Reactive Compatibilizer Precursors for LDPE/PA6 Blends. 1: Ethylene-Acrylic Acid Copolymers

Full Paper: Ethylene/acrylic acid copolymers (EAA) with different acrylic acid (AA) contents have been used as compatibilizer precursors (CPs) for blends of two grades of low-density polyethylene (LDPE) with polyamide-6 (PA). In the first part of the work, binary blends of the CPs with LDPE and with PA have been studied in order to get an insight into the interactions of the EAA copolymers with the blends components. It has been shown that the CPs form immiscible, yet highly compatible, blends with LDPE. Investigation of the binary CP/PA blends provided evidence that acidolysis reactions occur between the carboxyl groups of the CPs and the amine and amide groups of PA, with formation of CPIPA graft (CP-g-PA) copolymers, although these reactions need relatively long times to go to completion. In the second part of the work, ternary LDPE/PA/CP blends have been prepared and characterized with a number of techniques. It has been shown that the addition of only 1-2 phr of CP into the LDPE/PA blends is sufficient to enhance interfacial adhesion, to improve the minor phase droplet dispersion and to hinder co-alescence. The effectiveness of the investigated CPs increases with an increase of the AA content from 6 to 11 wt.-%. Partial neutralization of the carboxyl groups of EAA with zinc also seems to improve the CP efficiency and this effect is thought to result from an acceleration of the acidolysis reactions responsible for the formation of CP-g-PA copolymers.