In Situ Characterization of the Reaction-Diffusion Behavior during the Gradient Interphase Formation of Polyetherimide with a High-Temperature Epoxy System

Abstract

This study presents two novel methods for in situ characterization of the reaction-diffusion process during the co-curing of a polyetherimide thermoplastic interlayer with an epoxy-amine thermoset. The first method was based on hot stage experiments using a computer vision point tracker algorithm to detect and trace diffusion fronts, and the second method used space- and time-resolved Raman spectroscopy. Both approaches provided essential information, e.g., type of transport phenomena and diffusion rate. They can also be combined and serve to elucidate phenomena occurring during diffusion up to phase separation of the gradient interphase between the epoxy system and the thermoplastic. Accordingly, it was possible to distinguish reaction-diffusion mechanisms, describe the diffusivity of the present system and evaluate the usability of the above-mentioned methods.

Unravelling the interphase - bond strength relationship in novel co-bonded thermoplastic - thermoset hybrid composites for leading edge protection of wind turbine blades

“…In addition to the type of the morphology, the size of the interphase containing certain morphological pattern may also influence the fracture toughness: for blends of PEI/dicyanate, an increase in the layer thickness of the nodular and dual morphologies increased the fracture toughness [38]. A review of the literature shows that although there have been various studies in literature related to the interphase formation and morphology of the co-bonded thermoplastics and thermosets [8,15,18,26,32,33,[39][40][41][42], quite few studies are available on the effect of interphase of the co-bonded TPs and fiber-reinforced TSs on the bond strength [32,33] (note that the term "co-curing" is often used in literature for "co-bonding"). Furthermore, no such study in literature focuses on polyester, which is a resin used in the manufacturing of wind turbine blades, and TPs compatible with it, which are important for LEP applications.…”

Double-Decker-Shaped Polyhedral Silsesquioxanes Reinforced Epoxy/Bismaleimide Hybrids Featuring High Thermal Stability

“…Epoxy resin is one of the most important thermosetting resins and is especially useful for high-performance applications due to its good adhesion to most substrates, outstanding chemical resistance to solvents and moisture, and utility in various applications in composite, coating, painting, and insulating for semiconductor or electric devices [1][2][3][4][5][6]. Nonetheless, conventional epoxy resin cannot meet the requirements for thermal or flame resistance, and thus high thermal stability polymers such as poly(ether imide) or poly(ether sulfone) have been used in epoxy resin to enhance this property [7][8][9][10]. Furthermore, nanomaterials such as polyhedral oligomeric silsesquioxane (POSS), clay, or graphene have also been reported as viable modifications to the epoxy matrix because these inorganic materials usually possess a higher thermal stability than organic polymers [11][12][13][14][15][16].…”

Thermoset/Thermoplastic Interphases: The Role of Initiator Concentration in Polymer Interdiffusion

“…Although co-bonding may refer to the bonding of two parts with or without an adhesive between them [ 1 , 2 , 3 , 4 , 7 ], in this work we will focus on co-bonding without adhesives, where bonding takes place by the interdiffusion of polymers that are in contact as the curing takes place. The interdiffusion of the bonded polymers, and, subsequently, the curing of the resin result in the formation of an interphase [ 2 , 4 , 8 , 9 , 10 , 11 , 12 ]. The size and morphology of the interphase have been shown to depend on the gelation time and viscosity of the resin, the thermodynamic affinity between the polymers, and the physical state of the thermoplastic [ 2 , 4 , 8 , 9 , 10 ].…”