Engineering impact modification of anionically polymerized polyamide 6

Abstract

ABSTRACTA new approach to toughen anionically polymerized polyamide 6 (aPA6) is presented using an additive monomer that simultaneously polymerizes and undergoes reaction‐induced phase separation (RIPS) during aPA6 polymerization. In this work, the selection of additive, concentration, and reaction conditions are controlled in such a way to produce rubbery domains of the proper size and interparticle distance necessary for effective toughening without the diminishment of other engineering properties. This method circumvents the issues of particle dispersion and mixture viscosity that are commonly associated with other conventional methods of impact modification thereby making it an ideal system for fiber‐reinforced aPA6 reaction injection molding. Controlled phase separation, modulus retention, and increased crystallinity are achieved at low additive concentrations. The additive monomer used in this case is octamethylcyclotetrasiloxane (D4). D4 undergoes RIPS during aPA6 polymerization and simultaneously polymerizes to produce polydimethylsiloxane. Optimal properties to maximize fracture energy without reducing the modulus are achieved with 2 wt % D4. The fracture mechanisms are investigated and results show approximately a 3‐fold increase in energy release rate and a twofold increase in Izod impact energy. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46823.