Thermodynamics of Polymer Blends

Abstract

This chapter summarizes the thermodynamics of multicomponent polymer systems, with special emphasis on polymer blends and mixtures. After a brief introduction of the relevant thermodynamic principles -laws of thermodynamics, definitions, and interrelations of thermodynamic variables and potentials -selected theories of liquid and polymer mixtures are provided: Specifically, both lattice theories (such as the Flory-Huggins model, Equation of State theories, and the gas-lattice models) and off-lattice theories (such as the strong interaction model, heat of mixing approaches, and solubility parameter models) are discussed and compared. Model parameters are also tabulated for the each theory for common or representative polymer blends. In the second half of this chapter, the thermodynamics of phase separation are discussed, and experimental methods -for determining phase diagrams or for quantifying the theoretical model parameters -are mentioned.

Investigation of Phase Separation in a Partially Miscible Polymer Blend by Rheology

“…As shown in this figure, there is a significant difference in evolution of the scattering pattern for the 20/80 and 50/50 blends. These two profiles of the scattering pattern are similar to those reported in the literature, [22] corresponding to the NG and SD phase separation, respectively. It should be noted the scattering intensity remains nearly constant for the initial 600s in both cases, i.e., there is a delay in the onset of phase separation, [33,34] an induction period after a temperature jump inside the two-phase region.…”

“…The phase separation takes places when a homogeneous blend undergoes a change of temperature that forces it to enter either the metastable or the unstable region in the temperature-composition phase diagram. [22] There is a drastic difference between the phase separation mechanisms that occurs for the two cases. When the system is quenched inside the metastable region, the phase separation occurs via slow nucleation followed by growth of the phase-separated domains (NG).…”

Comparison of the Characteristics of LDPE : PP and HDPE : PP Polymer Blends

“…Blends of PP with linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE) and ultra low density polyethylene (ULDPE) have been reported to be miscible, partially miscible or immiscible (Li, Shanks, & Long, 2001Utracki, 2003).…”

Historical Perspective of Advances in the Science and Technology of Polymer Blends

“…The use of the glass transition temperature to define miscibility was not uniformly accepted by the scientific community as it was not considered to be a true thermodynamic transition. A separate theory was proposed involving a "domain" size to explain the glass transition temperature behavior for "miscible" blends without the requirement of mixing of polymer molecules at the segmental level [39,40]. SANS experiments provided the experimental evidence to confirm that mixing was occurring at the molecular (segmental) level in many of the blends defined as miscible from glass transition results.…”