous phase miscibility... 

PA/MXD PA-g blends with poly(m-xyltne adipamide) X12 < 0 indicated miscibility in amorphous phase miscibility increased with transamidation during agiug. 9... 

Amorphous phase Miscible Miscible Miscible Immiscible ... 

U semicrystalline at higher I content and no amorphous phase miscibility... 

Miscible Blends. Sometimes a miscible blend results when two polymers are combined. A miscible blend has only one amorphous phase because the polymers are soluble in each other. There may also be one or more crystal phases. Simple theory (26) has supported the empirical relation for the permeabihty of a miscible blend. Equation 18 expresses this relation where is the permeabihty of the miscible blend and ( ) and are the volume fractions of polymer 1 and 2. 

Blends of enzymatically synthesized poly(bisphenol-A) and poly(p-r-butylphenol) with poly(e-CL) were examined. FT-IR analysis showed the expected strong intermolecular hydrogen-bonding interaction between the phenolic polymer with poly(e-CL). A single 7 was observed for the blend, and the value increased as a function of the polymer content, indicating their good miscibility in the amorphous state. In the blend of enzymatically synthesized poly(4,4 -oxybisphenol) with poly(e-CL), both polymers were miscible in the amorphous phase also. The crystallinity of poly(e-CL) decreased by poly(4,4 -oxybisphenol). 

The basic issue confronting the designer of polymer blend systems is how to guarantee good stress transfer between the components of the multicomponent system. Only in this way can the component s physical properties be efficiently used to give blends with the desired properties. One approach is to find blend systems that form miscible amorphous phases. In polyblends of this type, the various components have the thermodynamic potential for being mixed at the molecular level and the interactions between unlike components are quite strong. Since these systems form only one miscible amorphous phase, interphase stress transfer is not an issue and the physical properties of miscible blends approach and frequently exceed those expected for a random copolymer comprised of the same chemical constituents. 

Obtaining good stress transfer is possible in systems where the mixture forms a miscible amorphous phase (where interphase stress transfer is not an issue) ... 

To promote the compatibility between the components, sPS/HDPE binary blends were mixed at 285 °C in a mixer with 5 and 10 wt% of SEBS and then thermo-compressed at the same temperature [33]. Crystallinity values, Tcj and Tm of sPS, as measured by DSC, decrease slightly with increase in SEBS content, in agreement with the expected miscibility of SEBS polystyrene block into the sPS amorphous phase. 

The PS/PEC blends are not shown. The presence of a single Tg for each blend composition is indicative of the presence of a single amorphous phase (2.3). and on this basis we conclude that i-PS/PEC and PS/PEC blends are miscible for trimethyl compositions in the copolymer from 0 to 20 moleX. The Tg of pure PEC is raised by only 12 °C with respect to PPO by the addition of 20 moleX comonomer, and this does little to raise the blend Tg at intermediate PEC concentrations. 

The difference of relaxation times in different domains makes it possible to observe the spectrum of one of the domains. Figure 10.23(a), shows the Ti-selected spectrum of PVPh/PEO = 40/60 [34]. Since the Ti of crystalline PEO ( 15 s) is much longer than that of the amorphous phase (—0.1 s), it is possible to observe the spectrum of crystalline PEO selectively (indicated by arrow in Fig. 10.23(a)). On the other hand, for the miscible PVPh-rich blend (PVPh/PEO = 58/42), the crystalline-PEO peak is not appreciable. This is in agreement with the above-mentioned results (Table 10.2). The signals of mobile domains/component polymers can be observed selectively by utilizing the weaker dipolar interaction between H. To name a few examples, the dipolar dephasing [128,131,152], the cross-polarization-depolarization [152] and the pulse saturation transfer [151] techniques have been applied. 

PA-g/poly(m-xylene adipamide) Miscibility in amorphous phase concluded from the negative values of Th miscibility increased upon transamidation during aging. Shibayama et al., 1995... 

High resolution 13C NMR spectroscopy was used to analyze miscibility of POM with terphenol (MW = 600 g/mol). The size of the heterogeneity in the amorphous phase was estimated as 1 nm. The IH spin diffusion analysis indicated a homogenous mixing on the molecular level [Egawa et al, 1996]. 

When dealing with miscible blends containing two crystalline components, several modes of crystallization are possible separate crystallization, concurrent crystallization, co-crystallization, etc. Only those blends in which both components are miscible in the melt are considered here (Table 3.3). PET/PBT blends were reported to be an example of separate crystallization [Escala and Stein, 1979 Stein et al., 1981]. A spherulitic crystallization was observed for the neat components as well as for blends with small amounts of one component, and the crystals of the minor component were included within the spherulites of the major component, which results in a coarsening of the spherulitic texture. Transesterihcation is, however, the reason for the homogenous amorphous phase. 

During crystallization of a miscible polymer blend, the composition of the amorphous phase changes, i.e., becomes poorer on the crystallizable component. In some cases, a liquid-liquid phase separation can take place as a result of the crystallization. This phenomenon will be discussed more in detail in the next section. 

PIB is shown to be partially miscible with the amorphous phase of PP at low concentrations. Hence, the behavior can deviate and exhibit some typical characteristics as in miscible systems... 

---