Phase transition of epoxy resin during isothermal curing monitored by ultrasonic velocity measurements

Influence of partial cross‐linking degree on basic physical properties of RTM6 epoxy resin

“…For a curing degree of 76.5% ± 2.5% the glass transition temperature crosses the curing temperature, T c , of 135°C. This has an important impact on the physical properties of the resin and its curing behavior . The gelation point is reached at curing degrees between 40% and 50%, as can be extrapolated from gel times and curing temperatures given in literature .…”

“…During the curing process a chemical reaction between epoxy groups and reactive groups of the hardener takes place. Depending on the curing treatment the material will pass either from liquid through rubber to glassy state, or from liquid to rubber state or from liquid to glassy state . Annealing of a glassy polymer at temperatures below its glass transition temperature results in physical ageing processes .…”

Isothermal epoxy-cure monitoring using nonlinear ultrasonics

“…At the same time, the effect of sonification (if any) is about the same as that of the low-frequency oscillations in DMA. Table 3 Ability of the used test methods to detect characteristic points during the epoxy cure ("þ " means ability, and "-" means disability; for the linear ultrasonics, data are taken from [5,[15][16][17][18][19]34]).…”

“…The use of ultrasonics also enables real-time quality control. The reported results demonstrate that ultrasonic measurements, which employ longitudinal and/or shear waves, are applicable for monitoring of thin epoxy layers [8][9][10][11][12][13][14] and for detection of gelation time when a viscous epoxy transforms into an elastic gel [5,7,[15][16][17][18][19][20].…”

Functionalization of multi-walled carbon nanotubes for enhancement of thermomechanical properties of dielectric epoxies

“…After curing, epoxies are rigid and the molecules are arranged in a configuration where their potential energy is a minimum. This arrangement depends on the curing parameters [128,129] and does not necessarily correspond to a smooth curved wrapping of CNTs. Even if such irregular structures have negligible effects on contact area of micro-scale fillers, it may result in significant interfacial contact surface irregularities for nanotubes which are only a few tens of nanometers in diameter and a few microns in length.…”