Spin coating of a polymer film on a substrate with topography is modeled. Nonnewtonian fluid behavior, solvent diffusivity within coating, and coating leveling are related using this model. The dependence of the coating step height on initial coating concentration, spin speed, feature radial position, and feature dimensions is investigated. For a large feature, the coating profile is dominated by centrifugal force, while for small features the coating profile is dominated by capillary force and the coating is more level. A glassy polymer skin is formed during spinning. The coating profile is then controlled by shrinkage after the skin is formed. The predicted step height is within 10% of that measured experimentally.

Solvent concentration is an important factor for spin-coated film planarization. Two techniques, one an on-line optical method and the other an off-line gel permeation chromatography method, have been used to investigate the coating concentration change during spinning. The experimental observations are compared with the spin-coating model predictions. The modeled concentration and thickness are in close agreement with experiment. Under certain conditions, the spin-coating model can be significantly simplified. These conditions are discussed.

Experiments were performed to determine how the physical properties of coating solutions affect the planarization of spin‐coated films. The planarization of lines 25 μm wide and 0.67 μm high by 1 μm thick spin‐coated films were measured for solutions composed of different solvent‐polymer molecular weight pairs. Three solvents (toluene, methyl ethyl ketone, and chloroform), which have different evaporation rates, were selected as a means of controlling the solvent concentration in the film. Four polystyrenes ranging from 3.10 × 10 5   to   8.30 × 10 3 weight average molecular weights ( M w ) were used. Because the film thickness in these experiments was kept constant, the differences in planarization were due solely to the differences in coating materials. For a given solvent, step heights were significantly reduced by lowering M w from 310,000 to 44,100 but remained unchanged for reduction below the critical molecular weight M c . The step heights were essentially equal (0.40 μm) for all three solvents for M w < M c . Estimates of the solvent concentration in the film indicated that the solvent probably evaporated within the first few seconds of spin. As a result, the film viscosity increased rapidly so there was insufficient time for leveling before the film became glassy.

The final physical properties of semi-crystalline blown films are highly dependent on the crystalline morphology and orientation of polymer chains within the film. Simultaneous on-line SALS (Small Angle Light Scattering) and IR (Infrared) temperature measurements were successfully used to study crystallization during tubular blown film extrusion of LLDPE. SALS patterns were recorded at various vertical positions along the bubble. For LLDPE, an undeformed spherelulitic structure is formed if the stress level during processing is not too high. The change in average scattered intensity with axial position can be described using multiple step Avrami kinetic processes in parallel. The first step accounts for crystal growth and corresponds to the well-known temperature plateau. The later processes start with the impingement of the growing spherulites and may reflect secondary crystallization and orientation processes. Because the magnitude of the average intensity is responsive to changes in process conditions, the on-line SALS system is potentially a useful tool for monitoring process-property interactions.

The focus of this investigation was to determine the effect of barrel rotation and screw rotation on the flow rate and viscous dissipation inside the screw pump-extruder. The screw pump-extruder was built to allow for barrel rotation and screw rotation independently. A Newtonian fluid, Polypropylene glycol, was chosen as the working fluid. The experimental results can be summarized by noting that the pumping capacity of the device was independent of which element was rotated at constant angular velocity and that barrel rotation generated higher temperature rise than screw rotation for the two screws evaluated. Also this analysis suggested that a large amount of viscous dissipation inside this extruder arises from the clearance flow. A new analytical model was proposed to evaluate the viscous dissipation for screw rotation. Calculations using this new mathematical model provided good agreement with the experimental data for both barrel and screw rotation.