Reactive compatibilization as a proper tool to improve PA6 toughness

Abstract

Polyamide 6 (PA6) is a widely applied thermoplastic, however, drawbacks as low notch impact strength and high moisture absorption hinder its commercialization. Seeking improvements for PA6, this work investigated blends based on PA6/maleic anhydride grafted ethylene propylene diene copolymer (EPDM-MA) with 1% maleic anhydride (MA). In the first step, blends were processed using a co-rotational twin-screw extruder, afterwards, pellets were injection moulded. Torque rheometry, impact strength, tensile strength, thermal deflection temperature (HDT), differential scanning calorimetry (DSC), contact angle and scanning electron microscopy (SEM) were performed and the main properties were defined. Torque of PA6/EPDM-MA blends increased compared to neat PA6. Only subtle decreases were verified in the tensile strength, elastic modulus and HDT parameters. Nevertheless, significant increases were observed for the elongation at break and the impact strength. EPDM-MA addition to PA6 did not affect its melting and crystallization parameters. Contact angle of all blends increased when compared to PA6, suggesting higher hydrophobic character of PA6/EPDM-MA blends. Improved results were collected for EPDM-MA 10%, reaching increases of 850% and 213% in impact strength and elongation at break. From SEM images, particles were observed with diameters ranging from 0.1 to 2 μm, which were well dispersed and properly distributed in the PA6 matrix; additionally, for the blends with 10%; 12.5% and 15% EPDM-MA, higher level of plastic deformation was reached corroborating with the significant increase in the impact strength and elongation at break.