Volume 3, Issue 1

An attempt is made to give a survey of polymer processing during the past 50 years, with a backward glance to earlier periods and to roots of development in related branches of industrial production. Selected topics are treated in some detail, with comments and comparisons, showing typical trends and forecasting possible progress in the near future: Extrusion, injection molding, blow molding, calendering and sundries. A separate chapter deals with the role of theory and experiment in polymer processing. Generally, it may be stated that in the main fields development is changing from a practical art to applied science. – For rounding-off the article is closed with some anecdotes and stories about pioneers in the front line of plastics progress.

Polymer-Polymer blends containing ethylene-methacrylic copolymers (EMAA) and polyethylene terephthalate (PET) (where PET is the minor component) have been investigated. The permeability properties and the morphology of these blends, when the polyolefin phase is mildly crosslinked with small amounts of an agent that preferentially crosslinks the ethylene copolymer was also studied. The permeability barrier properties of such polymer blends increase as the concentration of the crosslinking agents increase until excessive crosslinking takes place. The morphology of the blends – the size of the dispersed particles – change significantly as more coupling agents are used. These techniques afford us a novel technique to improve the permeability barrier properties by control of the particle size of the barrier polymer.

Qualitative and quantitative studies of laminar mixing in a corotating disk processor chamber were carried out experimentally and theoretically. Theoretical study of the flow field in a parallel chamber indicates the presence of an orthogonal circulation flow pattern with a double circulation pattern at constant radii. A color tracer was used for studying experimentally the laminar mixing. The experiments verified the theoretically predicted flow fields and showed that the two orthogonal flow patterns bring about a composition randomization throughout the volume. Quantitative measurement of interfacial area evolution helped in characterizing the laminar mixing behaviour of such a configuration.

The paper deals with the influence of the local mixing state on the product properties in a mass styrene-acrylonitrile copolymerization stirred tank reactor in steady state. Experimental investigations at different stirrer speeds have been carried out in a specially constructed bench scale reactor. The idealized models for microfluid and complete segregation were used to calculate the polymer mass fraction, the weight average polymerization degree and the molecular nonuniformity at the outlet of the reactor. The apparatus operated as an “ideally mixed” continuous stirred tank reactor under all chosed conditions as demonstrated by measurements of the residence time distributions. The results are: the segregation model describes the experimentals at low stirrer speeds and the microfluid model is appropriate at high agitator revolutions. Polymer mass fraction, weight average polymerization degree and molecular nonuniformity as functions of average residence time calculated on the basis of both the idealized models indicate intersection points. A high extent of microfluid must not tend to decrease the molecular nonuniformity. The agitator speed can be limited in such a way that it is just sufficiently high to approximate the residence time distribution of an “ideally mixed” continuous stirred tank reactor in order to avoid dead spots and channelling. Segregation is not dangerous for the reactor performance and the product properties.

A model is presented which can be used to predict the flow under consideration of fibre-matrix separation and fibre orientation during sheet-like parts compression molding of long fibre-reinforced thermoplastics for isothermal state. During a molding, fibre content and fibre orientation distributions are calculated from the separation and orientation equations, and the viscosity of composites is expressed as a function of fibre content and fibre orientation. Based on the viscosity, the model was developed using the finite element method, and random and unidirectional reinforced composites are simulated. By comparing the theory with experimental results, the model accurately predicts mold filling patterns for the composite materials.