Amorphous blend

Some of the most difficult heterophase systems to characterize are those based on hydrocarbon polymers such as mbber-toughened polypropylene or other blends of mbbers and polyolefins. Eecause of its selectivity, RuO staining has been found to be usehil in these cases (221,222,230). Also, OsO staining of the amorphous blend components has been reported after sorption of double-bond-containing molecules such as 1,7-octadiene (231) or styrene (232). In these cases, the solvent is preferentially sorbed into the amorphous phase, and the reaction with OsO renders contrast between the phases. 

Figure 7.8 gives some bundles of isochrones as supplied by a polymer manufacturer (GE). As we saw before, when comparing POM with PC, also here the higher rate of creep of a semi-crystalline polymer (PBTP), compared with the amorphous blend of PPE with PS, is obvious. 

Studies performed on the amorphous blends by DSC show the presence of only one glass-transition temperature in the blends which is intermediate between those of PBT and PET, changing in value with composition (Figure 2). This is the first evidence we have of the compatibility of both polymers in the amorphous phase. 

Based on the results of two amorphous compatible blend systems of 50/50 NC/PCL and 75/25 PVC/PCL, the following conclusion can be drawn. Compatible amorphous blend constituents show identical segmental orientation behavior, indicating good mixing at the molecular level. Thus, an amorphous compatible blend can exhibit the characteristics of a single homopolymer not only in its glass-transition behavior and mechanical properties but also in the uniform way in which the polymer chains orient. 

In summary, IGC is an experimentally attractive method for obtaining polymer-polymer interaction parameters in polymer blends at temperatures above Tm for a crystalline blend, and above Tg for an amorphous blend. This technique yields interaction parameters that are generally consistent with data obtained with other techniques such as vapor sorption, melting point depression, neutron scattering, and small-angle X-ray scattering (40). Advances in IGC of polymer blends will require increased experimental precision in order to improve the consistency of the data, as well as refinements of thermodynamic models to allow better interpretation of interactions in ternary solutions. 

Model C is mostly found for a blend of crystalline and amorphous polymers. In general, the miscibility for the crystalline/amorphous blends would be better in an amorphous component-rich system than that of a crystalline-rich system. For example, when the crystalline PEO composition is more than 60 wt% in PEO/amorphous PVPh, PEO in the blend showed two Tip relaxation times (Table 10.2) [34]. One of the two Tip agrees well with Tip... 

Modes of Segregation of the Amorphous Component during Crystallization in Crystalline/Amorphous Blends... 

Table 3.14. Thermal data on immiscible crystalline/amorphous blends (after Nadkarni and Jog [1991])...

Some examples of the final semicrystalline morphology in several immiscible crystalline/ amorphous blend systems have already been given in Table 3.21 for the discussion of the spherulite growth rate (Part 3.4.3.2). Some more information about this topic can be found in the articles listed in Table 3.23. 

Table 3.22. Global crystallization kinetics of the crystaUizable matrix in some crystaUine/amorphous blend systems...

Table 3.24. Examples of the melting behavior of the ciystaUizable matrix in some crystalline/amorphous blend systems.

For most commonly studied polymer blends, crystallization of the matrix occurs in the presence of a molten dispersed phase. The crystallization behavior of the continuous phase can be compared to that found for crystalline/amorphous blend systems in which the dispersed amorphous phase was in the molten state. 

In immiscible blends, the t-T principle does not hold. Eor immiscible amorphous blends it was postulated that two processes must be taken into account the t-T superposition, and the aging time [Maurer et al, 1985]. On the other hand, in immiscible blends, at the test temperature, the polymeric components are at different distance... 

The amorphous blends showed a single Tg with numerical value dependent on composition. The dependence of Tg on the weight fraction of HOCP (referred to the overall amorphous content in the blends) is shown in Table 6.1. The Tg values of the blends were also calculated by using the theoretical relation of Fox (34) ... 

In this section, we shall describe the various topologies of possible phase diagrams using the proposed thermodynamic model for a crystal-amorphous blend. Most polyolefin blends exhibit either an LCST or a UCST or a combination of both. In order to model the combined LCST-UCST or hour-glass phase diagram, the... 

TABLE 144 Characteristic Reducing Parameters and the Statistical Fit Data for Polymers and Amorphous Blends... 

Tsuji, H. and Del Crirpio, C.A. (2(X)3) In vitro hydrolysis of blends from enantiomeiic poly(lactide)s. 3. Homo-crystaUized rmd amorphous blend films. Biomacromolecules, 4,7-11. 

Prevost[72] prepared single phase, amorphous blends of amorphous semiaromatic nylons and semicrystalline nylons. The semiaromatic nylon was obtained via two steps. The 2-melhyl-l,5-pentamethylene diamine salt of (isophthalic and terephthalic)acid was first prepared by introducing 18,635.5 g 2-methyl-1,5-penlametltylene diamine, 5,128.5 g isophthalic acid, and 20,513.9 g terephthalic acid. Then polycondensation of the salt was carried out in an autoclave. The semiaromatic nylon thus obtained was melt blended with nylon-6,6 at 280 °C. The blend exhibited good resilience, as given in Table 6. 

The frequent interruption in the crystallization of a semicrystalline/amorphous blend with the incorporation of salt not only elevates its T, but also reduces the crystallization kinetics and G of the crystallizable component in both miscible and immiscible blends (Rocco et al., 2002 Rocco et al., 2004 Chan and Rammer, 2008 Florjanczyk et al., 2004 Acosta and Morales, 1996). Salt-free miscible PEO/PBE 60/40 blend exhibits an exothermic crystallization peak at -31 °C, but... 

The concept of a crystal-amorphous (also order-disorder) interface was first proposed by Flory (1962) for binary semicrystalline/amorphous blends. 

S Melting Behavior of the Crystalline Matrix in Crystalline/ Amorphous Blends... 

Ethylene-1-octene copolymer was also used as an amorphous blend partner of PA6 in PA6/ethylene-1-octene blend reactively compatibilized using PE-g-MA reactive copolymer (Sanchez et al. 2006). Because of the dispersed phase... 

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