Mechanisms for combining polyamide and epoxy and their effects on mechanical performance—A review

This paper provides an in-depth study in the various methods for toughening epoxy (EP) resin with polyamide (PA) across a range of length scales—from the atomic to the macroscopic. This allows for a fundamental understanding of the EP-PA system, as many of the atomic interactions and their kinetics inform the macroscopic mechanical properties. The kinetics of the EP-PA reaction prove that covalent bonding is energetically favorable, enabling chemical crosslinking between EP and PA. The two polymers can then mechanically interlock under a number of different processing conditions including forming a homogeneous mixture of the two, incorporating the PA into the EP in the form of fine particles, or adding the PA to an EP-fiber composite. Though each of these methods allows for the tailoring of processing conditions and final structures to an individual use, the literature shows that the underlying physical and chemical interactions can be applied to all EP-PA systems. Thus, lessons learned through the study of one EP-PA structure can be valuable in predicting the behavior of different EP-PA blends and material form combinations.