A new constitutive model with internal structure parameter is presented in this study for simulating orientation and deformation of polymer chain in the post/filing stages of injection molding process. Implementation of such a model is based on a hybrid finite-element/finite-difference numerical solution of the generalized Hele-Shaw flow. The simulation of a compressible viscoelastic fluid under nonisothermal conditions has not yet been discussed in most previous works. In addition to the distribution of pressure, temperature, density, and velocity, theoretical predictions also include shear and normal stresses, which can be used for subsequent calcula-tion of residual stresses. An amorphous material, namely a commercial-grade poly-styrene (PS), was used in the present work. Good agreement is obtained between the simulation and experimental pressure trace from this study.

In this study, the dynamic interfacial properties between an isotropic polymer and a thermotropic liquid crystalline polymer (TLCP) were investigated by measuring the time-dependent interfacial tension between them. As a TLCP drop retracts in a flexible polymer matrix, the evolution of its shape is recorded by microscopy. By fitting the ellipsoidal model of Maffettone and Minale, the model of Marrucci and Santo, and large deformation ellipsoidal models by Jackson-Tucker and Yu-Bousmina, the interfacial tension could then be determined. It was found that the retraction of a TLCP ellipsoidal drop in a flexible polymer cannot be described by these models as accurately as in Newtonian systems. The apparent interfacial tension obtained from these models evolves with time; the evolution is ascribed to the slow relaxation of domain orientation within the TLCP drop.

The deformation of a viscoelastic drop suspended in a homogeneous viscoelastic matrix is investigated. The drop and the matrix fluids are assumed to obey linear viscoelastic constitutive equations. Small-deformation analysis is carried out on the basis of the general solution for creeping flow around a spherical drop. The corresponding stress is calculated by extending Batchelor's approach to viscoelastic media for both small and large deformations. Good agreement was found between the model predictions and experimental results available in the literature.

We study the interaction between a surface-anchoring colloidal particle and a liquid-crystalline host, and in particular the formation of orientational defects near the particle. A mean-field theory based on the nonlocal Marrucci-Greco nematic potential is used to represent molecular nteractions in an inhomogeneous orientational field. An evolution equation for the molecular configuration tensor is solved numerically whose steady state minimizes the total free energy of the system. With strong homeotropic anchoring on the particle surface, three types of solutions may appear depending on initial conditions and particle size: Saturn rings, satellite point defects, and polar rings. The Saturn ring remains stable on micrometer-sized particles, contrary to previous calculations but consistent with experiments. A phase diagram is constructed for the three regimes. Based on the free energy, the most stable state is the Saturn ring for smaller particles and the satellite defect for larger ones.