Formation of short and long chain branches during the free radical functionalization of polyamide 6 in the melt

Polyamide 6 (PA6) was treated in the melt at 230 degrees C in a discontinuous mixer with diethyl maleate (DEM) and dicumyl peroxide (DCP). The grafting of DEM to PA6 chains was investigated by H-1 NMR analysis, and it reached easily up to 4.5 mol %. The grafted diethyl succinate groups (DES) can successively react with terminal ammo groups of different polyamide macromolecules, thus yielding branched polyamide macromolecules. The average degree of branching, determined by titration analysis, is about one per macromolecule under the used experimental conditions and can be improved by further blending with PA6. Thermal analysis of branched PA6 showed lower melting and crystallization temperatures than those of simply processed linear PA6. Blends of unmodified and functionalized polyamide showed a higher viscosity and a more effective shear thinning behavior than the simply processed linear PA6. Experimental evidence was discussed, and a possible reaction mechanism was proposed.