Epoxy and Polyurethane Networks in Thin Films On Metals—Formation, Structure, Properties

Trans-Interfacial Polymerization and Matter Transport Processes in Epoxy-Alumina Nanocomposites Visualized By Scanning Brillouin Microscopy

“…Already for pristine epoxies, heterogeneous structures of macroscopic dimensions ranging between some tens of nanometers and micrometers and differing in their mechanical stiffness have been reported in literature. [11][12][13][14][15][16] Note that the appearance of such heterogeneities suggests the existence of interphases between the related epoxy structures. In the context of this paper, an interphase consists of epoxy that connects distinct adjacent domains of homogeneous material.…”

“…For example, the existence of optically visible heterogeneities could not be confirmed by hypersonic velocity measurements, 17 whereas Brillouin microscopy on the same sample revealed acoustic heterogeneities roughly a thousand times smaller than those seen optically. 15,17 Taking into account the formation of specific interphases around the nanoparticles in epoxies, the challenging question arises as to what extent the initial sequence of mixing the nanoparticles into one of the epoxy reactants influences the formation of heterogeneities. Refractive index measurements have recently shown that the formation of epoxy networks may strongly depend on the mixing sequence of the three components, 8 the resin, the hardener, and the nanoparticles.…”

Interphases, gelation, vitrification, porous glasses and the generalized Cauchy relation: epoxy/silica nanocomposites

“…It was shown for epoxies that the specific refractivity is almost constant during polymerization at ambient temperature [28].…”

“…The pure epoxy (100 : 14.2) shows the highest tensile shear strength during fracture experiments performed on different epoxy mixtures glued on native aluminium [16,28]. The polymerizations were studied at 298 K when the chemical sol-gel and/or glass transition take place for all nanoparticle concentrations [16,28,29]. According to the model of Bansal and Ardell [30], the mean interparticle distance (surface-surface distance) between the silica nanoparticles can be estimated to be below 25 nm for all nanocomposites (see table 3).…”

“…These epoxies are slightly over-stoichiometric (stoichiometric: DGEBA/DETA (100 : 12)). The pure epoxy (100 : 14.2) shows the highest tensile shear strength during fracture experiments performed on different epoxy mixtures glued on native aluminium [16,28]. The polymerizations were studied at 298 K when the chemical sol-gel and/or glass transition take place for all nanoparticle concentrations [16,28,29].…”