Preparation and nonisothermal cure kinetics of DGEBA‐nanosilica particles composites

Abstract

Nanocomposites from nanoscale silica particles (NS), diglycidylether of bisphenol‐A based epoxy (DGEBA), and 4,4′‐diaminobiphenyl benzidine (DAPB) as curing agent were obtained from direct blending of these materials. This homogenous mixture was cured in the oven at a particular temperature for a certain time or scanned from room temperature up to 300°C in differential scanning calorimeter (DSC). Mechanism and kinetic of the cure reaction of nanocomposite and thermal stability of the cured sample were studied with FTIR, DSC, and thermogravimetric analysis, respectively. The effect of amount of nanosilica (NS) particles as catalyst on the cure reaction of DGEBA/DAPB system was studied by the Kissinger and Ozawa equations. The existence of NS particles with hydroxyl groups in the structure catalyzes the cure reaction of DGEBA/DAPB system, increased the rate constant, and shifted the exothermic peak toward lower temperatures with increasing amount of NS particles. The activation energies of cure reaction of pure DGEBA/DAPB system obtained from two methods were in good agreement and decreased when NS particles were present in the mixture. The isothermal cure reaction at 145°C in an oven was followed by measuring the disappearance peak of epoxide group at 916 cm−1 using FTIR. The diffusive behavior of cured samples was investigated during water sorption at 25°C and the experimental results fitted well according to Fick's law. Diffusion coefficient of cured sample containing 10% NS decreased in comparison to the sample without NS particles. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers

Highly dispersed nanosilica–epoxy resins with enhanced mechanical properties

“…Other researchers attribute the decrease in T g with nanosilica loading to the catalyzed reaction of epoxy with surface hydroxyl groups, which can lead to the formation of an amine rich shell around the nanoparticle and subsequent shifting of the epoxy/amine stoichiometry to induce higher cross-linking of the matrix [23]. The details of the effects of the Nissan nanosilica on kinetic constants of a different epoxy cure have also recently been investigated [24]. Still other researchers suggest that the compressive force due to the mismatch in coefficient of thermal expansion can aid in toughening at selected temperatures [25].…”

“…Enhancement in toughness has been attributed to suppression of polymer chain mobility at the nanoparticles' surface from attractive interaction revealed by an increase in glass transition temperature (T g ) and/or broadening of the dynamic mechanical loss peak [21]. Enhancement in localized chain mobility from repulsive particle interactions and/or formation of regions of enhanced free volume have been suggested to exist for some silica (SiO 2 ) nanoparticles and to lead to a decrease in T g with increasing particle loading [22][23][24][25].…”

Kinetics and thermodynamics of isothermal curing reaction of epoxy‐4, 4′‐diaminoazobenzene reinforced with nanosilica and nanoclay particles

“…Curing kinetics of epoxy resins have been studied with different techniques, such as Fourier transform infrared spectroscopy [13, 14], near IR [15], and differential scanning calorimetry (DSC) [16–22]. DSC is the most widely used experimental technique to obtain the degree and reaction rate of cure of thermosetting resins.…”

Curing studies of epoxy resin by 4,4′‐diaminoazobenzene as curing agent reinforced with nanosilica and nanoclay particles along with impact resistance and thermal evaluation

“…It was reported [20] that nanoscale silica particles can act as a curing agent for epoxy, if tin chloride was used as catalyst or when the amount of NS exceeded 20 phr. In our previous work [21] with 20% NS, without addition of diamine, no cure reaction occurred. This difference proposes, in DGEBA/DAAB/NS and DGEBA/DAAB/NC systems, that NS and NC particles with hydroxyl groups catalyze the reaction; therefore, maximum cure temperature was decreased.…”