Effect of Structure of Functionalizing Molecules on the Inter‐Macromolecular Reactions and Blending of Poly(ethylene‐co‐propylene) (EPM) with Poly(6‐aminohexanoic Acid) (PA6)

Abstract

Dedicated to Professor Giambattista Consiglio on the occasion of his 65th birthday Two different functionalizing systems, i.e., monohexadecyl maleate (= hexadecyl hydrogen (2Z)-but-2-enedioate) in the presence of dicumyl peroxide (= bis(1-methyl-1-phenylethyl) peroxide) or 4-carboxybenzenesulfonazide (= 4-(azidosulfonyl)benzoic acid), were used in distinct experiments to perform in a one-step procedure the formation of a EPM-PA6 graft copolymer, necessary to obtain a compatibilized blend, from a molten mixture of ethylene-propylene copolymer (EPM) and polyamide 6 (PA6). The characterization of the graft polymer by selective solvent extraction of the blends and the subsequent IR and NMR analysis of the various fractions established the occurrence of functionalization reactions preferentially onto the polyolefin with both reagents. Also the formation in good yield of graft copolymers at the phases interface was observed. Moreover, the morphology and thermal characterizations of the blends by means of SEM and DSC analyses were used to evaluate the compatibilization extent in comparison with blends obtained by the conventional two-step procedure or by the one-step procedure with commercial maleic acid derivatives.Introduction. -The one-step reactive blending of mixtures of polyolefins and polyamides was for the first time employed by Lambla and co-workers [1 -3] for blending low-density polyethylene (LDPE) or high-density polyethylene (HDPE) with poly-A C H T U N G T R E N N U N G amide 11 (PA11) by treatment with various peroxides alone or in the presence of maleic anhydride (MA), reagents that were used in low concentration to prevent or hinder sec-A C H T U N G T R E N N U N G ondary reactions. The removal of the ungrafted maleic anhydride favored the interchain reactions involving MA-grafted polyolefin macromolecules and the terminal NH 2 groups of the polyamide [4] [5]. These reactions are essential to achieve the compatibility necessary for the modulation of final properties [6] [7].Recently we obtained compatibilized blends of ethylene-propylene copolymer (EPM) and polyamide-6 (PA6) by performing the reaction in the presence of peroxide and a mixture of maleic anhydride/diethyl maleate (DEM) of different composition [8] with the concomitant functionalization of polyamide and formation of branched polyamide. The functionalization degree of the polyamide phase was generally very high (reaching up to 15 mol-%), favored by a larger affinity of polar DEM and MA toward the polar polymer phase. The grafting between the two polymers was affected by the extent of the polyamide branching, which consumed the functionalizing monomers [9].