Study of reaction between a low molecular weight, highly functionalized polyethylene and hexamethylenediamine

Abstract

Reactions were carried out between a low molecular weight, highly functionalized maleic anhydride-grafted polyethylene and hexamethylenediamine in a melt blender at 150 °C for various stoichiometric ratios of functional groups. For all compositions, two peaks were observed in the mixing torque data. The appearance of the first peak, observed soon after the introduction of the reactive mixture to the melt blender, was independent of composition. The second peak was composition-dependent. Gel content and FTIR analyses suggest that the first peak is a result of melting functionalized polyethylene and a reaction of the anhydride and amine functionalities, while the second was mainly a result of crosslinking. The time between the first and second peak defines a processing window, in which the reaction mixture is thermoplastic. Higher temperature melt processing of the thermoplastic reaction products converted these materials to thermosets. During this conversion, the progress of the anhydride-amine reaction was studied using FTIR, as well as by measuring the generation of the insoluble crosslinked material. The FTIR results reveal that the reaction between anhydride and amine moieties results in the formation of an amide intermediate, which then converts to cyclic imide at higher temperatures. The analysis suggests that the use of the FTIR anhydride absorption to assess the degree of reaction is misleading in these reactions. Mixing torque data from a melt blender for reactions carried out between maleic anhydride-grafted polyethylene and an aliphatic diamine suggest longer reaction times than previously proposed for such systems. Separate mixing torque peaks were observed for melting of polymers and crosslinking resulting from reactions between amines and anhydrides. Analyses suggest that assessing the chemistry and degree of reaction based on the maleic anhydride response in FTIR is misleading. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.