Volume 8, Issue 1

The problems of waste disposal have become major issues in Japan. Japan must deal directly with these issues. In early 1970s, “KOGAI” or environmental pollution already loomed as major problems. A number of technical innovations and systems were proposed to recycle various waste products. Based on those experiences, current situation of urban refuse, waste plastics, scrapped tires and scrapped automobiles in Japan and their challenges toward 21st century are discussed.

The design of internal mixers for the rubber industry has traditionally been based on the basis of intuition rather than a knowledge of the fluid mechanics of motions in the internal mixer. In recent years, efforts have been made to numerically simulate the flow and mixing characteristics in internal mixers. The simulation effort is important for the understanding of mixing mechanisms in the internal mixer, and furthermore, to provide a basis for rational design. In this paper, we develop a new model based on cylindrical coordinate hydrodynamic lubrication theory for internal mixers. This allows full consideration of curvature in an internal mixer. Numerical techniques are used to carry out the calculations of the pressure field and flux field for various rotors described in the patent literature. This is done for a Newtonian fluid in a fully filled mixing chamber. This type of calculation is of key importance in the design of flight arrangements on internal mixer rotors.

The polymer-metal interface in a sliding plate rheometer was modified by applying three fluoropolymer coatings to the plates in order to examine their effect on the wall slip behavior of a linear low density polyethylene. All three coating materials increased the slip velocity markedly. Furthermore, it was found that the critical shear stress for the onset of slip scales well with the work of adhesion of the interface, suggesting that slip is the result of adhesive failure at the interface.

Experiments were performed in capillary and slit rheometers to determine the effects of the presence of fluoropolymers at the polymer-wall interface on wall slip and extrudate distortion of a molten high density polyethylene. Two fluoropolymers were used to modify the interface. It was found that one of these decreased slip compared to the clean interface while the other increased slip. However, both were found to improve extrudate appearance, thus indicating that both adhesion promoters and slip promoters may improve extrudate appearance. The mechanism underlying this rather surprising conclusion is also discussed.

The maleation of polypropylene melt with a peroxide as free radical initiator has been carried out isothermally in a continuous flow reactor and in a batch flow reactor. The continuous flow reactor is designed to provide significant levels of extensional strain in the fluid while the batch flow reactor provides a simple shear flow with uniform residence time. In both reactors, less than 1 part per hundred of dicumyl peroxide (dissolved in xylene) is added to a preblended single phase mixture of polymer melt and dibutyl maleate. The relative extent of maleation is much higher in the continuous flow reactor than in the batch reactor with comparable shear strain rates and mean residence times. As the feed rate and the rotation speed are varied at a fixed temperature in the continuous flow reactor, the highest degree of maleation is obtained under conditions where fluid dynamics computations show the stretching of a fluid element to be the greatest. Hence, increasing shear alone leads to rather limited increases in extent of maleation. These results emphasize the importance of the detailed deformation field for carrying out functionalization reactions on polymer melts.

Non-isothermal, melt film-blowing is analysed by means of a nonlinear integral constitutive equation that incorporates shear history effects, spectrum of relaxation times, shear thinning and extension thinning or thickening. The temperature history, as predicted by the simultaneously solved energy equation, is introduced into the constitutive equation by means of the appropriate shift factor incorporated in the linear modulus of the constitutive equation. The resulting system of integrodifferential equations is solved by finite element discretization and Newton iteration. Bubble shape, velocity, temperature, stress and thickness profiles are predicted simultaneously. Predicted film thickness, temperature and stress profiles of blowing of polystyrene are compared with experimental data taken from the literature.

The problem of heat exchange and non-isothermal crystallization of a polymer film (leaving an extruder) on the surface of chilled rolls is discussed. Factors such as enthalpy of crystallization, unsymmetric boundary conditions and dependences of thermal properties of a polymer on temperature and degree of crystallinity are taken into account. The statement of the problem is based, first, on joint analysis of non-stationary energy balance equation and kinetics of non-isothermal crystallization and, second, on inclusion of dependences of thermal properties of a polymer on temperature and crystallinity into a mathematical model under discussion. The influence of technological and engineering factors on the quality of film is discussed.

A novel process to produce microcellular PVC foams with a very homogeneous cell distribution and cell densities ranging from 10 7 to 10 9 cells/cm 3 is described. Microcellular PVC foams with relative densities (density of foam divided by the density of unfoamed polymer) ranging from 0.15 to 0.94 have been produced. In this paper, experimental results on bubble nucleation and growth are presented. It was found that the bubble nucleation density increases with foaming temperature and eventually reaches a limiting value, while the average bubble diameter is relatively independent of the foaming temperature. A majority of the cell growth was found to occur in the early stages of foaming.

An experimental study of the development of orientation of mixed fiber and flake polymer compounds in polymer processing operation including extrusion and molding is discussed. Aramid fiber and talc and mica flakes are studied. The orientation of the particles is determined using wide angle x-ray diffraction. It is found that mixed particle systems lead to lower orientation of both fibers and flakes. The fibers tend to orient in the primary machine direction, while the flakes tend to orient perpendicular to the fibers. This is distinct from fiber compounds and flake compounds where fibers orient in the plane of the machine and transverse directions and flakes orient parallel to machine surfaces.