Study of Shear and Extensional Viscosities of Biodegradable PBS/CO2 Solutions

The purpose of this research is to study the pressure drop profiles of biodegradable polybutylene succinate (PBS)/CO2 solutions in a slit die and to measure the rheological properties of the solutions as a function of the blowing agent concentration. A slit die with four pressure transducers has been designed to describe the effects of shear rate, temperature, pressure, and gas content on the shear viscosity and extensional viscosity of the flowing PBS/CO2 solutions. The low shear rate viscosity of the pure polymer was measured using a cone and plate rheometer. Extensive experiments were conducted to investigate the polymer/gas solution viscosities at five different shear rates, three temperatures and five gas contents. Cross-Carreau model and generalized Arrhenius equation were used to describe the shear-viscosity behaviors of PBS/CO2 solutions. The extensional viscosity of solution was modeled based on Cogswell’s equation.

Rheological Behavior of Mixtures of Polystyrene with HCFC 142b and HFC 134a

The processes for the production of thermoplastic foams, often in the shape of extruded sheets or boards, are largely dictated by the rheology of the mixture of a polymeric matrix with a blowing agent. This paper focuses on the theological behavior of mixtures of polystyrene (PS) and physical blowing agents (HCFC 142b and HFC 134a), examined using a commercial on-line rheometer mounted on an intermeshing co-rotating twin-screw extruder. The PS resin was extruded while the blowing agent was injected at high pressure and various compositions. The extent of plasticization was found to be dependent on the blowing agent concentration and its type. The effects of type of blowing agent, composition, pressure, shear rate and temperature on the theological response were measured. These variables were incorporated into a generalized mathematical model, which described the viscosity of the PS/blowing agent mixture over the studied range.

Rheological Behavior of Ethylene-Octene Copolymer Vulcanizates: Effect of Blowing Agent and Precipitated Aluminium Silicate Filler

An experimental study of the rheological behaviour of aluminium silicate filled ethylene-octene copolymer vulcanizates in extrusion containing blowing agent has been carried out. The cell morphology development has been studied through scanning electron microscope. Rheological properties of unfilled and aluminium silicate filled systems with variation of blowing agent, extrusion temperature and shear rate have been studied using Monsanto processability tester (MPT). The total extrusion pressure (ΔPT), apparent shear stress (x), apparent viscosity (ηa), and die swell (%) of the unfilled and aluminium silicate filled compounds have been determined by using MPT. It is found that there is a reduction in stress and viscosity with blowing agent loading. It is observed that incorporation of blowing agent led to decreased shear thinning behaviour resulting in an increase in power law index. The viscosity reduction factor (VRF) of unfilled vulcanizates is found to be dependent on concentration of blowing agent, shear rate and temperature, whereas VRF of aluminium silicate filled vulcanizates is found to be independent of shear rate and temperature but dependent on blowing agent concentration.