Dielectric analysis as curing control for aminoplast resins—correlation with DMA

Processing

“…Examples range from various epoxy systems [45,46,65À67] or unsaturated polyesters [1] to aminoplastic wood adhesives [68] and polysulfide based sealants [69]. Dielectric Analysis (DEA), according to ASTM E 2038 and E 2039, measures the changes in the dielectric properties of a thermosetting resin that take place during the cross-linking process.…”

Dielectric analysis monitoring of thermoset curing with ionic liquids: From modeling to the prediction in the resin transfer molding process

“…Although DEA has been used successfully for a variety of different materials including cement, wood panels or dental resins and a multitude of manufacturing techniques such as pultrusion and autoclave processing, no complete study with ionic liquids as hardener, that is, from modeling up to an industrial composite manufacturing process, has been published until now to the best knowledge of the authors. Due to the ionic nature of the imidazolium salts, difficulties regarding its high conductivity in combination with DEA as characterization method are expected, which could affect cure prediction modeling and in situ monitoring.…”

“…Due to the ionic nature of the imidazolium salts, difficulties regarding its high conductivity in combination with DEA as characterization method are expected, which could affect cure prediction modeling and in situ monitoring. This issue was so far only covered briefly by Pretschuh et al during cure monitoring of aminoplast resins for particleboard manufacturing when using the ionic accelerator ammonium nitrate . They observed “deceleration effects” during cure monitoring with DEA in comparison to dynamic mechanical analysis (DMA).…”

“…For high-purity epoxy resins, which are typically needed for the electronic industry to avoid chemical or galvanic corrosion, the ion content is often around 50 ppm or less, whereas for ionic liquid cured epoxies it can reach values three orders of magnitudes higher, up to 100 000 ppm. [12] Although DEA has been used successfully for a variety of different materials including cement, [13] wood panels [14] or dental resins [15] and a multitude of manufacturing techniques such as pultrusion [16] and autoclave processing, [17] no complete study with ionic liquids as hardener, that is, from modeling up to an industrial composite manufacturing process, has been published until now to the best knowledge of the authors. Due to the ionic nature of the imidazolium salts, difficulties regarding its high conductivity in combination with DEA as characterization method are expected, which could affect cure prediction modeling and in situ monitoring.…”

Adhesive systems for low formaldehyde emission wood-based panels

“…Immobile groups originated by polymeric processes result in dielectrical conductance decrease. In recent years, DEA technique has been described for the characterization of polycondensating phenoplast and aminoplast wood binders [78,79].…”