Thermoplastic Toughening of a Semiaromatic Polyamide with an Amino-telechelic Polyethylene

Semiaromatic polyamides are used for metal replacement in advanced engineering applications to reduce weight and improve efficiency, but their range of application is limited by their inherent lack of ductility and toughness. Here, we combined semiaromatic polyamide poly(hexamethylene terephthalamide-co-isophthalamide) (PA6TI) with up to 30 wt % amine-terminated polyethylene (PE(NH₂)₂) by high-temperature melt compounding, which was suggested to lead to the formation of PA-PE block copolymers at the interface between the PE(NH₂)₂ and the PA6TI. This resulted in PA6TI/PE(NH₂)₂ blends with smaller, more uniform particle sizes than in PA6TI blended with nonfunctional PE or the commercial impact modifier, maleic anhydride-functionalized styrene-ethylene-butylene-styrene (SEBS) under the same conditions. The PA6TI/PE(NH₂)₂ blends and the corresponding glass fiber-reinforced composites consequently showed significantly greater increases in room-temperature tensile ductility and fracture energy with respect to unmodified PA6TI, as well as maintained mechanical stability at high temperatures, and only modest decreases in stiffness and strength, even at high PE(NH₂)₂ contents. These improvements were attributed to the crystallinity of the PE(NH₂)₂ particles and to improved morphological stabilization and matrix-particle adhesion, consistent with the presence of PA-PE block copolymer at the matrix-particle interfaces.