Maleation of polypropylene and EPDM through reactive extrusion using the Alder Ene reaction.

摘要

An investigation into the site-specific functionalization of several polymers within a co-rotating intermeshing twin screw extruder was initiated. The Alder Ene reaction between maleic anhydride and the inherent double bond of polypropylene and EPDM, was chosen for the high temperature environment of the extruder to accomplish the desired reaction. In order to improve the incorporation of maleic anhydride into the polymer, several Lewis acids were employed as catalysts in the reaction. The reactions were carried out in a round bottom flask, a batch reactor, a batch mixer, a single screw extruder and a co-rotating intermeshing twin screw extruder. Characterization of the maleated products by FT-IR, {dollar}sp1{dollar}H NMR, DSC, and GPC was used to differentiate between site-specific attachment and free radical grafting of the functionality. Polyisobutylene was used to carry out preliminary studies on the high temperature application of Lewis acids in the Alder Ene reaction. A low molecular weight polypropylene wax (Polypol-19) was chosen as a model material to study the kinetics of the reaction and identify reaction parameters useful for reaction optimization purposes.; The degree of functionalization was determined by infrared analysis, though an alternative method, explored with EPDM, also showed a direct correlation between the level of maleation and the mechanical properties of an ionic network formed by neutralizing the maleated rubber. Temperature and maleic anhydride concentration were found to be the most significant factors for this Alder Ene reaction. Increased temperature and maleic anhydride reactant concentration were found to improve the extent of reaction.; The Lewis acid, which was employed as a solid or mixed in phase with molten maleic anhydride, improved succinyl anhydride incorporation with reduced acid concentration. Among the Lewis acids examined, aluminum chloride gave rise to the greatest improvement of succinyl anhydride incorporation, at least into the rubber. Ruthenium chloride was found to improve the extent of reaction in Polypol-19, degraded polypropylene and EPDM. Employing the Lewis acid in phase with the reactant (maleic anhydride) was shown to lead to higher conversion. Unlike the homogeneous catalyst system, the applicability of second order kinetics to the heterogeneous catalyzed system provides immediate evidence of this phenomenon. In general, even in the absence of catalyst, the application of a second-order kinetic model to the measured succinyl anhydride results, was not valid over the entire temperature range studied due to side reactions, particularly vinylidene isomerization and homo-polymerization of maleic anhydride. (Abstract shortened by UMI.)