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The flow and processing behavior of commercial plastics is determined not only by the characteristics of the base resin but also by the presence of additives of various kinds. In this study the influence of a number of additives on the rheological behavior of molten ABS was investigated using a capillary extrusion rheometer and a Weissenberg rheogoniometer. The additives studied included molding lubricants, rubber impact modifiers, flame-retardant additives, and residual unreacted components remaining from the polymerization process. The mechanisms by which these species affect flow characteristics are described.

Fiber spinning experiments were carried out with an α-methyl styrene/silicone block copolymer under various sets of spinning conditions. The behavior observed was very sensitive to the ambient axial temperature profile employed along the spinline and to the initial melt temperature at the die. By optimizing these parameters, very high draw ratios (>400 to 1) could be achieved. Under less optimum conditions, filament rupture and instabilities such as draw resonance, accompanied by periodic diameter and spinline tension fluctuations, were noted. Tensile stress and axial velocity gradient profiles were obtained along the spinline under a variety of spinning conditions. These profiles, together with an independent: rheological characterization of the polymer, provide insights into the mechanisms giving rise to the various types of behavior observed.

A new capillary rheometer incorporated in an instrumented transfer molding press has been developed. This rheometer is effective for determining the viscosity characteristics of thermoset molding compounds under both isothermal and typical molding conditions. In examples of the rheometer's utility, the power law indices of two commercial epoxy molding compounds have been determined to be approximately 0.7. Additionally it has been shown that preconditioning typical epoxy compounds at 47 percent relative humidity causes a viscosity decrease of about 40 percent owing to plasticization of the epoxy resin.

The capillary flow instability resulting in extrudate distortion has been studied for ethylene polymer melts using a molecular structure approach. It is found that the instability initiates at a critical value of elastic strain energy independent of (average) molecular weight for linear polyethylene. Once the flow breaks down, a slip interface within the melt is formed near the capillary wall, causing an abrupt increase in volumetric throughput. The velocity gradient within the melt remains continuous through the instability, however. Low molecular weight species present in the molecular weight distribution of linear polyethylene tend to suppress slip. Blends of linear and branched polyethylene exhibit instability behavior characteristic of both components throughout the entire range of composition. Results are discussed in terms of specific molecular mechanisms.

Studies of polymer morphology under ideal conditions approaching equilibrium structures have been shown to be valuable in the development of an understanding of the relationship of properties to structure. Practical fabrication operations do not permit the achievement of equilibrium structures in commercial products and its is therefore necessary to study the effects of processing on the actual structures that result. In addition, an understanding of the effects of processing variables on properties permits the development of fabrication operations which can be directed toward the improvement of properties. Topics covered include the effects of hydrostatic pressure during processing, effects of combinations of pressure and thermal history, relationships between thermal history and crystallization rates in isotactic polymers and the kinetic and morphological effects of flow deformation on crystallizable plastics.