Binary polymer melt

The stmcmre factor of an ideal binary polymer melt is evaluated within the random phase approximation (RPA) according... 

For both linear and star polymers, the above-described theories assume the motion of a single molecule in a frozen system. In polymers melts, it has been shown, essentially from the study of binary blends, that a self-consistent treatment of the relaxation is required. This leads to the concepts of "constraint release" whereby a loss of segmental orientation is permitted by the motion of surrounding species. Retraction (for linear and star polymers) as well as reptation may induce constraint release [16,17,18]. In the homopol5mier case, the main effect is to decrease the relaxation times by roughly a factor of 1.5 (xb) or 2 (xq). In the case of star polymers, the factor v is also decreased [15]. These effects are extensively discussed in other chapters of this book especially for binary mixtures. In our work, we have assumed that their influence would be of second order compared to the relaxation processes themselves. However, they may contribute to an unexpected relaxation of parts of macromolecules which are assumed not to be reached by relaxation motions (central parts of linear chains or branch point in star polymers). 

One convenient strategy to interpret these results is to review the molecular characteristics of binary blends as extracted from polymer melt rheology [40]. The influence of short chains (M < Me) is to effectively decrease the plateau modulus and the terminal relaxation times as compared to the pure polymer. Consequently, the molecular weight between entanglements... 

However, the validity of the polymer theory was extended to include cyclic and spherical particles, i.e also for more polymerized silicate melts, by Pretnar (1968), Baes (1970), and Esin (1973, 1974). Pretnar assumed that in binary silicate melts, short chains n < 5)... 

Figure 3.25. Phase diagram of a binary polymer blend with miscibihty gap (UCST) and intersecting crystal/melt coexistence curve. The curve is extrapolated into the miscibility gap. Quenching routes A to D are explained in the text. For routes B and C, the quenching-induced phase...

As in the case of macrophase separation, the two competing terms of enthalpic and entropic nature govern the thermodynamics of block copolymers. Similar to binary polymer bends the phase behavior of diblock copolymer melts is primarily controlled by the segregation strength and the volume fractions /a and /b = 1 - /a of the two blocks. Being covalently bonded, repulsive blocks are prevented from separating on a macroscopic level. Hence, the segregation into A- and B-rich domains... 

Notably, interfacial tension in two-phase low viscosity systems has been recognized and studied since the nineteenth century. Indeed Clerk Maxwell [138] discussed it in an 1879 Encydopedia Britannica review. Various researchers developed methods and made measurements of the interfacial tension in the nineteenth century and early twentieth century. Measurements for combinations of polymer melts, however, date back only to the 1960s [139-142] and generally accepted values were available by the 1990s [143-146]. We summarize data for various binary systems in Table 1.1. 

Bitinis et developed for the first time a novel and industrially scalable PLA-NR blend prepared by melt mixing blends at 5,10 and 20 wt% of natural rubber to analyze the effect of the NR concentration on the blend morphology. Figure 7.5 shows SEM micrographs of the blends fracture surfaces where it is observed that the size of the rubber particles is similar for 5 and 10 wt% but increases for the blend at 20 wt% from 1.15 to 2.00 pm. In general, in an immiscible binary polymer blend, the size of the dispersed phase increases as a function of the concentration of the minor phase in the blend, due to coalescence phenomena. ... 

Consider a DDC system that contains a binary liquid solution of polymer melt and blowing liquid. As the decompression is effected above the boiling point of the solvent, the volatile solvent phase vaporizes to cool the melt by taking latent heat from it. Assuming that the two species are non-reacting and form a homogeneous binary phase, one can write an energy equation ... 

Introducing fillers in the melt of a binary polymer mixture leads to the following consequences. The main effect is a selective adsorption of one of the components at the interface with the solid. Above the critical point in the phase diagram (for the systems with UCST) polymer melt is a solution of one component into another. The thermodynamic interaction parameter Xab depends on temperature and melt composition. The interaction of each component with the surface is characterized by the thermodynamic parameter of interaction between one of the components and the surface, Xsa or Xsb-In such a system, selective adsorption proceeds, depending on the relation between Xsa tid Xsb- The selectivity of the interaction of the polymer mixture components with the solid plays an important role in the thermodynamic behavior of a filled polymer melt. Let us consider some simple thermodynamic... 

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