Possibilities of formation or modification of polymers by means of chemical reactions during processing (polymer processing)

Abstract

AbstractThe trends for polymeric engineering materials are marked by the search for defined thermomechanical, plastic‐elastic stability of dimension, and surface properties. This trend is caused by the demands for higher usage values of the polymers and more efficient processing technologies. The greatest chances are granted to the chemical modification and reactive compounding of known polymers to reach the aims of this development. Thermodynamically, most of the polymers are incompatible with each other and no sufficient disperse distribution is reached by only physical mixing. During the last 10 years a good compatibility at the interfaces has been found as one supposition and the influence of the viscosity of the polymer components and of the shear rate in the mixing machine as a further supposition to reach a fine‐dispersed distribution. Polymer composites with fibres and fillers are a further importent group of materials. The properties of composites are also determined by the interactions in the interfaces, by the dispersity of the fibres and fillers, and by the physical properties of the interfaces. Polymer‐analogous reactions, polymer blends, and polymer composites with and without low molecular reactants in the melt are decisively influenced by the parameters of the compounding machine. The quality of mixing, distribution of the residence time and of the shear rate, and the temperature profile of the reaction mixture are essential criterions for the course of the reaction. Continuous and quasi continuous technologies as, e. g., extruders and internal mixers are preferred. The lecture will deal with the present state and technical possibilities. Polymer syntheses in screw extruders are a new trend for the future. All these possibilities offer prospective chances of development.