Polymer-diluent mixtures phase changes

The different phase equilibria and transformations in polymer-diluent mixtures that have been discussed can be illustrated by the schematic diagram given in Fig. 3.23.(105) Process [1] represents the usual melting or crystalhzation of polymers with a conformational change occurring during the transformation. A diluent may or may not be present in the amorphous, or liquid, state. III, wtule state I represents the pure crystalline phase. Transformations in this category were discussed... 

The homopolymerization of ethylene is often carried out with a mixture containing four components monomer (M), polymer (P), diluent (D) and initiator (I). The phases which may co-exist are solids (c), liquid (1), vapor (g) and a supercritical fluid phase (s) which may upon a change of temperature, pressure or composition separate into a liquid and a vapor phase. The components coexisting in a given phase will be written within a parenthesis, the phase will be labeled with a superscript and coexistence of two or more phases will be indicated by a slash (/) for example, the notation (MD) /(MPDI) indicates that a vapor and... 

Solvent selection was also proven to affect the resulting structure in temperature-induced phase separation (TIPS) (Lloyd et al. 1990 Gu et al. 2006 Lu and Li 2009). Diluents such as phthalates promote the formation of irregular fuzzy structures (Lloyd et al. 1990). PVDF membranes prepared from dimethyl phthalate (DMP) as a solvent showed larger spherulite structures compared to that of membranes prepared from DBP, or mixtures of DMP with dioctyl sebacate and dioctyl adipate. It can be ascribed from these differences that the degree of polymer-solvents interactions influences the extent of PVDF crystallization (Lloyd et al. 1990 Gu et al. 2006). Using different types of solvents, the crystallization temperature of PVDF during TIPS can also be changed. A more complex mechanism is indeed expected for a combined solvent system. For instance, in the PVDF/DMAc/TEP system, TEP (weaker solvent) acts as a latent solvent in the immersion precipitation process (Liu et al. 2012). 

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