Effects of mixing temperatures on the morphology and toughness of epoxy/polyamide blends

Abstract

ABSTRACT:A new mixing process was explored to increase further the fracture toughness and to investigate the toughening mechanisms of epoxy/nylon blend. In this process, without mechanical mixing, the mixtures of epoxy and premade nylon 6 powder were heated without the curing agent to specific temperatures, referred to as the "mixing temperature." For epoxy/nylon blends, at sufficiently high temperatures, a semi-interpenetrating network-like structure can be developed at the interphase via the reaction between the amine end group and the epoxide group. The depth of interphase and the extent of reaction depends on the mixing temperature. The strong dependency of the fracture energy on mixing temperature reveals the positive effect of the newly developed structure at the interphase. The increase of fracture toughness is possibly due to the enhanced crack fingering bifurcation/deflection mechanism resulting from the lamellae developed in the interphase and the enhanced plastic deformation of epoxy as a result of preyielding of the interphase.

Cure behaviors and mechanical properties of carbon fiber-reinforced nylon6/epoxy blended matrix composites

“…Their low toughness, especially in the presence of sharp cracks, reduce their applicability in various industries. Hence, improved toughness of brittle epoxies is greatly desired [11][12][13][14][15]. The toughness of epoxies has often been successfully enhanced by incorporating a second phase, such as rubber [16] or thermoplastic polymers [17].…”

Clay induced thermoplastic crystals in thermoset matrix: Thermal, Dynamic mechanical, and morphological analysis of clay/nylon‐6‐epoxy nanocomposites

“…It is extensively used as coatings and adhesives in automotive, construction, and aerospace segments because of its excellent physical, chemical and mechanical properties . It possess outstanding stiffness and strength that make it a useful matrix material in advanced structural composites . Despite such desirable properties, epoxy resins are extremely brittle in nature due to highly cross‐linked structure and glassy nature.…”

“…Toughening of epoxy has often been successful by incorporating rubber or thermoplastic polymer as second phase such as polysulfone, polyester , poly(ether‐imides), poly(ϵ‐caprolactone) , and polyamides . The thermoplastics polymers are preferred over rubber since they do not decrease the inherent properties of epoxy matrix as in case of rubbers .…”

A novel flame retardant of spirocyclic pentaerythritol bisphosphorate for epoxy resins

“…Thermoplastic materials are being used for toughening the epoxy resins instead of rubbers because mechanical and thermal properties are not sacrificed to the same extent as when rubbers are used. Therefore, more attention has recently been give to the modification of epoxy resins by high performance tough thermoplastics, such as polyethersulfone, polyetherimide, carbopolyimide, and polyamides 4–6. In this work, polyamide (PA‐650‐I) is chosen as a curing agent because of no toxicity, good adhesion and flexibility, easy operation and wide ranges of curing temperature, and variable composition.…”