Amination of polypropylene‐g‐(maleic anhydride) using reactive extrusion

Abstract

AbstractWe report synthesis of a radical scavenging aminated thermoplastic polymer through reactive extrusion of polyethyleneimine (PEI) with a polypropylene and polypropylene‐graft‐maleic anhydride (PP‐g‐MA) meltblend. The reaction was confirmed using acid orange 7 (AO7) amine density assay, toluidine blue O (TBO) carboxylic acid density assay, Fourier transform infrared spectroscopy (FTIR), and a migration assay. FTIR spectra revealed a reduction of the asymmetric stretching of the maleic anhydride (MA) carbonyl group at 1777 cm−1 and the emergence of the maleimide carbonyl peak at 1702 cm−1. AO7 supported surface orientation of grafted amine groups by introduction of 7.22 nmol cm−2 primary amines, corresponding to the reduction of surface carboxylic acids quantified by TBO from 12.46 nmol cm−2 to 0.43 nmol cm−2. After incubation (40°C, 10 days) in ethanol, acetic acid, and water, < 0.1 mg cm−2 PEI migrated from the materials, supporting the covalent nature of the grafting. Antioxidant activity was demonstrated exhibiting 5.90 and 4.31 nmol Troloxeq cm−2 in aqueous and organic environments, respectively. Results indicate a successful condensation reaction during reactive extrusion, producing an aminated thermoplastic polymer with antioxidant activity for target applications such as food packaging, wastewater treatment, carbon capture, and others.