Optimizing the Magnetocuring of Epoxy Resins via Electromagnetic Additives

Abstract

offers a non-contact method of curing, with minimal substrate heating. Early attempts at AMF methods employed ferric oxide nanoparticles that were prone to aggregation and scorching of the resins. [5] This limited the technology to water-based formulations. Magnetocuring advances AMF induction through incorporation of Curie temperature (T c ) controlled modifiers, also known as Curie magnetic nanoparticles (CNP). Our previous magnetocuring work explored the adhesion strength for different substrates, adhesives, CNP loading, and heating properties of CNP. [1] One of the key advances in our magnetocuring methodology is preventing overheating, the main disadvantage of ferric oxide nanoparticles. Resin scorching is prevented by matching the T c of CNP to the resin activation temperature. As T c is approached, CNP's lose their ferromagnetic properties. [6] The resin temperature cannot extend beyond T c , which can be tuned by adjusting the CNP's chemical composition. However, heating rates are limited to 1.2 °C s −1 and tuneable T c are needed to pair with thermosets possessing variable temperature activation-from 80-200 °C. High saturation magnetization (M s ) is an important parameter required to obtain high heating rate. [7] However, tuning T c may result in undesirable changes in M s . [1,8] Optimization of heating rates and tuneable T c need to be compatible with good mechanical strength and nanoparticle colloidal stability within the organic resins.Generally, the heating rates of CNP can be tuned through composition, surface coatings, particle size, and percent loading. [9] However, these factors may lead to undesirable shifts in material parameters of CNP magnetic anisotropy, magnetization, and Curie temperature. Hence, other methods of temperature control were explored, that is, increasing thermal conductivity of the resin by addition of carbon allotropes. Carbon allotropes such as carbon nanotubes (CTUBE) and carbon nanocoils (CCOIL) can increase modulus and impart electromagnetic shielding. [10] Reinforcement of epoxy nanocomposites by the addition of carbon allotropes increases mechanical strength, thermal/electrical conductivity, and electromagnetic wave absorption. [10c,11] CTUBEs are composed of hexagonal rings of carbon atoms; helical variants are referred to as CCOIL. CCOIL possess additional non-hexagonal cycle carbon, such as cyclopentadiene and Magnetocuring of adhesives refers to the curing of an epoxy + Curie temperature controlled magnetic nanoparticles (CNP) composite using a suitable alternating magnetic field. The controlled heating of the CNP results in remote, wireless curing without resin overheating. However, typical CNP possess only a fraction of the heat output of ferric oxide nanoparticles, quantified as the specific absorption rate (SAR). Previous investigations of epoxy + CNP adhesives revealed a SAR of 5 W.g −1 , which is 10-100× less than that of ferric oxides. Here, it is demonstrated that SAR can be improved to up to 60 W.g −1 by tuning CNP composition and by the addition of c...

AC magnetorheology of polymer magnetic composites

“…The formation of nanosized (~20 nm) particles of the spinel phase is confirmed. The particles possess a 5wt.% surface coating 2 The magnetic properties of the CNP are evaluated using a physical property measurement system (PPMS, Quantum Design) equipped with a vibrating sample magnetometer and an oven. 2 Table 1 lists the magnetic properties of the CNP.…”

“…CNP of composition Mn 0.9 Zn 0.1 Fe 2 O 4 are synthesized using the hydrothermal method, as previously described. 1,2 The resulting vacuum dried nanoparticles are used for the two-layer functionalization, first with oleic acid to minimize agglomeration and second with an epoxy (BADGE) monomer to improve the thermoset initiation during magnetocuring. The surface functionalized particles (Mn 0.9 Zn 0.1 Fe 2 O 4 /OA/BADGE) are used for all the magnetocuring and magnetorheometry experiments.…”

“…Magnetocuring is an emerging technology platform to cure thermoset resins using alternating magnetic fields (AMFs). 1,2 This technology exhibits several advantages, e.g., precise and remote control of temperature, no resin scorching, ability to cure temperature sensitive substrates, energy efficient, etc., and is therefore highly relevant to sports, automotive, and aerospace applications. The filler particles, aka Curie nanoparticles (CNP), serve as heaters that initiate chemical crosslinking in magnetoadhesives upon AMF exposure.…”

“…The filler particles, aka Curie nanoparticles (CNP), serve as heaters that initiate chemical crosslinking in magnetoadhesives upon AMF exposure. In magnetocuring, [1][2][3] magnetic hyperthermia, [4][5][6][7][8][9] drug delivery, 10,11 tissue engineering 12 and magnetic cooling 13 applications, CNP suspended in carrier fluids are used for controlled heating. The specific temperature profiles depend on the efficiency of the AMF absorption of the CNP.…”

“…1A). 1,2 Magnetocuring of magnetoadhesives offers remote, wireless, and touchless thermoset curing and considered as more energy efficient, since indirect substrate heating is avoided. Previous investigations of magnetocuring achieved temperature control and MPa-magnitude shear adhesion strength by (1) CNP loading, (2) elemental composition, (3) magnetic field strength, (4) electromagnetic additives based on carbon allotropes, (5) non-ferrous porous and glassy substrates, and (6) resins of varying viscosity.…”