| During melt-melt blending of two polypropylene melts in a co-rotating twin screw extruder, the distributive mixing performance is studied using the interfacial reaction of two functionalized macromolecular tracers, which were separately blended into each of the polymer melts. The two reactive tracers are anhydride and primary amine functionalized polypropylenes. The former was prepared by introducing the anhydride functional group into terminal double bonds in a low molecular weight polypropylene through a two-step hydrosilylation reaction. The latter was obtained by an imidation reaction of the anhydride functionalized tracer and 1,6-diaminohexane. The two polymer melt streams, which included one of the reactive tracers respectively, were fed into the twin screw extruder from the hopper, as well as from a downstream position along the twin screw extruder through a single screw extruder. During the mixing process, when the two polymer melt streams meet each other, interfacial area is created and the two functionalized tracers react with each other at the growing interface.; Due to the high viscosities of the polymer melts, diffusion was negligible during the short residence time in the twin screw extruder. The fast reaction kinetics guaranteed that this interfacial reaction was mixing controlled during the extrusion process. Some preliminary experiments verified that the reactive tracers were compatible with the high molecular weight polypropylene. The reaction conversion was linearly related to the generation of interfacial area, or the mixing performance during the melt blending process. Using the sampling plates located upstream and downstream of a kneading block, polymer samples were collected, as well as from a dual strand die at the exit of the twin screw extruder. The reaction conversions at these three positions were determined by analyzing the decrease of the relative peak height of the anhydride groups in the samples in FTIR spectra. Therefore, the mixing profiles can be described by evaluating the development of the reaction conversion along the extruder during the mixing process. Various experimental variables, such as melt viscosity, flow rate, screw speed, kneading disk staggering angle and thickness, were explored based on their effects on the mixing performance. Using white pigmented pure polypropylene, the degree of fill along the twin screw extruder was also studied at the same experimental conditions as those employed in the mixing experiments. (Abstract shortened by UMI.)... |
