Preparation of sulfonated polypropylene and its dyeability

Abstract

In this thesis, a two-step process is invented to prepare sulfonated polypropylene (SPP) from chlorinated polypropylene (Cl-PP) via thiolation and successive oxidation in order to enhance the dyeability of polypropylene (PP). With a short thiolation reaction time of three hours in a NMP solution, 1.7~20.5% of sulfur can be incorporated into a polypropylene bulk effectively. Chlorine-thiol substitution and hydrosulfide conversion were examined by elemental analysis, and their behaviors as a function of the SH/Cl ratio can be explained using an equilibrium model between hydrosulfide and accessible Cl at a given time scale. Oxidation of thiol has been done successfully using hydrogen peroxide. The evolution of oxidation intermediates such as sulfoxide, sulfone, sulfinic acid, and sulfonic acid can be identified by Raman and FT-IR analyses. SPP can be stained by basic dye very effectively, and its dye uptake reaches 190mmol-dye/kg-polymer for 3.6mmol-S/g-polymer. This ability is 20 times more effective than that of Cl-PP on a molar basis dye uptake. Thus, it is clear that modification is done effectively for enhancing the dyeability of polypropylene. Thermal stabilities of the thiolated polypropylene (TPP) and the sulfonated polypropylene are characterized by TGA. Thermal stability of the polypropylene according to substituents is increased as following order: -SH > -Cl > $-SO_3H$. Glass transition behaviors are characterized by DMTA and temperature modulated DSC. The glass transition temperature (Tg) of TPP and SPP is increased as the content of substituent is increased. Two glass transition peaks are observed for Cl-PP and TPP with low content of sulfur. PP/Cl-PP and PP/SPP blends systems are investigated. Cl-PP can be well dispersed in polypropylene in a short mixing time. The Tg of the Cl-PP blended in PP lowered compared to the bulk Cl-PP. In the PP/SPP blend, SPP with lower content of sulfur shows better dispersion. SPP with low content of sulfur can...